Miles in Michigan

I just moved to Colorado, and my C5 (with a brand new 402 that I never got a chance to drive at sea-level) doesn't feel that peppy. I just checked an online calculator, and was surprised to see 5200ft of altitude costs almost 20% of power!

Any advice on what's best? Single turbo, twin turbo, any of the various types of supercharger? I don't need tons of power, but this freaking altitude is costing me about 100rwhp, which I'd like to have back

bensonortho

I have one of the early PISC procharger kits on a stock engine and love it down here in Denver. Plenty "peppy" for any type of street driving. Check with Randy Reese at Dashworks in Denver. He may suggest a new tune to start before making big mods.

Gary

7LitreC5

They all work fine at altitude. There are many, many people in Colorado Springs/Denver running all forms of FI.

If you decide to use an SC just pulley it to make 2psi more than you want and you will be ok. For instance if you want 6psi, pulley for 8psi.

master blaster

go turbo.....if you drive to sea level you dont have to change pulleys/tune.

Whiteonrice

You lose about 1" of manifold pressure per 1,000 feet. 5,000' = -5" or sea level barometric pressure = about 30". where you are = 25". Quite a loss, get a S/C...

Vince99FRC

If you do a SD tune will the car adjust if you go from high altitude to sea level?

7LitreC5

It should be fine because of the MAP sensor. It senses the altitude change because the air density goes up.

Miles in Michigan

Sea-level is about 14.7psi, knock 20% off that, and I'm at 12psi ambient air pressure. If the supercharger/turbo makes more than 3psi, I'll be doing better than sea-level, and anything above that would be a bonus.

I wasn't planning on forced induction when I got the 402. It's 10.9:1 static compression (72cc chambers, .054" gasket), about 8.2:1 dynamic, with a 238/244 cam. How much boost can I use with the heads I've got? 5-6psi okay? I think that's all I'd want to run. That ought to give like ~630rwhp at sea-level, and ~500 in this pathetic excuse for an atmosphere. I don't think I'd want much more than 500 at the wheels in a daily driver.

7LitreC5

In my experience you need closer to 5psi to put back the horsepower that you loose. At least you do where I live (7000 feet).

STAGED

Wastegated turbos... because if you take a road trip and go back down to sea-level, you'll overboost on a mechanically S/C'd setup. Wastegated turbos (provided wastegate is properly implemented and sized) will keep boost levels in check regardless of altitude. Only thing that'll happen when you go down to sea level is you'll spool up faster.