I'm on a roadtrip across the US. If you saw a black Evo with NJ plates that's me. Anyway, I was in the the Rockies and my car felt like ****. The gas didn't help either. But I was wondering if anybody knows the hp drop with 91 octane gas at high altitude (around 10k ft?)?

 

I don't know what the loss is, but it feels quite a bit different when I go to a lower elevation. I am around 4500ft with 91 ****.

 

yeah i have 91 octane also argh

 

The exact power loss would depend on your state of tune, weather conditions, etc etc.

FWIW, NHRA high altitude compensation is 6% for trap speed, which is most closely related to horsepower. So I'd say 6% from altitude, and 4% from lower octane. But, that's conservative; it could be much more, or a little less.

In turbo cars which use manifold absolute pressure to dictate the boost curve, the power loss isn't very large at high altitude. For those which use boost pressure, it's greater. And for those that use air-mass/combustion, it's almost nothing. Just some random info.

-Adrian