I thought I should share this info for those who can't see 1.2bar on their stock 997tt.

I have the car for almost a year now, have tried everything to achieve 1.2 bar without success (3rd, 4th 5th gear pull at low rpm, in cold and hot days, incline, different fuels etc). In the beginning I could see 1.1bar holding for 1-2sec and then dropping.

Just recently it was becoming increasingly difficult to achieve 1.1 bar and progressively impossible. Max boost was down to 1.0bar. Period.

Replaced both mafs with new ones. Old mafs voltage were within spec and no cels or other faults were triggered.

After installing new mafs and reset the ecu by pulling the battery for couple of hours, boost is again 1.1 bar and holding! Still not 1.2 bar but 1.1 is achieved very easily and maintained for 2 secs or so.

Conclusion: Bosch MAFs have issues. Lets say they are getting "tired" over time and are not up to their job 100%. I believe at some point they will throw cel and error, but this will take time and only after their efficiency has dropped significantly(mine never did).
I suggest they should be replaced every 3-4years, regardless.

After having restored boost to 1.1bar as it used to be, I was wondering if there is a leak or some turbo problem holding boost down to 1.1bar instead of 1.2bar. I decided to try what i have tried in my previous car which also had bosch mafs and had boost problems as well. Unplugged both maf cables, reset ecu by pulling battery and went out for a test. At first boost was 1.1bar, but after several pulls I saw 1.2bar and then again 1.2bar and holding. I saw repeatedly 1.2 bar in sc and 1.0 bar in normal mode, effortlessly.

When I plugged back maf cables, max boost was down to 1.1 bar again.
Maybe DME allows for 1.2bar only when very specific circumstances are met (outside temp, altitude etc), but now at least I know that I don't have a leak or any other problem...

I don't know why 1.2bar is so easy when running "mafless"...

So that's my story (in brief) of my quest for the notorious 1.2bar.

Mat911

 

1.2 bar is achieved in my car only at full throttle in overboost. Otherwise I never see 17psi. My car is an 07 with many miles. I'll have to keep an eye out though, thanks.

Ken

 

Interesting experiment, thanks

 

thanks for the input Matt

david

 

If you car is not throwing a CEL with MAF's unplugged then I would run it as such.
My Proto tuned 997TT runs mafless tune(Speed Density).

 

ive been having the same issue ive only been seeing 0.8 Bar ,car feels like she is choking upward in MPH may i should clean my Mafs ? and see what happens ?

 

I wouldn't try to clean the MAF. Just disconnect them, reset the DME by pulling the battery cable and have a go. My car was running just fine with MAFs disconnected, no cels. DME scan revealed two errors registered for the two mafs, but car was running great, boost was at 1.2bar. As others reported when mafs are disconnected DME switches to MAP.

 

No cels, and boost is up to 1.2.

Anyone knows if running with MAFs disconnected on a stock car, will cause any problems on the long run?

Anyone tried this?

 

okay just disconnected the MAFS and car hit 0.9 Bar ,no CHK light Either ,so i will clean them today . reset the Battery and give it ago later on ,If she doesn't hit 1.1 or 1.2 at that point ill call the dealer and Have them replaced not sure how i will convince them to do so but its worth a shot since its still CPO and No CEL car wasnt Breaking up this time also ..

 

P>S Do you think it maybe the Diverter Valves ..

 

I can only speak of my experience, and the steps I had taken.
But since you are giving it a try, I just want to point out the "reset" part again. For example the first time I tried with mafs unplugged I didn't get 1.2bar instead it was again 1.0 bar. At that time I had allowed just 15min of battery reset, and maybe that wasn't enough to fully reset the DME. Next time I unplugged the battery for all night, and next morning after 2 wot pulls car was boosting 1.2bar repeatedly in SC and 1.0bar in normal mode.

At that time I knew that MAFs were the culprit of my low boost.

 

Very interesting...got a picture of where to unplug the MAF's. Wondering if I should try this on my 775 Evo set-up. Anyone with more input, good or bad, please post it.

 

Behind your air box.