absolute pressure, altitude, safe boost

[mobythevan]

A lot of us make general assumptions on what is a safe boost to run without an intercooler and with the stock fuel pump. To be better informed you should take into consideration absolute pressure in the intake manifold. I am sure a lot of people already understand all of this, but it may benefit some newer people. It really didn't occur to me until I started raising my boost with an IC installed.

 

First of all, I am a little over 6000' altitude. That puts me at approx 11.7psi atmospheric pressure. Sea level is 14.7psi atmospheric pressure. Whatever boost you run, that your gauge reads, adds onto atmospheric pressure. If someone at sea level runs 10psi boost they have 24.7psi pressure in the intake manifold. Me, only 21.7psi. I have to run 13psi boost to get to the same manifold pressure as a person running 10psi boost at sea level.

 

I just want to make sure everyone keeps that thought when you try to determine what a stock fuel pump can support, when stock head gasket will blow, etc. Make sure you know the altitude that other people are running a certain boost at. I am now running 14psi on my car which only equates to 11psi at sea level. I am using the stock pump, but don't want someone at lower altitude to try the stock pump at 14psi and blow up just based on my results.

 

I know this is basic boost knowledge, but it really didn't sink in to me until recently. There is also air density to look into.....

[Guest znow white]

I didnt know that thanks moby now i know what all those guys were talking about when they asked about elevation on the 1/4 runs. I didnt really know it had that much of impact thanks again always with the useful tips moby

 

Hussein