From out of no where SURGE!

[Schmitty]

Last week I upgraded my inlet and added a boost gauge (thanks to Tom and Jay's help). Everything ran well on Saturday and Sunday. Yesterday I take the car out in the morning and it runs fine. I go out in the afternoon and head to EP, everything is fine on the way there. On the way home while getting on the highway, I accelerated down the ramp (15PSI boost) clutch to shift and it sounds like I have a turkey in my engine, then the BPV makes it's mario coin sound. This continues every time I boost more than 5 or so PSI.

I come home, and change the spring in the BPV (was blue with no shim, so I swap to yellow with no shim) and no more turkey sound but, it wont hold very much boost.

Today it surges again and i check all the hoses I can without removing the battery box. AFAICT all the hoses are on and in good condition. The hose coming off the BPV (the big one) is on but is easy to slide off with out moving the clamp. I also saw that the tube going to the boost gauge solenoid is pinch so I freed it up. Rev the engine and BPV works fine a low boost, go out and test drive, anytime i get above 5PSI it gobbles, then the the BPV *chings*

So I am thinking that the BPY isnt operating fast enough, which could be remedied by using the softer yellow spring, but then it won't hold the proper amount of boost.

Any ideas on what else to trouble shoot? Any clue why this would happen out of no where?

(I may cross post this on MSF and 247)

 

[VTEC8YA]

I had that same problem. I actually was running the blue plus 2 shims, held boost excellent, shifting through the gears there was virtually (what seemed to be) no lag. I went with the yellow and it wasnt holding boost for shit. You should try putting the 2 shims in with the yellow once, see how that works.

I am also running the cobb ap, I guess keep that in mind also.

 

[goodhart]

Are you sure what you are experiencing is compressor surge or just a fluttering BPV/BOV. There is a difference.

 

[Schmitty]

I had that same problem. I actually was running the blue plus 2 shims, held boost excellent, shifting through the gears there was virtually (what seemed to be) no lag. I went with the yellow and it wasnt holding boost for shit. You should try putting the 2 shims in with the yellow once, see how that works.

I am also running the cobb ap, I guess keep that in mind also.

OK, i guess I'll try yellow and shims. where exactly do you place the shims?

 

[Schmitty]

Are you sure what you are experiencing is compressor surge or just a fluttering BPV/BOV. There is a difference.

Which one sounds like you are killing a turkey?

 

[VTEC8YA]

I bet what your getting flutter is all. I get that no matter what spring I use. If you just boost a little bit... say half throttle. I think the shims go on the bottom. I think they will only seat in there one way. Dont quote me on that. You can try explaining your issue to Patti over on 247. I think they are a forge employee.

 

[VTEC8YA]

[video=youtube;nCj6Spwl1CU]http://www.youtube.com/watch?v=nCj6Spwl1CU[/video]

Surge.

 

[VTEC8YA]

Some serious surge. And they think this is cool.

[video=youtube;LZUbo_mNDZM]http://www.youtube.com/watch?v=LZUbo_mNDZM[/video]

 

[Schmitty]

sounds more like this, but the second one you posted sounds similar.

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[DrWebster]

 

[dmention7]

If it was fluttering I'd expect to hear it more at low boost. My BPV flutters quite a bit at low boost, but at full boost, I let off the gas to a nice solid whoosh.

If you say the BPV still makes its notorious "pching" shortly after letting off the gas, I'd guess the BPV isn't opening quickly enough. I'd try using the softer spring, and double check your vacuum line routing.

 

[goodhart]

Real compressor surge happens during spoolup/high boost, not when you let off of the gas. Compressor surge happens when the turbo is flowing A LOT of air and the motor can't actually ingest all that air. A turbo makes boost inside the compressor housing, it isn't like a roots blower/positive displacement blower that works by stacking air in the intake manifold. When air starts stacking up on a turbo car and gets stacked all the way back to the compressor housing, then surge happens. The stacked air starts stopping the spinning compressor wheel or trys to turn it backwards. When you try to stop a compressor wheel going 80,000RPMs, bad things happen.

Compressor surge is common on 2.0l motors with the 61mm turbos. The 2.0l spools the turbo to high boost levels too fast and makes more air than the motor can take in. You can try to get rid of surge by going to a larger exhaust housing/wheel, to make the turbo spool up slower. You can get bigger cams, bigger intake manifold, port the head, to try to be able to take in more air. You can goto a bigger displacement motor that can take in more air each stroke.

A ported shroud/anti-surge cover has passage ways for the backing up air to come back out the front of compressor housing and into your intake pipe to try to avoid reverse flow pressure waves from causing surge.

Basically you can't have your cake and eat it too. If you spool a big turbo too fast you get surge.

This is a pretty good explanation of what real compressor surge is, so it is pretty doubtful that what you have is true surge.

 

[dmention7]

Well, the same thing can happen when the throttle plate slams shut and the turbo is still spooled and trying to cram air into the motor. It's obviously a much more instantaneous and short-lived phenomenon than the truly dangerous type of surge you described (and Luke illustrated in his first vid), but the phenomenon is the same.

The type of surge you're describing kills turbos. The type of surge that results from an insufficient bypass/dump setup can "merely" increase wear.

 

[Schmitty]

Thanks for all the feedback.

I'm gunna double check the lines and re-clamp the hoses tomorrow before porky's, maybe set a softer spring if I have time.

Here is a crappy video i made, you can here the goofy sound when I let off in third gear.

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[dmention7]

Yeah, that sounds like nothing serious. Most likely just the BPV not opening quickly enough. I bet the softer spring will fix you right up.

 

[Schmitty]

if you're right and I suspect you are, WTH would cause the spring to be too stiff all of the sudden?

 

[dmention7]

Dinno. Did you tee the boost gauge line off the BPV line?

 

[Schmitty]

yup, put it at the same spot Tom put his. and it wasn't until 3 days after the install that it started doing that.

 

[Big Nate]

This sounds like an install error.(sorry) I think if we can take a look at Porky's we will be able to figure it out.

Also did your forge come with a new hose clamp for the large dump pipe?

Not telling your that is the issue but it will fix the small issue you have.

Also The shims go on the top side of the valve. The side that doesn't move to dump pressure. Was there a lot of white grease on the internals of the valve? if not then you could have a sticky mess in there. That can get fixed by doing a valve service and regrease the seals.

 

[VTEC8YA]

Yea.. I puchased new hose clamps for my forge when i installed. The stock ones just seemed a little to loose for my likings.