This is not directly related to a turbo 2gnt ... but it could be I guess it could be.

I've had some nasty surging problems on my 3000gt vr4 since installing a hardpipe/fmic kit. It's bad enough that I cannot stand to drive the car.

The symptoms:
At partial throttle, the car will build up some boost (usually around 2-4psi). At this point the car is at around 2k rpms and begins to surge. You will hear the turbos make a "pssh, pssh" noise in sets of two. You can watch the boost gauge rise/fall in tune with the sound. The gauge jumps from 4psi to 0, 0 to 4psi. As this happens, the car will buck violently due to the absent metered air.

This is VERY annoying. However, if you go WOT the car will hit the 10psi its set at and pull nicely w/o surging.

The surging is most prevalent at low rpm/low load situations.

Things I have tried:
I did a z06 MAF and MAF-T upgrade and I think the surging is actually worse. However, the violent bucking resulting from the surge doesn't happen because I have the MAF-T placed right before the TB and after the BOV.

I haven't tuned the car with the MAF-T yet but when I go WOT, the surge still seems to occur.

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From what I understand, the surge is being caused by "too much" air being pushed into the engine. The turbos produce more than enough air at low rpms/low load and the air has to go somewhere. The BOV is supposed to relieve the pressure but since the throttle plate is still open the air has nowhere to go but back to the turbo and out where it came from.

This is how it was explained to me by several 3s guru's from 3si.

I want to keep the hardpipe/fmic kit at all costs but I am not sure what to try.

I have been seeing some well-built turbo cars with 2 BOV's. One in the standard location near the throttle body and one near the intercooler cold side end tank.

Why do they do this?
Would it combat my surge?

My vr4 has a pretty complex piping route. However, some of these shop cars I'm seeing have piping routes that are almost as complex.

Any comments on what else contributes to surge? Air turbulence? Any info would be appreciated.

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97 Eclipse RS auto *SOLD* - super 15g 92 3000GT VR4 - t3/t4 60 trim 95 Talon TSI AWD

This is something i was looking at when thinking of upgrade options for my eclipse. Your the first i have heard that has experienced it. Possibly a Apexi boost controller will help since you can adjust boost by RPM level. Are you running stock turbo's?

Edit: never mind you have 15g turbo's. The way i understand this is the turbo is spooling too fast for the engines ability to ingest the air forced into the intake, the air rebounds back to the turbo compressor fins. Apexi boost controller might slow the boost curve down, i am not sure really.

If you can get your hands on a copy of the compressor maps and plot the boost curve to see how much you need to retard the boost response.

Terry
96 Eagle Talon ESI....Daily driver

97 Eclipse.........

Any way to loosen the BOV spring a bit? I know that some of them are adjustable. Other then that, a bigger BOV migbt help.

surging the compressor skikikikkkkitters

your bov isnt doing its job

edit: lube up the piston or valve in your BOV

_ _ _ _ _ _ _ _ _

96 Black ESi
91 Red TSI AWD (RIP)
02 WRX


"turnin wrenches for nine hours in the pouring rain, just to get the beast up and running again"

Aerospace Certified TIG welder for Precision Castparts in Portland, OR.

JoshSpair.com

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Megasquirt powered 420A
Custom turbo system

http://www.ms-custom.com

ah i see wasnt really thinking in that direction, thank you sir

Terry
96 Eagle Talon ESI....Daily driver

97 Eclipse.........

Here's a thought...

The VR-4 has some pretty damn comples vac line routing.... I know, I just rebuilt the motor in one...

Anyway, are you sure all the vac lines are hooked up? Cause the Wastegates and BOV's are controlled by the computer I think... one vac line wrong and weird shit can happen...

Only car with crazier vac line network is a 93-95 RX7.

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Megasquirt powered 420A
Custom turbo system

http://www.ms-custom.com

Okay, to address some of the info I didn't provide :

I have td04hl "super" 15g turbos. I use a proboost mbc and it's currently set at 9-10psi.

I use a pressure testing device that I insert into the intake tract where the filter/mas normally goes to test for vacuum leaks. I have a pressure gauge on one end and a fitting that attatches to my air compressor on the other. I can feed in 20psi before I get a vacuum leak at the oil cap. Otherwise, it is sealed.

I have minimized the vacuum scheme immensely. There are only wastegate, bov, and fpr lines in the car. Everything else has been eliminated.

Any info regarding the BOV near the intercooler end tank?

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97 Eclipse RS auto *SOLD* - super 15g 92 3000GT VR4 - t3/t4 60 trim 95 Talon TSI AWD