Help Im Getting Huge Compressor Surge

[LBR33]

Hi guys,

Iv been getting huge compressor surge under light and medium throttle when the boost guage reads positive boost -1 - 5 odd psi normally.

My mods are as follows

R33 gtst s1 auto running 11 psi

fmic, safc, gcg s2 highflow, full zorst, stock bov

iv been told it could be the stock bov (might need to get a aftermarket plumback one) or the throttle body is too small and i need a XF one or the computer needs to be replaced with a standalone unit and the compressor surge can be tuned out

Any advice would be helpful thanks

[paulr33]

never head of tuning the compresor surge out, sounds bogus.

is it on gearchange or when you back off on the throttle? if so then it sounds like bov is too tight or may have even failed / no longer working properly.

if its during boost build then it could be pressure drop or the compressor has something wrong with it

[Dale FZ1]

Has it surged from the time you fitted it, or commenced doing something unusual only recently?

Surge basically happens because the compressor is attempting to pump more air than the engine can ingest - the literature describes how a series of pressure reversions occur between the throttle and impeller. Generally it should be at less than full throttle, and under some load (boost) as you describe.

DO check your BOV.

cheers

[LBR33]

I cleaned the bov but no change, im thinking i might need a aftermarket plumback bov but would it need to be tighter or looser spring.

Lee

[BHDave]

Can you please confirm when it happens.

Either when you are accelerating with the accelerator held in one position (which would be surge). The car would then like to bounce back and forth and generally act silly.

Or when you lift off so you get a bit of flutter (reversion) before the bov opens.

Or when you do a partial lift off the throttle when on boost (so all of a sudden all the compressed air can't get past the partially closed throttle body) and then it bounces around and acts stupid again. You'd have to have modded the stock bov and blocked the bypass for it to do this though.

[REdgtst]

I too have this same problem.. I have fmic, pfc, ppod, zorst, bosot controleler running about 11 psi. My air flow sensor is maxing out occasionally/quite often under full throttle, but i dont beleive this to be the problem.

Minme surges on medium throttle: on heavy and light throttle i dont really seem to notce it. On heavy throttle i get knock levels around the 130 - 140 mark (ie very bad) and check engine light flashes up due to stock airflow sensor maxing out (5090mV).

Took it back to tuner and he believed it to be a turbo problem. A few friends of mine beleive it could be the wastegate and it may need to be ported (dude from work apparently had this same prob: got his wastegate ported and it fixed it).

I was just going to get a whople new turbs to fix the prob (plus it is on my wanted list for future upgrades!)... But this help would be much appreciated if anyone has a solution....

Havnt really had a chance to get my prob sussed out fully yet due to time and money constraints.

Also when lifting off throttle and changing gears my boost controller over boost light is flashing up (ie im getting boost spiukes) light is set to come on at 1.4 bar however boost gauge is not showing levels near this..... which seems a bit weird... would this be due to the spike bieng almost instantaneous for a very short duration which the boost gauge would not be able to pick up due to it not being able to update its display in time b4 it is reduced back down to safe level. Would this be likely due to the wastegate not operating correctly?..

Sorry for shite grammar buit typing in heurrry as bosses are watching over my should er and getting shitty with the anount of time is spend onte net.

cheeers chris

[LBR33]

i get these two problems

Either when you are accelerating with the accelerator held in one position (which would be surge). The car would then like to bounce back and forth and generally act silly.

Or when you do a partial lift off the throttle when on boost (so all of a sudden all the compressed air can't get past the partially closed throttle body) and then it bounces around and acts stupid again. You'd have to have modded the stock bov and blocked the bypass for it to do this though.

But the interesting thing is that i havent modified the stock bov at all or blocked it off

Lee

[paulr33]

compressor surge occurs when pressure past the compressor outlet is greater than the pressure the turbocharger's compressor wheel can actually supply.

surge when accelerating:

what sort of boost readings are you seeing on your gauge(s)?

surge on gear change:

can you try swapping with a known working rb25 bov to see if that helps the on gear change surge?

[LBR33]

Its surge when accelerating when the boost guage reads -1 to 5 odd psi normally

[wolverine]

the factory BOV is as soft as you will get, going to an aftermarket BOV will make it worse as they usually have (effectively) a higher spring rate.

[LBR33]

So what can be done then

[wolverine]

from my understanding you can't tune around it effectively.

has the turbo just been installed?? the original GCG 500hp Hiflows had issues with compressor surge that i believe was fixed. the 450hp GCG rebuilds didn't have the same issues.

perhaps call GCG and pick their brains.

[The Dan]

mmm. GCG Highflow, what more can I say?

[LBR33]

How about a bigger throttle body would that allow the extra air to be sucked in

[REdgtst]

Had a bit of a play around this morning and mine appears to be occurring in the mid range but by the time it hits about 4 and a half it dissappears (well at least i dont notice it as i am too busy watchin the road keeping it straight). Does yours do this and then appear to fix it self as it winds out near the red line?

My boost gauge (factory one) when it occurs i notice the guage bouncing around and the car surging like someone is flicking a switch cutting the power. Plus watching my tacko it does not move at a constant speed (it sort of surges as the car surges).

I dont get the problem when i lift off throttle.

I still use the stock BOV.

My thoughts are there is something wrong with my wastegate or my exhaust is a little bit restrictive, it has a second dog box muffler and no cat.

[Sydneykid]

GCG S2 high flow (discontinued) and standard computer don't work together, upgrade the ECU.

Some tuning tips;

1. During the boost build rpm, tune it with as much ignition advance as it will take, use extra fuel (richness) to control the detonation. This ensures that whatever airflow the turbo is producing is ingested by the engine (throttle body size is irrelevant at partial throttle openings).

2. Retard the exhaust camshaft timing, usually around 4 degrees

3. Some mild tuning of the VVT change over point sometimes helps

4. In the surge rpm zone, check the pressure drop from the turbo to the plenum. It should be almost zero, more than 1 psi is not acceptable. Look closely at the pipework and the intercooler.

5. In the surge rpm zone, compare the inlet plenum pressure and the exhaust pressure (the lambda sensor point is a good reference). There should be almost zero difference, more than 1 psi is not acceptable. Look closely at the dump, cat and exhaust.

The above (with carefull tuning) will eliminate almost all of the compressor surge, maybe even all of it. Whatever remains you will have to manage via judicious use of the throttle.

Hope that helps

cheers

PS, this is a unique problem to the GCG S2 (500 bhp) high flow, the S1 (450 bhp) has not had one sinlge problem on the 6 or so cars we have fitted them to.

Edited January 17, 2006 by Sydneykid

[Shaun]

I had the exact same problem with GCGs highflow turbos on my R32 gtst. Huge compressor surge on light throttle; they told me my BOV was the culprit, so i changed to a Tial item and that didnt fix it. They built me three turbos in the end, all of different confugurations, and none of them worked. I already had a Microtech, front mount, and all the other usual mods. After changing turbos for about 3 months (i got really good at it!), i told them to just give me an off the shelf Garrett and stuuff the high flow to hell. I never looked back, and the GT30 was excellent although the boost threshold was a bit high for the street (0.82ar turbine housing).

As i understand it, the problem was that the compressor wheel is way too big, and it was trying to force more air into the engine than it can ingest. It therefore, goes back thru the inlet tract and makes that awful choofing sound.

GCG fit huge comp wheels in the standard type housings, and then mate them up with small turbine wheels trying to get the best of both worlds. It doesnt seem to work on some cars.

Someone please correct me if my theories are mistaken.

I should mention that Brett at GCG was excellent throughout. He had my car tuned, didnt charge for the subsequent turbos, and carried out mods for the GT30 conversion for next to nix. their customer support, in my experience, is excellent.

[R31Nismoid]

It works if you tune/set it up right.

its not a case of bolting on and driving away.

The people i know with GCG's have no issues at all.

[Shaun]

It works if you tune/set it up right.

its not a case of bolting on and driving away.

The people i know with GCG's have no issues at all.

<{POST_SNAPBACK}>

No shit its not a case of bolting it on and driving away. You really do write some stupid shit man. I read your posts all the time and am constantly shaking my head.

I know many people with GCG turbos as well, and none of them have had problems either, however, i did have a problem, and it seems several other people in this thread have had the exact same problem. Is it possible that someone out there, who you dont know, is having problems with a high flow?

Im sure, as Gary indicated above, you can significantly minimise compressor surge with successful tuning, however, i decided not to take this route and am sharing my experiences with the author of this thread.

I hate your sarcastic posts Nismood freak.

[Swiper the Fox]

No shit its not a case of bolting it on and driving away. You really do write some stupid shit man. I read your posts all the time and am constantly shaking my head.

I know many people with GCG turbos as well, and none of them have had problems either, however, i did have a problem, and it seems several other people in this thread have had the exact same problem. Is it possible that someone out there, who you dont know, is having problems with a high flow?

Im sure, as Gary indicated above, you can significantly minimise compressor surge with successful tuning, however, i decided not to take this route and am sharing my experiences with the author of this thread.

I hate your sarcastic posts Nismood freak.

<{POST_SNAPBACK}>

hey..easy Shaun...are you trying to take my "cranky pants" mantle off me...lol

I had compressor surge with HKS2530's, believe it or not.....but i had it tuned out by the best GTR tuner in Australia (my opinion)