Boost Surge and Engine Surge

[DSM_Nick]

I am a new member so figured this would be where to post, I also looked at some other threads but they weren't quite the same problem I am having. I have a 1992 Eagle Talon TSi.

The problem to me seems to be a type of surging of the car when acclerating. Probably the best way I can describe it. It only happens when I am accelerating or wide open throttle. The boost will get up to its normal 9psi about and then jump to 12, to 10, to 11, sometimes to 14. While it does this I can feel the car surge. It started doing this after I put on the AEM tru-boost gauge and boost controller. You have to set your wastegate spring pressure on the gauge and I think that could be it. Cause when I set the gauge to OFF and it runs the turbo on wastegate pressure it only boosts 9psi at most, but does this with no surging. This is not bov flutter, and pretty sure its not compressor surge. Definitely could use some input though and was wondering what the wastegate spring pressure is on an Evo III Big 16g. Because, I have the 16g on it now and it does it, it also did it when i had a 13b on the car. The only difference was it jumped at lower psi with the 13b that was stock.

 

[DSM_Nick]

Talking to some people I think it might be compressor surge. But not sure, would greatly appreciate some input or help still though

 

[Illmat1c]

What else did you mod? Did you just swap the turbo out?

 

[xioca]

Alright so your using an electronic boost controller? and your guage is electronic too? (not actual pressure reading via analog dial?)

 

[Bud92gsx]

Whats the big deal with compressor surge anyway? Does it hurt anything. I'm talking about when the BOV flutters..Does it hurt anything?

 

[xioca]

Yes it is bad.

 

[need2boostpsi]

aren't compressor surge and BOV flutter different? Compressor surge is bad for the turbo compressor wheel and BOV surge happens when you slowly let off the gas while in boost, Right?

 

[DSM_Nick]

Yeah I only swapped the turbo. That is it for now, and even before I swapped it. I could get my stock turbo to surge depending on what I set the wastegate spring pressure setting at.

And yes it is an electronic boost controller and gauge. It reads digitally but directly off of a vacuum line. And compressor surge is bad, definitely bad. Plus different from bov flutter.

 

[blacksheep86]

I was having a problem that sounds very similar to what your having. My boost would hit 15, then 12, 16, 13. I changed my plugs and wires an hour ago and the car pulls harder than it ever has before. As far as I know you don't really feel compressor surge. When I would hit 15 my car would buck while the boost was fluttering up and down.

 

[Bud92gsx]

This thread started by me might give you a little more info on the same problem happening to me.You my freind are getting flutter, not surge.....http://www.dsmtuners.com/forums/turbo-system-tech/321087-compressor-surge.html

 

[DSM_Nick]

I was having a problem that sounds very similar to what your having. My boost would hit 15, then 12, 16, 13. I changed my plugs and wires an hour ago and the car pulls harder than it ever has before. As far as I know you don't really feel compressor surge. When I would hit 15 my car would buck while the boost was fluttering up and down.

Hmmm, yeah it does spike and jump. Plus seems faster and shifts harder when it is doing that. But all of my plugs and wires are good, so I know it is not that. One more thing is that I am not totally sure about feeling compressor surge, but I do agree you shouldn't feel it much.

 

[DSM_Nick]

"This is bad because it causes your compressor wheel to spin backwards, which spins your turbine backwards, and puts backpressure on your engine, normally in pulses, which can make your car jerk, and hurt your drivetrain."

"'m sorry I should have been more specific..I'm getting flutter not surge. Only when I let off the throttle, not under boost. "

Here are two quotes from your link to your thread bud. The second one would be by you, and both verify that I have surge, as I have come to know now. Because for one my car does pulse and surge from it. Number two is that it only happens on load while accelerating and not letting off the throttle, (so not bov flutter). Number three would be that I can control this surging by adjusting my wastegate spring pressure to different psi's.

 

[Bud92gsx]

Sorry again. I meant I get flutter when I let off of the pedal under boost, not get flutter under boost without letting off the throttle.. My car does not do anything funky, as in no drivetrain shock. Engine stays strong, not sputtering or any of the sort...

 

[DSM_Nick]

I know, I came to understand that through your thread Bud92. Thanks though, it still helped some. And in your case that is flutter then. To solve mine I just need to figure out my wastegate spring part.

One more question for anyone is....How do you eliminate/reduce compressor surge?

 

[Bud92gsx]

Crushing your BOV. DO NOT CRUSH TOO MUCH OR YOU WILL GET ALOT OF FLUTTER..Take of your BOV, put in vise, and proceed to make the center section flat or concave...That should help with your BOV opening before it's supposed to...
I hope that helps a bit. Did you read the link in my link, about that guy who went boarding and got surge?


Or another option is to go back to the 13g, or switch to a 14b. Some turbo that isn't as efficiant as the EVO 3..

 

[DSM_Nick]

Crushing your BOV. DO NOT CRUSH TOO MUCH OR YOU WILL GET ALOT OF FLUTTER..Take of your BOV, put in vise, and proceed to make the center section flat or concave...That should help with your BOV opening before it's supposed to...
I hope that helps a bit. Did you read the link in my link, about that guy who went boarding and got surge?


Or another option is to go back to the 13g, or switch to a 14b. Some turbo that isn't as efficiant as the EVO 3..

Yeah I did check out that link in your thread. It was different, but pretty informative. You still only answered about BOV flutter by messing with the BOV. Plus i wouldn't crush it anyways, ha. This surging I could get with the "13g" as well as the 16g to do it. Just all depends on the wastegate pressure I set my gauge to.

 

[blacksheep86]

I suppose you could try taking out the boost controller and gauge and see if it stops to help narrow down the problem.

 

[tkelly27]

A few things, compressor surge can occur under any engine conditions, open throttle or not. If you don't have a bov, the puff puff sound IS compressor surge. Compressor surge happens when the pressure is too high and the flow is not enough so it pushes the air out the compressor. It MUST happen when you don't have a BOV or when it's not set properly.

BOV flutter is when the valve lifts, relieves the pressure then without enough pressure to keep it open it closes again until enough pressure is built up to open it again.

If it is compressor surge you should be able to hear it and you shouldn't be able to get above a certain boost threshold. Once you go past the surge line the air starts going back through the compressor until it has dropped down to a low enough pressure or a high enough flow rate to return to boost making happy time.

The only thing you've changed from stock seems to be the boost controller and the wastegate. I've never heard of anyone getting compressor surge on a 16g, let alone a 13g which is a factory piece, so it's probably something in the boost controller and or the wastegate.

Does someone have a MBC you could borrow? That would diagnose the EBC. I don't know how to verify operation of a wastegate. Maybe on a bench with a compressor?

Just to throw this out there, you get a good clean pull at 9psi, but anything more and the boost jumps around and it starts bucking? I almost want to say fuel cut, do you know what that feels like?

 

[blacksheep86]

so can you feel the jumps in boost? like as in the car jolts each time the boost fluctuates?

 

[Bud92gsx]

Nope..I just get flutter. But today I'm installing a 2g mas, and an uncrushed BOV. TO help with this problem..

 

[GlassAndMarrow]

I was having a problem that sounds very similar to what your having. My boost would hit 15, then 12, 16, 13. I changed my plugs and wires an hour ago and the car pulls harder than it ever has before. As far as I know you don't really feel compressor surge. When I would hit 15 my car would buck while the boost was fluttering up and down.

When you say "bucking" my car is doing the same thing. a frriend told me to change my injectors due to fuel cut but i don't know. what u think?

 

[DSM_Nick]

A few things, compressor surge can occur under any engine conditions, open throttle or not. If you don't have a bov, the puff puff sound IS compressor surge. Compressor surge happens when the pressure is too high and the flow is not enough so it pushes the air out the compressor. It MUST happen when you don't have a BOV or when it's not set properly.

BOV flutter is when the valve lifts, relieves the pressure then without enough pressure to keep it open it closes again until enough pressure is built up to open it again.

If it is compressor surge you should be able to hear it and you shouldn't be able to get above a certain boost threshold. Once you go past the surge line the air starts going back through the compressor until it has dropped down to a low enough pressure or a high enough flow rate to return to boost making happy time.

The only thing you've changed from stock seems to be the boost controller and the wastegate. I've never heard of anyone getting compressor surge on a 16g, let alone a 13g which is a factory piece, so it's probably something in the boost controller and or the wastegate.
Does someone have a MBC you could borrow? That would diagnose the EBC. I don't know how to verify operation of a wastegate. Maybe on a bench with a compressor?

Just to throw this out there, you get a good clean pull at 9psi, but anything more and the boost jumps around and it starts bucking? I almost want to say fuel cut, do you know what that feels like?

Yeah it is definitely the boost controller and the wastegate causing it. And true about compressor surge, it happens when under load and from bov flutter. Just slightly differently, I think I said otherwise earlier though. I seemed to have fixed the problem by lowering the wastegate pressure on my gauge to 8 psi. Now it doesn't do it, and when I was running the car with no boost controller and just on wastegate, it seemed to peak at 8 to 9. So I think I am in the right range now. Runs pretty good, but still not as fast as I would like, but oh well.

No, I do not know what fuel cut feels like. What does it feel like and do?

 

[DSM_Nick]

Oh and yes I can feel the car surging as if I was letting on and off the throttle. That is probably the best I can explain it. So not really a jolt. But the boost did jump with the surging when it was happening

 

[DSM_Nick]

Also one more thing I forgot to ask. Since I already know not to vent my stock bov to atmosphere. Would it be a good idea to get an aftermarket bov that does? Shouldn't cause any bov flutter if I get the right one, right?

 

[blacksheep86]

no you should still recirculate. are you still having the same problem you were?