quick kpa question

screamer69 · Post by **screamer69** » Mon May 15, 2006 2:23 pm

when reading over 100 kpa (boost ) how do u work it out on the say 165 kpa

do u do it as 165 or do u work it out on the 65

ive never been good at getting my head around kpa and psi

Bernard Fife · Post by **Bernard Fife** » Mon May 15, 2006 2:49 pm

screamer69,

100 kPa is zero boost at a bit above sea level. Your 'ambient' air pressure may be different depending on your elevation and the weather. Every 6.9 kPa above ambient is equal ito one psi of boost. So if your ambient pressure (baro) is 100 kPa, and you show 165 kPa in MegaTune, then you are seeing (165-100)/6.9 = 9.4 psi of boost.

Note that if your ambient baro pressure was 80 kPa (in Colorado, for example), then at the same 165 kPa you would have (165-80)/6.9 = 12.3 psi of boost. The engine would see essentially the same operating condition though (except that the exhaust back pressue would be lower, which is what the baro correction is for). Since the kPa is a more constant figure, that's what we use.

Lance.

screamer69 · Post by **screamer69** » Mon May 15, 2006 2:55 pm

thanx lance !!!

finally got it now !!

robert