I have a surge problem with the standard turbo on my VIII in 4th and 5th.
My mods are as follows-
ebay O2 housing
AVO down pipe
trust Ti exhaust
cat delete
piper cams (similar duration to 272's with more lift)
Motec ECU
Meth injection 75% with 0.8mm jet
Australian 98 ron fuel
MR bov
running 28psi peak (on the gauge)
Is this common and is there something in my mods (or missing from the mods) that is causing it?

I have searched but didn't find a good answer.

 

running 28 psi on a stock 8 turbo..... i thought it was only safe up to 23 that could be the problem... unless i am geting my facts mixed up.

 

Define your "surge ploblem" please.

 

I had a friend running 30psi on the stock 8 turbo w/ meth and supporting mods. Car made 390hp and 420tq! Car didnt have any surging as far as i know when i drove it or when he drove it. But running that much boost can cause surging.

 

Yea actually... answered to quickly. By surging are you talking about compressor surge?

 

Sorry,

yes I believe it is compressor surge. The boost needle vibrates rapidly and the car feel hesitant.
It happens when I go WOT at say 3000rpm an the car builds boost rapidly.
When it starts surging, I can lift off and then boot it again and the surging will stop around 50% of the time.

Does this help?

BTW the gauge is saying 28psi but it probably reads high, as the tuner was going to tune for around 26 psi.

 

Is the alky injection kicking in at the point where the surging occurs?

 

Your saying it surges while the turbo is still spooling and while your foot is on the gas? Compressor surge is the noise you hear when you lift off the throttle. Its sorta like a fluttering noise.

 

Although Megavar specifies WOT,I think that compressor surge can also occur under part throttle conditions as well as when totally lifted off the gas pedal. I think that I have experienced it when initially flooring the car(not an Evo) while it starts to build boost as well. But it's been a long time and that was on a car w/o a BOV.

 

I forgot about partial throttle also. On my 240 it was really bad when my Blitz BOV was improperly adjusted. It still did it under partial throttle though.

 

well like you said your bov was improperly adjusted. megavar, could your bov be causing the problem?

 

Compressor surge is when the compressor is flowing more air than the engine can pyhisucally flow at a particualr RPM. You can look at the surge line on a compressor map...it is on the left hand side of the map.

The noise you hear when you lift off the throttle is really BOV flutter, it's not compressor surge. Many people like to call it 'internet surge' because of the misconception.

It looks like the OP is talking about true compressor surge, where the turbo is spooling fast enough in higher gears that the engine cannot handle that amount of airflow at that low of an RPM.

Looking at our compressor map though, it looks like you would have to build about 20 psi of boost before about 2600 RPM for surge to occur. How much boost are you building and at what RPM when your are experiencing this? You said it happens at about 3000RPM. Do you have any logs of RPM and boost logged? I can't really see how you can get surge at 3000RPM on the stock turbo, but if you are building 20 psi around 2500, then I could see it being possible.

Eric

 

Thanks for the clear up. I was always under the impression that compressor surge was when the turbo spun backwards.

 

Sorry for the slow replies.
The car is building 20psi in fifth by about 2700-2800rpm if I open up from 2500rpm or below. It's a little hard to be exact when I have to flick my eyes from one gauge to another.
The surge occurs when I build boost rapidly starting from below 3000rpm. The car hits 28psi rapidly and then surges up till I hit 4000rpm (approx) then it clears.
If I start accelerating hard from 3100rpm or above, I don't seem to have any surging.
Does this clear up the questions?
btw the bov is an MR bov.

 

Maybe a better aftermarket bov with the proper adjusting can do the trick.