Hi guys,

So I was out with my tuner last night doing some street tunes before tonight's Midnight Mayhem racing here in Vegas. I have an 8 lb spring in the 44mm wastegate and have the AEM Tru boost controller. Up until now I've had the A boost setting at 40 (duty cycle). This kept me at a solid 11psi on the gauge. So all is going well for about 3-4 pulls. Then all of a sudden I start getting boost spikes to 13, 15, and even 17.5 psi! At 13 psi I can kinda hear some flub flub flub at the tailpipe, which I am thinking is spark blowout. (Running TR6 plugs gapped at .032). I'm not concerned with the spark blowout because I'm going to be swapping in some BR7EF's gapped down to about .026 soon and hope to keep the setup at 15 psi.

What bothers me is why would my wastegate all of a sudden stop opening? I tried turning the A setting all the way down to 10 and still nothing... spikes. I set it to OFF, same story, spiking. Up until last night, it would limit fine.

Setup:
2002 Camaro LS1 (Stock), + LS9 Cam, 4LShittyE, Stock 3.23 rear
60lb injectors (these were getting to 114% duty cycle at one point last night, during the spikes, normally at 90%)
Walbro 400 in tank with Racetronix Hotwire kit, stock FPR/rail, etc.
44mm Ebay Wastegate
On3 76mm Ball Bearing Turbo, Rear mount
Zeitronix Wideband
Ebay Intercooler
Snow Methanol Injection (2-16psi progressive setting)

The weird thing is, I can go WOT up to 9psi, then back off the throttle to about 45% and it stays between 9-13 psi (foot controlling it vs wastegate). I know that's not the safest way to do it, but we showed no knock even at 17 psi (Timing is way conservative 6 degrees up high).

I haven't gotten under there to check it out yet, but was wondering if anyone had any tips of what to look for?? Obviously loose or disconnected vacuum lines, but with a loose line, wouldn't it work off spring pressure to limit boost? I'm a little confused. Any help is appreciated. Racing tonight, and would hate to blow it / half throttle it.

Thanks!

 

ebay wastegate? Could be a failed diaphragm in the wastegate. Id pull it off the car & see if you can move it freely by hand.

 

Hmmm, would a failed diaphragm prevent the wastegate from opening? or would it rather cause a boost leak? (Trying to wrap head around the concept and all the differnt pressures here... lol)

 

If it were a boost leak it would be very tiny. The gate has a valve guide similar to the ones on the heads.

Sometimes the valve can get burs or other issues that won't let it open smoothly. Need to pull it off and look it over.

 

Okay, so take the WG apart, check the internals, make sure the valve will move freely (when spring is out), and reassemble, checking the diaphragm for leaks too. That's the general idea.

I'm sensing that you guys agree that it's definitely wastegate related. Could it be something with the solenoid? Could a failure of that cause something like this?

 

unhook your boost contoller and route the port on the wg that goes to your boost controller to your intake manifold, it should just go to your spring pressure

 

What does that do? How would that fix the problem? Confused.

 

That would take the boost control out of the loop. If it's still creeps it would defiantly be a wastgate problem.

 

Ahhhh, I understand. Isolate the problem. Got it.

Thanks, guys, everyone, for your input.

 

Update: Hadn't had a chance to run this down until tonight. Turns out it was as simple as the vacuum line had blown off the fitting on the compressor. I guess thats important, right? LOL. Thanks for helping out with ideas guys. Glad I didn't have to replace the WG.

 

"the vacuum line had blown off the fitting on the compressor."

Zip ties are your "bestest friend".................

 

Yup. It was zip tied... but I had been on for over a year. Not sure how it came off. A fresh new zip tie is on it now. Tight! All the other lines are zip-tied as well.

 

use proper hose clips !