Boost creep/spike with bolt-ons?

[97SpyyderGST]

After searching through post after post for an answer, we have only gotten more confused. The car is a 1997 GS-T, automatic, stock t-25, PaceSetter manifold, Apex N-1 catless DP and cat-back, removed boost control solenoid, Dejon upper IC pipes w/turbo XS flange, TXS recirculating BOV. Under acceleration, the car shoots to 24+/- psi and fades back to 10-15 as the revs max out. Sometimes it hits what we assume is fuel cut where power is cut completely.

We have heard the following fixes:
ported/upgraded o2 housing
external wastegate
porting of wastegate area of turbo
leaking/misalligned exhaust components
leaking intake/intercooler piping
malfunctioning/stuck wastegate

We called both the sales and tech line for Turbo Garage today and both said that the exhaust should not cause boost creep with a stock turbo and that an external wastegate would never be necessary with the stock turbo. They are the only people we have ever heard that said it had to be that either we had a boost leak or the exhaust parts had not been lined up or were leaking. Both were completely sure of what they said, though we were not, so we figured we had to consult you guys.

What do we need to check, and how to do we do it? How do you check the wastegate actuator to see if it's working properly? Is there an easy way to check for boost leaks without taking things apart and buying new gaskets? The car is used for autocross and can no longer be run until we get the problem fixed. Thanks ahead of time for any assistance.

 

[oldman]

Sounds like you don't have either boost spike or boost creep, you have all out boost.

1. boost creep = boost hitting a set level first and slowly increases as rpm increases.
2. boost spike = boost hitting a higher level then immediately drops down to disire setting.
3. all out boost = boost shooting straight up and doesn't come down but in the case of T25, it will drop at upper rpms.

Unless you didn't describe the problem correctly, I'm almost certain you have three. However, it's not impossible to have combination of 1,2 and 3. You mentioned you've removed the bcs, how is the actuator hooked up right now?

 

[97SpyyderGST]

You mentioned you've removed the bcs, how is the actuator hooked up right now?

My fault on that. It's the bcs restrictor that was removed, and the hoses were hooked up the same as before. We're going to take a test drive to try to diagnose which of those three is actually occurring, but please feel free to post while we're out

As far as I can remember from driving the car, it fades back out relatively quick, so it may be boost spike.

 

[oldman]

My fault on that. It's the bcs restrictor that was removed, and the hoses were hooked up the same as before.

Test run with the compressor nipple connected directly to the actuator nipple with everything else in between bypassed. If boost holds at about 10-12 psi, either the bcs is bleeding off too much air or there's a leak on the hose that goes from the T to the actuator. If problem persists, you either have leaks on the hose you just used to test with or the actuator isn't opening.

 

[97SpyyderGST]

We haven't gotten to retest with the hoses connected as described, but here's some video clips of what it does. Sorry about the low quality of the video, our firewire isn't working on this computer. It's only like 5 mb, though.

video

 

[oldman]

Kind of inconclusive but I'm leaning more toward boost spike. Although T25 is known to spike but 20+ psi is high. Do the actuator test and post back.

 

[97SpyyderGST]

http://www.jumptronix.com/2g_go_faster/Faqs/WasteGateSolenoidRestrictionFAQ.htm

That is the same page we used for reference to remove the BCS restrictor. It brings up some questions...should we plug the BCS in while we test drive it or not? Is it easy to recognize which hose needs to be connnected to what? We hope to get this done tonight, but we don't wanna mess things up.

 

[oldman]

My plug has been just hanging there for 9 years since I removed the BCS so it would be safe to leave it unplugged.

Connect a hose (use a fresh hose so you know there're no leaks) from the nipple on the compressor housing (on the top of turbo) directly to the actuator nipple (on the bottom) and don't worry about the rest, make sure you tug away any loose hose during test run.

 

[97SpyyderGST]

OK, sorry for the delay but work started to interfere with the car. But, we did the bypass last night and I took it on a test drive to work today. On the way to work it did fine, it was like I was driving a new car (sort of), but on the way home my "Check Engine" light came on. I will be around the computer all day if you were to need any more info on the car to make a "diagnosis" . Thanks alot for your help.

 

[oldman]

OK, sorry for the delay but work started to interfere with the car. But, we did the bypass last night and I took it on a test drive to work today. On the way to work it did fine, it was like I was driving a new car (sort of), but on the way home my "Check Engine" light came on. I will be around the computer all day if you were to need any more info on the car to make a "diagnosis" . Thanks alot for your help.

1. So with the BCS bypassed, you're boosting solid at 10-12psi? Be more detail.

2. Did your boost condition changed again when the CEL came on?

3. Reset the ECU by removing the neg. terminal on the battery, plug in the BCS and see if CEL re-appear.

4. If CEL does re- appear, take the car to Autozone and have them pull the code for you if you don't have a logger.

Post back.

 

[97SpyyderGST]

Boost would hang out between 9-12, but with full throttle I could hold the pressure at 14. You can always throw in the boost gauge may not be reliable factor. When CEL came on nothing changed that I could notcie right away, I am still getting used to a car that doesn't spike to 20+ psi. But I am going downstairs now to plug in the BCS to see if that is the problem with the CEL. Ill post back as soon as I finish. Thanks alot, you have been very patient with us.





EDIT: I do not need to reconect the tubing do I?

 

[oldman]

Thanks alot, you have been very patient with us.

Glad to help.

I do not need to reconect the tubing do I?

No, but I would cap it off so dirt wouldn't get inside in case if you want to use it later.

 

[97SpyyderGST]

Now that the BCSs electrical connection is reconnected the CEL doesnt seem to want to come back on. But, RPMs seem to running about 200-300rpms lower than normal. Other than that, boost is still hanging out in the safe range, if I just slowly work my way to up speed than it will run about 6-7 psi. Only thing that worries me is the RPM problem. Any relation to the BCS by-pass?

Thanks again!

 

[oldman]

What is your vacuum reading at idle? I suspect you have boost leak. Perform a leak test, the real one and see if that will solve the idling problem. You also shouldn't be boosting 15 psi at wot with the just the stock actuator hooked up. This can also be cause by boost leak, which will delay the actual pressure from reaching the actuator, kind of like what the bcs was doing. In any case, everything now seem to point to boost leak. http://www.vfaq.com/mods/ICtester.html