# Does Compressor Surge Kill Turbos



## markpriorgts-t (May 23, 2004)

i have recently blocked the recirc valve on my R33 GTST and am getting varied opinions on how compressor surge ( the flutter noise ) effects the turbo

whats your thoughts

Heres the sound


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## SteveN (Aug 6, 2002)

ON throttle, yes.

Off throttle MUCH more unlikley than people like to tell you on the internet with no proof at all.

Rumour was made up to sell people DVs, and it works.

Theory is it would shorten the life a little, reality is something else will kill it 99% of times before compressor surge will.

I ran a car HARD for 13k+ at 30psi boost with no DV with no problems.

I never run them on my cars, and never had a prob.


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## David (Apr 25, 2003)

The rumour mill doesnt sell recirc dump valves to every OEM manufacturer of a turbo engine though :')


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## Jim27 (Jul 1, 2004)

I'm more inclined to believe that the factory recird DV setup is fitted to allow a simpler AFM solution. The compressor surge is air being forced backwards through the intake system, which would give screwy airflow readings as the AFM can't distinguish between air entering or exiting the system - either way it passes over the AFM element. This in turn could possibly cause poor running/emmission problems. The recirc system gives somewhere for the air to go without forcing it back out the intake system (IMHO).


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## kismetcapitan (Nov 25, 2005)

possibly, but when I look at the stock recirc piping, I can't help but to think Rube Goldberg engineered the thing for Nissan...


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## Spearmint (Aug 7, 2005)

I've been querying this as well. (What was) HKS SSQV fitted to an RB25DET making 493 ath @ 1.6BAR.

I am not sure if it would be wise to stick with the VTA or not. I obviously do not want to go killing £1200 worth of turbo just to find out. FWIW I have a friend who runs his SR20DET at 1.2BAR with no VTA and no problems thus after 2 years of constant day to day hard usage.


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## tyndago (Oct 24, 2002)

SteveN said:


> Off throttle MUCH more unlikley than people like to tell you on the internet with no proof at all.Rumour was made up to sell people DVs, and it works.
> Theory is it would shorten the life a little, reality is something else will kill it 99% of times before compressor surge will.I ran a car HARD for 13k+ at 30psi boost with no DV with no problems.I never run them on my cars, and never had a prob.


Im with him. I hate BOV /DV. They leak way too often. Leaking BOV means more turbo speed to get the same amount of boost. That will kill a turbo.


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## Jamie_stevens (Apr 5, 2005)

i never had a problem on my last car with no dump valve, i've a friend with a cosworth with a t34 running some 350bhp + with no recirc, dumpvalve, sounds great and has no probs! temporarily Blanked mine off to eliminate a possible boost leak..sounds great!!


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## SteveN (Aug 6, 2002)

David said:


> The rumour mill doesnt sell recirc dump valves to every OEM manufacturer of a turbo engine though :')


NOISE SUPPRESSION DEVICES. 

Same reason many airboxes are so restrictive.

Many workshop manuals actually call it that.

Customer buys a new car, it chirps and chatters like ****, they take it back thinking something is wrong. Ive seen that happen with people buying lightly modded jap imports then taking them back to the dealer as you hear it chatter.

Your average standard new car buyer doesnt want loud exhausts, induction noise, chatter, nothing at all.

And like said, theory is there is a tiny difference, and on a car expected to last 150k+ it might become an issue. But on a modified engine, something else will kill it.


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## kismetcapitan (Nov 25, 2005)

Sean, the World Challenge R34 - did it have dump valves? what boost?


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## huskyracer (Jun 23, 2007)

Never seen a 100% compressor surge related failure in seven years of tuning turbocharged cars, but, i have always got off the throttle if I experienced bad surge under load. The surge you get when you close the throttle shouldnt do any harm as the exhaust side is no longer being driven. In the early days of turbocharging, there were plenty of rumors about claiming the nut retaining the compressor wheel could be undone, but again, I have never seen it with my own eyes.


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## tyndago (Oct 24, 2002)

kismetcapitan said:


> Sean, the World Challenge R34 - did it have dump valves? what boost?


Super Taikyu - none. Word Challenge none. 1.6 bar.


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## kismetcapitan (Nov 25, 2005)

ah dammit. The HKS thing was working fine for the month or so I've had it. I'm running without BOVs from tomorrow, see if that gets rid of the lag I've always been thinking has been coming from that BOV.


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## i4dat (Sep 29, 2006)

So in other words there isn't any harm with removing the recirc valves other than the dislike of the extra volume when you lift off of throttle.

But what would happen on stock turbos? Would there be an increase or decrease of lag? Or no change?

What about your AFMs? Would there be a drivability issue without the recirc valves installed?

Hmmmmm. Something else to ponder!


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## markpriorgts-t (May 23, 2004)

In regard to the afm i think it will just cause the car overfuel slightly which may cause pops, bangs and flames nothing to drastic, as its getting air both ways


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## i4dat (Sep 29, 2006)

> In regard to the afm i think it will just cause the car overfuel slightly which may cause pops, bangs and flames nothing to drastic, as its getting air both ways


Ha, pops, bangs and flames......... nothing wrong with that. Except for maybe scaring cats and old ladies. :squintdan 

I wonder what would be the most efficient way of removing/bypassing them.

Would it be better to just remove them and cap of the tubes or use block off plates on the actual mounting flanges?


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## GTR RGT (Aug 29, 2006)

If any air enters after the AFM's the car will over-fuel. But I agree with markpriorgts-s, I dont think it will make much differnance. 

You'll soon find out if it starts missing but not quite. Like a stutter. 
Also black lambda and plugs


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## markpriorgts-t (May 23, 2004)

i4dat said:


> Ha, pops, bangs and flames......... nothing wrong with that. Except for maybe scaring cats and old ladies. :squintdan
> 
> I wonder what would be the most efficient way of removing/bypassing them.
> 
> Would it be better to just remove them and cap of the tubes or use block off plates on the actual mounting flanges?


i used a piece of 1mm sheet metal, copied from the gasket that sits between the flange and recirc, worked a treat


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## kismetcapitan (Nov 25, 2005)

A VTA will also cause momentary overfuelling.


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## pitbull (Sep 1, 2006)

when i blanked mine off it gave me the normal stalling you get with a vta bov


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## kismetcapitan (Nov 25, 2005)

ever since fitting a VTA I've never experienced any stalling. Which is odd - an R32 GTS-T I drove for a few months LOVED stalling with it's HKS valve fitted.


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## SteveN (Aug 6, 2002)

VTA or recirc has NOTHING to do with chatter or stall.

How much air each one will flow, and how strong the spring the spring is (so how much/easily it opens) is what affects it when you have a dumpvalve of some description fitted.

If either there is more air to release than the DV can, or the spring is that tight its not opening much, then you will get chatter out the turbo inlet too, simple as.


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## kismetcapitan (Nov 25, 2005)

fixing my leaky BOV literally made my day - it has turned my car into a lag-free monster. True, I've got the thing set so it doesn't release much air, but I'd rather have no BOV and shorter turbo life. Cause you'd enjoy those turbos so much more.

If my BOV acts up again, it's going into the bin.


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## pitbull (Sep 1, 2006)

see mine started stalling when i blanked it off but why whould my car cut out if i blanked it off


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## RamRod (Apr 28, 2004)

I heard most rally cars don't a a recirc valve.

I bet its to save the CAT. I imagine that allowing air to flow back out of the air intake will cause extra noise and extra fuel. The unburnt fuel will cause pops and bangs in the exhaust and more than likely destroy the CAT.

So its a bloody environmentalist invention


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## tyndago (Oct 24, 2002)

RamRod said:


> I heard most rally cars don't a a recirc valve.
> 
> I bet its to save the CAT. I imagine that allowing air to flow back out of the air intake will cause extra noise and extra fuel. The unburnt fuel will cause pops and bangs in the exhaust and more than likely destroy the CAT.
> 
> So its a bloody environmentalist invention


Not on a MAP sensor car.


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## NISFAN (Oct 11, 2003)

Many still believe that a 'stalled turbo' is one that has just gone from 120,000+ rpm to zero in a fraction of a second:chairshot ...........

.............then apparently the boosted air reverses and comes back out the compressor causing the turbo to turn backwards.  

I think that is a legend that needs to live on  , so yes it causes mega damage, that chatter sound is the turbine wheel trying to get out through the housing.:thumbsup:


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## tyndago (Oct 24, 2002)

NISFAN said:


> think that is a legend that needs to live on  , so yes it causes mega damage, that chatter sound is the turbine wheel trying to get out through the housing.:thumbsup:


Compressor wheel.. you can hear the compressor wheel, not as much the turbine wheel.


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## SteveN (Aug 6, 2002)

NISFAN said:


> Many still believe that a 'stalled turbo' is one that has just gone from 120,000+ rpm to zero in a fraction of a second:chairshot ...........
> 
> .............then apparently the boosted air reverses and comes back out the compressor causing the turbo to turn backwards.


The amount of people who think that its bizzare.

Do they think suddenly there no exhaust gas spinning the turbine side?


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## carlsworth (Aug 4, 2006)

surge can kill turbos, ...

but, it has to be soooo bad...like hitting a brick wall when blasting it...and over a period of time....it wont kill the turbo instantly..
so with that in mind, if your stupid enough to keep blasting the car, when you can physically feel theres a problem, then tough


carl


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## i4dat (Sep 29, 2006)

Well are we really talking about track/race cars or daily drivers.

I would think that it would be more prone to damage a high boost track car then a stock boost car.

Right????


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## carlsworth (Aug 4, 2006)

prone to damage a high boost track car then a stock boost car.



right....
how many stock boost cars dyou hear that have surge problems...
anyways, its the massive boost a turbo runs thats the problem, there are many factors, the biggest being the shape and angle of the compressor wheel


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## pitbull (Sep 1, 2006)

so how likely is it i would kill my turbo if i take my bov on my stage 1 gtst and would it still be ok at 400/450 bhp?
also why would the car stal;l at idle when i take the bov off?


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## SteveN (Aug 6, 2002)

Carl- We are talking about OFF throttle compressor surge (ie chatter) not on boost.
On boost is WAY worse, and is down to bad mapping and bad turbo selection.

Pitbull- I dont know how weak the turbo you using is, but IMO it will be fine, it will die from other reasons a lot sooner than a snapped shaft from comp surge.
No idea why it would stall. It shouldnt unless you have left a pipe undone.
Ive removed the stock recirc on 200SXs which run very similar managment and they run fine.
AFM equipped cars only normally play up if there is a boost leak post AFM.


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## pitbull (Sep 1, 2006)

i may have a boost leak!!!!
also i never blanked off the bov i pulled the vacum pipe off and blocked it off so ot would stop the bov working unless my bov is leaking?


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## carlsworth (Aug 4, 2006)

*Carl- We are talking about OFF throttle compressor surge (ie chatter) not on boost.
On boost is WAY worse, and is down to bad mapping and bad turbo selection.*



oooops, sorry,...guess i should read the whole thread


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## SteveN (Aug 6, 2002)

pitbull said:


> i may have a boost leak!!!!
> also i never blanked off the bov i pulled the vacum pipe off and blocked it off so ot would stop the bov working unless my bov is leaking?


2 problems there- 

Yeah, chances are you have a boost leak from somewhere.

And once on boost the BOV will leak like **** without the vac pipe connected, as there needs to be equal pressure both sides, the spring dont do all the work, so you will be having bad fuelling, high charge temps, and massivley overspeeding (and killing) the turbo.


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## pitbull (Sep 1, 2006)

whats the best way to test for boost leak
i think i may make up a steel plate a gasket to go in the bov position


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## Porsche911r101 (Oct 26, 2003)

thats not compressor surge, thats compressor stall, when u have no dump valve when you let off the throttle the air comes back through the blades.

"compressor surge" is when the turbo tries forcing too much air that your engine can take in, and so the air comes back and stalls the blades whilst your still on WOT 

this may have already been explained as ive only read page 1, lol.


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## Tony G (Jun 2, 2003)

I'm running a 200 sx engine in my E36 without any DV and its fine so far:smokin: 

Tony


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## roadie (Feb 6, 2006)

Just pulled the plug on the BOV about an hour ago.....
Chopping the air and lovin' it....


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## ExScoobyT (Jan 6, 2004)

If by pulling the plug you mean removed the control line from the plenum -this is a very bad thing. This line helps to hold the BOV shut when under boost, without it your relying only on spring pressure.......


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## SteveN (Aug 6, 2002)

ditto, in fact i told you not to a few posts above...


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## roadie (Feb 6, 2006)

Na, I diconnected it and ran the line off a nipple that is boost only. The spring is quite tight and needs a the combination of boost/vacuum to open. Now the pressure is relatively equal on both sides of the valve so it wont open. This will do until I cap the BOV flange...


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## kingsley (Aug 26, 2002)

Back in the 80s Kawasaki made a production turbo bike (GPz 750 turbo) that had no BOV. Fluttering sounded great if you didn't use the stock airbox (which absorbed the noise).

I'm sure if Kawasaki thought it would have been a problem they'd have engineered something, but they didn't.


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## uglymother (Apr 11, 2007)

I blanked my standard BOV on my RB20. The wastegate chatter sound is lovely.

I have done about 60,000km in my R32 now, drive it hard I had it on the dyno 4 weeks ago. 233BHP est at the fly, but was running well lean, so i got a nismo fuel pump. She now flies compared to before i fitted the pump. Now the turbo is smoking a little, but she has done 190,000km now.

So i would say it does **** all, just makes a great sound and stops people thinking a ford is driving towards them.


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## paul cawson (Jul 3, 2003)

Not having a dump valve will give you more turbo lag, why do people think Nissan fits them for the fun of it:chuckle:


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## SteveN (Aug 6, 2002)

paul cawson said:


> Not having a dump valve will give you more turbo lag, why do people think Nissan fits them for the fun of it:chuckle:


A lot more people either notice no difference or find the exact opposite of what your saying than saying it increases it.
Id like to see some datalogging to prove something either way, but it wont happen.

Main reason why on a standard car? Noise suppression devices, same as resonator boxes, ruffled inlet pipes, and crappy restrictive airboxes. DVs are not all about "lag"...

Ive even seen TV journalists complaining about induction noise etc, never mind the amount of owners ive seen taking their car back to garages due to funny noises its making...


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## paul cawson (Jul 3, 2003)

SteveN said:


> A lot more people either notice no difference or find the exact opposite of what your saying than saying it increases it.


Thats just what people think without having all the facts, if you look at engineering papers on the subject the results are indisputable


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## Vips (May 13, 2007)

This article explains the benefits of re-circs.

AutoSpeed - The Zero Cost Recirculating BOV


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## SteveN (Aug 6, 2002)

paul cawson said:


> Thats just what people think without having all the facts, if you look at engineering papers on the subject the results are indisputable


Theory and reality are 2 different things, in the car world more than anything.

Can have all the books and papers you like, it dont make it an accross the board fact.


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## tarmac terror (Jul 16, 2003)

I have removed all my std BOVS and piping however in terms of sound it just makes the normal 'tssschhhh' sound as it did when the BOVS were fitted!!!! I get none of the 'chattering' at all ?????

I completely agree about the BOVS being for noise supression and not much else. 

I am a little perplexed as to why my GTR doesnt experience the sounds you guys describe after removing BOVS.

TT


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## Vips (May 13, 2007)

SteveN said:


> Theory and reality are 2 different things, in the car world more than anything.
> 
> Can have all the books and papers you like, it dont make it an accross the board fact.


I wouldn't say theory and reality is very different with regards to engineering. Most people progress their cars through the ideology of a race car, whereby these re-circ valves are indeed not in use, however the car's also undergo extensive maintenance and part replacements in order to sustain their configuration.

I agree that most individuals remove re-circ's simply for the noise but fail to realise the excess pressure which is encapsulated within the region.

I'll have to go with Paul on this one, as there are far too many reasons for the original configurations.

It still seems however, everyone has a different pov on this matter. For instance Corky Bell also suggests, the system is simply to reduce noise, but does not discuss any drawbacks to the erratic pressures.


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## hpt_simon (May 20, 2006)

i have the same .........problems?.........as tarmac_terror, i remooved my bov and have the same sounds without it. Now and then, i do hear abit of the chattering noise, but not as much as i´ve hear with friends subarus or cosworths. could this be due to a boost leak¿


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## SteveN (Aug 6, 2002)

Vips- 
Again though, theory shows it will do this and that, reality generally seems to show unless its an extreme circumstance its either nothing you can feel or time, or something else causes a problem before that does.
I dont care what anyone else does, thats up to them, but through the years of running hgh boost and no BOV on countless different cars (mine and friends) with no real ill effects, makes me personally not that fussed if I run one or not.
Same as a LOT of top tuners, many dont run DVs and say they junk, tho some swear by em...
Anyone else, its up to you, but I read books and internet info, take note, then try it myself as theory and across the board reality is far far different with most modified car things.

TT+Simon-
Mine is exactly the same. But that almost DV type psssst noise is still coming from the filters, as per chatter would, as i checked.
Think its maybe just simply a mixture of not enough air backed up in the system, combined with long and complex inlet piping and ruffled inlet pipes, just massivley dampen the noise.
Its not a problem anyhow.


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## Toady1 (Dec 2, 2007)

can someone explain what they mean by compressor surge?


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## markpriorgts-t (May 23, 2004)

mine still going strong BTW  

basic explanation-:

instead of the excess air generated by the turbo either being Recirculated into the intake manifold or being dumped to atmosphere (most aftermarket DV's do this) it gets shot back to the turbo, the turbo blades are spinning so fast that they chop the air resulting in the noise in the vid on the first post. 

now some people think that this stalls the turbine blades and causes damage, personally i think there spinning to fast to get stalled/stopped and just plough through the air

quite a good explanation here - Turbo Stall Click Me


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## chaz_r33_gtr (Aug 6, 2005)

Interesting thread... A bit of info on compressor surge (albeit from a an axial compressor from jet engines perspective).

Compressor surge is defined as something causing a disruption in the pressure gradient (and hence airflow) across the compressor blades reversing direction. Typically you have a lower total pressure at inlet side and higher total pressure at outlet side of a compressor (turbo). In a jet engine there are multiple compressor stages hence pressure at the last stage is way above ambient 50 Bar +. 


When suddenly someting occurs stopping the air flowing e.g. closing the throttle on a car engine or airflow separation (i.e. airflow stall or compressor stall if you like) over the rotor or stator blades in a jet engine then the pressure gradient cant be maintained and the high pressure air reverses flow direction and surges out the front of the jet engine or in the car case back out through the air filters. That is a single surge. Surging is when the flow direction keeps oscillating back and forth through the compressor. On jet engines this is very bad because of pressures involved and if it occurs for more than a few seconds usually leads to mechanical failure. The rotors in a jet engine or compressor wheel on a car turbo certainly doesnt stall and stop it as people have said just slows down. Its the airflow that stalls and then reverses direction resulting in a surge.


Anyone still awake i will ask questions later LOL 

Be


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## GTR_Nismo_bc (Jul 31, 2007)

Toady1 said:


> can someone explain what they mean by compressor surge?


This is what it sounds like.
YouTube - R34 GTR SIGNAL AUTO STREET RUN


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## beaumackenzie (Jan 21, 2008)

Jim27 said:


> I'm more inclined to believe that the factory recird DV setup is fitted to allow a simpler AFM solution. The compressor surge is air being forced backwards through the intake system, which would give screwy airflow readings as the AFM can't distinguish between air entering or exiting the system - either way it passes over the AFM element. This in turn could possibly cause poor running/emmission problems. The recirc system gives somewhere for the air to go without forcing it back out the intake system (IMHO).



not compleley true, behind the bov is still, uncompressed air, all the way back to where it joins the induction piping again, 

when the bov opens that still air now starts moving back toward the AFM, at the same rate the air coming through the bov is moving, so if your running 10 psi that still air is compressed a little, but not nearly enough to stop the back flow through the afm. 

a friend of mine has a turbo charged XR6 ford falcon(4litre straight six twin cam)

that back spools massiveley as they didnt come with a bov from factory.


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## budget_crx (Jan 10, 2008)

Many of he Turbo Buick owners have been running with blow off valves on thier turbos for over 20 years and have had absolutely no problems because of the compressor surge. I like to play it safe so I installed a BOV anyway...


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## Toady1 (Dec 2, 2007)

GTR_Nismo_bc said:


> This is what it sounds like.
> YouTube - R34 GTR SIGNAL AUTO STREET RUN


that R34 sounds lovely! the engine i mean not just the turbo chatter!


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## Richf (Feb 8, 2007)

I've recently had problems with my bov not working properly so it was like running without one at all , the key thing that happened as well as lag increasing was the pressurised air coming back from the turbo screwed up the afm and also pressurised the engine as the air went back into the cam covers via the breathers , so everytime i backed off the throttle the engine smoked very badly


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## SteveN (Aug 6, 2002)

Richf said:


> and also pressurised the engine as the air went back into the cam covers via the breathers , so everytime i backed off the throttle the engine smoked very badly


Personally id say thats a badly designed breather system setup more than anything.


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## Dynamix (Nov 1, 2007)

I chose no, but in saying that it will shorten the life of cermamic turbos. Look how many drag cars or top jap cars run without a bov. It's just one less bit of gear you have to worry about leaking or going wrong. So standard turbo's (ceramic) use one, aftermarket turbo's i wouldn't. Simple.


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## paul cawson (Jul 3, 2003)

Dynamix said:


> Look how many drag cars or top jap cars run without a bov.


True but how often do you lift fully off the throttle on a drag car


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