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Old 12-19-2011, 02:05 AM   #1
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Default Overboosting. Any ideas?

Background: '99 running FM2, Hydra, 2.5in FM exhaust with cat deleted, still sourcing the wastegate can signal/pressure line from turbo cold side housing, running FM's new 8psi wastegate can and bracket, turbo's hot side is ported about half as much as the Begi photos. Car is in need of tune but drives fine ish.

So here's the story. Car hits 8psi like it should, then creeps a hair to 10psi ish at 5k rpm, then just keeps building. At 5500- 5800rpm it gets high enough to hit the Hydra's 15psi boost cut and shut the car down for a sec till I let off. Really tired of not being able to drive the car like it should be. Car hasn't been driven much due to unrelated issues. No manual/electronic boost control, just the boost signal from the turbo to the wastegate can. I've checked that the flapper moves its full range. Swapped the can with an old one and still does it. Only running FM's base map at the moment. Thought it might be ignition timing related. So messed with base timing. Down a few degrees still does it. Up and the car is ....more fun.....but still does it. Though maybe timing could be forcing turbo spool like an unwanted anti lag. I could handle 1-2 psi of creep in cold weather but this is crazy.

Any idea's? Searched the forum but can't find anything. A little about creep here and there but nothing that seems to be on this level.
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Old 12-19-2011, 02:08 AM   #2
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Try changing your boost signal from the turbo->wastegate to directly pre throttle body->wastegate
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Old 12-19-2011, 03:00 AM   #3
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Ok how would this help? Not saying it won't, so no disrespect. I've heard this is good for when the boost drops at higher rpm due to intercooler pressure loss. Just in my head, if I tap my pipe to source signal just before throttle body wouldn't there be in theory less pressure to push the wastegate open? I know there will be enough to do it. It's just I have more boost than I want, not that it's dropping off.

Other question is: My intercooler piping is all FM silicone pipes. Only hard piece is the BOV/intake sensor piece. For this idea that cool? It's only 8in from the throttle. Better to tap in just before BOV or just after? Also If I do try this the pipe is aluminum or stainless is a Lowes brass fitting ok for a long term thing or go crazy and find someone to weld?
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Old 12-19-2011, 03:52 AM   #4
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what happens when you disconnect the actuator altogether? Just keep the flapper wide open and do a pull. If it still does it then you need to port the **** out of that turbo or go ewg
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Old 12-19-2011, 04:20 AM   #5
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^ is my next move, it just got cold out and the turbo was still hot from the last test run. A lot of people have an FM2 or similar. I can't imagine this being a need for EWG. Nothing in my setup is odd or crazy custom. Calling FM tomorrow, but looking for ideas.
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Old 12-19-2011, 04:31 AM   #6
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What's the downpipe look like? Wastegate flapper getting hung up on something?

+1 to a pull with the flapper unhooked.
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Old 12-19-2011, 04:54 AM   #7
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FM cast outlet/downpipe. I can move the flapper through full sweep with it unhooked. I do have a small leak at the downpipe to exhaust gasket. I do mean little, just a small burble at idle. New gasket on the way.
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Old 12-19-2011, 10:02 AM   #8
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FM cast outlet/downpipe. I can move the flapper through full sweep with it unhooked. I do have a small leak at the downpipe to exhaust gasket. I do mean little, just a small burble at idle. New gasket on the way.
Turbulence fail.
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Old 12-19-2011, 12:07 PM   #9
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if anything the turbulance will cause him to make less boost up top, not more.
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Old 12-19-2011, 12:16 PM   #10
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if anything the turbulance will cause him to make less boost up top, not more.
I discovered my DP studs stretched in Arkansas a few years ago when the car suddenly overboosted to the 18psi limit.
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Old 12-19-2011, 01:56 PM   #11
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I'll hurry up and get my gasket here. I trust Hustler's input. I do agree that a "turbulence" would do the opposite, but I've had more bizarre stuff happen in the past with other cars go wrong that made less sense. Wasn't driving the car much, just got it going again, had a few exhaust backfires happen that blew the gasket out, and now this is a way more noticable problem then I remember. So unless a small bang of fuel in the exhaust suddenly made my turbo work way better than it did before, it's worth a shot for a couple dollar gasket. Need fixed anyway.
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Old 12-19-2011, 05:53 PM   #12
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One idea that's being discussed as an idea is my deleting the cat making the exhaust to0 free flowing. 1: did the delete in august I think, didn't do this the little I drove it then. 2:I could maybe see a little creep but not 15psi at 5500rpm on a 8psi wastegate can.
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Old 12-19-2011, 06:01 PM   #13
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One idea that's being discussed as an idea is my deleting the cat making the exhaust to0 free flowing. 1: did the delete in august I think, didn't do this the little I drove it then. 2:I could maybe see a little creep but not 15psi at 5500rpm on a 8psi wastegate can.
That would not surprise me. I could not make less than 16psi in my car with 3" exhaust with the old BEGi set-up.
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Old 12-20-2011, 09:39 PM   #14
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^ This. You are running almost the exact setup I was on my 95 and I couldn't get it under control. I had a full FM2 kit with their 3" dp to a 3" exhaust with just one magnaflow muffler. I sent my turbo to Blouch for porting but that still didn't solve it. I was hitting 17psi by redline. When I called FM, they told me to add a cat/muffler... EWG is the ultimate answer IMHO.
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Old 12-20-2011, 10:16 PM   #15
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Send your turbine housing to BEGi and have them port the wastegate.

I had the same problem with my FM2 setup, took it to a machine shop and had them port it a little bit, didn't even help the problem at all.

Called BEGi up, Steph had me send the turbine housing in, they ported it.

I got the turbine housing back, installed it, problem completely gone. Now holds solid at whatever I want it to - no overboost whatsoever. They did an INSANELY better job at porting it than the previous machinist hat.
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Old 12-21-2011, 02:05 AM   #16
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So just got done earlier checking the timing belt. All was well, one more thing down for ideas on what could cause this. Timing tensioner was a little loose. Well... the belt was. Just cracked the tensioner blot loose let the spring pull it in a hair then tightened. Talked to FM and long story short was recommended to put a restrictor in the exhaust if all checked out well. Thinking along the lines of a gasket replacement with a 2 1/4in hole. I'll cut some aluminum tomorrow and see if it helps. Maybe try a 2in hole and another with a 2.25in hole. I'm hunting for couch change for fun money broke at the moment so needs to be an easy fix/cheap. No monies for a cat to be put in.

Just seems counter productive to put IN a restriction. Just goes against the grain to un-make something better.
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Old 12-21-2011, 02:12 AM   #17
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so did you disconnect the wga and try it?
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Old 12-21-2011, 02:36 AM   #18
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so did you disconnect the wga and try it?
+1. Putting a restriction in defeats the purpose entirely.
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Old 12-21-2011, 01:45 PM   #19
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Disconnecting the WGA is going to be this afternoon. Have left over spine problems from the military and can only bend over around the hood so long. I work better on my back Figure I'll do a disconnected pull this afternoon and if that doesn't give me ideas on the problem then shoving a restrictor in he exhaust is probably my last idea.

Just for a ballpark, a disconnect WGA run should only net maybe 4psi max at redline? Obviously if I still hit 15psi cut without the can connected I'm Fing lost.
Then it's a housing port at begi.
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Old 12-21-2011, 01:57 PM   #20
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forget the restrictor idea. its overcomplicated and completely unneccessary. retarded if you ask me. whats the point in choking up the motor and killing power just to keep pressure in check?

disconnect wga, do pull, if you still overboost you need porting or ewg. the end
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