Need some help, I don't post much but I read a lot and I cant seem to find anything on this. Working on 2004 996tt just rebuilt the engine due to # 6 rod failure. I can't get it to make boost. Car is modded with k24 turbos, AP y-pipe,5 bar fuel press regulator, Ap air box and fabspeed exhaust, AP diverter valves, Pauter rods. I am a 20yr Porsche tech and have built many engines. All that said this is where I'm at.
No codes at idle, Turbos spin freely waste gates are closed, Passes both smoke and pressure test @20psi. Since it is known that tuned cars eat maf I have swapped with a known good unit = boost sometimes if ease into throttle. Also would make boost high rpm but not clean kinda broken up. Threw p1508 in limp mode until clear code. Swap MAP = no change, Check diverter valves closed like they are suppose to be , even block off = no boost. Swap p75 = no boost. Replace spark plugs coil packs look good = no boost.
Im thinking this maybe of some issue camshaft deviation b2 is -6 while b1 is 2ish. Actual angle is 0 at idle and both climb to 30deg when reved. All seems to be fine. I just remember that on 7.8dme that the threshold is 5deg on NA cars not sure if it applies to turbo cars. My problem is that its b2 that is -6 and misfires are on b1. I have yet to have a Cam retard code. I know it is probably something simple Im just running out of ideas and about to pull engine and go over every detail.

 

I just went through some camshaft/misfire issues on my car.

I'll have to look at my data when I get home tonight, but I don't think your camshaft deviation and actual values are a problem. Post the numbers at dead cold start after sitting overnight for deviations/actual/rpm and again after 5 mins idle, and again after a drive to be sure and I will cross-check, but I think mine are in the same ballpark as you though.

Check your variocam solenoid brackets that are in the same area as the coilpacks, they become brittle and break and can cause misfire codes as the actuator/solenoid can't stay seated in the cylinder head. I've read that they will cause errors for misfires on bank opposite of the cracked bracket.

 

You should post this in the technical info forum and get an answer from a Porsche Master engine builder

 

Seattleturbo, thanks for help, Ill log data tonight with the piwis. I looked close at the brackets when I put it together but I'm not rulling anything out I'll look again. Thanks

 

Thise codes are a sign of a massive boost leak. What did u touch when you were working on the car? Have you messed with your throttle body?

 

996tt550, Pressure test intake full system to 20psi = no leak, I have not touched the throttle body minus doing a re-calibration for p1508 code.
thread re-posted in technical area

https://www.6speedonline.com/forums/...301-303-a.html

 

I had this issue with the p1508 and my throttle body was dirty it didnt look it but i cleaned it and put a new gasket on and i never had it again.

Throttle body or maf sensor.

 

Have you tested from the turbo outlet? If you test just at the intake by the filter box you won't detect a BOV stuck open I believe.

 

You are correct. I pulled the bov and tested separately. I even took them off and plugged the holes

 

What are you doing for intake piping? One member recently had his collapse (!) and the result was low boost, is this possible? Does the car struggle to breathe? Fuel pressure good? Fuel filter new?

 

https://www.6speedonline.com/forums/...minutes-2.html

This thread has some info on what happens when the cam timing is set wrong, may be of some use

 

And996tt, Thanks for thread link, I studied it before posting. BLKMGK, I don't think that's a problem but I'll check out all the intake plumbing and make sure.

 

Honestly it seems like a long shot to me too but others have seen it and it did solve a problem for someone recently. If the charge piping is solid, the turbos spin properly, and the intake side good then there's not a whole lot left except throttlebody is there?

 

IDK , Ill put it on my list. I kinda stepped away to take a breath. I'll start back on it this afternoon.Thanks for help