How much Boost Lost due to Altitude?

[SheepDog]

I posted this in the "Taste of Home" forum as well, but maybe this is a better choice.

I have recently installed a Procharger on my 17' GT with a P-1x headunit, and a 3.5" Pulley. I live in Colorado and was wondering how much boost loss others at this altitude are seeing? I was under the impression that the 3.5" pulley would be good for somewhere around 12 psi at sea level, but I am only seeing between 6-7 psi at redline. I also have Kooks headers so that should also create about a 1lb loss in measurable boost, but is losing another 4ish PSI reasonable at 5500 feet?

 

[CobraCO]

I live in the Denver area at close to 6000 ft. I am running a KB 2.8 with a 3.00 inch pulley. No other mods other than tune of course. That pulley would net me about 17 lbs at sea level, so I hear, but here it is about 14-15 lbs. If I go to the top of Mt Evans at 14,000 ft I see about 8-9 lbs, but still pulls strong, though it is not like you can really open it up on that road. LOL Corrected for altitude and running 100 octane tune my car is 701 at the wheels.

 

[MG0h3]

I lost 2/3 psi from sea level to 4k’.


Sent from my iPhone using svtperformance.com

 

[TVSed GT]

It’s my understanding you can expect about 1psi drop for every ~1000-1500’ elevation

 

[einehund]

I know my Shelby makes a whopping 3 PSI at the top of Pike's Peak!!