Boost leak or other?

[joesansone17]

I have a 1997 GS-T Spyder. When I drive regular, I get good boost and I can shift at 4500rpm. The more I get on the gas the car begins to stumble and backfires at about 2500 rpm. Basically it feels like the car wants to shut down. Ive gotten some suggestions of boost leak and some of a fuel pump. The guy that owned the car before me did a boost leak test on the intercooler piping but found nothing. But who else had this problem and what did you do? thanks.

Some Facts of the car:

86000k
Greddy uicp and licp
Hks ssqv (vented)
hks 3in downpipe
3in testpipe
greddy SP catback
K&N filter and aluminum intake

 

[skinnykenny84]

Do a tune up, sounds like either A) you are getting too much fuel or B) not enough spark.

It really sounds like the ignition is missing. Probably because you fouled them due to the vented BOV, go with NGK BPR7ES plugs gapped to about 0.026". Magnecore 8.5mm wires, etc.

Its actually hard to determine your problem without knowing if you are talking about a stutter or true fuel cut.

who are you replying to exactly?

 

[skinnykenny84]

Which means you still don't fully understand what triggers fuel cut. If you understand that fuel cut is triggered by your MAF reading, why would you not understand that you're hitting fuel cut at 15psi (higher maf reading) but not 13psi (lower MAF reading).

Ok Im with you now, just had to read the bouncer thing again. Well give me a yes or no on the maf. Can a bad maf cause fuel cut? If that were the only problem?

 

[kenamond]

Ok Im with you now, just had to read the bouncer thing again. Well give me a yes or no on the maf. Can a bad maf cause fuel cut? If that were the only problem?

Reread oldman's post #18 in this thread where he's listing things that can cause fuel cut. Note #2 in the list.

 

[oldman]

Well give me a yes or no on the maf. Can a bad maf cause fuel cut? If that were the only problem?

Yes.

 

[joesansone17]

OK, I found out my car has a garret fp-big 28 turbo. Before I peaked 17psi in 3rd gear usually. I turned the boost down to 13psi and now I can shift at about 4500 rpms in every gear now. I take it that the turbo that is on my car may not be the best turbo for me now right. I read up on the turbo and it says it gets full boost from 3000 rpms to redline. I was hitting constant 15 psi at 3000. could this be a problem?

 

[kenamond]

OK, I found out my car has a garret fp-big 28 turbo. Before I peaked 17psi in 3rd gear usually. I turned the boost down to 13psi and now I can shift at about 4500 rpms in every gear now. I take it that the turbo that is on my car may not be the best turbo for me now right. I read up on the turbo and it says it gets full boost from 3000 rpms to redline. I was hitting constant 15 psi at 3000. could this be a problem?

That was confusing.

What do you mean: "Before I peaked 17psi in 3rd gear usually." A boost spike?

And what is the significance of: "I turned the boost down to 13psi and now I can shift at about 4500 rpms in every gear now." You mean you can't run higher than 4500rpm without a problem? You should be able to run to redline if you don't have any problems, and that's at 7000rpm.

And: "I take it that the turbo that is on my car may not be the best turbo for me now right." The FP Big28 will get you to the 350hp mark if you have the supporting mods and tune. Do you want to go past 350-400hp? The FP Big28 is certainly not too big for any DSM. If you're running into fuel cut problems, you can turn down the boost. If you have problems at 11psi boost, it surely isn't fuel cut.

And finally: "I read up on the turbo and it says it gets full boost from 3000 rpms to redline. I was hitting constant 15 psi at 3000. could this be a problem?" The fact that the B28 gets full boost at 3000rpm is a good thing for many folks. This usually means that it doesn't pull as hard at higher rpm (like 6k+), but many folks (myself included) bought a B28 for that feature. The fact that you were hitting 15psi at 3000rpm is not bad. That's what the turbo should do.

The bottom line is that you need to figure out what's wrong with your car. It doesn't sound like the turbo at all. Either you're trying to run too much boost and hitting fuel cut or you've got other problems. Figure out which it is.

Do a proper boost leak test and fix all boost leaks.
Check your plug gaps.
Make sure your boost is not set too high for your setup.
Get a logger.

Basically, check into the various possibilities that several of us have already told you about.

Good luck.

 

[chanley talon]

I would check your tps sensor as well and timing . It sounds like you also need to modify your maf if you havent already . Just a suggestion!