West-se

So if MS is reading 160 Kpa, that means Im running 60 Kpa of boost ? I remember reading that 100 Kpa is normal atmosphere pressure. If MS logs 165 Kpa im trying to figure how much boost im running. Would I then take 165 and subtract 100 to get 65 Kpa as actual total boost ?

Sean

Rex4Life

Yes the MS reads in absolute pressure. So 101.3 kpa is atmospheric pressure at 14.696 psia which equal zero boost.

In rough numbers, every 33 kpa above 100 kpa is worth about 5 psi of boost--that means the 165 kpa is about 10 psi of boost.

pmrobert

As an aside - to be totally accurate, the amount of "boost" would be equal to the measured absolute pressure minus the ambient pressure. ~100 kPa is a good number to use at sea level but, for example, ambient pressure at 10000 feet is ~70 kPa and only ~30 kPa at 30000 feet. don't expect much performance on top of Mt. Everst at 29K feet! Of course, the only part of the engine that would care about ambient pressure under boost would be the turbo compressor. As far as chamber filling, etc., is concerned, 150 kPa absoulte is 150 kPa absolute no matter what the ambient is. Actually, you'll get slightly better performance in a lower ambient pressure environment under boost due to more effective exhaust scavenging.

-Mike

West-se

thanks guy, I am at sea level