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Compressor Surge-Does it Really Matter

SMB315

By SMB315,
in Engines & Forced Induction

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BHDave Grand Master

BHDave

Posted
Posted

Yep, it's a problem.

Best bet is to fit a turbo that is matched to your engine or to mask the problem get a boost controller that can reference boost against revs so you aren't trying to stuff too much air into the engine at low revs.

hayes_666 Apprentice

hayes_666

Posted
Posted

Sorry to still seem slow, but how do you mean cant swallow you mean that the turbo is so large that the boost goes so high the turbo stalls untill it gets enough exhaust gas to get going again?, Would have to be one hell of a efficiant turbo to do that?,

Nathan

DoughBoy Veteran

DoughBoy

Posted
Posted

It's more airflow levels rather than extreme presure ratio i.e. the turbo's producing 100 squares of air at 5psi and the engine can only "swallow" 30 squares, so air comes back out the intake system via the turbo. The main reason for it is the exhaust housing is too small - if you go up a size (or two) in exhaust size it should sort the problem out by bringing on the turbo later, when the engine can make use of the airflow.

Lithium Grand Master

Lithium

Posted
Posted
Sorry to still seem slow, but how do you mean cant swallow you mean that the turbo is so large that the boost goes so high the turbo stalls untill it gets enough exhaust gas to get going again?,  Would have to be one hell of a efficiant turbo to do that?,

Actually the opposite, it takes a badly matched turbo to do that - at least one that is badly matched to the engine it is bolted on to. This is the reason you can just leave the same exhaust wheel on a turbo and bolt on bigger and bigger compressors to move more and more air into the engine. A very efficient turbo strictly speaking would be PERFECTLY matched to the engine, shoving just the right amount of air for the engine into it over a wide rpm range.

Warpspeed Experienced

Warpspeed

Posted
Posted

The needle might turn into a blur, and you will hear the dreadful noise, the engine might not not be terribly happy either abut the rapid pressure fluctuations. The effects can vary quite a lot from hardly noticeable to turbo end engine shattering violence. It all depends on how bad the surge is.

All turbos can surge if the compressor flow drops below a certain value. As lithium says bigger and bigger compressors surge at higher airflows. There is a myth that huge compressors will force more air through the engine. It simply is not true.

If the engine has 10psi boost with a small compressor, and you fit a humongous compressor wheel that also makes 10psi boost. The engine just sees 10psi and flows EXACTLY the same amount of air. It might be more efficient at the top end, but if you have a decent intercooler, that does not matter either.

Suppose the air going into the intercooler is 120C and 50C coming out. You fit the monster compressor wheel and the air going into the intercooler drops to 90C, and the air coming out of the intercooler to 47C. Hardly worthwhile doing. If it also now surges, you have wasted your money on that "hi Flow"compressor wheel.

tang0 Proficient

tang0

Posted
Posted

so are you saying that hitting my 0.80 bar at 2800 rpm with a standard turbo is not good, i mean, it hits that, the the car seems to be pulling pretty hard, still going faily slow, but uphill, in 3rd, doing 40kmh at 0.80 bar seems the turbo is spooling up v fast for under load ...

just wondering ..

Coxy_ Collaborator

Coxy_

Posted
Posted

I was getting some compressor surge in my car when I was running the boost too high- the boost needle would hit the right amount of boost straight away but it would take the car a second or two for you to feel the take off- you're better off lowering it down a little until it stops doing it or you could do some damage eventually- my turbo has got a small leak because of it........@##$$#%$#!!! hehe

hayes_666 Apprentice

hayes_666

Posted
Posted

My car runs, from 2800rpm 5psi boost then at 3800rpm she reaches full boost (10psi) the needle is steady, she pulls well but not really hard untill 4300rpm, i just assume that the engine is just more efficient at those revs, as on the standard turbo it didnt get going till the same revs but came on boost earlier????.

Nathan

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