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    Loss of Boost Pressure

    Hey All,


    I was on a drive with some friends today and we decided to head up the mountains we've got up here on some newly paved roads. The drive was a lot of fun and we had a blast as we left early on sunday morning to avoid traffic.  Cars that went up, 997.1 Carrera S, 997.2 GT3, 997.2 GT3RS, 997.2 Turbo S, 997.2  Turbo (my car), and a Ferrari California.   when we reached the top we got to an empty parking lot for a skiing slope, so we had some fun and did some standing races....however both my turbo and the turbo S were exeriencing major boost loss, I was getting only.4 bar and sometimes even less..... has anyone else experienced this at high altitude? we were at about 2400 meters above sea level! as soon as we headed back down, we were both back to normal again??  please let me know if anyone else had this happen.






    Re: Loss of Boost Pressure

    Turbocharged engines have an altitude sensor that reduces boost pressure as the altitude rises. This is to avoid over-revving the turbocharger which can spin faster (with less restriction) due to the less dense air.

    So boost reduction is something normal on principle. Now, whether at 2400m it should be down to 0.4 bar, it's something only Porsche know. Also if any of the systems are defective there must be fault codes that can be read using the diagnostic equipment.


    "Form follows function"

    Re: Loss of Boost Pressure

    0.4 is surerly not normal......fluctuation of 0.2 bar can happen based on ambint temp and altitude.

    dont forgt that porschees turbo engins deliver hp through boost and that would be too much of a discrepancy.......

    Speed has never killed anyone, suddenly becoming stationary... That's what gets you.

    Re: Loss of Boost Pressure

    I had the same experience when driving my previous 997.1 Turbo over a pass in the Swiss alps. Major loss of boost...


    997.2 Carrera S in Carrara White. PASM-Sport Suspension (-20 mm), PSE.

    987.1 Boxster S in Arctic Silver with 'Martini Racing' design. H&R Monotube Coil-Over Suspension, H&R Anti-Roll Bars, Sachs Racing Clutch, Single-Mass Flywheel, Recaro Pole Position Seats, PSE.

    Re: Loss of Boost Pressure


    Thanks guys....I will be asking my dealer to check with porsche, cause if it was just my car I would assume something was deective, but the brand new turbo s with less than 2000 kms had the exact same problems so maybe it was something with the sensors? but as you guys mentioned, the drop of boost from 1 to .4 and at only 2400 meters shouldn't happen at's not like i was summiting everest ! these altitudes are reached frequently all over the world and I doubt that Porsche would design a car to drop that much in its performance levels.  needless to say the other cars in the group could finally give us a run for our money :):)

    Re: Loss of Boost Pressure

    I drove my turbo s to 11,000 feet (3000 m) and saw at least 1 bar of boost and strong power. Curvy road so I didn't stay on it long at any given time. I did notice more turbo lag when pulling from low revs (2500) but that is to be expected. I know for a fact that BMW's compensate for altitude. They simply boost to an absolute manifold pressure value. Of course standard for the 335i is 8.5 pounds normal so going to 11  psi in New Mexico at 5200 feet is not extreme. (Absolute BMW manifold values would be 23 psi in both cases). 

    It would seem that Porsche would do the same having a more sophisticated turbo design and definitely larger blower wheels. However, Porsche doesn't mention compensation in their literature whereas BMW does.


    Re: Loss of Boost Pressure

    so it seems that after plugging my car in to the PWIS II tester and error code did appear, something about an air leak error.  the head of the garage told me that this was the 3rd Turbo to have this problem and that at some point i'd have to leave it for the day so they can run a proper diagnostic to see where the actual problem is.  They replaced a faulty sensor on one of the other turbos and never had that problem since, which is most likely what they will do to my car after the eliminate an actual leak.  the turbo s that was with us on that drive up the mountain had the same error message as my car, so i guess they will be spending the day together in the porsche garage to get better aquianted. :)



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