I am looking at purchasing a 2005 S4 avant as my vehicle for driving to the mountains. I was wondering if there was anyone that has had experience with the 4.2 V8 at high altitude (10,000ft+). Does it lose alot of power or is it still pretty strong? I am used to a WRX turbo and I am worried that a NA car might not do as well up there. I am pretty set on getting the V8 so there is no use trying to talk me into the Biturbo .

 

If no use in talking about the turbo, you can follow the standard power loss percentages at altitude for NA engines.
At 10,000 feet, that's usually a 25-30% engine power loss depending on other weather conditions.

So, if your car has 300 HP now, it would have 210 - 225 HP.
Yes, you'll definitely feel it!


Here's a chart I've seen. It's based on more horsepower to start, but the ratio is the same and you can do that math.

 

I don't have anything as scientific as the last post, but I can tell you first hand that you will definately feel a loss in power with the 4.2 at altitude. I hardly ever get the car into the mountains though so for me it's not a big deal. One other thing I've noticed with this motor is that it's very sensitive to heat and humidity. In other words, my car seems to run its strongest when the outside temp is about 66-67 Degrees F and it's damp out, (high humidity). Once it gets into the 80's or above, I can tell I'm down on power.

Other than that, this motor is awesome.

 

Just got back to LA from Utah (5,500 ft). Definately loss in power, and my buddy's S60 R was a wee bit faster. But the S4 was still a blast.