Boost Creep...Help needed

[frsh13]

Whats goin on everyone, I have some boost creep problems. My wastegate has like a 6psi spring in it, when I get on the gas the wastegate cracks open but the boost doesnt hold at 6psi. We were trying to figure out what was wrong with it today, we changed vaccum lines going to the wastegate and nothing....still creeps upwards of 16psi.

We checked all the basic stuff today, vaccum lines (good), wastegate spring (red, good). And still nothing. The only thing that got it to hold @ 6psi a little bit better was when we played with the hard/soft setting on my Greddy RS bov, but it still creeps an insane amount. Im thinking since its not the Wastegate it must be the manifold right?? Im running an IAP manifold that has had the dump tube rewelded, Tial 38mm WG, GT32. Someone help me out here, anything im missing? I want to be sure its the manifold before I shell out the dough for a groundzero or AMS manifold.

and i do not have a boost controller

[Florida240sx]

Where is your signal coming from? For my signal it goes like this.

[Florida240sx]

Here we go. Main thing is to make sure your sources are tapped inbetween the fpr line tap and the fpr itself.

[Edub1]

I came off the big line that went to the charcoal can. I tee'd everything into this so it all has a very accurate reading of manifold pressure.

[frsh13]

We hooked the wastegate up to the main vaccum line with a T fitting just to see if it was getting enough vaccum, no change. And the BOV is hooked up with a good source of vaccum also.

[frsh13]

Im thinking maybe because I have a 2.5inch downpipe and 2.5 inch exhaust, could that do it?

[98240]

no I have the same and I dont have any problems

[rotorimp]

I have a handheld vacuum/pressure tester I got at checker. Use something like that to ensure that the gate is functioning properly. Kind of sounds like a weak manifold signal? I do not think a manifold change is going to fix your problem. the dump off of your WG--where is is plumed into or is it open--This is the Tial WG with two nipples? which one are you hooked up to?

[C-Kwik]

Make sure there are no restictions in the dumptube. If the pipe necks down too much or even re-enters the main exhaust stream at a poor angle, it may cause enough restriction to cause boost creep. Confirm the WG is working properly as well.

[Edub1]

You can also test your WG by hooking it up to an air compressor blow thing. I used this to set my boost controller.

Also, with my internal WG unhooked and wide open my car will see 5lbs so if the WG is a small one you might get creep, but 16lbs is just crazy - I'd have to think the WG is broken.

[frsh13]

We pressure tested the wastegate with a hand held pressure tester, it sounds like its opening right when it should be. The dump tube is not run back into the exhaust, its just goes down maybe 8-12 inches after the wastegate and releases to atmosphere. The dump tube does start of with a bend in it, its not even a severe looking bend so I dont think thats it, but im gona pull the dump tube off tonight or tomorrow just to check it out.

[Edub1]

Do you know how much pressure it took to open it? You can T it to your boost gauge, pressurize both real slow and see where it opens.

[klattr1]

IAP manifolds have been known to boost creep...just like some other manifolds have out there as well (Boost Designs)...its more to do with the design/placement/opening of the wastegate on the collector...

the problem with most 240sx top-mount turbo manifolds is that its hard to incorporate a wastegate inlet tube that is parallel or not so perpindicular to the exhaust flow through the manifold...there's usually not enough room between the firewall, shock tower or master cylinder to properly do it...you gotta think how hard its making for exhaust to bypass the turbine (90 deg. turn out of the collector, 90 deg. turn within the wastegate valve area, and then however its routed from there)...

[Edub1]

Yes, a perpendicular WG will vent pressure but not force from gas velocity.

I think one problem might be that our motors are large for 4 cyl motors and should probably use a stage III turbine. As I mentioned, my car will boost to 5 lbs with my Wg flapper disconnected and wide open. I also hear spool as soon as I touch the gas, as in very light load and cruising. This has to shorten the life of the turbo.

I think a stage I wheel is simply to small for a 2.4L. Since I need my turbo rebuilt, I'm going to upgrade to a stage III.

[klattr1]

I think one problem might be that our motors are large for 4 cyl motors and should probably use a stage III turbine.

I think a stage I wheel is simply to small for a 2.4L. Since I need my turbo rebuilt, I'm going to upgrade to a stage III.

upgrading the turbine wheel is only going to lessen backpressure, which isn't going to really help his boost creeping situation.