# Dyno figures, let's open a can of worms!



## barry P. (May 9, 2010)

I probably need to explain that this is not meant to stir up trouble but to perhaps make people aware that Dyno figures should not be regarded as the road to the holy grail.
I bought my car over four years ago and within a short period of time of buying the car, about 1 hour!, I went to Matt at The Racing Line to get him to remap the car. If I remember correctly it eventually gave about 590bhp on his Dyno Dynamics rolling road. Matt told me at the time that due to the size of the turbos about 620 is the max you will get due to how much air they can flow. A few months later I had downpipes fitted and larger injectors and asked Ryan G to map it at Surrey Rolling Road, on that Dyno Dynamics on a very cold winters day with an air temp of 1C we got about 620 bhp and 620ftlb. It has stayed in this configuration for three years and I've been very happy with the performance however the black soot was a pain in the backside so I decided to have it remapped using the V5 Ecutek and new ASNU injectors. The car was remapped by a different tuner and was mapped on their rolling road which was a different make to the Dyno Dynamics. I got a printout after mapping which showed a figure of 675bhp, similar to most other cars at this stage on this particular dyno.
I am good friends with another GTR tuning company, they also remap GTRs using Ecutek and were concerned that customers were finding it difficult to understand that this particular company's stage 4 maps were only getting about 620-630bhp on the Dyno they use whereas the other company were producing readouts of 675 for the same stage of tune. I was asked if I would run my car on the same dyno to get a comparison.
So today I headed up to a Dyno Dynamics rolling road, my car which I have a rolling road print out for 675bhp produced 606bhp on the Dyno Dynamics rollers!!
The rolling road operator told me he had also had a stage 4.5 with bigger turbos which had produced over 720bhp on the other make of turbos give 594bhp on his Dyno Dynamics.
This got me thinking about the comment from Matt at TRL all those years ago that the standard turbos will only flow 620, perhaps we should take these stage 4 figures with a pinch of salt, I seem to have lost 70bhp in four months.


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## AdnanK (Jun 11, 2013)

Interesting.

I'll keep an eye on this thread.


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## terry lloyd (Feb 12, 2014)

barry P. said:


> I probably need to explain that this is not meant to stir up trouble but to perhaps make people aware that Dyno figures should not be regarded as the road to the holy grail.
> I bought my car over four years ago and within a short period of time of buying the car, about 1 hour!, I went to Matt at The Racing Line to get him to remap the car. If I remember correctly it eventually gave about 590bhp on his Dyno Dynamics rolling road. Matt told me at the time that due to the size of the turbos about 620 is the max you will get due to how much air they can flow. A few months later I had downpipes fitted and larger injectors and asked Ryan G to map it at Surrey Rolling Road, on that Dyno Dynamics on a very cold winters day with an air temp of 1C we got about 620 bhp and 620ftlb. It has stayed in this configuration for three years and I've been very happy with the performance however the black soot was a pain in the backside so I decided to have it remapped using the V5 Ecutek and new ASNU injectors. The car was remapped by a different tuner and was mapped on their rolling road which was a different make to the Dyno Dynamics. I got a printout after mapping which showed a figure of 675bhp, similar to most other cars at this stage on this particular dyno.
> I am good friends with another GTR tuning company, they also remap GTRs using Ecutek and were concerned that customers were finding it difficult to understand that this particular company's stage 4 maps were only getting about 620-630bhp on the Dyno they use whereas the other company were producing readouts of 675 for the same stage of tune. I was asked if I would run my car on the same dyno to get a comparison.
> So today I headed up to a Dyno Dynamics rolling road, my car which I have a rolling road print out for 675bhp produced 606bhp on the Dyno Dynamics rollers!!
> ...


About time this was mentioned - only one tuner is getting these high numbers on their dyno - these cars are a piece of cake to tune ( for experienced tuners ) they should all be around the same figures with the same hardware

Saying that a good air conditioned dyno cell / room would help with higher figures


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## TAZZMAXX (Mar 9, 2010)

Does anybody actually believe dyno figures that aren't measured at the crank?


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## goRt (May 17, 2011)

And here's autotorque getting 665 bhp /~630 torques on its dyno:
http://www.gtr.co.uk/forum/433218-stage-4-a-2.html#post4572290

All we can do is rock up to the same dyno on the same day and get our tape measures out!


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## Dings (Oct 8, 2015)

If I was going to go with any dyno I would go with dyno dynamics....as far as im aware they are the closest to correct bhp...although all dynos can be fiddled depending how good the tuner wants to look


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## Simonh (May 24, 2002)

A dyno can never give you an accurate power reading it is only ever a record of the power for that car on that day in those conditions with that operator.

your best bet for using a dyno is to go back to the same place with the same dyno and same operator and see the difference that the mods or tune have made. Taking the car to another dyno for measurement will only measure the difference between dynos and operators not differences in power output.

The 1/4 mile is the best way to get a reflection of the actual power your car is making there is a chart that is floating around on here somewhere that shows this and time and again it has been proven to be correct.


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## Richf (Feb 8, 2007)

There is a comparison tool here , although the dynapack data is a little screwy the rest looks about right , especially comparing Dyno Dynamics to a dynojet for example 

Toyota Supra MKIV : MKIV Specifications


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## terry lloyd (Feb 12, 2014)

Sadly the higher numbers are a good selling point - if your giving realistic figures most people wil go elsewhere thinking there car will be quicker with the higher bhp figure - i personally think the power curve is the best thing to look for


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## Litchfield (Feb 26, 2008)

Having seen your graph Barry I think you should question the operator


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## barry P. (May 9, 2010)

From looking at the graph produced today and the earlier graph there appears to be some differences in the shape of the graph. Today's Dyno Dynamic graph the boost appears to drop off quite early, which means peak power is showing at 5500 then tailing off and the torque doesn't seem to be holding unlike the V5 graph which is holding both torque and power really well. I have been in touch with the V5 tuner who has suggested a few possibilities as to why there is the large discrepancy between the two figures, these could be due to the way in which the dyno is being operated, or car issues such as a boost leak.They have offered to have a look at the car and try and resolve what is going on which is great customer service, as I said at the beginning of this thread it is not a witch hunt and I have complete satisfaction with the company but would like to try and find out what is going on.


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## I.am.Sully (Oct 13, 2015)

I think I've found the answer, 


Has your door speaker blown Barry? 


Recently posted by TurboFreak.

'This week the speaker in the passenger door has blown, the bass sounds terrible... I knew I shouldn't have bought that car' :runaway:


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## mindlessoath (Nov 30, 2007)

use 1/4 mile times. yes there are many factors for this too, but generally much better measuring stick.

you could use a race logic performance box too. its not perfect as well, but much better than just a dyno alone.

a car that dynos 700hp might put down slow ass times because of a worn clutch, but it sure could put up big dyno numbers... which are worthless due to the clutch.

thats why on top of the facts the op brought up, a dyno number is bullshit


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## HUGHS1E (Jan 20, 2015)

We need to take a group to pod, different stages of tune, or a roll out at brunters

But as long as your happy numbers don't matter.

But your car is just injectors and downpipes?


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## barry P. (May 9, 2010)

HUGHS1E said:


> We need to take a group to pod, different stages of tune, or a roll out at brunters
> 
> But as long as your happy numbers don't matter.
> 
> But your car is just injectors and downpipes?


That's one of the reasons GTRMart ran his airfield day to get a comparison between cars.
Mine's stage 4.25 so yes, injectors and downpipes but standard turbos. The more I look at the graph from today it makes sense to me for it to be a boost leak from the way the boost is acting and the way the torque and power drops off early.Todays graph is showing maximum power at 5500 which is not normal for a GTR map. I'll get it over to the tuner and hopefully they can put it back on their dyno and see what shows up


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## barry P. (May 9, 2010)

I.am.Sully said:


> I think I've found the answer,
> 
> 
> Has your door speaker blown Barry?
> ...


That's probably the answer :chuckle: My dad told me when I was younger that anything with four wheels or t#ts is going to give you trouble!


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## terry lloyd (Feb 12, 2014)

Are you sure its not just the heat from today backing off the power ?


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## rob2005 (Apr 26, 2015)

Subscribed opcorn:


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## Jonndogg (Oct 27, 2012)

I believe the chassis dyno in question returns very close to manufacturer quoted figures when testing stock vehicles.

Dyno dynamics is big in aftermarket tuning but not at an OE level as a development tool. Most of the manufacturers of this type of equipment are unheard of in the aftermarket world because of the investment required for a fully representative test cell. The best equipment can still be used incorrectly however.

What about the FBO guys in the us running "600whp" on stock turbos.?? That's the real pinch of salt requirement even with e85!


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## goRt (May 17, 2011)

barry P. said:


> That's one of the reasons GTRMart ran his airfield day to get a comparison between cars.
> Mine's stage 4.25 so yes, injectors and downpipes but standard turbos. The more I look at the graph from today it makes sense to me for it to be a boost leak from the way the boost is acting and the way the torque and power drops off early.Todays graph is showing maximum power at 5500 which is not normal for a GTR map. I'll get it over to the tuner and hopefully they can put it back on their dyno and see what shows up


How come today's tuner / dyno operator didn't notice the boost problem?

Sent from my E6653 using Tapatalk


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## goldgtr35 (Aug 15, 2012)

OOOOOOOOOOOOOOOppps boost leak
:flame::flame::flame::flame::flame:


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## barry P. (May 9, 2010)

goRt said:


> How come today's tuner / dyno operator didn't notice the boost problem?
> 
> Sent from my E6653 using Tapatalk


He wasn't asked for any diagnosis, it was purely a power run to see how it compared. It was only when I got home and compared the power/torque graph with my previous graph I noticed how the boost seemed to drop which seemed a bit strange to me although the original V5 tuner didn't give me a boost graph. Hopefully I can get a slot on the other dyno in a couple of days and see whether they think everything is still ok.


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## TAZZMAXX (Mar 9, 2010)

Hot day = thin air

What was the ambient temperature like on the day of the last dyno run?


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## JapFreak786 (Aug 29, 2003)

Can I ask what the role of the operator is in terms of set-up and producing figures. I guess there may be some calculations but in layman terms, shouldn't a car be stuck onto the dyno and just "ran"?


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## barry P. (May 9, 2010)

Here's today's graphs, would any experienced Dyno Dynamics experts like to comment from what they can see from the graphs?


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## ChillyFly (Aug 14, 2015)

Barry interesting thread, but did the dyno you ran on today give a DIN normalised output? I remember speaking to Ian Litchfield about this last time I was there (my car hasn't been on the dyno yet, I'll save that for the Phase 5 ECUTek map), but the dyno software normalises for density altitude. I.e. ambient pressure in Milibars, air temp, humidity (less of a factor) so that running on a dyno on a freezing cold day with a high ambient pressure should give exactly the same power output on the graph as running on a hot day with low pressure. I.e. they are normalised to a standard atmosphere, which is 1013.2Mb and 15c at sea level.

Also his dyno measures transmission drag (i.e. deceleration) on the wind down after the power run, and corrects the power output at the wheels to give flywheel BHP.

What you said yesterday is quite right though, BHP figures are pub talk beyond a certain point. As you know the only way to back to back race engines is on the same dyno.

I am interested to know if the boost control on the GTR is relative to ambient, or absolute pressure. Ian? Anyone? Assuming it's absolute, then air pressure changing with weather systems shouldn't make any difference, and to a point, neither should driving up a mountain range! But if it's relative to ambient pressure, as in the good old days of drilling a number drill hole in the wastegate actuator a la Renault 5 turbo etc to bleed off some pressure from the wastegate actuator line, then obviously the power output will still change with ambient air pressure on the day.

We need someone like Ian to give the detail on the dyno, I am sure it is far more complex than what I have written here...


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## ChillyFly (Aug 14, 2015)

Have you got more graphs of different runs showing the boost? If so, was the boost drop off like that on every graph? It seems remarkably linear and almost 'controlled' for a boost leak...


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## terry lloyd (Feb 12, 2014)

ChillyFly said:


> Barry interesting thread, but did the dyno you ran on today give a DIN normalised output? I remember speaking to Ian Litchfield about this last time I was there (my car hasn't been on the dyno yet, I'll save that for the Phase 5 ECUTek map), but the dyno software normalises for density altitude. I.e. ambient pressure in Milibars, air temp, humidity (less of a factor) so that running on a dyno on a freezing cold day with a high ambient pressure should give exactly the same power output on the graph as running on a hot day with low pressure. I.e. they are normalised to a standard atmosphere, which is 1013.2Mb and 15c at sea level.
> 
> Also his dyno measures transmission drag (i.e. deceleration) on the wind down after the power run, and corrects the power output at the wheels to give flywheel BHP.
> 
> ...


There is a air temp sensor in the inlet combined with the Maf - depending on how its mapped it will pull timing / add fuel when it reaches certain perameters (air temp) -with it being hot today the car may have backed the timing off giving a lower bhp result


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## barry P. (May 9, 2010)

ChillyFly said:


> Have you got more graphs of different runs showing the boost? If so, was the boost drop off like that on every graph? It seems remarkably linear and almost 'controlled' for a boost leak...


They only did three runs and printed off the "best" one.


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## moleman (Jun 3, 2002)

5252?


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## Richf (Feb 8, 2007)

Did you get a chart of the fuelling ?


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## goRt (May 17, 2011)

moleman said:


> 5252?


Torque vs BHP, but what's plotted isn't clear.

Sent from my E6653 using Tapatalk


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## monkeynuts1 (Jan 17, 2014)

barry P. said:


> That's probably the answer :chuckle: My dad told me when I was younger that anything with four wheels or t#ts is going to give you trouble!


And a empty wallet


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## Teaboy (Apr 24, 2016)

moleman said:


> 5252?


5252 only happens when bhp vs ftlbs scaling is the same and you can see in the graph that the axis for them is not. Looks like the RPM scaling is off unless the dyno operator decided to call it a day at 6250rpm because peak power had already been made at around 5600rpm. The shape of the graph looks typical of a GTR at that level of tune. Boost falls away at about the right rate as the turbo's run out off puff. I don't see anything that suggests a boost leak but you never know. The DD dyno in shoot 44 looks to be using a transmission loss of around 21% which could be different to the initial dyno run that was said to use the over run to calculate drag to produce a fly wheel estimation. The is a lot a variables BUT 70bhp is a lot


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## Trevgtr (Dec 24, 2012)

Simonh said:


> The 1/4 mile is the best way to get a reflection of the actual power your car is making there is a chart that is floating around on here somewhere that shows this and time and again it has been proven to be correct.


I've found that on remapped cars there is a lag built in to gear changes, so small that many people don't even notice it, but at say 0.2 seconds extra per gear change, that slows remapped cars by 0.6 seconds on a standing 1/4 run, compared to a stock car.

So although a 600 bhp stage 2 car will pull harder and feel quicker, it won't be any quicker than stock over a standing 1/4 mile. In 5th and 6th gear it will pull away.


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## VIB 17 (May 15, 2015)

Would be good to have a dyno day so you would be able to compare cars with same/ different stages by different tuners all on the same dyno with same conditions! Who's 4.25 is the 'best' ! ***128539;


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## Theskycankill (Apr 27, 2015)

It is not the ET on a quartermile run it is the MPH achieved this will give a true indication of power !

Too many variables on ET,good driver,launch technique,suspension set up etc.

A dyno should be thought of as a way to measure modification improvements,that's it.

Use the same one same operator,and forget what other people/companies claim.


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## Richf (Feb 8, 2007)

Trevgtr said:


> I've found that on remapped cars there is a lag built in to gear changes, so small that many people don't even notice it, but at say 0.2 seconds extra per gear change, that slows remapped cars by 0.6 seconds on a standing 1/4 run, compared to a stock car.
> 
> So although a 600 bhp stage 2 car will pull harder and feel quicker, it won't be any quicker than stock over a standing 1/4 mile. In 5th and 6th gear it will pull away.


I would be amazed if the delay in shifting was anything like that or would have anything like that kind of impact in 1/4 mile


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## Teaboy (Apr 24, 2016)

The sad truth is this, numbers sell. If you didn't know how subjective dyno numbers could be and you where a prospective stage 4.25 customer then the promise of higher bhp figures is probably going to be a major consideration. People want to get the most for there money and it's hard to ignore a tuner claiming 40bhp more than most for the same level of tune. The GTR is a known quantity and in the hands of good tuners with similar stage 4.25 parts the is going to be little to no difference in ultimate bhp tuner vs tuner. If your AFR's are right and the turbo's are run to there limit and you put as much ignition timing in as you can get away with regardless of tuner the end results will be the same. The is no magic formula to make 40bhp more than every one else. I am not for 1 minute suggesting this but if you wanted to improve dyno results the is lots of variables at the operators discretion that will have an effect on numbers achieved including but not limited too: over inflation of tyres, strapping the car down loosely, not putting the air temperature sensor in the right place, transmission loss used to calculate fly wheel bhp. Then the is the ability to run more boost and a bit more ignition timing for a single run on the dyno to generate good numbers but with the tune being to highley strung to be repeatable on the road then both could then be pulled back a tad so the car is safe on the road. Yes it was capable of making the number but when the car is released back into the real world where it is going to get a kicking in every gear and maybe a track day or 2 you are going to be at the same level of tune as every one else.


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## Lukes R35 GT-R (Mar 1, 2015)

Trevgtr said:


> I've found that on remapped cars there is a lag built in to gear changes, so small that many people don't even notice it, but at say 0.2 seconds extra per gear change, that slows remapped cars by 0.6 seconds on a standing 1/4 run, compared to a stock car.
> 
> So although a 600 bhp stage 2 car will pull harder and feel quicker, it won't be any quicker than stock over a standing 1/4 mile. In 5th and 6th gear it will pull away.


Do you get this mainly 1st into 2nd


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## moleman (Jun 3, 2002)

Teaboy said:


> 5252 only happens when bhp vs ftlbs scaling is the same


Ah, OK. That would explain it.


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## CT17 (Mar 25, 2011)

goRt said:


> All we can do is rock up to the same dyno on the same day and get our tape measures out!


Willies and Wallets too.
That's what Rolling Roads and quarter mile shootout are about isn't it? :chuckle:


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## Litchfield (Feb 26, 2008)

Looking at the graphs the 3 things that jump out straight away are why does the boost cut at low rpm as the boost limit will be over 1.2bar at that point, why did the run end at 6,200rpm when the rev limiter will be around 7,200rpm and why is the torque only 600lbft on a dyno dynamic yet the car is making 1.2+bar? 

My first question would be was it run with traction control on. A dyno dynamics won't be able to control the front roller speeds correctly (not ideal for the fwd clutch) so the ECU might think it has wheel spin and pull back the power in an attempt to get the speeds the same. We have seen this many times. Was the rpm set correctly, fuel quality, intercooler temps etc etc there are so many variables before people jump to a conclusion that either dyno must be wrong or there is a problem with a car. You could take the same car to different dynos on the same day and still get a difference. 

It's a shame some question our work and motives.

Dyno results will always "open a can of worms" as you'll always get people wanting to believe different things.

We can only quote the results as we achieve them. A standard GTR will produce standard figures including Nissan's press car which we ran for Evo magazine a couple of months back. It's not just the GTR, our Focus RS, M2, M3 GTS etc etc are exactly as advertised (helped by the fact many of these OEs use the same dyno manufacturer as us). If we wanted to massage egos and market high figures we would have bought the much cheaper dynojet and not invested in something that cost over double even the next most popular option. The dyno is a development tool for us and it is important we use the best tools that are close to a manufacturer for good reason.

We have used many brands of dynos over the years and where our previous stage 4.25s would make 620-630bhp (as advertised) they still produce similar numbers on our dyno now. We also regularly do before and after runs when re-tuning other people's conversions and they also produce around 610-620bhp. However there is more to it than maxing the boost, sensible AFRs and running as much ignition as it would take. This is where our improvements have come from.

It's very easy for others to say that it must be just marketing to entice customers in, but I have yet to see another Stage 4.25 tune that we haven't been able to improve upon by some margin. Not many companies have the combination of their own development cars, unlimited internal dyno time and experience to invest in producing something more than just a tweak to Ecutek's example files. It would be short sighted to think the above combination would not yield any additional power over our previous offerings.

If people don't want to believe that, nothing we say will change their minds.

Iain


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## Kenco (Jul 25, 2003)

Nice response Iain


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## slapshot (Jan 30, 2016)

Isn't there considerable variation in power output between cars anyway due to the hand built nature of the engines?


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## Adamantium (Jun 24, 2002)

slapshot said:


> Isn't there considerable variation in power output between cars anyway due to the hand built nature of the engines?


not that I've seen.

They dyno them at the factory, if there was an unacceptable range they'd fix it.

I think various forms of trade descriptions act mean they have to give within a certain tolerance of manufacturers claims.


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## terry lloyd (Feb 12, 2014)

Was good to see Litchfield taking time to comment and explain things - Helps to put a lid on these can of worms


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## Trevgtr (Dec 24, 2012)

Lukes R35 GT-R said:


> Do you get this mainly 1st into 2nd


No, every gear change, a very slight pause before power resumes, almost unnoticeable, hence why most haven't noticed it


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## Adamantium (Jun 24, 2002)

Trevgtr said:


> I've found that on remapped cars there is a lag built in to gear changes, so small that many people don't even notice it, but at say 0.2 seconds extra per gear change, that slows remapped cars by 0.6 seconds on a standing 1/4 run, compared to a stock car.
> 
> So although a 600 bhp stage 2 car will pull harder and feel quicker, it won't be any quicker than stock over a standing 1/4 mile. In 5th and 6th gear it will pull away.


Where did you "hear" this?

I've seen many a datalog from the ecu whilst driving on the road that show linear acceleration with seemingly zero effect on a speed/time graph. The only indication of a gear change being a drop in rpm.

0.2 seconds would be an enormous lull in acceleration on a car with a gear change as fast as this.


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## mindlessoath (Nov 30, 2007)

all I have to add is, there are a lot of bad tuners or tuners that never invested time as Lichfield points out. you could just get a tune, or you could get a tune from someone who has invested time and research into tunes for the best possible tune. but hey, people keep saying tuning for the gtr is easy tho.
I would argue there is a huge difference between the two.

I also don't think its good to ever just get a dyno graph from some rando.. my monies would be on dyno tune so they can use the dyno as a tool and not a useless measuring stick. of course a street tune to go with it for fine tuning since load on the dyno is not the same as on the street.

also density altitude also affects horsepower in both dyno numbers and 1/4mile mph but as long as the da is supplied its more helpful to the numbers.


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## Teaboy (Apr 24, 2016)

Is the a graph from the first dyno? What is the difference in power at the wheels?


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## barry P. (May 9, 2010)

Teaboy said:


> Is the a graph from the first dyno? What is the difference in power at the wheels?


The graphs posted are from the Dyno Dynamics runs. The wheel horsepower from the V5 tune and run was 528bhp which was corrected to 674bhp. The Dyno Dynamic run yesterday wheel horsepower was 480bhp which was corrected to 606bhp.

I have been in contact with the V5 tuner and the car is going back to their workshop next Monday so they can check the car over and run it on the dyno again to check everything is ok, it drives fine and doesn't feel like it only has 606bhp.


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## Teaboy (Apr 24, 2016)

So transmission losses seem to be calculated very similarly. It just seems to have a 50whp difference dyno to dyno. It is good that your V5 mapper is going to look at it to make sure that mechanically it is ok and maybe shed some light on why you got low readings on the DD dyno. Hope your car is fine. Only way I can see to put this to bed is post your V5 dyno graph after they have looked at it and then run it again on the DD dyno after. Any difference found at that point must just be down to the way the 2 dyno's measure power. Be very interested to see.


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## Trevgtr (Dec 24, 2012)

Adamantium said:


> Where did you "hear" this?
> 
> I've seen many a datalog from the ecu whilst driving on the road that show linear acceleration with seemingly zero effect on a speed/time graph. The only indication of a gear change being a drop in rpm.
> 
> 0.2 seconds would be an enormous lull in acceleration on a car with a gear change as fast as this.


I don't want to throw Barry's thread off course. I started a thread all about the lag ages ago but the response was the same as now, no-one recognises the lag.

0.2 seconds was my best guess at the lag time, it certainly isn't less than 0.1 seconds. If you tap your desk with a finger nail while watching a digital clock in seconds, 6 taps per second is about right, so approx 0.16 seconds per tap, that's about the same as the lag.

Run the car on normal boost and gear changes in R mode feel instant, put it into high boost and the lag is there over 5k rpm on all gear changes with absolute mechanical repetitiveness (for want of better words) there's nothing random about it.

I had Dan check it out sat next to me with his laptop, he tweaked a few things and said there was no issue it was normal, so maybe it's something that tuners won't talk about? I actually don't have an issue with it, to me it's just an interesting point of fact that goes unrecognised.


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## Adamantium (Jun 24, 2002)

So Dan fixed it with a few tweaks?

Is it possible that it was accidentally wrongly configured on just your car? I know there's a lot of check boxes that need to be ticked every time a car is remapped, it's very easy to miss one out.


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## Litchfield (Feb 26, 2008)

It is difficult to compare dyno figures at the best of times but you defiantly can’t compare the “wheel HP” figures between our Maha dyno and a Dyno Dynamics (or any other) as they use completely different setups to measure power that happen to use the same name in their calculations. 

The wheel HP numbers for the dyno dynamics should be the accurate figure and the engine/crank figure will be the repeatable result for the Maha.

The Dyno dynamics uses twin rollers so will have 2 contact points vs our single roller for each axle. The Maha measures everything that is connected to the engine including the rollers, electric motors on both axles etc. It then measures the same connected items during its coast down phase to work out the total drag factor at each rpm point.


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## King_Rat (Jan 22, 2012)

I had a great deal of lag, then fixed my gearbox so can now slam it into 4th again. My power figures from MGT didn't jump all that remarkably over what I previously had (60 hp) but the map itself compared to the old one is the difference between night and day (admittedly I changed to a Link and engine rebuild). Can't say I know a lot about these things as only drive (tinker and pay for) the car. But mostly on my travels any talk of HP is mostly BS.


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## Trevgtr (Dec 24, 2012)

Adamantium said:


> So Dan fixed it with a few tweaks?
> 
> Is it possible that it was accidentally wrongly configured on just your car? I know there's a lot of check boxes that need to be ticked every time a car is remapped, it's very easy to miss one out.


No, Dan checked it out and said it was normal. 

Tuners don't recognise that it exists. I can feel that it exists.


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## mindlessoath (Nov 30, 2007)

Litchfield said:


> It is difficult to compare dyno figures at the best of times but you defiantly can’t compare the “wheel HP” figures between our Maha dyno and a Dyno Dynamics (or any other) as they use completely different setups to measure power that happen to use the same name in their calculations.
> 
> The wheel HP numbers for the dyno dynamics should be the accurate figure and the engine/crank figure will be the repeatable result for the Maha.
> 
> The Dyno dynamics uses twin rollers so will have 2 contact points vs our single roller for each axle. The Maha measures everything that is connected to the engine including the rollers, electric motors on both axles etc. It then measures the same connected items during its coast down phase to work out the total drag factor at each rpm point.


just wondering what your maha dyno says the drivetrain losses are in coast down?
Nissan claims 10% but most tuning shops see around 12% give or take depending on hp. just want to see another data point.


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## mindlessoath (Nov 30, 2007)

Trevgtr said:


> No, Dan checked it out and said it was normal.
> 
> Tuners don't recognise that it exists. I can feel that it exists.


via motec, this is how the gr6 works
shift speed explained in detail by motec
does that help at all?

your clutch could also be slipping, it would show in your ecutek TCM logs


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## Adamantium (Jun 24, 2002)

I've never known any gear change lag in any I've been in including my six gtrs all of which had been remapped, that's why I think something is up with your car


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## Anders_R35 (Jul 20, 2011)

I haven't noticed any gear change lag going up in power. I'd say is quicker since the Nismo hack was installed.


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## Teaboy (Apr 24, 2016)

Litchfield said:


> It is difficult to compare dyno figures at the best of times but you defiantly can***8217;t compare the ***8220;wheel HP***8221; figures between our Maha dyno and a Dyno Dynamics (or any other) as they use completely different setups to measure power that happen to use the same name in their calculations


I would have thought that WHP is the only universally measurable parameter on all load type dyno's. Fly wheel estimations is where different people and different dyno's have different ideas.


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## Teaboy (Apr 24, 2016)

Litchfield said:


> The Dyno dynamics uses twin rollers so will have 2 contact points vs our single roller for each axle.


Technically this is not true. If the DD dyno is set up and operated correctly on a power run the car climbs up onto the forward of the 2 rollers and no longer contacts the rear roller giving you the same single contact point as your Maha. This is important and if you are the said V5 tuner might go in your favour because if the car was restrained to heavily and not allowed to climb off the rear roller it will result in a lower whp figure.


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## Trevgtr (Dec 24, 2012)

Adamantium said:


> I've never known any gear change lag in any I've been in including my six gtrs all of which had been remapped, that's why I think something is up with your car


It's far too mechanically repeatable to be a fault, plus Dan confirmed no faults.

Drop to normal boost and there's no lag. Raise the boost and it's there. I'm talking a lag that many I don't think would even notice. MY13 car.


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## Evo9lution (Aug 24, 2013)

Trevgtr said:


> It's far too mechanically repeatable to be a fault, plus Dan confirmed no faults.
> 
> Drop to normal boost and there's no lag. Raise the boost and it's there. I'm talking a lag that many I don't think would even notice. MY13 car.


Get a VBox on it and test it ...


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## Tim Radley (Aug 3, 2013)

barry P. said:


> Here's today's graphs, would any experienced Dyno Dynamics experts like to comment from what they can see from the graphs?


Lack of inductive pickup for rpm is a big problem on your charts. Especially when scaling off the car tacho which can be miles off actual rpm. You can't measure wheel slip either.

Problem with dyno's are a combination of many issues. Poorly educated operators, laziness, bs corrections, inflated numbers, plain lies, etc.

If you want to see who makes the best engines, look at race results. Or race your friend side by side. Recently had a GTR customer repeatedly beat his mate despite a 340bhp deficit on the dyno charts.

Don't see dyno's winning races. Bul****t stops when the flag drops


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## Adamantium (Jun 24, 2002)

Didn't Schumacher win a few races by cheating?


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## Jayman (Jun 30, 2012)

Adamantium said:


> Didn't Schumacher win a few races by cheating?


LOL love it!!


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## goRt (May 17, 2011)

barry P. said:


> The graphs posted are from the Dyno Dynamics runs. The wheel horsepower from the V5 tune and run was 528bhp which was corrected to 674bhp. The Dyno Dynamic run yesterday wheel horsepower was 480bhp which was corrected to 606bhp.
> 
> I have been in contact with the V5 tuner and the car is going back to their workshop next Monday so they can check the car over and run it on the dyno again to check everything is ok, it drives fine and doesn't feel like it only has 606bhp.


Any update Barry?

Sent from my E6653 using Tapatalk


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## keithmac (Mar 1, 2014)

Quarter mile trap speed is a better indicator, no fluffing the results..


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## barry P. (May 9, 2010)

Yes, Iain's been excellent sorting it out :bowdown1: 
A couple of issues came to light, the AWD drive clutch was crapping itself at about 5500 and limiting the power to the front wheels. Litchfields removed the transmission and reshimmed the AWD clutch which has sorted that problem.
In the datalogs the fuel trims were out and Iain also noticed the wastegate duty cycle was different to what he expected, he suspected the dump valves were leaking slightly so they removed the valves and blanked them off which gave a significant improvement. He had some used OEM dump valves which he fitted and we seem to be back not far off the original power figures from his dyno. The readings are slightly lower but that could be explained by the air temps as it is now much warmer than in Nov when it was originally mapped.
I'm very happy with Litchfields response to the issues and are now looking forward to collecting the car tomorrow. :thumbsup:


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## Adamantium (Jun 24, 2002)

Glad it's sorted Barry.

I remember hearing that running the car on a dyno that doesn;t have driven front rollers puts extra strain on the 4wd clutch (which is TINY btw.) and that this problem is exacerbated as the power of the car climbs.

I wonder if running it on the dyno dynamics is what contributed to AWD clutch crapping itself.


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## dudersvr (May 7, 2003)

keithmac said:


> Quarter mile trap speed is a better indicator, no fluffing the results..


Exactly that the et will show torque and the terminal will show HP I owned a Dyno Dynamics and running an R35 on one is a nightmare, better on a hub dyno or a dyno that runs the front rollers from the back rollers the latest DD software does have a specific R35 mode, there is a formula somewher that if you input weight and et and terminal will give a very accurate HP and Torque figure. If a car as heavy as an R35 runs 10's it has to be in the mid 600hp bracket with similar torque.


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## Chronos (Dec 2, 2013)

barry P. said:


> Yes, Iain's been excellent sorting it out :bowdown1:
> A couple of issues came to light, the AWD drive clutch was crapping itself at about 5500 and limiting the power to the front wheels. Litchfields removed the transmission and reshimmed the AWD clutch which has sorted that problem.
> In the datalogs the fuel trims were out and Iain also noticed the wastegate duty cycle was different to what he expected, he suspected the dump valves were leaking slightly so they removed the valves and blanked them off which gave a significant improvement. He had some used OEM dump valves which he fitted and we seem to be back not far off the original power figures from his dyno. The readings are slightly lower but that could be explained by the air temps as it is now much warmer than in Nov when it was originally mapped.
> I'm very happy with Litchfields response to the issues and are now looking forward to collecting the car tomorrow. :thumbsup:


Glad the AWD clutch issue is sorted, sounds like it had a hard time! Did you get any indication from the car of this issue when it was happening? traction on dash?

So what dump valves did you have that where failing?? OEM? As it looks like the temp replacement OEM ones sorted the issue...?

Tell you what, R35 tuners over the last few years quality of service, and knowledge is just getting better and better across the well knowns, when I used to own an evo 5 years back it wasn't half as good and a lot where cowboys! , and that's being generous.


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## dudersvr (May 7, 2003)

barry P. said:


> Yes, Iain's been excellent sorting it out :bowdown1:
> A couple of issues came to light, the AWD drive clutch was crapping itself at about 5500 and limiting the power to the front wheels. Litchfields removed the transmission and reshimmed the AWD clutch which has sorted that problem.
> In the datalogs the fuel trims were out and Iain also noticed the wastegate duty cycle was different to what he expected, he suspected the dump valves were leaking slightly so they removed the valves and blanked them off which gave a significant improvement. He had some used OEM dump valves which he fitted and we seem to be back not far off the original power figures from his dyno. The readings are slightly lower but that could be explained by the air temps as it is now much warmer than in Nov when it was originally mapped.
> I'm very happy with Litchfields response to the issues and are now looking forward to collecting the car tomorrow. :thumbsup:


Good to hear im off to Litchfield Tuesday for V5 software and gearbox software


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## Teaboy (Apr 24, 2016)

Barry P out of curiosity did they dyno before they fixed it to help diagnose the faults? If so was the figure comparable to that produced by the DD dyno? Any more graphs?


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## barry P. (May 9, 2010)

Teaboy said:


> Barry P out of curiosity did they dyno before they fixed it to help diagnose the faults? If so was the figure comparable to that produced by the DD dyno? Any more graphs?


I went up to Litchfields on the Mon and Iain put it on their rolling road and logged several different parameters. It was about 40bhp down on the initial dyno v5 session in Nov. Three significant issues were seen, firstly the AWD clutch was slipping badly, secondly fuel trims were not constant and thirdly wastegate duty cycle was very high which suggested there was a boost leak. The power figure was quite a bit higher than the dyno dynamics however this could be explained by the fact that the Maha gives the AWD clutch an easier time when on the dyno. I know Charlie at Surrey Rolling Rods will no longer run R35 on his dyno because of this issue.
Iain had the car back on Tues, they removed the gearbox and reshimmed the AWD clutch then refitted everything and ran it again on the rollers, it improved the power output but was still low. They took off the dump valves and fitted some plugs to blank it off, these gave an immediate improvement. Iain kindly gave me FOC some OEM dump valves which they had in the workshop from customers upgrading to his own dump valves, he also did the initial diagnosis dyno runs free of charge. I have the latest graph, it's about 8bhp down from the original but the weather was much warmer on this run but torque is 13ftlb higher.


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## dudersvr (May 7, 2003)

The only consistent runs we got on a DD wes when the car was able to run RWD


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## keithmac (Mar 1, 2014)

A lot to go wrong, how many miles between initial "good" dyno and the next one that prompted all the problem finding/ transfer clutch problems?.

Don't think time should be an issue either, friction surfaces don't nornally wear out when nothing's moving.


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## Teaboy (Apr 24, 2016)

Glad you got it all sorted Barry. Dose it feel different now it's all sorted as I recall you saying it still felt normal after the low figures from the DD dyno?


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## Teaboy (Apr 24, 2016)

Just looked back at your original post and the DD dyno was 70hp down over your original Maha run. You said above that with a few faults you where 40hp down on the same dyno it was mapped on so the seems to only be around 30hp difference between the DD and the Maha. This figure is now believable and might go some way to explain why lots of people quote around 650bhp on a good stage 4.25 and the Maha seems to rate them at around 680bhp. Any plans to revisit the DD dyno to put this to bed? I'm not suggesting the Maha dyno reads hight or the DD reads low and I'm not bothered wich has the more accurate number but if you can prove the is around a 30bhp difference between the 2 dyno's at stage 4.25 power levels it would answear a lot of questions.


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## Adamantium (Jun 24, 2002)

Why would you go back to a DD when probably the most knowledgable and trusted DD operator known to the forum (Charlie at SRR) refused to run GT-Rs now due to the damage the dyno does to the 4WD clutch?

Unless the front rollers are driven somehow, it sounds like a bad idea to put a GT-R on the dyno.


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## goRt (May 17, 2011)

barry P. said:


> ... I have the latest graph, it's about 8bhp down from the original but the weather was much warmer on this run but torque is 13ftlb higher.


I was under the impression that the ISO standard used to create the corrected values on Iain's dyno was specifically to account for atmospheric changes???


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## dudersvr (May 7, 2003)

1


goRt said:


> I was under the impression that the ISO standard used to create the corrected values on Iain's dyno was specifically to account for atmospheric changes???


We had an older MAHA dyno before the DD and that worked out hp on transmission loss, you did a run and then let it run down in N so not sure that you could even do that in a R35 on that MAHA, as far as accuracy on a DD we dynoed a Diesel Golf 140 hp and it came out at 139 and an M5 V10 that came out at 509 so both 1hp down on manufacturers figures. The M5 had been in the day before with an Ebay induction kit and made like 460 hp which caused an argument as the guy was saying the dyno was wrong etc, he bought it back the next day with the stock bits on and hey presto correct power, but I would only run mine on one in RWD.


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## Tim Radley (Aug 3, 2013)

Interesting post.

Can someone with actual experience explain how they do a coastdown test on a GTR please?




dudersvr said:


> We had an older MAHA dyno before the DD and that worked out hp on transmission loss, you did a run and then let it run down in N so not sure that you could even do that in a R35 on that MAHA, as far as accuracy on a DD we dynoed a Diesel Golf 140 hp and it came out at 139 and an M5 V10 that came out at 509 so both 1hp down on manufacturers figures. The M5 had been in the day before with an Ebay induction kit and made like 460 hp which caused an argument as the guy was saying the dyno was wrong etc, he bought it back the next day with the stock bits on and hey presto correct power, but I would only run mine on one in RWD.


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## dudersvr (May 7, 2003)

Tim Radley said:


> Interesting post.
> 
> Can someone with actual experience explain how they do a coastdown test on a GTR please?


Maybe the newer MAHA does not work that way but our old one did and as someone remarked it was coming back with transmission losses of like 150 hp on higher power cars thats lost energy which means friction which means heat, that much heat in a short rundown would prob be a melted box LOL


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## Tim Radley (Aug 3, 2013)

dudersvr said:


> Maybe the newer MAHA does not work that way but our old one did and as someone remarked it was coming back with transmission losses of like 150 hp on higher power cars thats lost energy which means friction which means heat, that much heat in a short rundown would prob be a melted box LOL


Yes i've said this many times before about the amount of losses. Physics are physics and you don't add 200bhp of trans losses by doubling the power of the engine otherwise the trans would seize.

The Dyno Dynamics uses a fixed loss estimate on a 4WD, from memory about 22%. So no coastdown that i'm aware of.

Still keen to hear how the coastdown is done on the newer MAHA though if anyone has any input. Anyone have a video of it being performed?


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## Teaboy (Apr 24, 2016)

Adamantium said:


> Why would you go back to a DD when probably the most knowledgable and trusted DD operator known to the forum (Charlie at SRR) refused to run GT-Rs now due to the damage the dyno does to the 4WD clutch?
> 
> Unless the front rollers are driven somehow, it sounds like a bad idea to put a GT-R on the dyno.


What damage dose it cause?


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## dudersvr (May 7, 2003)

Teaboy said:


> What damage dose it cause?


4WD clutch, we had a guy said we damged his on a power run I called SVM and they said no way, if you spend all day mapping then maybe.
Mark at Abbey just attaches the rear hubs to his hub dyno and leaves the front on axle stands with wheels off on a 996 Turbo, Litchfield clearly have no problem but I can go RWD at the push of a button so I can run any dyno.


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## Tim Radley (Aug 3, 2013)

Here is a log from both road and dyno on the same car. See the circled channel "Transmission Front Drive Percent". This shows what the 4WD clutch has to deal with on an unlinked 4WD rolling road compared to the road. It's pretty clear that it's not a good idea to run like this for long!!


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## Teaboy (Apr 24, 2016)

I did hear last year that the owner of a GTR blamed a DD operator for a ETS problem. If by any chance it's the same car then my understanding is that the ETS locked in AWD. This is no fault of the operator and only happens when the ETS clutch pack has worn to the point where the ball bearings can climb all the way to the top of the ramps in the ramp plate and then dislodge into a position where they lock the ETS in AWD. This may well have happened on the dyno because the ETS was under full load but it was always going to happen on the road as the friction plates in the ETS wear to the point it becomes inevitable.


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## Teaboy (Apr 24, 2016)

Tim Radley said:


> Here is a log from both road and dyno on the same car. See the circled channel "Transmission Front Drive Percent". This shows what the 4WD clutch has to deal with on an unlinked 4WD rolling road compared to the road. It's pretty clear that it's not a good idea to run like this for long!!


That is eye opening Mr Radley. I would have thought that on an unlinked dyno the ETS would go to full lock and torque to the front would be around the 50% and just sit there not oscillate like it shows. Just goes to show.


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## Tim Radley (Aug 3, 2013)

Teaboy said:


> That is eye opening Mr Radley. I would have thought that on an unlinked dyno the ETS would go to full lock and torque to the front would be around the 50% and just sit there not oscillate like it shows. Just goes to show.


You can never have too much data!

It's the same on other 4WD cars too. Plenty of dyno's have fried VW/AUDI Haldex setups too.

The problem is the ecu's don't know that the car is stationary and on a dyno so it gets confused over how much wheelspin between front and rear it actually has. The dyno is trying to maintain a steady ramp rate over all 4 rollers at the same time too. It becomes a PID battle and neither wins. I'd hazard a guess that with the muddled control scenario that the power curve is not truly representative of actual road power too.

Even in full closed throttle coastdown the GTR runs a minimum of 1.5% to the front diff, its only when the car pulls up to speed zero that it fully disengages the AWD clutch to 0%.


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## Teaboy (Apr 24, 2016)

Tim I was lead to belive the problem with running a Haldex equipped car on a 4WD dyno is that they are predominantly FWD and are incapable of a true 50 / 50 torque split front and rear.

Can I ask what gear the above road log was done in? I assume 3rd or higher where the car has good grip on the rear tyres and dose not need to vector much torque to the front. Would a pull in 1st / 2nd gear look the same or do you think it would look more like the unlinked dyno log?


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## Tim Radley (Aug 3, 2013)

Teaboy said:


> Tim I was lead to belive the problem with running a Haldex equipped car on a 4WD dyno is that they are predominantly FWD and are incapable of a true 50 / 50 torque split front and rear.
> 
> Can I ask what gear the above road log was done in? I assume 3rd or higher where the car has good grip on the rear tyres and dose not need to vector much torque to the front. Would a pull in 1st / 2nd gear look the same or do you think it would look more like the unlinked dyno log?


Depends on the vehicle. I've a new RS3 and it can run up to 100% to the rear and feels very much a 50/50 to rwd car rather than old fwd understeer feel associated with earlier Audi's.

But any active diff that can vary the torque by a large margin is going to struggle with unlinked rollers. Mechanical 4wd diffs won't have this issue.

The road log was 3rd, the dyno log in 5th. I could try and find same gear data but it means digging through a mountain of log files. But to answer your question typically the lower gears run a much higher percentage split to the front. When acclerating hard, a stock engine car will run say 40% front in 1st gear, 20% in 2nd and maybe 10% in 3rd if that with some grippy tyres. On a launch the torque split is far more stable than the 3rd gear I just showed, especially if you have your torque delivery dialled in well. I can only guess the TCM slows the ROC down to protect the 4wd clutch in that high torque first gear. Maybe when I have more time I can sort through data and run an analysis of ROC for front diff torque per gear


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## Teaboy (Apr 24, 2016)

Tim Radley said:


> Depends on the vehicle. I've a new RS3 and it can run up to 100% to the rear and feels very much a 50/50 to rwd car rather than old fwd understeer feel associated with earlier Audi's.
> 
> But any active diff that can vary the torque by a large margin is going to struggle with unlinked rollers. Mechanical 4wd diffs won't have this issue.
> 
> The road log was 3rd, the dyno log in 5th. I could try and find same gear data but it means digging through a mountain of log files. But to answer your question typically the lower gears run a much higher percentage split to the front. When acclerating hard, a stock engine car will run say 40% front in 1st gear, 20% in 2nd and maybe 10% in 3rd if that with some grippy tyres. On a launch the torque split is far more stable than the 3rd gear I just showed, especially if you have your torque delivery dialled in well. I can only guess the TCM slows the ROC down to protect the 4wd clutch in that high torque first gear. Maybe when I have more time I can sort through data and run an analysis of ROC for front diff torque per gear


Yeh the new RS3 is a nice car Tim congrats. About time Audi sorted the horrendous under steer issue that's plagued them for years. RS3 should wipe the floor with the new Focus RS and has a lot of tuning potential. New RS6 is greatly improved also and a bit of a beast with a remap. 

Would love to see any data you can dig up. I think what we are seeing is the ETS working hard as you would expect on a non linked dyno but did not expect it to look like that. It could well be that it looks like that in a lower gear pull where the rear breaks traction and it has to send power to the front. For a power run or 2 I don't know how concerned I would be watching the ETS work hard but within its design parameters. If the wheel speeds front to rear showed a major difference I would abort a run because you know the clutch plates in the ETS are taking a beating. As i know you know On the DD you look at tractive effort before you run the car up. At that point if it doesn't look right you don't run it, further more if it doesn't look right the is normally an underlying problem with the ETS to begin with. Only my opinion Tim and not saying I am correct.


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## Anders_R35 (Jul 20, 2011)

dudersvr said:


> I can go RWD at the push of a button so I can run any dyno.


Will that give an accurate figure though, running a 4wd car in 2wd?


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## dudersvr (May 7, 2003)

Anders_R35 said:


> Will that give an accurate figure though, running a 4wd car in 2wd?


TBH I see the dyno as a safe way of tuning a car the hp means nothing if you always use the same dyno and operator if the figure goes up you have acheived what you wanted if its less then back to the drawing board.


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## Tim Radley (Aug 3, 2013)

dudersvr said:


> TBH I see the dyno as a safe way of tuning a car the hp means nothing if you always use the same dyno and operator if the figure goes up you have acheived what you wanted if its less then back to the drawing board.


That is providing the dyno operator and his weather station are used precisely. I've seen big changes just from operator error.

For sure it's safer to tune on a dyno. Trying to test knock on a 1000bhp GTR in a high gear at 7500rpm on the road is a bad idea. Downside to the dyno is the frying the 4wd clutch we all just discussed.

One problem I have witnessed is that mapping on the dyno sometimes doesn't represent the road conditions. The last 2 dyno's I used allowed me to get more timing into the engine than was possible on the road. I know the road limits through my extensive logging software but the dyno would allow more. If i'd trusted the dyno then I would be giving the owner an unsafe engine back. Food for thought.

Any input yet on coastdown tests from the various dyno brand operators? It's a test I used to perform all the time when I had a Dynojet chassis dyno. Just curious how others perform it and whether that could be part of the reason for reading differences.


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## dudersvr (May 7, 2003)

My car is on Litchfields dyno now and they explained the front rollers are powered so no risk to the clutch.


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## Teaboy (Apr 24, 2016)

FTAO Tim. Maybe it's the mode the dyno is run in, Came across this today. Stock gearbox with the exception of a clutch, Ecutek map, over 700whp and around 700ftlbs, stock wheels, stock tyre size, 32psi in tyres, Dyno Dynamics run in shoot F6 and car run in 4th gear. This one looks exactly as I thought it would until I saw your log above


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## Tim Radley (Aug 3, 2013)

Teaboy said:


> FTAO Tim. Maybe it's the mode the dyno is run in, Came across this today. Stock gearbox with the exception of a clutch, Ecutek map, over 700whp and around 700ftlbs, stock wheels, stock tyre size, 32psi in tyres, Dyno Dynamics run in shoot F6 and car run in 4th gear. This one looks exactly as I thought it would until I saw your log above


When i click the image its tiny. Can't really read what it says


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## keithmac (Mar 1, 2014)

I suppose the only real fail safe way would be to mechanically link the front and rear rollers at 1:1 ratio for awd cars then?.


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## Teaboy (Apr 24, 2016)

Sorry Tim, any better?


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## mindlessoath (Nov 30, 2007)

Drivetrain Power Loss - The 15% "Rule"- Modified Magazine



> Coast-down tests are sometimes used on a dyno to attempt to measure frictional losses, but because this test is not dynamic (meaning they're not done while accelerating, but rather while coasting to a stop with the direct drive gear engaged but the clutch depressed so that the engine and transmission aren't linked) it really only captures steady-state drivetrain losses as well as rolling resistance. So rather than attempting to convert your vehicle's dyno-measured wheel horsepower to a SAE net horsepower figure using a percentage or a fixed horsepower value, you're far better off accepting the fact that these two types of horsepower measurements aren't easily correlated and forego any attempt at doing so.


but anyways... the gtr takes great measures to reduce drivetrain losses in stock form.


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## Tim Radley (Aug 3, 2013)

Teaboy said:


> Sorry Tim, any better?


That's much better yes. Wonder why the Dynapack did what it did then?


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## pulsarboby (Nov 3, 2012)

Just to recap what Iian said earlier really.........providing the dyno is operated correctly (vehicle data input isn't skipped) then figures given at wheels should be relatively correct, but power @fly is always a guestimate by what ever dyno unless its tested on an engine dyno test bed.
We went for a Dyno Developments awd system which was a very expensive purchase compared to others on the market but prior to purchase I did a lot of research into which was the best type as its a purchase we could not afford to make twice.
The dyno relies on input from the operator to gauge the most accurate readings.
We have run a few GTR'S now and so far the figures have been mostly accurate with Litchfeilds various stages of tune and figures quoted by them. 

Here are some notes you should be aware of when having a vehicle tested on most dyno's:

1. vehicle weight, drivetrain type, estimated power, transmission mode all generally need to be entered by operator

2. Scaling rpm from vehicle to dyno is paramount to give an accurate figure (many don't bother)

3. Strapping techniques also play a big part in accuracy. On an awd car if you strap the car harder at rear than front you are then putting a higher loading so more tractive effort on rear rather than = effort on both front / rear rollers

4. ramp setting of dyno...i.e A fast drag car or cars running in excess of say 1000bhp will need to be run in the high ramp setting as the dyno processor speed will need to be higher in order to give an accurate reading. If a low powered car is run on higher ramp setting it will give a false readout. Figures will be higher than they really are, both torque and bhp.

4. We have a weather station in dyno cell so we can input the (at time of testing) correct temperature, humidity and barometric readings all of which play a huge part in the final power readings so figures must be reset after every car which has run or once again you will get an inaccurate false reading.
Also to note......If the dyno software is all good then it will take into account various input readings, pressures to give an accurate as possible reading every time (input the wrong info or no info and your likely to get a very false reading)

5. You should always have the same dyno operator testing the car.
Using a different operator will mean you have a different looking graph (even on the same day & same dyno) The way each individual loads and releases the car on a run will have an affect on the power / torque curve and way the graph looks.

There are many ways to cheat figures (just being honest with you) but at the end of the day its just a lie nothing is achieved & no comparisons can be made by earlier runs at a different stage of tune on the same car on dyno, so honesty is always the best policy to see whether you are making gains or losses with some modifications.
The figures are what they are sometimes people go away unhappy as think there car is making more than quoted power others are over the moon as go away with a higher figure than they anticipated.
As Iian rightly said.......its a diagnostic tool mainly which is an aid to mapping and seeing gains / losses in a controlled safe envoiroment.
The rest of it iare just pup bragging rights & genital waving lol


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## ES800 911 Turbo (Nov 17, 2021)

Tim Radley said:


> That is providing the dyno operator and his weather station are used precisely. I've seen big changes just from operator error.
> 
> For sure it's safer to tune on a dyno. Trying to test knock on a 1000bhp GTR in a high gear at 7500rpm on the road is a bad idea. Downside to the dyno is the frying the 4wd clutch we all just discussed.
> 
> ...


 Very true. Data logging on the road is much better than dyno tuning alone. 
, but of course its not always easy to do logging on the road.. You get far better cooling and airflow on the road which can not be replicated on a dyno..


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