3 Turbos

I've posted this on the 951 email list and on the racing list - what do you guys think here?

I have this (this was on the racing list also - don't know how many 951 owners there are there?);

Autothority Stage II chips version 2.5
2.5" Test pipe
"O-ring" block
Widefire Ring Headgasket

SRF MAF Level 1 (with K&N filter)
Garret Turbo Level 1 (water/oil cooled)
Tial 46mm Wastegate
ARC2 - piggy back computer
ARM1 Split Second air/fuel indicator
Greddy Profec B adjustable boost controller
VDO Mechanical Boost gauge

Billet adjustable fuel pressure regulator
Stainless steel braided fuel lines
SRF 2.25" Intercooler Pipes

With this setup I have on my Profec B, it is set at “14.7lbs on low boost – **** is maxed” and “18lbs at high boost – **** at midway/12 o’clock” – FYI, no matter where I turn the **** for high boost, it won’t boost past 18lbs even in the low gears - BTW Balance is set to "sharp", although I have adjusted that t mild and back - still the same.

I can hold 14.7lbs all the way to redline on “low boost control “ – but on high boost control at 18lbs, I can only see 18lbs until approximately to 4800rpm, then it drops back to about 14-15lbs. I think it was able to hold 18lbs to redline before – but not sure. It does seem to hold 18lbs in 1st and 2nd gear and sometimes 3rd gear if the weather is cool enough but will still drop back to about 15lbs past 4800rpm some of the time. But for practical purpose of this discussion, 3rd gear will drop boost back to 15lbs. This by the way is on 100 octane fuel.

Is there something wrong, or do I need to change chips or is there a leak somewhere. I’ve tightened all the vacuum lines on top of the engine including the 2 big hose’s for the boost controller. My fuel pressure at idle with the vacuum connected is set at 40lbs – I’ve tried 38 - 40 - 42lbs also – but I still have the same problem. I also checked my BOV and that was ok too.

It seems to be getting worse, but it is a slow drop off of boost - not like hitting a brick wall like others have said. Could this be an exhaust restriction? I have no cat, but the collapsing of the dual wall pipe after the turbo downpipe sticks in my mind.

My Profec B's dip switch's is set to "external wastgate" - should it be set to "external wastegate with overboost protection"?

Other than that small problem, the car runs great!

Thanks! Steve

nine-44

Wastegate spring getting weak? I know it i a problem with the stock WG, how old is the Tial? I'd also be checking for splits in intercooler hose boots. 18psi is kinda up there, maybe split a line?

Water944t

How much boost does the Level 1 Garret make? If you can only get 18lbs out of it, it doesnt sound too odd that it 'runs out of breath' after 4800RPM, as the stock turbo does the same thing, only at less boost, right?

The wastegate spring could be a culprit as well. It isnt an overboost issue unless my understanding of overboost symptoms is way off. I am pretty sure triggering over boost is more of a 'car feels like it hit a brick wall' kinda of thing.

I read through the post again, and my second thought is: maybe your injectors are maxing out and therefore you arent getting as much hot exhaust to the turbo...less thermal energy? Like it has asthma? Crazy visual, a wheezing car, but maybe? It isnt as noticable in the lower gears cause they just whiz by at that power, but the longer gears are more affected? Are you seeing any problems on the ARM?

How long have you had the car, if I may ask?

3 Turbos

Tial is 1 year old - new boots and lines - I don't think there are any splits - everything seems tight with no leaks - I'm thinking exhaust restriction, because the boost drop is so mild - I mean you know its there, boost rolls off pretty smooth

3 Turbos

Walt944T - I understand that "overboost" as you do - I hope we are correct cause that would eliminate the "overboost" problem.

I was told that the Garrett can put out 30lbs and the Tial will hold 36lbs

I've had the car since almost new early 1988