gt30

[A80Avant]

sounds like gentle fluttering and if you use a needle style boost controller you can see the needle tremble.

[AndyP]

what does surge sound like???is it the compressor stalling??maybe like a fluttering noise???

http://www.youtube.com/watch?v=nCj6Spwl1CU

[cooperquattro]

sounds like gentle fluttering and if you use a needle style boost controller you can see the needle tremble.

needle "bounces" so you cant read it properly......
so now i am very worried,mine does this quite often,mainly under load,if you go to the next gear down and give it some it stops.....
so how do we stop this ????????gt3582r

[cooperquattro]

http://www.youtube.com/watch?v=nCj6Spwl1CU

cheers andy,thats the noise i was trying to explain

[A80Avant]

i cant be bothered to read this whole thread so apologies if this has already been said.

if you are going fit a gt30 you should really have port work done at least on the exhaust side and/or use 7a cams. Basically improve on stock head and cams. I am currently running gt30 0.86 on my s2 with stock head and cams ~8.5:1 compression. We had a lot of problems mapping out surge in the high gears. car now spools later to prevent this from happening. Please ask Dmitri for details.

can't really see why you had problems with the 0.82ar, as on my stock head and stock adu cams I had NO surge on any gear with that hotside. must have been the ABY cams or narrower intake pipes or exhaust manifold that made the difference.

prj has written already and could shed some light on your setup.

porting is good whichever setup, even in stock s2/rs2. 7a cams I would only consider on bigger turbos or large hotside.

[A80Avant]

needle "bounces" so you cant read it properly......
so now i am very worried,mine does this quite often,mainly under load,if you go to the next gear down and give it some it stops.....
so how do we stop this ????????gt3582r

When does it do it? Which gear? What ar do you have? Pm me as its not relevant to this thread

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[prj]

can't really see why you had problems with the 0.82ar, as on my stock head and stock adu cams I had NO surge on any gear with that hotside. must have been the ABY cams or narrower intake pipes or exhaust manifold that made the difference.

prj has written already and could shed some light on your setup.

porting is good whichever setup, even in stock s2/rs2. 7a cams I would only consider on bigger turbos or large hotside.

He had stock head and stock cams. And yea it surges in 6th even on 0.82 A/R...
Has done this on every car so far. So with 0.63 A/R on non-ported head it's just stupid...

FYI 0.82 A/R spools up quite early in high gears too. About 3400 rpm you have full boost in 6th and you get some surge. No surge on 7A cams or ported head and std. cams.

[cooperquattro]

so its down to flow to the turbo,not flow to the inlet??
how can this be "dialed" out

[prj]

so its down to flow to the turbo,not flow to the inlet??
how can this be "dialed" out

It's down to the engine not being able to swallow the air the turbo is producing.

To dial this out, you have to limit the boost in the ECU to a value where it does not surge for every RPM point.

Or you can increase the flow capability of the engine.

[A80Avant]

He had stock head and stock cams. And yea it surges in 6th even on 0.82 A/R...
Has done this on every car so far. So with 0.63 A/R on non-ported head it's just stupid...

FYI 0.82 A/R spools up quite early in high gears too. About 3400 rpm you have full boost in 6th and you get some surge. No surge on 7A cams or ported head and std. cams.

Sure but from 2800rpm which you cruise on 70mph and you want to overtake you get absolutely nothing till 3400-3500. So you have to downshift all the time.

For track use its fine. For everyday I found it pretty darn annoying.

Adu cams didn't surge on .82 and stock head with SQ. EM. So it may have been those differences that made it so.


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[DJones]

It's down to the engine not being able to swallow the air the turbo is producing.

To dial this out, you have to limit the boost in the ECU to a value where it does not surge for every RPM point.

Or you can increase the flow capability of the engine.

My .82 will surge in 4th and 5th if running more than 1.8 bar.

@PRJ would a 7a ex cam help me or make it worse?

[prj]

Sure but from 2800rpm which you cruise on 70mph and you want to overtake you get absolutely nothing till 3400-3500. So you have to downshift all the time.

Yes, you have to downshift all the time, that's kinda the point of a big power turbo car.
Downshift and smile each time you hit the loud pedal.

[prj]

My .82 will surge in 4th and 5th if running more than 1.8 bar.

@PRJ would a 7a ex cam help me or make it worse?

It would make your car laggier off boost, but it would also make it surge less.
Then again, your car is so light that you should be having both 7A inlet and 7A exhaust anyway.

[A80Avant]

Yes, you have to downshift all the time, that's kinda the point of a big power turbo car.
Downshift and smile each time you hit the loud pedal.

If you can get to do the same with a slight more press of the pedal, its faster!

sent with Nokia 5110

[DJones]

It would make your car laggier off boost, but it would also make it surge less.
Then again, your car is so light that you should be having both 7A inlet and 7A exhaust anyway.

Thanks, I have both so will have to have a play. Oh it's a ported head too.