boost problem. 6psi falling to 2psi....

[smg944]

well i have a pretty weird boost issue. it builds 6psi of boost by 4k rpms then falls to 2 psi by 6500 rpms. did a boost leak test and found a leak in the ic which i sealed. i still hear a slight leak near the intake manifold and the injectors. but doesnt seem like it would cause this much of a boost drop. i looked through some threads and didnt find a similar boost problem. i have read on some wastegate problems also so i checked the acutator and arm. everything seemed ok. any ideas of what it could be? thanks in advance.

 

[grnchevyz]

i still hear a slight leak near the intake manifold and the injectors. but doesnt seem like it would cause this much of a boost drop.

You would be surprised at how little of a boost leak you need to kill your performance. Remember, if it builds boost and it has an alternate way to exit it'll use it. Fix all leaks and then see what happens.

Could also be your BCS. (Boost Control Solenoid) It seems to me that stock you should be seeing 10-11PSI and full spool should be around the 3500-4000k rpm.

Please fill out your vehicle profile to help us point you in the right direction quicker.

I am only assuming you are 100% stock here.

 

[smg944]

sorry about that, i still need to setup my sig. well i have a 91 gsx, evo 3 16g, turboback exh, safc 2, intake, walbro 255, stock other then that. where is the bcs? i think that could be it considering the turbo line goes directly to the wg actuator. if there is a bcs shouldnt it tie into that line? i am new to dsm's and the way they work. btw thanks for the reply.

 

[grnchevyz]

Here's a diagram showing the BCS or Wastegate Solenoid.

Also, do you have a AFPR (Adjustable Fuel Pressure Regulator) Cause if not, yo're definitely overrunning your stock FPR with a 255.

 

[smg944]

i found that wastegate solenoid disconected. where does it connect to? by the diagram looks like somewhere on the intake. i have a k&n filter so i dont have the air cleaner body.

 

[grnchevyz]

You should have a spare port on the stock intake pipe for the Solenoid. the top side goes there, the bottom side to the wastegate actuator. OR if you want to see if that's your problem, run a line from your wategate actuator and T it off on the RIGHT nipple on the intake manifold. Go for a ride, you should see 10-11PSI. If indeed you see this, go ahead and connect the BCS back to the wastegate. Make sure you use the RIGHT nipple and not the LEFT one that goes to your BOV.

Also, you didn't answer the AFPR question? Do you have one with that 255 pump?

 

[smg944]

my wastegate solenoid has one of the nipples cracked off. so i cant connect it. i put on a manual boost controller and it did nothing even with it all the way shut. am i connecting it wrong? i went from the turbo out elbow to the bc then to the wastegate. and it did nothing.

 

[grnchevyz]

Your boost solenoid is broken. Get yourself a Manual Boost Controller or an Electronic one to replace it.

Slowboyracing.com $50. when calling ask for Jon Nye (ext 12) He'll do you good.

Once you have it, we can connect it. not only will it give you what you should see stock, but also the ability to turn it up a notch or 2

You still haven't told me if you have an AFPR for your 255 fuel pump. That is a crucial piece if you don't have one.

 

[smg944]

i already put a boost controller on and it didnt help. btw i dont have an afpr. i need to install one. but if my afrs where that rich wouldnt i bog out? it does in my rx7 anyway. i am thinking something with the wastegate actuator?

 

[fp-green-95tsi]

Is the wastegate arm is connected to the flapper still?

 

[smg944]

yes the wastegate arm is still connected.

 

[smg944]

how can i test the wastegate actuator? possible that could not be holding?

 

[grnchevyz]

Hook up a vaccuum line to the wastegate nipple and the other end to the RIGHT nipple on the intake Manifold. You can also T the fuel pressure regulator vaccuum line.

If all goes well you should see ~10PSI

Edit: Sorry forgot you were 1G...there maybe no right nipple on the IM...in that case do the FPR 'T'

 

[smg944]

tested the wg, it doesnt open till 11 psi, its fully open by 12 psi. i replaced the injector o-rings, and intake gaskets. put in a new upper intake hose. i also ran some sea foam through the engine and noticed some smoke coming out the manifold. so i am guessing my manifold is cracked to the point of losing this much boost? if its not that i am lost...

 

[Dream On]

Check to make sure the boost controller is hooked up right. For ones with the knob on the side and looks like a " T ", hook the wastegate line into the bottom, and the boost source (like from the j-pipe or BOV line) to the opposite side of the adjustment knob. If this is right, then I'd look at your intercooler. They seem to corrode where the inlets are and get holes in them. If there are holes, jb weld the entire pipe.

 

[91etalon]

its not a boost controller problem or a boost leak. your problem is most likely an exhaust leak before the turbo. check to see if your manifold to turbo bolts are on tight. they have a tendency to come loose. if thats not your problem then your wastegate is stuck open. check the actuator to make sure its still attached to the actual wastegate.

 

[smg944]

i also believe it is comming from the manifold. the only thing is that i cant hear it at all. i figured a manifold leak would be fairly loud. i think my wg is shut, ill get a pic and post it up. when i did the boost test it didnt move till 12psi. also i have tried removing the boost controller with no luck.

 

[91etalon]

its not shut if anything its open. if it were shut, you would build unlimited boost. if you cant find a leak on your manifold then its not that. From what youre describing the leak would be obvious. try removing your o2 housing and see if your internal wastegate is broken in anyway.

 

[smg944]

if the wastegate was always open wouldnt it build more boost by redline? it boosts to 6 psi by 4k rpms, and then it drops to 2 psi by redline. i know there is a manifold leak, it just seems like if the boost was leaking that bad, i would hear it. when i get the new manifold, i will also check the o2 housing. thanks for the advice.

 

[91etalon]

no, you build boost while the wastegate is closed, once it opens the boost stops. So if youre not building boost you either have an exhaust leak at the manifold or the wastegate is open. You saying you can't hear an exhaust leak is leading me to believe its the wastegate thats stuck open. oh yeah dont check the o2 housing, check the turbine housing.

 

[smg944]

ok got the new manifold on with new gaskets, also checked the wg and it was shut. no luck, i have better boost responce, but no full boost. same thing 6psi by 3500 rpm and 2 psi by redline. could the ecu be pulling timming or something? i am pretty stumped on this now. i am going to do a boost test again to see what that shows. i dont hear any kind of leak though....

 

[91etalon]

ok got the new manifold on with new gaskets, also checked the wg and it was shut. no luck, i have better boost responce, but no full boost. same thing 6psi by 3500 rpm and 2 psi by redline. could the ecu be pulling timming or something? i am pretty stumped on this now. i am going to do a boost test again to see what that shows. i dont hear any kind of leak though....

when you removed the o2 housing did you check for leaks around the wastegate? or any cracks around it? The stock wastegate actuator is set for 8.5 psi i believe so it should absolutely not boost any less than that. if you say the internal wastegate is good and has no cracks then your actuator is probably the problem. Try replacing that.

 

[oldman]

1. What is the purpose of your SAFC?

2. No AFPR = FPR overrun with the 255 pump.

3. What did the boost gauge registered on the best of your boost leak test?

4. Have you carefully check the turbine housing for cracks like already suggested?

5. When you said the wastegate doesn't open till 12psi, how do you know this, did you apply pressure to the actuator.

6. Have you check the turbo itself for free spin and shaft play?

 

[smg944]

actually now that you said that there was a good crack there. it was about 1.5" on each side of the wg opening. but it was fairly fine. i just dont understand why its droping when i get closer to redline. i would figure it was stay consistant at 6psi.

the best boost test came out with 13 psi. i couldnt hold any higher. but that was before i redid the injector o rings. i havent checked since.

when i did the boost test is when i noticed the wg opening at 12psi.

the turbo spins freely with much shaft play.

 

[smg944]

ok here is something new. i did a timing check and when my cam notches are at tdc posistion, my crank notch is at 25-30* btdc. now, there is a white paint spot that reads tdc with the cam gears. is this how it is saposed to be or did someone paint the white spot on there? also how do i know the timing is not all messed up? my idle is a little low but seems to be ok along with my normal driving rpms. lasly could the timing be cause my boost issues?