# MAF Vs Speed density mapping. Pro's and cons.



## Hodge (Aug 8, 2013)

Just interested in people's opinions in which is better and the pro's and cons of the 2 really.
What's everyone's thoughts???


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## Adamantium (Jun 24, 2002)

Think you are asking on the wrong forum personally.

They both have advantages. A good ecutek mapper can give you the best of both worlds by choosing the right mapping strategy for the right zones of the map.


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## WingedBeast1968 (Sep 18, 2009)

MAF for drivability and manners; very accurate. 
SD to remove the MAF from the inlet tract and reduce intake restriction.
I don't understand having both 

Just worked it out


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## gtr mart (Mar 29, 2004)

Did you give this any more thought Hodge? You sticking with your MAF set up or going SD (or assume of the map sensor) as an alternative?


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## David (Apr 25, 2003)

What you need is map/maf I helped write the strategy for
Jlr 8 years ago now but it seems other manufacturers seem to be taking a while to catch up and find a way around the patents it uses.


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## keithmac (Mar 1, 2014)

Not GTR related but I've found MAF better than speed density most of the time (smoother and more accurate). Speed density is a best guess based on air temp and manifold pressure, MAF is actual measured airflow.

Some cars use SD on throttle transitions and drop back to MAF for steady state running.

If you haven't topped the airflow capability of the MAF I'd be tempted to keep it (unless it's causing a big restriction for the turbos in draw through).

I tried a lot on the GTO and ended up going for a blow through hotwire MAF setup.


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## scoooby slayer (Jun 13, 2009)

Ryan could map it with an old bbc computer and some duck tape and it would still run perfectly ***55357;***56841;


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## gtr mart (Mar 29, 2004)

LOL the above comment :chuckle:

My interest in this is trying to reduce inlet restriction to help ease the load on the turbos. It also removes MAFS which helps with reducing complexity (if you rely on the existing MAP sensors anyway, introducing SD hardware will simply increase complexity) 

and then it would also reduce mapping difficulties through MAF tubes (mine are not great)


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## thistle (Oct 27, 2007)

OEMs are moving away from MAF sensors, but they use throttle angle, pre and post pressures, air and coolant temperatures in inlet manifold filling models. Not friendly for aftermarket extreme tuning compared to a VE table referenced by RPM and MAP with temperature correction.


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## David (Apr 25, 2003)

thistle said:


> OEMs are moving away from MAF sensors, but they use throttle angle, pre and post pressures, air and coolant temperatures in inlet manifold filling models. Not friendly for aftermarket extreme tuning compared to a VE table referenced by RPM and MAP with temperature correction.


This is what I was involved with the map sensoris basically the transient input and the maf if there to correct the model steady state as it's accuracy steady state is far greater. Using both less 3% airflow error is achievable


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## thistle (Oct 27, 2007)

MED17 doesn't seem to miss them as they are optional. The previous advantage of steady state accuracy now appears a liability to correct bigger errors than they solve due to contamination, ageing and reliability. Interesting to read your patent, ME7 was doing long term adaptation with MAF in the 90s with transients by pressure sensor. What was the difference with the JLR method?

I had to add a simulated inlet manifold filling spike to a throttle opening transient on a box to convert a Subaru PowerFC to speed density, but code changes in the GTR and Evo didn't need it. The GTR appeared to use a hybrid method of load estimation, not just MAF/RPM. A bit like the boost control, not really mod friendly when you want to be able to double factory power easily and all you have is disassembly with no funktionsrahmen. The funktionsrahmen for my MED17 is 15000 pages, but it is still on a plate compared to reverse engineering it like the GTR.


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## Hugh Keir (Jul 25, 2001)

Tuned a 950 BHP R34 GTR with a Motec ECU using a MAF, then converted to a speed density system, it had great road manners with both, started well in all weathers.

On the R35 I think that you could do with the air temperature sensor relocating to after the intercooler rather than before, so that the injector duty cycle would be accurately calculated before worrying about speed density.

After the above sensor relocation, I would go for speed density on a high performance engine though.


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## gtr mart (Mar 29, 2004)

How does the SD system integrate with the R35 management.

And

How would an SD / map sensor (I assume the MAP sensor is required when running on SD) run at low engine speeds?


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## thistle (Oct 27, 2007)

Hugh: Gotboost Performance R35 GT-R Speed Density Kit - gotboostperformance.com

gtr mart, on Cobb you choose SD or MAF to flash and the main difference is a VE table is used instead of MAF calibration. Ecutek offer blending, but in my testing I saw no downsides to pure SD so kept it simple with a VE map in real time so it could be tuned live which is IMHO essential for a good SD setup, you don't want to turn off your engine to map a 16x16 table in fine and appropriate detail. Tuned properly like this I saw no problems at low engine speed, I blinded myself final testing and couldn't tell any difference.


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## gtr mart (Mar 29, 2004)

That's tickled me thistle, as I was just coming on here with the same gotboost link.

I would love to delete my mafs and their kit offer this functionality. Is this kit installed with a plug that goes into the original MAF plugs (albeit with the actual MAFS deleted) which then feed the results into the original MAF harnesses and as such require no retuning?


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## thistle (Oct 27, 2007)

Only one IAT sensor is used in the OEM setup although both MAFs have them. So the MAPT sensor's temperature signal is fed back into this.

You still need to tune SD with modified code and the appropriate VE table.

If you had done an SD tune which kept the MAFs in place on Cobb, and then used this kit to move the temperature sensor to the pressure side, as Hugh says there will be a difference in temperature and therefore the calculated engine load will be lower as the temperature will read higher. As a result your ignition would be more advanced which would likely produce more knock correction, and your mixture would become lean resulting in positive fuel trims.

An SD tune done using pre turbo (near to ambient) temperature sensors as in the OEM MAFs would tend to overestimate engine load as the pressure side temperatures increased due to intercooler heatsoak. This would result in retarded ignition and negative fuel trims. Whilst this error is in a safe(ish) direction, it is best to tune in the changes you want to values like this rather than have them occur by accident. The theoretical concern is that whilst the lambda would be corrected the ignition timing could be excessively retarded which results in higher exhaust gas temperatures, higher exhaust valve, manifold, turbine and (if fitted) catalytic converter temperatures. Since there are no actual EGT sensors this condition would go uncorrected. Theoretically the hot exhaust valves could be damaged or could be a focus for preignition. Certainly a melted cat is bad news, they tend not to breathe as well (whether the varieties having fur or those of monolithic construction).

Forgive my old style engine management ramblings, I'm back into this stuff again after a break of 3 1/2 years, this time on Bosch, but I have it all on the brain again


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## gtr mart (Mar 29, 2004)

Well it's fascinating and something I am very interested as part of trying to maximise the well running and efficiency of my car. I do find it confusing with my level of base knowledge. Any suggestions as to where I can go to build my knowledge of this?

If I wanted to delete my MAFS and move to this, then (on Cobb) could I 'simply' install the kit and get someone like Ben Linney to provide mapping for me?


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## thistle (Oct 27, 2007)

Yes but you may want to have the map for starting it up the first time and plan the project with your supplier


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## Litchfield (Feb 26, 2008)

GTR Mart, if you are looking for a SD kit we offer them for £235+vat


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## Fryman (Sep 4, 2014)

most interesting read!


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## victorgarage (Jun 10, 2019)

What sd maps are the best now guys
Cobb v3


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