2G Car spiking @ 4K rpms and then blowing off & backfiring.

[95GSX400]

I have a 95 GST that has been converted to a GSX. It's run off a black box ECU, e85, built from bottom up. Hans 20g turbo with a 9 blade adjustment. Obviously internals are built, car is dyno'd at 400hp at 30lbs.

HERE IS MY ISSUE, when I lay into the gas it will boost fine till 4-4.5k rpms then blows off and back fires. Now what confuses me the most is that is real only in 1,2,3 and a little in 4th. I do not have a catch can yet (which I think my be my problem), I'm reading 14.6 on my wide and it feels like it's getting a lot more fuel than air. I'm new to the DSM world so any advice will help.

Well between 14.6 & 15.4 on the wideband.

 

[Dsmkauai]

14.6 when WOT? That's way to lean bro if that's the case. Your going to melt things if your not careful. Did your ECU reset or something? Need more info also it would really help if you fill out your profile.

 

[95GSX400]

No I didn't reset the ECU, sorry I'm on mobile so I will fill it out when I get to a pic. Car is running, eagle rods/je pistoms, head has been redone with 272 cams/Evo 9 camgears. It didn't do this when I got it, it started doing it when I ate a STI alive from a dig. Any advice on where to start?

 

[pauleyman]

Youve made no changes since racing the sti?

 

[95GSX400]

Zero

 

[jakk220]

What PSI are you at when it starts happening? And what were your AFR's at full boost when you raced the STI and it was running good.

 

[pauleyman]

What do you mean blows off. And why would you think its a catchcan problem?
What have you checked?
Feels like its getting more fuel than air? What on earth does that mean?

Check spark? Mechanical timing? Compression? Have you checked anything? Does it idle? Does it free rev to any rpm? Does it drive at part throttle ok? To what rpm?

Any objective info would be helpful to diagnose your problem.

 

[Dsmkauai]

Did you do a boost leak test

 

[jakk220]

What do you mean blows off.

I was wondering the same thing. If by blows off you mean your blow off valve is opening then you might have a bad blow off valve.

 

[95GSX400]

Yes it idles, it runs fine, as long as I don't lay into it. It will go past 4500rpms if I am not in full throttle. I'm gonna check the spark plugs in the morning. It seems like it's getting to much fuel, hence the backfiring.

I have not done a boost leak test, I live in a place where there isn't much room to work on your car. I plan on taking it to my buddys shop in the morning to see if they can figure it out. It's on e85, tuned on a black box on 30lbs. I appreciate some of your comments but no need to be rude.

I know what I'm doing but this is my first DSM. So please point me in a direction that could make it do this. I'm going insane.

 

[Dsmkauai]

Sounds more like a boost leak to me real simple test and can be done with a simple bike pump or air tank. Owning a DSM or any turbo car it's somthing you should be doing on a regular maintenance schedule.

 

[jakk220]

No one is being rude. We are just here to help you figure the issue out. But if you want help you also have to answer the questions we ask to the best of your ability and take the steps and advice that we give (Especially the Wisemen. Most of them know these cars better than the guys who designed them).

Your first step as stated above by DSMKauai ^^ is to do a boost leak test. You could just as easily not be getting enough air and causing a rich condition with backfiring. A lot of things can cause backfiring. Not just too much fuel.

Please go back and re read the post and answer all of the questions for your best results.

 

[pauleyman]

Yes it idles, it runs fine, as long as I don't lay into it. It will go past 4500rpms if I am not in full throttle. I'm gonna check the spark plugs in the morning. It seems like it's getting to much fuel, hence the backfiring. I have not done a boost leak test, I live in a place where there isn't much room to work on your car. I plan on taking it to my buddys shop in the morning to see if they can figure it out. It's on e85, tuned on a black box on 30lbs. I appreciate some of your comments but no need to be rude. I know what I'm doing but this is my first DSM. So please point me in a direction that could make it do this. I'm going insane.

You said it all right there.....you have not done a boost leak test. Stop diagnosing and perform the test.