Boost doesnt stabilize

[Crazybobmundo]

Ok so Im done with my NA-->T Swap and Im using the grey harness in my 87, works fantastic. All gauges are operational. Headlights work now after some alteration if anyone read my previous posts when I was doing my swap.

But anyway I bought a new boost controller from ebay (who cares its just a check valve) but I think it might be inop. I adjusted it so it boosts 11-12 psi but when I gets there it just goes down to 7psi again.

I was wondering does that mean I have a boost leak? the boost controller is inop after 12psi? is the factory BOV leaking? I need help I want my 12psi...

Or is this normal and I just dont know since I never owned a turbo.

 

[MKIIINA]

its normal for boost to fall off around redline, but that seems to be a large drop off. this maybe due to an inefficient exhaust (ie stock), exhaust leak, boost leak, or a weak wg actuator.

you can add some shims to the wg to help hold it closed for longer and stabilize boost but might lead to FC.

 

[Crazybobmundo]

its normal for boost to fall off around redline, but that seems to be a large drop off. this maybe due to an inefficient exhaust (ie stock), exhaust leak, boost leak, or a weak wg actuator.

you can add some shims to the wg to help hold it closed for longer and stabilize boost but might lead to FC.

Well I have shims already on the wg. I also have a 3" Dp with factory cat back and a grape fruit lancher as a tip.

Also I doesnt do it at redline, it does it way before.

Exhaust leak...that might be one problem...I think I do have one of those. Ill keep checking. Weak waste gate actuator maybe...

The engine has like a million miles on it too so the turbo is probably worn too much. Oh well Ill live with it untill I decide what I want to do with the car.

 

[Fletch124]

Your problem is the ebay boost controller. We tried one on my buddies mk3 and we couldnt get it to hold boost for anything. We took it off and shimmed the wastegate instead and now it holds 10psi all the way to redline.

 

[Crazybobmundo]

Your problem is the ebay boost controller. We tried one on my buddies mk3 and we couldnt get it to hold boost for anything. We took it off and shimmed the wastegate instead and now it holds 10psi all the way to redline.

Hmm. Well how many washer or whatever did you use? I shimmed mine but you would think that even with the boost controller it should stay at 10psi because the shimming puts the new MAX pressure to 10 am I wrong?

Or theoretically should it do 10 when the BC is removed from the system.

I just figured even if the MBC is inop that the shimming would be doing its job. But its at 7...

Hope that makes sense to someone. Regardless I will remove the MBC and see what the max pressure is after that.

 

[Crazybobmundo]

BTW, Fletch124 it was you that posted on an old thread that you hooked it up backwards on your friends MK3...

I did that and it worked and overboosted to 20psi because I didnt turn the knob the otherway. It was all the way closed but now Im 1 click up from fully closed and it still does barely 11 then drops.

So I guess we had the same problem almost. Ill remove it and see what happens.

 

[boogum7]

Buy a ~$20 boost controller from Dr. Jonez on the forum.

i bought one and now I it 10psi steadily until redline. :biglaugh:

 

[CajunKenny]

For what it's worth, my wastegate is shimmed with three washers (I forget the thickness) and mine boosts to 11 on 70 degree+ plus days without fuel cut. On colder days, she starts creeping up to 12-12.5 and fuel cut shows her ugly head!

 

[87witmoreboost]

Sounds like a classsic case of a bleeder boost controller. Instead of a ball and spring which leaks a consistent pressure, I bet you are running a bleeder boost controller. It basically lets a certain amount of air by, in a really inconsistent way.

Buy a Dr.Jones MBC for sure. $30 shipped and you'll hold your boost wherever you want.

I'm also right over in Pelham - prob 10 mins from you.


Edit: On other thought, how long is the tube from the boost controller to your wastegate? If it's long, your vaccum line will have a slow response to tell the wastegate to open. You'll initially boost high, and once pressure has equalized, you'll be at a lower pressure.

Again, get a Dr. Jones MBC and make a real short tube from it to the wastegate.

 

[Crazybobmundo]

Pelham huh? You should show off your supra someday then.


The vacuum line is pretty long, so yeah thats probably where my F-up is. The boost controller is actually located next to the IC hole on the fender wall. Ill try shortening that and see what happens.

But I cant buy anything right now Im broke. Thanks for everyones input.