Got a few questions that I need to clear up.

The stock turbo has like a 15mm internal wastegate, how in the hell can you not get boost creep at higher rpms with a wastegate this size? Is that what the built in fuel cut is for?

Is that why when you get a fuel cut defense you need to port the wastegate to prevent boost creep?

Or do I have this all wrong?

thx

 

I used to own a TII. Under stock boost levels and with stock airflow levels you are fine. Once you go to a full exhaust, you DO get creep. I ported my wastegate and it helped a good bit. Didn't fix it 100%, but it wasn't a problem really after I ported it.

 

oh i get it. The backpressure of the stock exhaust system restricted flow so much that the turbo could never spin fast enoughe for boost creep to be an issue huh?

Just curious, but what is the stock psi of the TII turbo, 5 or 7?

 

i think its 6ish......mine has full rb exhaust and it sees 8psi normally, and sometimes 10-12, but i am careful of that.

 

The '87-88 TII was designed to hit 6.2psi at 2,000rpm and maintain that to ~5,000rpm at which point boost was to taper off to 5.4psi at 6,000rpm. Yamaguchi 2nd gen book pg 50.

 

is 10-12 psi too much boost for the stock turbo? or for the stock engine?

so 6ish for 87-88 TII what about the 89-91 TII

 

at 12 psi the stock turbo becomes inefficent,meaning it is creating more heat than boost, whitch isnt good. the stock intercooler is said to be good up to 15 psi. mind you were talking efficency here not breaking point, i regually run mine at 10psi, its a stock tuirbo and waste gate. on a really cold night it sees almost 15psi. the motor should stand about 15-20psi providing its a cool charge with enough fuel and no detination, remember thats what kills these motors is detination, the seals cant handle it. i am unshure what opperating boost is for the s5. i hope this helps.


EJ