1G Cutting out under boost??

[tsi1991awd]

My problem arises when I am under boost. When under normal driving conditions, the car runs and drives just fine.

When I am building boost, the car will stutter and the BOV will go off repeatedly until I let off the gas.

It SEEMS like fuel cut, but it isn't. I almost guarantee that. Rewired Walbro 255, AEM AFPR, 1000cc injectors, fuel pressure at 43.5psi. There is no reason there should be fuel cut, especially with the eprom chip settings. MAFT is zero'd out and set for 450cc injectors. SAFC is zero'd out.

What happens is I am getting up to about 20psi and the car will stutter very fast and each time it does, the blow off valve will go off. Sometimes this happens at lower boost levels, but mainly around 20. I have the MBC set for 25psi.

The plugs are NGK BPR7ES...plug wires are brand new NGK's. Plugs gapped at .28 and I am wondering if it could be the coil pack or something? Like I said, under normal driving it is fine, but under boost is where the problem arises.

Any ideas?

 

[Colt4G63 also]

Could it be that your BOV is just blowing open?

 

[Bluefire16]

Sounds like compression surge.....

YouTube - True Compressor Surge

 

[tsi1991awd]

Sounds like compression surge.....

YouTube - True Compressor Surge

It doesn't sound like that though. It is hard to explain what happens. I will try and shoot a video with my phone tonight...hope it catches everything.

 

[DSM_IKE]

Thats about what mine sounds like. What causes compression surge and how do you fix it?

 

[tsi1991awd]

Thats about what mine sounds like. What causes compression surge and how do you fix it?

Did you even read the text in the video?? It tells exactly what causes it.

 

[DSM_IKE]

Yes i did, im still unsure what exactly causes it, but ok.. The real question is what do i need to do to fix compression surge? Mine is pretty bad when under load it 3rd 4th and 5th.

ok so i looked up more on compression surge and it makes sense. Didnt explain very well in the video. But i still need to know how to fix the issue..

 

[tsi1991awd]

Yes i did, im still unsure what exactly causes it, but ok.. The real question is what do i need to do to fix compression surge? Mine is pretty bad when under load it 3rd 4th and 5th.

ok so i looked up more on compression surge and it makes sense. Didnt explain very well in the video. But i still need to know how to fix the issue..

Not 100% sure....if it is TRUE compressor surge like in that video, it is basically saying the compressor is causing unstable balance in airflow....I would assume turning the boost down would be ideal BUT they were only running 20 pounds in that video so.....I have no idea.

 

[DSM_IKE]

wel im only running 15 psi and its been getting a little worse, before it didnt do this at all, but it started in 4th and 5th gear just at 12 psi it sounds just like compression surge. But lately its gotten worse and is now doing so in 3rd gear as well.

 

[tsi1991awd]

See, I don't think mine is compressor surge because the blow off valve is going off....I'd think with that compressor surge, it would be the turbo chirping and everything.

Here are two videos I took from my phone last night. You can see in the first one, it starts between 20 and 25psi and the last one around 28psi. In the second one, it is at 25psi.

ImageShack: Host and Share your Photos and Videos - prv.mp4

ImageShack: Host and Share your Photos and Videos - 1113002358.mp4

 

[tsi1991awd]

Nobody else has any ideas? Think this is true compressor surge? How do I fix the problem??

 

[GRAVEDIGGER]

I don't see anywhere where you've said you've done a boost leak test. Have you done one yet? If not, that is where you need to start.

 

[tsi1991awd]

Boost leak test was already performed already. I have been battling an idle surge issue too...found 2 leaks right before and right after the GM MAF. This did not sure my idle surge and there are no leaks while the car is doing this. I really dont understand...car drove fine one minute and the next does this.

 

[Marty Staggs]

The BOV should not open under boost UNLESS there is a misfire causing spikes in intake pressures. The BOV is not the issue - the misfire is.

Surge at idle? This is confusing and sounds like a tuning issue.

In that video, there was compressor surge because the turbo was operating outside of its design - wrong turbo.

 

[tsi1991awd]

The BOV should not open under boost UNLESS there is a misfire causing spikes in intake pressures. The BOV is not the issue - the misfire is.

Surge at idle? This is confusing and sounds like a tuning issue.

In that video, there was compressor surge because the turbo was operating outside of its design - wrong turbo.

I do not know that the BOV is opening up. I was under the impression that the "barking" sound had something to do with the BOV. But now I know it is compressor surge.

Idle surge has nothing to do with what the car is doing under boost (the video)

And so what you're saying is the 20g turbo isn't meant to boost 25 pounds? That's operating outside of its design...crossing the surge limit? I don't think so. This is when the turbo is alive. Please clarify what you are saying.

 

[khomza]

It probably just sounds like th BOV is opening up, but it's actually air ramming back in to the compressor wheel (as far as I understand). I didn't get compressor surge until I installed my FMIC with my big 16g, and once I installed the hx-35 I get A LOT of compressor surge if I dont let off the throttle after boosting to equalize the pressure. Just try that, if you build boost then stop accelerating but still have boost in the system let off the throttle all the way then get back on it and it should stop.

 

[Marty Staggs]

And so what you're saying is the 20g turbo isn't meant to boost 25 pounds? That's operating outside of its design...crossing the surge limit? I don't think so. This is when the turbo is alive. Please clarify what you are saying.

That turbo in that video is an Innovative aftermarket turbo and the wheel/housing selection is wrong.

 

[tsi1991awd]

It probably just sounds like th BOV is opening up, but it's actually air ramming back in to the compressor wheel (as far as I understand). I didn't get compressor surge until I installed my FMIC with my big 16g, and once I installed the hx-35 I get A LOT of compressor surge if I dont let off the throttle after boosting to equalize the pressure. Just try that, if you build boost then stop accelerating but still have boost in the system let off the throttle all the way then get back on it and it should stop.

But what about the times I am at full throttle? That is when it happens. I am building boost at full throttle and then it cuts out like that. Or if I am at part throttle building the boost up, it cuts out like that. SO I am not sure what you mean by let off the throttle to equalize the pressure.

Also, Marty, this turbo is an MHI TD05-20g, so I am not sure what you are talking about.