Compressor Surge Question

[snozzle]

Hi all,

Before i start, i am not referring to the noise a turbo makes when you come off throttle and a blow off valve is not in operation. This is not another one of those noob threads..

Im referring to compressor surge when on full boost WOT... its suprising how many tuners dont even know that this is possible?

Now.. my friends car has just recently got a full tune done as his new engine is well and truly run in now.

Its running a GT3082r with a 0.82 ex housing at 1.5bar on a stock stroke forged SR20DET via a 6boost manifold. Its running Brian Crower 280 degree cams, tuner hasnt bothered dialling them in yet..

Now we have noticed that when he has reached full boost a small chu-chu-chu noise starts from the turbo/air filter side but then slowly dissapears as the revs climb above 5500-6000rpm.

Im convinced that this is some sort of compressor surge where the air is being pushed out of the turbo faster than that the engine can recieve forcing some air back onto the compressor wheel.

So my questions are..

Will dialling the cams in help this problem as the intake cam could possibly opening too late or am I on the wrong track here?

If not, how do we stop this from occurring without having to resort to getting surge slots drilled into the compressor housing?

Cheers.

oz

Edited September 20, 2010 by snozzle

[BoostdR]

Advance the Exhaust cam to bring efficiency higher in the rev range. Bringing boost on slower is the key. A greddy EO1 will also fix it as you can map boost against rpm.. Prob Kyles 6boost manifold working too well.

[Dale FZ1]

It is a fair bit of compressor for the engine. Are you averse to having the housing milled?

I'd tend to agree with Matt; playing with cam timing will realise changes in the gas trapping dynamics and the rpm where things come together. Seems that addressing it by at least trying to dial the cams would help.

Alternatively if you have good boost control, why not drop 2-3psi in that range?

Depending on your rpm ceiling you might then pick up more mid range efficiency by dialing cams to suit that arrangement. Win-win if you could achieve that.

Edited September 20, 2010 by Dale FZ1

[discopotato03]

If I had to use one of those GT3082R turbos I'd look at buying a port shrouded compressor housing for it , Garrett make them now .

Alternatively he could just buy a GT3076R minus the turbine housing and slot it into the one his current turbo now has - same .

Broken record I know but I'd buy the real 52T GT3076R because its map is better and should have slight spool and transient performance vs the 56T GT3076R . Either would be better IMO than a GT3082R on an SR20

Your calls .

A .

[snozzle]

Thanks for the excellent replies guys,

Just what i was after.

oz.