Any propeller heads out there? i need some help.

Currently Stage 1 ZZP SC on my 2.4l auto, about 8psi of boost according to them on a 3.4 pulley. Stage 2 bumps it to 11psi via a 3.1 pulley, or so they say.

I'm happy with 8psi given the high compression of my engine and dont want to strain it as it is my DD and still not 100% paid for.

Currently at 300ft above sea level, but moving shortly up to 4,600ft...the rule of thumb i've heard is air density drops 3% for every 1000' of elevation.

So 4300' difference gives me 12.9% less air density, and the same reduction in power.

If I put the stage 2 pulley on when I arrive, and subtract 12.9% from 11psi, it is almost 1.42psi less at the higher elevation? So 9.5psi.

Do I have it right? Or there some non-linear method to calculate boost at altitude?

 

At higher elevations you will not get as much boost due to air density.. I would recommend going with an even smaller pulley than recommended to make up for it. As long as you have the cooling mods to support it.

 

You are correct, you're going to have density issues and slightly less pressure and power loss...but lowering the pulley size even more may increase boost but it will still be as inefficient if you go too small. Heat will still be produced and you will still at some point create more heat than quality air pressure and you'll be going backwards no matter how much boost you're producing. Hotter air will always counteract pressure built.