930 engine boggs down
 

On the way to Mt Tremblant this weekend, I noticed that my engine boggs down and really starts to buck only at 2200-2800 rpm ( just before and slightly after the turbo kicks in). It seems to only occur on 1/2 and lower gas tank and when it is extremely hot out and ONLY in 4th gear..
I'm thinking maybe a vacumn issue with the fuel tank maybe ??
Any ideas ? Engine is a 1986 stock turbo.

- Elevation?
- Fuel pump?
- bad gas?

BTW, why are you in 4th gear at around 2200 RPM? I'm assuming you get bogged down in 4th and before 28000 rpm?

Two things come to mind.
First how much power does a 3.3 liter motor with 6.5 or 7 to 1 compression put out at 2200/2800 rpm? Not much.
Things don't start to happen until you are over 3,000 rpm.
As you go up in altitude the gap in hp between pre-boost rpm's and boosted rpm's gets greater and greater.
At 5,000 feet a 3.3 under 3,000 is a dog. No power, no boost.
If you suspect a vacuum problem it the fuel tank, just pull over and open the gas cap. Whoosh and you found the trouble. No whoosh, tank is ok.
My advice is to drive this car uphill over 3,000 rpm. In fact I don't know of any Porsche engine that is happy at lower V-8 type rpm's.

Thanks guys. I had absolutely no problem coming home from Michigan ( went there after Tremblant). However it was cooler and kept a full tank of gas most of the way. I'm pretty convinced that it was a humidity/temp thing ( sort of a density altitude problem like when you fly a plane).