"02996ttx50

hope you've got 6 hands! LOL cheers and good luck

powdrhound

I'll do some logs next time I'm at the track. Might be a couple of weeks as temps are plummeting here this week into the single digits.. I'm sure Kevin will be able to shed some light on this also once he sees the logs.

mdurbahn

I'll hold the laptop for you

powdrhound

Sounds like a plan!

noble1978

I've been told when my turbo was pressure leak tested at 20psi the oil filler cap had to be held down to prevent leaks. Is this normal?

"02996ttx50

huh, wha?! news to me.

Macster

My two cents' worth is I think this is the key:

I have seen it on my old GIAC tune, my old Eurodyne tune, my mate's Proto tune... my problem was solved by Tim who tunes my car and with a MAFLESS set up seems to disappear for everyone I talk to.

Based on reading through the thread my diagnosis would be the MAF is just not able to deal with the extra air flow brought about by the tune/changes to the engine. Just like a tuned engine can overwhelm the clutch so too can it overwhelm the ability of the MAF to measure the air being consumed by the engine.

The above is tempered a bit by some lingering concern about the car's fuel system being able to supply sufficient fuel under all conditions.

I do not know at what HP levels the stock fuel system begins to prove inadequate. Also, this assumes the stock system is in perfect working order. The Turbo fuel delivery system is rather complex and there's a lot to go wrong.

"02996ttx50

^somewhere above 550 crank assuming one has installed a 5 bar fpr i would imagine fuel ( or lack thereof ) can become an issue, which this reads like so i'm with you on that. but it does not read like a maf issue to me, but i'm "guessing" too.

..and mac, the quote you referenced was from a contributor, not the op. i don't believe the op is mafless? he indicated in his original post, he has already replaced the maf. even still, that doesn't sound like maf issues at all. or not any i have had, should say.

noble1978

Gents, here are two runs i've just completed.

The highlighted yellow shows me in 3rd flooring from 2.5k rpm and holding there.

The green shows me simulating how i can get the boost up there. You'll see my foot is at 45% is then i put it down a little then it's when I back off slightly i get the boost to start ramping up then I can put the foot down again (this area in red text in the green background.

Hope this helps you guys to help me.

"02996ttx50

i'll be until the guys that can read logs chime in. sorry to hear of your continuing drama. geez, these little things can drive ya nuts!

993GT

what fuel are you running?
looks like a mess IMO...car is making plenty of boost, ign. timing is jumping around pretty bad (because way to advanced to begin with on boost), and is pretty lean...
Just had another look at it in the 'yellow' area, boost is definitely low during WOT pulls...I still think N75 isn't operating correctly, the boost flare when letting off makes me think wastegates are tight enough
Edit again, noticed a few post above you mentioned the oil filler cap...
Fix that then re-log...could VERY likely be your issue, you ARE leaking boost on the manifold side...

noble1978

It's a new N75.

You think the timing is bad? it's a softronic tune.

noble1978

you think the cap could cause the issue where i back off I seem to get full power?

noble1978

993GT, i'm receiving mixed messages ref the boost leak check.

When applying a test 20 psi at the intake manifold and the engine TDC should there be pressure at the oil cap or not?

If yes then I agree fixing that leak may help but if pressure is not meant to be there then it's just a symptom of another problem.

993GT

You don't want timing jumping around like that, it is compensating for detonation/knock..ie very aggressive tune or the fuel you are using is inadequate....worth a re-log after fixing the boost leak.
Yes oil cap holds air pressure, if it's leaking you have a boost leak. Intake manifold has a large air line going to the oil tank.