Watching your last video several times I noticed that the noise you have is apparently when the car is cold. The other thing that struck me was that in each instance I heard the noise you were turning left. The first time was after you backed out of the garage and went down your driveway. The second time was when the car stalled. I was wondering if you can remember if you had the steering wheel cranked all the way to the left. If so that brings to mind a couple of things. One the noise is the pressure being relieved in the power steering pump. Two since it is cold it is thicker than normal and is not being relieved quickly enough. Which could cause the belt to slip until you straighten the wheels.

As to it happening when you come up on the clutch. Could you be coming up on the clutch and instinctively turning the wheel.

Just something for you to think about.

YEOW! That works out to about 18 pounds of boost by my calculations!
To convert kilopascals to pounds per square inch(KPA to PSI), multiply the kpa value by .14503773773020923.
No wonder traction control is kicking in..........
Are you sure your wastegates are functioning properly?
If there's THAT much boost, no wonder the airbridge is popping off!
Andy :wavey:

Yeah, could be. I'll have to play closer attention to what I am doing with the steering wheel when I hear that noise. And there is no law against more than one thing making a similar noise, I suppose.

Well, there are suppose to be 10 lb springs in each of the two wastegates. I opened them up and checked the color coding myself. The vacuum lines appear to be hooked up to them running from the intake manifold. I put them back on myself when I put the exhaust back on recently. That's when I found that one of the connections was loose. And I used the inspection cam to check to make sure that the vacuum hose was still on the back of the intake manifold.

I guess I need to put a camcorder in position to monitor the boost gauge sometime. I really don't like taking my eyes off of the road at all when I'm bearing down on the gas pedal.

Interestingly enough, I am looking at a data page in EFILive that shows the values for each PID selected. It stores MIN, AVG, and MAX values. There are two PIDs for manifold pressure, it seems, that are registering PSI. But the values for MAX don't make sense. SAE.MAP shows a MAX of 22.5 psi, and GM.MAPBOOST_DMA shows a MAX of 22.60 psi.

I doubt this is a measure of actual BOOST conditions coming from the turbos, but I'm asking Mike Carnahan about what those values actually mean.

Bryan at LME told me the engine could handle 25 psi of boost easily, but I don't believe the STS turbos can deliver that much airflow to a 427 cid engine. Aaron Scott did have bigger turbo housings put on the turbos, but even so, they are not really very big at all compared to others I have seen.

Certainly the AFR ratio didn't act like it was going way lean because a lot more air than expected was being pumped into the engine. AFR was running around 11:45:1 at the time of boost, which is actually pretty safe and not at all lean.

Well, I got a reply back from Mike Carnahan telling me how much boost was being produced, according to the log file:

Mike apparently thinks I am still babying the car too much. :D

Besides, if it will break the tires loose like it did at 3.62 lbs of boost, what good will it do continuing to push the gas pedal to generate 10 lbs of boost? :hehehe:

Yesterday I got in the T-bolt clamps I ordered, but still waiting on some different diameters of tubing I ordered to tackle the airbridge couplers.

I think you're going to need to get some stickier tires....at the cost of they wear out quicker. But you can't have it both ways. I had Maxxis tires on my CTS V when I first got it. They gripped very well (.96 g's)but only lasted 15K miles. I put Nexxen's on after that but they start squealing at .70 g's, but I have almost 20K miles on them now. Probably have another 5-10K left on them. And I really don't drive them hard, at least not all the time. :D

But with upwards of 800HP you may need racing slicks....:reddevil:

Hah! I tried racing slicks on my GTO way back when, and let me tell you, the term "slick" is well deserved when the roads get wet. I wound up going sideways down a road when it started to rain.

Besides, I think I would rather have the rear tires as the "fuse" in the drivetrain instead of something else that would be expensive to fix.

But all in all, the tires on the car now were supposed to just be a stop gap fix anyway. When Aaron Scott had my car he was constantly complaining about the tires not griping on the dyno drum and wanted me to buy a set of tires from him. Instead I found a passable set of tires and wheels from a guy on this forum, and got them instead. Of course, when I told Aaron I had them, then suddenly it wasn't that big of an issue to him. Quite honestly, from what I have had to fix on the car, I don't see how the car could have even reached power levels for that to be an issue on the dyno anyway. The incorrect throttle body alone (gold bladed LS7 style) would have triggered REDUCED ENGINE POWER conditions. But anyway, I didn't put the tires and wheels on the car till I got it back home. The tires wouldn't be my first choice to buy anyway, but they are better than the age hardened Michelin's that were on the car.

Got a new tune this morning so I loaded it up and took a test drive. Cold startup is still a bit rough. Low speed driving or really any gear when the rpms are around 1,000 has some surging. But the high rpm in gear at low speed isn't there any longer.

Throttle response crispness is much improved but could use some more work, I think. Only wound it out a little bit in fourth gear, but mostly just took it easy and enjoyed the drive.

Showing some AFR spikes where it gets lean in a few spots, usually after light gas pedal pressure at cruising speed with low rpms. Like 18.00:1 or so. Short Term Fuel Trims dip way down into the minus figures at the same time.

Ah, but it's getting there. It's very driveable as is, but still some rough edges that I hope won't take too much time and effort to smooth out. Besides, the more miles I get on the car this was the more it will build up my confidence that the car won't just up and die on me.

For a side note on tires, I'd look no further than the Nitto NT 555R II Extreme...if you want some serious stick rain or shine (well at least some stick in the rain). I know guys that use this tire as their HPDE rain tire and also autocross very well rain or shine. You get darn near R-compound stick'em, but complete streetability...they just won't last long (~10K miles). They also make this in a drag tire if you aren't worried about great corner grip.

Yeah, I had Michelin PS2s on the car originally, and I can't complain about them. After that blow out on Connie's car, I would actually consider run-flats if I could find them in C5 Z06 sizes. Had that happened to the C5Z, the car would have likely had to be towed just to have the tire replaced. And who knows how long to get one in, as likely no one local carries them in stock around here.