GLH dogs out under full throttle

[ajakeski]

I took the GLH out for it's first trip longer than a couple blocks today. It runs great, but if I go wide open it feels like it cuts out at about 4000 RPM. The boost gauge shows 12 pounds of boost when it does this.
If I go easy on the throttle and ease it up in revs, I can get things closer to 5000 rpm without anything cutting out.
This is my first turbo, so I'm learning as I go.
It feeld to me like it's making too much boost too fast and the couputer is cutting things off.
I would appreciate any help.
Here are the specs on the car:
1986 GLH Turbo with Turbo I intake and turbo.
Ported exhaust manifold, 2.5 inch swingvalve, 2.5 inch exhaust, no cat, exits to a one chamber muffler.
MP Logic module #P4529871
Underdrive crank pulley.

[minigts]

I'm not going to tell you this IS the problem, but I was running +20s and had the same issue. Dropped the fuel pressure and it got better the lower I dropped it. Just be sure not to run it too low and use a air/fuel meter if you have one.

[ajakeski]

It's running the stock fuel injectors with the 190 l/hr pump from FWD.

[ajakeski]

Here are some photos of the nearly finished product:

[blk86trbo]

Great looking Omni!!! Cam timing off a tooth?

[ajakeski]

Some research shows it may be the throttle position sensor. I'll try a new one tomorrow.

[onerippinturbo2]

hey, very clean Good Looking Heap. i would go the tps way as well.

[OmniLuvr]

that is one clean omni! wow, anyways, how accurate is your boost gauge? it almost sounds like overboost to me, so are you running t1 log intake or are you running blow through with an intercooler? i think logs overboost at like 10 or 11 psi, which is pretty high without an intercooler anyways.

so does it just shut off or kind of cut-out/misfire? and can you rev it up to a higher rpm without boost, or does it only cut-out after 10 psi? and what are you using for boost control?

do you have any pics of under the hood?

[cordes]

Great looking Omni!!! Cam timing off a tooth?

I too would think the cam timing could use a second look.

[ajakeski]

It's a straight turbo I log intake, no intercooler. When it cuts out, it's like the rev limiter has kicked in. It's like it hit a wall. This happens at about 4000revs. If I go easy, I can rev over 5000 rpm and use the boost.

[cordes]

It's a straight turbo I log intake, no intercooler. When it cuts out, it's like the rev limiter has kicked in. It's like it hit a wall. This happens at about 4000revs. If I go easy, I can rev over 5000 rpm and use the boost.

I might think that it is overboost, or perhaps pulling timing severely due to detecting knock then. Pull the codes to see if you get an overboost code.

[roachjuice]

holy sh!t!!! good looking omni!!!! +1 on the overboost. turn the boost down a bit.

[ajakeski]

The only controller is the computer. The wastegate actuator is stock too.
Should I use a grainger to dial it down? Or maybe go back to the original computer?

[turbovanman²]

It's a straight turbo I log intake, no intercooler. When it cuts out, it's like the rev limiter has kicked in. It's like it hit a wall. This happens at about 4000revs. If I go easy, I can rev over 5000 rpm and use the boost.

Back off the boost, if it doesn't go away, I would guess at a bad MAP or TPS.

[ajakeski]

Any suggestions on how to dial back the boost?

[cordes]

Any suggestions on how to dial back the boost?

You can run direct manifold vac to the WG can. That should net around 6-7PSI.

[shadow88]

IF it's overboost it will set code 45. IF it's not there, there's no need to look in that direction. The OP never mentioned if the new tps made it into the car and if the cam timing was checked. It sounds like it's off to me too. Nice looking GLH!

[Turbodave]

Andy, my first turbo car did the same thing, and cam timing was my issue. give me a call if you need any help troubleshooting, could probably swing by one evening during the week.

Dave

[ajakeski]

I put the original computer back in. Runs like mad now.
What are the thoughts on the FWD stage I ECU? I'm thinking that may be the next mod.

[turbovanman²]

If you've converted over to 87 wiring, the MP stage II is the best computer from what I've seen and heard. www.boostbutton.com can easily make you one, or I guess he can do one for the 86 LM.