I haven't troubleshooted an N75 valve yet but from my understanding of what it does it seems like that would be your culprit. If the N75 is stuck open wouldn't that basically run the turbos on wastegates? You're likely running 1 bar wastegates so to get to .9 bar or so is probably about right.

Someone please correct me if I'm wrong, but this is probably what I would replace if I was in this situation.

 

No it was not tuned on a dyno. The tuner is sending me a file that commands 10% more boost just to see if that changes the actual boost.


My tuner has been amazing providing support way past the call of duty.


Unfortunatly being in Ottawa Canada there are no Porsche pros around.


Im not going to let this one get me though. Its gonna get figured out if it kills me.

 

I disconnected the N75, plugged the diverter valve hoses and even tied the wastegates shut and still only .9 bar. The issue has to be a leak, internal or external but cant figure out why the boost leak test is holding a solid 30psi.

 

try unrestricting the inlet tubes to turbos more then 1 person in the past choked their 20g's and couldn't get it right until they let them breathe.

i dont know how modified your stock exhaust but to get full use of the 20g's i remember 3" being almost a must.

also id put in a new boost solenoid just cause

 

OK sounds good. I will try the inlet idea and the solenoid since its under $40 Canadian here at the dealer. Thanks!

 

UPDATE:

Well Im still at the same point.. kind of. After my friend took apart the Diverter Valve system and tested it he concluded the system was Mechanically sound.

I decided to once again tighten the wate gate actuators. This time to my surprise I was able to see 1.1 and even 1.2bar for a bit in the higher rev range of 2nd and 3rd gear. This was a shock because I did this before and it made no difference and all Iwould see was 1bar max at redline. In fact I would only see 1bar even when I unplugged the wastegate actuators when in theory I should have over boosted.

So not sure why it made a difference but since it did I tightened them up a few more turns but unfortunatly it had no affect (still seeing 1.1 - 1.2bar for a breif second at redline).

32Krazy! was kind enough to sent me a pair of 1bar wastegates that came with his tial 3071 turbos for free!!! They may need to be modified a bit to bolt up to the K24s butonce I recieve them I will make them work and see if there is any change.

I also just thought of something. Last year when I was trying to figure out if I had an issue or not I pinched the lines going to the wastegate actuators. At that time I didnt know enough about the system and though I would run off of sapring spressure but in fact you over boost if you do this. Thing is I didnt over boost then either (the car had stock k16s and 1 bar tune). The car still ran 1bar just like Im limited to right now so the problem must have existed back then I just didnt realise I had a problem since I was only running a max of 1 bar.

To me after eliminating the wastegates the only thing it could be is the Diverter valves bleeding the pressure. But my friend checked the system and I replaced the 710Ns with Billet DVs and I have the same problem. Maybe I will put the stiffest spring in the DVs and see if that makes a difference. I'm using the middle spring right now which in theory should be enough.

 

sorry for the delay. package mailed out today ups international. should have them by the time the snow melts!

 

lol

 

solid move from 32. that will come back around.

still agreeing with you.. you have some minor leak, somewhere somehow. frustrating beyond words!

so whats with the two friggin holes that wouldve been covered by a mfg tag?! i sure would give that a 2nd look.. and sorry if i keep repeating myself, but have you ruled OUT both check valves since the n75 is a new bosch yes?

it's gonna be something minor and something you've already passed by or perhaps ruled out is my guess.. stupid game this, i empathize. leaks.. well, they suck.

 

lol ya I'm guessing you're right in that it's going to be something very app errant once I see it. Haha

I checked the one check valve that connects to the n249 (solenoid for the diverted valves) but didn't check the other one. Is the other one the infamous #16 check valve? When I did the boost leak test air was not coming out of the plastic hose that connects to the drivers side turbo intake pipe. If I'm not mistaken that means that check valve is good. Maybe Markski or another expert can chime in on that. And maybe they can tell me what other check valves or anything else that can affect boost.

Also I sealed those holes on the turbo backing plate. No idea what that was about. Even the shop that built the turbos were at a loss. But a small leak like that wouldn't restrict me from seeing a target boost level. For that to happen the leak would have to be like a 1/4" hole.

If it's a leak that is causing my problem it would have to be affecting a system from working properly or a boost leak like an intercooler hose popping off at above 1 bar and then slipping back in place as the boost reduces.

It's crazy hot today so no motivation to look into it today. I'm gonna take mental vacation. lol