eaglefreak138

Well my problems from my other posts have been solved. Anybody who is tuned whether its GM Stage 1 or aftermarket and is experiencing higher vacuum while cruising off the throttle and fluctuations in boost without explanation should check the lower map sensor and the plate that is mounted onto on the lower charge pipe. I have read this happened to a couple people but not many but I must have been losing boost through a crack around the mounting plate for the past couple weeks and it finally gave way. I have a big rectangular hole in my lower charge pipe and the map sensor was hanging from another set of wires above. To the dealer I go on a flat bed tomorrow.

whopper

Good find!!!! Hopefully that is the end of the problem. :)

SS fan

Cool beans...didn't think it could be the Forge....

eaglefreak138

Same as the Cobalt SS thread I found online. The MAP is still bolted to the plate and the plate(plastic weld i guess) blew perfectly leaving the perfect hole for the plate. PITA having to figure out getting a tow, getting my daughter to school, getting to work all not knowing if the part is in stock since it's a Sunday so I'm not sure if I'm getting a rental or just a ride back and forth.

I really don't know why GM would make a pressurized system out of plastic piping especially if they are offering GM upgrades to push boost levels. Since I don't see very many having this issue I'll chalk it up to one of the few defective pipes and hope the next one holds.

firemangeorge

If I recall correctly, when you 1st got the GMTU, you had an issue with the contact between the lower Tmap and AC compressor? Then you had the IC washer/shimed for clearance?

So. If that was the case, you could have damaged or cracked the plastic casing through that early contact. Before you moved the IC.

Just trying to theorize on how that plastic plate could just blow out. I think maybe it got a little help from the previous contact. Maybe cracked it or loosened it.

eaglefreak138

I was thinking the same. Not positive.

I forgot a little bit what it was like dealing with all the issues when I was moving my '99 Grand Prix since my cars since have been stock. Now it all comes back to me lol. You gotta pay to play.

eaglefreak138

Ok, so the SS should be done tomorrow. That being said... I don't have the money to go upgrading pipes.

Should the factory charge pipes hold up to the GM upgrade's higher psi considering that's what they're replacing the broken one with?

Should a Forge bpv work Ok with the stock piping or does it run me the chance of blowing the sensor out of another pipe?

firemangeorge

I'm still running the stock pipes on mine. No problems.
The Forge BPV shouldn't be a factor. Not like it increases the boost. It just makes the boost work efficient in theory. Plus it's "adjustable" with the springs if you do tune it and start getting higher boost numbers.

eaglefreak138

Email from my service Mgr...
"It's done. Roger got 25 lbs boost on the roadtest. Washing it now. See you this afternoon."

:-) gained 2psi it seems and that's with the stock bpv!

eaglefreak138

Well, got her back. Sure am boosting up in the 25psi mark. Areas of the power band that I thought were weak spots have been remedied.. I.E: 40mph-WOT and the rest has just flat out improved. I guess I wasn't getting the full benefit of the GMTU due to the leak. Since it looks to be in great shape and handling the boost so far, I'm gonna keep running the stock valve and see how it goes then switch to the Forge to see if there's a dramatic difference. I'll decide then if I want to keep or sell the Forge bpv.