I posted this over on rennlist last week but there doesnt seem to be much traffic on the turbo forum over there, so i was hoping for more of a response here...

6/23
I have a stock 07 TT and was wondering what boost you are all seeing, particularly past 5k rpm. In normal mode I am getting 10-12 psi up to 5k rpm and in sport mode I am getting about 15psi up to 5k rpm. Once I hit 5k the boost seems to really roll back down to 4-6psi up until redline. I tried searching but most topics deal with boost in the sweet range 2-5k. I have read some places that people are getting sustained 10/11 psi boost up until redline. I just got my spark plugs changed and want to make sure something isnt wrong, put back in incorrectly. What #'s are you all seeing?

37k miles
2007 turbo
no mods, completely stock.<!-- google_ad_section_end -->

6/28
I did some further experimenting. It seems that If i creeep up to 4k rpm not trying to get boost...and then once at 4k rpm i mash it, I am only getting around 4-6 psi up until redline. In 3rd gear if i floor it at 2k rpm my boost will climb to 12psi but once I hit 4900 rpm the boost drops drastically back down to between 4-6 psi from 5k - redline. I get decent boost aroun 13psi in 6th gear if i floor it at 2500 rpm, but i cant see what happens after 5k...because i will be going 180 mph
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any help?

 

check the spark plug properly gapped and/or misfires, delays...any DTC?
check for boost leaks (hose clamps to ICs), and or fillup 93 octane fuel.

My car with tune actually rockets (I mean really rockets) at 4K-7K RPMS...boost increases not tapers off. Boost gauge limited to 1.0- 1.2BAR~17.4PSI.

 

thank serpentene for your response, but i need an apples to apples comparison to see if something is indeed wrong...ie leak or other problems...

come on, someone else has to have a stock turbo with no tunes or anything that has brought it over 5k rpm????

 

Check you diverter valves- They go bad very often and limit the boost

 

brian - i am also located in NJ, with the 90 degree weather the last week, what psi's have you been seeing?

 

i will only get up to 14psi in 6th gear...otherwise i max out around 11-12 psi but when i let off the gas i see the psi spike to 15 psi for a split second...is this normal? One would think simply bringing it to the dealer would be best, but i did that and it was a friday and apparently the techs didnt feel like putting any effort into it so they just said 'car is fine'...so i need to try and pinpoint the problem and bring it back with, check the diverter valves or check for this leak...this = not so much fun

 

I have not notice a difference in the psi, but then again I haven't driven the car too much in this weather.

I did put the diverter valves in, so as to avoid a potential problem in the future. They do cause the turbos to spool up a little faster, but in reality it will not fail like the factory equipment.

If your car is not holding boost, I definitely feel the you should look at the diverters.

 

I can recommend someone to take the car to if you need to have it checked. He is very good and located upstate NJ.

 

Which dealership did you take it to? Jack daniels off of 208?

 

I don't think there is a problem. If your car was flashed, then I would say yes there is a problem.

 

VTG turbos on the Mezger engine do not have diverter valves like the 996TT. I doubt they are failing.

 

What fuel are you using?

If your ambient temperatures are in the 90s and higher, and you are doing a series of higher speed WOT runs, your boost and timing may be pulled as your IATs climb. If you have checked your hose clamps at the Y pipe and throttle body and they are okay, my guess is what you are experiencing is probably normal.

As for DVs, I don't know of anyone with a stock configuration Mezger 997TT that has experienced a recirculation bypass failure. There are 700+ HP turbos running with stock valves with no problems.

 

This is a very simple answer.....

Stock ECU lowers boost as revs climb above 4500.. Revs up---Boost down.

Nothing wrong with your car. (I thought the same thing about mine)

Flash your car and boost will stay pinned as long as your on throttle--all the way through redline.

ECU flash will be the best $$$ you have ever spent--on anything---period!!!

 

Agree

AGREE

It was really hot and humid a few days ago and I noticed that boost didn't get up to 15 unless I was in 4th gear or above and below 3k rpm and wot.

 

wow i never realized that after 4500 rpm it scales back boost...does it really stay at 6psi from 4500 - redline??? everyone is experiencing that?

even if you floor it at 4k rpm it never gets over 6psi boost, i know the tune is the best $$$ u can spend, just gotta make sure my engine/turbos are working at 100% before i start tweaking ECU's, i dont want to run into a nightmare