Can you solve my boost mystery?

[Bluechulappa]

First off let me say I searched, but no information I have turned up so far has helped me solve my problem.

The PROBLEM:
My car has overboosted since before I can remember. I have tried using a manual boost controller to set the boost at the lowest setting possible but I would still hit fuel cut. I then bought a Greddy Profec B electronic boost controller and I have set the boost once again to the lowest possible levels and still hit fuel cut like no other.

I recently rebuilt the motor so I figured I would use no boost controller to try and achieve a stock boost level for break in... still hit fuel cut in every single gear and now at 4000rpm. Even in fifth gear.


Mods:
Apexi Intake
935 motorsports 3"DDP recirculated
3" Test pipe or 3" Cat
3" HKS sport turbo exhaust

Now I know the BPU mods will raise the boost naturally, right? Is there a way for me to run 10 pounds or less of boost? Or am I at the final stage of BPU and now I have to get fuel mods?

Is my wastegate bad? Boost leak? Is this normal? I just can't figure it out. I respect fuel cut cause I know it prevents the engine from destroying itself from over boost but I want to run less than fuel cut.... even if it's stock levels. IS IT POSSIBLE with the mods listed?!?!?!?!?:cry:

 

[87n/a_supra]

same thing happend to me, check the vacuum lines to the wastegate make sure you have everything hooked up right. the guy i got mine from had the powersteering idle up vacuum line hooked to the waste gate. get back to me if that helps.

 

[Bluechulappa]

Yea the lines are run correctly.

 

[87n/a_supra]

do you have an aftermarket boost gauge in it if so how much boost are you running

 

[Bluechulappa]

Yes I have a prosport boost gauge. It mostly spikes and hits FC at 12psi on the gauge.

 

[87n/a_supra]

im afraid you have a tough one there sir.

 

[JonoTurbo]

You shouldn't be hitting FC with those mods at 'stock' boost. Check your wastegate actuator to see if it actually works, also make sure the wastegate isn't frozen shut or anything.

You don't have a boost leak because then you would be running too little boost, not too much.

 

[87n/a_supra]

^^ what he said lol. he helped me fix mine, like i said i had the same problem.

 

[dumbo]

I got a dp off ebay and it stopped my WG from opening, but one from 935 I cant see that being a problem, i would physically check your wg/actuator, put regulated air to it and see what presure it opens at, i hit 15psi because of my issue on a GE block/pistons.... :nono:

 

[mk3tattoos]

you can drill out the plug on the afm and back out the screw alittle and see if that helps out. but it sounds like something is not hooked up right.

 

[Bluechulappa]

At what pressure should the wg open? Cause I have a spare wg and it opens easily when I hook it to a bicycle pump. Not so much the wg I'm running on the turbo. It was hard to push open with that or at all?

 

[nightmare]

If you figure it out.. please post up your findings on this. I'm having similar problems with my car. And I have my controller turned all the way down. My car does the same thing every gear spikes around 12.5lbs and hits fuel cut. But mine surges when doing half throttle take offs. I have about the same BPU's as you. The only thing I've changed recently was I adjusted the TPS and replaced the turbo with another used stock one. Are you still running the stock BOV?

 

[supradjza80]

I have heard of issues with certain DDP's, even some BIC DDP's that can cause the wastegate to get held shut or not to open as far as it normally should.

1st - you should take any boost controller off the vehicle and just run off the wastegate, the controllers can only make the boost level higher then the base wastegate boost, not lower. The wastegate sets the minimum boost pressure.

2nd - sounds like your boost is actually spiking (somewhere between 10 and 15 psi is the normal FC location on the stock turbo with those mods) so it is very unlikely you have a boost leak, but it doesn't hurt to check it. My car hit fuel cut with very similar mods but does it at 8/9 psi...I still need to find the boost leak. (somewhere in the 16 year old IC pipes i am guessing)

3rd - you have a DDP so you should easily be able to tell if the wastegate is opening at all or if it is closed the whole time. If you don't hear it open and the car is hitting 12.5psi without a controller on it, you have a problem with the wastegate, or you have interference between the gate and the DP.

hope this helps.

Dave

 

[Bluechulappa]

I have heard of issues with certain DDP's, even some BIC DDP's that can cause the wastegate to get held shut or not to open as far as it normally should.

1st - you should take any boost controller off the vehicle and just run off the wastegate, the controllers can only make the boost level higher then the base wastegate boost, not lower. The wastegate sets the minimum boost pressure.

2nd - sounds like your boost is actually spiking (somewhere between 10 and 15 psi is the normal FC location on the stock turbo with those mods) so it is very unlikely you have a boost leak, but it doesn't hurt to check it. My car hit fuel cut with very similar mods but does it at 8/9 psi...I still need to find the boost leak. (somewhere in the 16 year old IC pipes i am guessing)

3rd - you have a DDP so you should easily be able to tell if the wastegate is opening at all or if it is closed the whole time. If you don't hear it open and the car is hitting 12.5psi without a controller on it, you have a problem with the wastegate, or you have interference between the gate and the DP.

hope this helps.

Dave

I agree with you on just running the stock vacuum hose for the wg without a boost controller. That's how it SHould work! For me I had better luck with my ebc plugged in. The boost came on less hard and I got it to redline once by accident without FC.

My ddp is recirculated back into the exhuast so I cannot hear it.

I think I may test it out by putting a different wg on the turbo to see if thats the problem. Any other suggestions? So this isn't normal to be hitting FC with these mods and running without a boost controller right?

 

[supradjza80]

Is your wastegate shimmed? If not the base boost on a stock turbo/wastegate is 6.8 psi. So if you are hitting 12 lbs without any other boost control you have a problem and that is not normal. Some people report higher boost readings from from the exhaust upgrades but still no where near 12. my car with the wastegate shimmed (5 washers), the DDP and straight out exhaust was 8/9 psi only.

 

[Bluechulappa]

Is your wastegate shimmed? If not the base boost on a stock turbo/wastegate is 6.8 psi. So if you are hitting 12 lbs without any other boost control you have a problem and that is not normal. Some people report higher boost readings from from the exhaust upgrades but still no where near 12. my car with the wastegate shimmed (5 washers), the DDP and straight out exhaust was 8/9 psi only.

No my wastegate is not shimmed. And yea without a boost controller it goes to 12 or past to FC. So think it's the wastegate?

 

[supradjza80]

No my wastegate is not shimmed. And yea without a boost controller it goes to 12 or past to FC. So think it's the wastegate?

based on the above information yes, I would check the wastegate and also make sure the DP isn't the real cause of the problem (IE - preventing the wastegate from fully opening or opening at all). I am going to guess the problem most likely is caused from the DP.

Did this problem occur with the stock DP? Or did it start occuring once you had the 935 motorsports downpipe. And as an FYI the 935 piece is the same as the eBay DP.

 

[Bluechulappa]

Honestly I dunno. I haven't had the stock exhaust for about 2 years since I got the car. I'm pretty sure the DP is not causing the wastegate to open fully. Plenty of room in there when I looked last.

My engine and turbo had 197,000 miles on it and had sat in a warehouse for 9 years so could it just be old worn wg? I just completed a fresh rebuild but didn't have the funds to do the turbo at the time.

 

[ilovemysupra]

You shouldn't be hitting FC with those mods at 'stock' boost. Check your wastegate actuator to see if it actually works, also make sure the wastegate isn't frozen shut or anything.

You don't have a boost leak because then you would be running too little boost, not too much.

 

[Bluechulappa]

Yea at this point I'm pretty sure it's the wastegate malfunctioning. I applied pressure to it with a pump and it barely moved but I dunno how much pressure it needs to move. My spare wg moved with just a tad of pressure but it's also not having to open the wg door...