So we don't have any dedicated turbo tuners in this area so I'm trying to narrow down some options before taking it to the shop.

Car was running great at the track then started running like a boxster all of a sudden. Checked the gauge and then was making ZERO (0.0) boost (so, like a boxster) at WOT. I've had a few boost leaks here and there and I'm pretty sure if I had a boost leak big enough to cause zero boost that I could hear it at WOT. Couldn't hear jack, no sputtering, just no boost. Car also idles fine, unlike it does when leaking boost.

In addition a stinking smoke is coming from right side exhaust, especially on accel and startup and what seems like oil mixed with the soot. Oil is not coming through the headers though upon inspection. Car is also throwing CEL for O2 sensors. P0155, P0050, P0150.

It seems I have two possibly unrelated issues biting me at the same time. The only issue I've been able to gather that could cause both is a blown turbo but even that is iffy because the other turbo should make SOME boost. Inspected both turbo's and both move freely on the cold side. The wastgates also still move fairly easily. I'm less concerned about a boost leak than the smoke.

From asking around I think I should check DV's and N75 valves, but neither of those would solve the smoke from the tail pipe. Can bad O2 sensors cause a complete stoppage of boost? I know one can cause smoke for sure even if loose (which they weren't).

So, another episode of guess that problem.....

 

yeah, thats exactly what this awful game is called. the only time ( and i mean ONLY time I've had NO boost as you describe was under incredibly hot temps ( summer tracklike conditions ) and after trying to find leaks any leaks i found my check valves were bad. thats the 75 the one up top the plenum and the other that is near it. whatever they are all called.

the strangest part was that after cool downs the car would act/run normally until i again got it super hot and the leak maximized itself!? which makes no sense. i changed ALL check valves "it" has never happened again. i'm sure none of the foregoing will help you but it wasn;t for lack of trying lol. so the game continues

 

How many check valves are there?

Do you remember part numbers?

 

were in GA. are you? i use buckhead imports in smyrna ga and they have an in house tuner thats familiar with porsches. they can also diagnose some of the problems your having. if you need a reference, (i can't remember his screen name) the guy who painted his tt bright green with a full teacart kit has use them as well. theres a few gt3 guys that use them also

 

there are 3 counting the n75 as i understand it. one above the plenum and another that looks like a small round piece of fishing tackle. really.

my tech just arrived with them after we kept messing with my wg's ( over boosting but connected to the boost LOSS issues you describe/i had ) and we found the leak at the check valve at the top of the plenum ( when pressure testing the freakin thing whistled dixie ) and we simply changed them all. issues solved. never occurred to me to ask part #'s. they are very inexpensive though, i know that. since i didn;t have to pay for em.

 

N75 valve: 996 110 129 72

Check valve #1: 996 110 135 70

Check valve #2: 996 110 145 71 (Dealer calls it a vent line)

According to my shop guru the N75 valve rarely goes bad.

 

Awesome, thank you!

 

good find. re n75. all it takes is to go bad once and I've been told exact same thing.

 

Agree all it takes is once but its true they rarely go bad.

 

Agreed too. My N75 valve just gone bad and it produced weird boost numbers.
But in your case, i am not sure if its only a boost leak or a bad valve. Usually you get a P0234 error. Your error codes are different.
So get it to a shop.

Oh btw, my bad N75 valve got this part number. 996.605.155.00

 

the car should make at least wg pressure... no boost at all i have never seen....
im guessing turbos... boost leaks dont do this... a bad n75 usually works opposite- overboosts.... because its not working,,,, durametric logs would be nice

 

No boost at all would mean both turbos went bad simultaneously though right? That sounds far fetched. Im fairly certain one of them is jacked but hard to imagine them giving up at the same time

 

what marks said also has bearing on my event(s) also since i didn't have NO boost i had vastly reduced boost and also OVERboost and that's what pointed us to the leak and bad valves. agree as thought earlier you may have something entirely different going on.

 

Pressure test the car correctly start with that.

 

... just noticed.. the smoke from tailpipe wont have anything to do with any of these valves. but i think that occured to you also. toasted turbos? i think youre onto something