my car is setup to push 6 lbs of boost. when im driving or just cruising around, boost is fine. but if im ever getting on it and bring it all the way up to 6 lbs, the car stutters and the boost seems to go from the 6 down to 5 or 4 and then back up to 6, and this continues until you let off the gas.

i currently have an exhaust leak coming from where the downpipe bolts up to the turbo thats at the bottom. (bottom bolt is missing) is this the problem?

thanks

Unless the leak is really bad I doubt thats it. Even if it is bad it still shouldn't effect WOT permorance much. It sounds like your running lean. Are you using a 12:1FMU, stock injectors, upgraded pump? Check your air/fuel ratio if you have a WBo2. If not I hope you at least have a fuel pressure gauge so you can make sure your fuel pressure is increasing with boost.

Like SilvrEclips said I would check the air/fuel ratio to see what your at. Then check fuel pressure to make sure your getting enough fuel. A nice set of gauges is always a good investment and will let you know if something goes wrong. Don't think the exhaust leak would cause this unless it's major.

no gauges unfortunately, and walbro 255 pump. my buddy says it seems like theres a hard boost leak somewhere. i removed all intercooler piping and find no holes in anything, none of the welds or hose couplers. so last thing it could be is intercooler which doesnt look the best. it has crushed and wrinkles all over it in different spots. i found an exact replacement on ebay for 10 bucks off of a 1g. im gonna get that and see what happens.

A boost leak will not cause this problem as long as its not major. Our cars do not have a MAF before the turbo like the 4g63s do so even if you have a boost leak the motor/ecu doesn't know it.

Originally posted by Babbz413
no gauges unfortunately, and walbro 255 pump. my buddy says it seems like theres a hard boost leak somewhere. i removed all intercooler piping and find no holes in anything, none of the welds or hose couplers. so last thing it could be is intercooler which doesnt look the best. it has crushed and wrinkles all over it in different spots. i found an exact replacement on ebay for 10 bucks off of a 1g. im gonna get that and see what happens.

Why is the last thing the intercooler? You have no idea what your AFRs are under boost or WOT. You do not know your fuel pressures. What are you using for fuel management? What is your static fuel pressure set to?

You cannot realistically expect to get any solid suggestions unless you give us some data to work from.

I am willing to bet its leaning out. You need to do some more investigating with details as Dave said.

We need to know what setup your running and kind of supporting hardware you have.

Terry

no fuel pressure regulator. im only running on 6 lbs of boost. stock injectors with a walbro 255. i understand my problem may not be very answerable being as i have no afr gauges. but this car has been under this boost setup for 2 years now. and this has just started. its now at the point to where as soon as it starts getting into boost, 1 lb, it does the jittering. so based on the given info, my car has begun to run lean?

Lean condition.

If I'm reading this right, you have stock injectors, but don't have a rising rate fuel regulator. If that's the case, you've been lucky, because that is not a "6 psi setup".

Agreed with ez...

Are you not using a rising rate regulator?

Also, are you using an FCD or Missing Link?

And lastly, you have absolutely no gauges installed?

Originally posted by eclipse982nrRST
Agreed with ez... Are you not using a rising rate regulator? Also, are you using an FCD or Missing Link? And lastly, you have absolutely no gauges installed?

Sounds like a recipe for a bomb :thumbsup

Originally posted by CODE4

Originally posted by eclipse982nrRST Agreed with ez... Are you not using a rising rate regulator? Also, are you using an FCD or Missing Link? And lastly, you have absolutely no gauges installed?

Sounds like a recipe for a bomb :thumbsup

Sure does, but each to their own.

We will still help you find your problem hopefully, but give us some more info...what is your entire turbo, fuel and ignition setup you have going on here?

6psi is safe for stock... internals. Not stock equipment overall. You can run 6-8 or so on stock injectors, but need a 12:1 FMU, like the Vortech. Any higher boost than that and you get incredibly high fuel system pressure. You will melt your pistons if you keep boosting at that level and don't upgrade your fuel system. If/when you get an aftermarket elec. fuel control unit, you can mess with bigger injectors, 1:1 RRFPR, etc. As is though, you can only marginally up your injector size as long as you drop your fuel rail pressure, but even then that won't make a difference as long as you don't have some sort or rising rate regulator. And get gauges for gosh sake! lol You don't need them ricer-visible, but you need to know what your engine is doing!

Partially incorrect Justin.

At 6 psi your fuel pressure is at 110psi (with 12:1 FMU). The fuel pump will max out anywhere from 110-117 depending on age/wear of pump (walbro 255HP). So.....after 6 psi your no longer getting anymore fuel and your leaning out.

eh, I got lucky then! Had a low mile car when I first boosted - ran 8psi and had 12.0/11.8 up to redline. But yes, I agree, older pump looses efficiency so 6 would probably be a better max to say.

i have a 12:1 fmu walbro 255lph stock injectors. set at 6 lbs boost and has been this way for the last years. correct, no gauges except for boost. i wasnt saying that last thing to check for the problem overall was intercooler, i was saying that as far as checkin for boost leak. id say 70% of the fins are wrinkled on the bottom. my car has been sitting in my garage the last 3 weeks and its time for me to start getting at it. what should i do first then? hookup afr gauges? is my fuel pump dying? shitty injectors? shitty fuel filter? all of this possible?

like i said ive been running this for the last 2 years and this all of a sudden started so it hasnt been running lean all the time with the setup.

thanks again...

Pull your spark plugs out and see if they're damaged or discolored. If there just kinda black then your probably fine with fuel and you should look at your map sensor, coil, plug wires, etc. If the porcalin is ripped off of the electrode, YOU HAVE A PROBLEM.

bad spark plugs was the culprit. thanks.

Were the plugs damaged?

Were they white or black?

I wouldn't just stick some plugs in it and drive or it could happen again.

P.S. -You should use colder plugs also for a turbo application.

Just trying to help.

Originally posted by Yo
You should use colder plugs also for a turbo application.

It really depends on your setup, most all are fine with stock heat up to around 12 psi, as long as your AFR's are okay. GST's use 6's up to like 15, but they're better designed from the get-go.