nize

okay, so with the tial, if something wrong happens to the control line (cut, loose, crimped, etc.), there's no failsafe and the possibility of dangerous overboosting exists.

special tool

absolutely

streckfu's

Only if the line is crimped preventing the pressure signal from getting to the Tial. If the line gets cut, you'll just bleed pressure.

special tool

Daniel - this is incorrect.
My boost shot up to about 40 psi when my boost line came unscrewed.
This has happened before also - with silicone hose.

streckfu's

OK. So then the hose is not capable of purging the pressure as the turbo builds it. Kind of like using a garden hose to fill a bucket that has a straw for a drain?

special tool

Well, in my case, the line prevented signal from both top and bottom. So ONLY the 1 bar spring was holding backpressure. Remember - in a real wastegate, this is the rating of the VACUUM signal necessary to open the gate, NOT the backpressure. My 1 bar spring is capable of holding at least 60 psi backpressure - because this is where I am at around 40 psi intake pressure.

If the signal would have remained intact to the side port, it would have opened at exactly 1 bar every time.

streckfu's

Is the K26 capable of generating 40psi of manifold pressure?

nize

daniel; this is what i've been trying to tell you all along. even the stock turbocharger is capable of generating boost faster than it can be purged, at least via a leak the size of your pinky finger as demonstrated by the banjo bolt.

do you have a tial? do you have an aftermarket boost gauge? do you have the stock air intake system? if so, you can simply try removing the banjo bolt to see for yourself what happens (be careful, boost will spike).

i believe this is another reason the stock wastegate (though it may be weak/inadequate/whatever) is still a better choice for longevity. since backpressure can open it, it would never let you build more than ~25psi of boost, even if everything else failed.

so perhaps the porsche factory designed the 951 wastegate to open via backpressure as a failsafe ?

streckfu's

I do have a Tial, MBC, and gauge. I don't think I'll be trying any experiments....

I'm a bit thick headed at times but I was trying to get at the cause of the spike....

special tool

yes, on a Hayabusa.

streckfu's

But not on a 951?

special tool

no - the air would be 700 degrees.

streckfu's

toddk911

"I have a backpressure GUAGE in my 951!!"

Cool!! Did you ever get a chance to do before and after with stock to 3" exhaust or before and after with cat/no cat??

A.Wayne

We use GT35R to see 40 psi on A Busa !