MAP value oscillates

maztah · Post by **maztah** » Sat Jun 17, 2006 12:31 am

when the MAP value oscillates, does that mean there is vacuum leak?

Bernard Fife · Post by **Bernard Fife** » Sat Jun 17, 2006 11:52 am

when the MAP value oscillates, does that mean there is vacuum leak?

Not necessarily.

Lance.

ptegler · Post by **ptegler** » Sat Jun 17, 2006 9:44 pm

a fluctuating manifold vacuum can tell you a WHOLE LOT about the way your engine is running. (if you know what you're actually looking at. A Very good write up at .... http://www.centuryperformance.com/vacuum.asp
Â
Paul Tegler
ptegler@cablespeed.com (ptegler@cablespeed.com)
Posted by email.

maztah · Post by **maztah** » Sun Jun 18, 2006 2:37 am

i have a TBI setup. the MAP oscillates around 1 to 2 kpa especially during cold start.

lmacneill · Post by **lmacneill** » Sun Jun 18, 2006 9:27 pm

A cam with a high-lift or long-duration can also cause fluctuating MAP values...

My camshaft has 0.515" lift and 275-degrees duration on the intake, and 0.541" lift and 285-degrees duration on the exhaust. My MAP reading constantly (and seemingly randomly) fluctuates from 43 kPa to 50 kPa at idle... Smooths out just a little bit as the engine goes faster, but there's always a fluctuation of at least a couple kPa no matter what the engine speed.