Took my 96 993tt in since the max reading on the gauge was .5 bar.


They ran the 2 or 3 gear full throttle test and got .58 on the attached boost pressure guage. Called Porsche Tech and was told .58 was within spec.

And they billed me, even though I have the Pre-owned warranty, "well there was nothing wrong so they will not cover, we have to bill you for it"

They attached a copy of the tech manual "reading must be between .6-.7 bar".... but since porsche tech said .58 was aceptable.. all is normal and "BILLABLE". The copies were of: 21 02 01 Checking Boost Pressure and 21 67 05 Checking vacuum control unit of the bypass flaps on the turbocharger."

 

FELKER
The test in 3rd gear is more meaningful than 2nd as the motor will be under more load. The boost will peak at around 4500rpm then reduce towards peak power 5750rpm then raise again towards the limiter.The actual amount of boost you see will vary according to atmospheric conditions and whilst 0.58 bar may seem low, if it was at 5750 rpm and the conditions were right, it is probably enough to give you your 408ps. The only way to be certain is to dyno the car.

 

From wut i've read from the internet before, i think the boost is supposed to reach 0.8 bar when full throttle in 3rd gear after 3000rpm.

 

John,
Your boost numbers sound low to me. I've owned my '97TT 5 1/2 years, it has never failed to reach .8 bar on the gauge quite easily, under all conditions. Boost is controlled by your engine computer. At full throttle, once the controlled limit of .8 bar is reached (somewhere around 3000-3500 rpm, unless revs are rising really fast like in first or second gear, in which case .8 bar would be reached at a higher rpm) the computer controls the wastegate holding boost at .8 bar to redline.
Find a level road where you can run some 0-100 tests against a stopwatch. If you can break 10 sec. you're OK. My TT (which is 100% stock) does this in 9.6, to an indicated 100, admittedly there is a little speedometer error in our cars.
Please post your results. Good luck.

 

John: Your max. boost reading sounds low to me also. You should be hitting .8 bar in third and fourth gear quite easily, IMO.

 

I agree with Dick and Jack. .58 Bar in 3rd gear at 4,000 RPM seems way too low. If you floor it at 3,000 RPM, you should see .8 Bar fairly quickly.

It sounds like your ECU is in the 'limp' mode. I had that happen once and the maximum I saw was .5 Bar. I disconnected the battery for about 15 mnutes and reconnected it. The engine resumed showing .8 Bar under heavy loads again.

What is your Boost readout showing?

Rick

 

From what I've read up and heard from many of my 993TT friends, your suppose to see 0.8 bar of boost pressure on full throttle. Off course slight fluctuations are normal but 0.5 to 0.6 is a bit low IMHO.

 

FELKER,
My experience is in line with Dick's. You should be hitting 0.8 bar boost at full throttle in almost all gears (never tried first) in most conditions. I think I hit it on every single run which is once every 2/3 days throughout the year (hot/humid conditions as well as freezing temps, fuel is always 94 octane but results are same for the recommended 93 octane). Was this a problem since acquisition of vehicle or a recent development? Anyway, in either case, perhaps you should try what Rick recommends or simply go to another dealer! Maybe the reluctance in acknowledging the issue had something to do with having to make a warranty claim. Good luck and let us know how you made out.

 

THis is a problem I have had since I bought the car from this dealer in DEC 2001.

The boost sensor has been replaced, At that time I was complaining that the boost ONLY read to .4. Now reads to .5.

The .58 was obtained by the tech when he did the attached meter.

Off to another dealer to check.

 

John,
Without a doubt this car is in limp mode. Has anyone bothered to run an OBD check? This would be the first thing I did. These cars are set in the ECU to hit .8 bar under full boost no later than 4K. If it isn't then the computer is telling the valve to open the wastegate. It could be a function of the boost valve as well. The wastegates ate set at .4 stock and the valve will control them to what ever the ECU is set at. These valves do fail and this could be the problem. It is located on the passenger side of the motor just forward of the intercooler under the shroud.

 

John - make sure to let us know what you find out at the other dealer.

 

FYI. Checked my boost pressure the other day and had no problems getting 0.8 (Ambient temp was 30 Deg C.)

 

Hello Rick,
I saw your posting from 2001. I have 993 twin-turbo with 540 HP engine kit.
Since about 4 weeks I have some problems with my boost.
Fresh resettet by disonnecting the battery for about 20 seconds it will run with 0.9 - 1,0 bar ( reding 0.8).
After two minutes the atmospheric pressure ( detectet by Porsche Bosch System Tester KTS 500 ) will go down from approx. 980 mBar to 700 mBar. In this phase the boost is dropping from 0.9 down to 0.5 bar. This is a normal function of the Bosche ECU, which protects the turbo chargers. But nobody knows how this is happend. We changed nearly everything without any success.
I`m wondering you have some experinece with this, since your problem sounds similar.

Best regards

Thomas form Germany

 

Welcome to the board Thomas..

Regardless of the HP, it sounds like timing and boost is being pulled..

A few things to check.. And if you don't know if they have been replaced, I'd replace them..

Plugs

Plug wires

MAF

Cylinder temp sensor?

Boost/pressure sensor..

And of course, the Bypass valve.. If you have the factory Bosch unit the diaphram can/will tear in age. Thus dumping boost into the intake system and directing it back into the turbochargers..

 

Hi Kevin,
thxs for the answere. Timing is OK. No retard ! Only the ambi-pressure is goining down after a while and after disconnecting the battery. This will happened whiles idleing as well whilest driving. After the Porsche system tester says 700 mbar pressure the boost is down at approx. 0,5 bar.
This is a normal function to protec the turbos. Otherwise they will brake.
The big question is: Why is the ambi-pressure dropping from around 1000 mbar down to 700 ?

I changed everything except the the two original plastic bypass valves and the plug wires.
Some people told me, that maybe the throttle housing is defect. But I cannot see, where a defect at this very solid part should happens. All is aluminium and the butterfly axis is tight.
Today I will change back for the original 408 BHB turbocharger.
The pressure sensor is not connected to the ECU. Why do you think, that could be the problem ?
What was your specific problem ? And what was the solution ?

Best rgds

Thomas