Hi,

what boost pressure should I get with the stock exhaust?

It's getting to ~6 PSI on accelerating when I try to get it up, but at normal driving it stays around 3 accelerating, around 0 cruising.

It seems that the backpressure keeps the turbo charger from working. What had the engineers at GM in mind when they did the turbo setup?

Stock number will make you want more. Do the boost fooling and the numbers will rise 1-3 psi or more. So while your getting 0-3 psi just driving, it will go to 2-5 psi. Boost will also sustain at 10 psi on hard accel.


It's the wate gate duty cycle not the backpressure. WGDC is 65% at idle and drops from there. Boost fooling takes WGDC to 99.7% and let's the back pressure do it's job.

THX, I'll have to think about that! It's good to know that those values seem pretty normal.

At idle, the wastegate lever is fully up and sits very tight just as it should, but there's a slight vacuum on the intake. Does 'fully up' mean 65% duty cycle?

I've got an EGT gauge too, but it isn't installed yet. I'll put it on before anything else --- overheating the engine would be a very bad thing ...

Lee,


With the pyro you would see how nominal your EGT's are stock (450-600*F). When you fool your boost and sustain 10-15 psi you'll see EGT's at 1000*F and climbing, not to mention IAT's.

The pyro goes post turbo --- I'll have to look up here what was mentioned as EGT limit for that. When it's installed, I'll have to do some towing to find out where I actually am then.

When towing with the broken vacuum pump, I've seen coolant temp getting close to 100C on some inclines, so I turned on the cabin heating and eventually backed off the pedal to stay below 100C. I'll have to find out if she's going to generate more or less heat now with boost pressure, and the EGT will be a better indication of overheating problems than coolant temp.

If I'd fool up the boost pressure, I might run into serious overheating problems and thereby end up with a poor overall towing performance.

Your EGT and coolant temp. will be alot lower with the pot. switch on 12-15 psi and towing than towing with no boost.

That would be cool :)

If I try it out, I'll keep you updated of the results I'm getting.

your boost numbers seem about half of what i had stock.check for leaks around the doughnut gaskets on the crossover pipe. when i changed mine out i picked up about 2 psi. i didn't even know they were leaking until i noticed soot on other parts around the flanges.