hello
my car ran nice and smooth...and strong.
its basically a buschur stage 4 on 93 octane. i have previously outlined my frustration with the dying out problem on another post.....
about my stages, we put it together in stages so i know where and when my problems started. meaning, we put stage 1 and 2 in, i drove it a little, stage 3, drove it, stage 4, drove it, then custom tune....so i know the dying out thing is not from the 264 cams etc....started after we did the intake and filter.
anyway, when i had car tuned by al, he said u have a slight boost leak....but the car ran very smooth and fine. (the boost leak was caused by the pipe that connects up to where the turbo goes not being completely flat and leaking from the gasket, thanks buschur) i had it ground flat and had zero boost leak.
now when im at partial throttle around where the turbo spools up, the car will sometimes "shudder," and i hear the bov release pressure in quick succession. i dont know how to describe it.
i asked the folks at ams about this, as they fixed the boost leak and have done some other work on my car and they said this is normal....they said at the point where vaccuum and boost are about equal this is what happens....when i give it a lot of throttle, or a little, it wont happen.....its at about 40% throttle. it feels almost like the fuel cutting in and out very fast. u can hear the bov pst.pst.pst.pst very fast then at about 5k its gone....
didnt do this with a slight boost leak, ran just as strong and very smooth....
is this normal??
ill tell ya, im ready to go back to stock and/or just sell this f'in thing....
thanks

 

Well, why not put the stock accordian turbo inlet pipe back and see what happens? It's certainly worth a try considering the multiple 'issues' others have noted w/ these hard inlet pipes.

 

what kind of BOV do you have. that probably has a lot to do with it

 

You are getting compressor surge. The turbo is spooling up too fast and sending too much air into the engine for it to take. You can fix it with a larger A/R exhaust housing. You can also fix it with a surge-ported compressor housing.

It is not your blow off valve. But the valve will often open when you get compressor surge since it sends very high boost spikes into the intercoler pipes.

Compressor surge can damage the turbo bearings, so it is really best to avoid it.

 

thanks for the input you guys.....i would have put the accordian intake back on, but the bov on the hard pipes would have to be moved etc.....i think im gonna have it done anyway.....would this solve my problem of too much air into the engine, shapeGSX?
i could kill 2 birds with one stone.....
can anyone enlighten me on what an A/R exhaust housing is and a surge ported compressor housing??
thanks guys

 

It could be the DV leaking, or there isn't enough "Vacuum/pressure' signal to the DV.. Another thought is have you upgraded your plugs? You might be getting boost spike that could cause a misfire if your using the stock plugs at the stock gap.

Oh and the upgraded filter does cause the MAF readings to be off slightly, at that RPM Range and throttle position, you could be hitting a lean condition (which was happening to me occasionally on cold days)

 

Ok, I assumed that a buschur Stage 4 included a larger turbo. That is not the case. If you still have the stock turbo, then it probably isn't compressor surge. Though your post sure did make it sound like it was.

Yeah, I'd look at the blow off valve as the culprit. Or perhaps some IC pipe clamps are loose.

 

i dont think its clamps...just had the whole system tested for boost leaks and slight leak was fixed. now it shudders under partial throttle at at around 4k.
dont think its the plugs, had those changed when i did the bigger injectors about 1k miles ago. though it does almost feel like an "engine missing" situation, the way the car bucks.
hmmmm. well im taking it in tomorrow.....

 

i hate BoV... cant people see from the various posts in evom that they just arent worth the pain?

 

As much as I don't want to see anyone w/ their car troubles, it really would be a great experiment to see if it turns out to be the BOV or the inlet pipe by only changing out 1 item at a time. It would help MANY people out there. (myself included!!)

I just remember seeing so many threads about irratic MAF readings when a hard inlet pipe had been installed. (regardless of brand) I think the majority conclusion to these mods was that the pipe let too much air in for the MAF to read properly, thus causing the stumble. But the more I think about it, the more I come to the conclusion that it doesn't make any sense at all.

My theory is that the engine vibration is being transmitted to the MAF by using a hard pipe. This is what's causing the mis-readings of the MAF. When I installed the Cusco hard inlet pipe, I noticed how the flexible the accordian inlet pipe was (not to mentin how restrictive it was). Also, the entire airbox that bolts to the MAF rides on rubber bushings to isolate vibration. I remember reading some articles about the WRX having issues with their MAF when an aftermarket induction was installed. Their MAF's used to take a crap, and I believe SCC theorized that it was the vibration that destroyed the MAF.

I'd really like to know if anyone w/ the Samco silicon inlet pipe (if I recall, only Nino sold them) has had any stumbling, part throttle, or idling issues w/ them? Their shape is very close to the designs like the RallyArt, Cusco, AEM, etc hard pipes. If they're not having any problems w/ the Samco unit, then it has to be vibration problems with the MAF.

 

I'm going to say it's definitely the BOV...i have the same setup, and under partial throttle-when my clutch starts to slip- it will studder slightly

 

I think its the BOV, I have a greddy type s. Only other mods are turboback exhaust and k&n drop in filter. Im having the same sort of issue.

 

how do u guys drive it that way?? mine shakes so bad the whole car bucks like a horse......

 

mine seems to be fine, driving with the type S here, only problem i seem to have is the valve opens way too easy, but its supposed to be that way...i just hate the whistle at light throttle around 10-15 in Hg of vacuum pressure, where its not closed or open enough but slight enough to allow the air through causing the whistle. That is my only complaint on mine.

 

this cant be normal........