EA81

[asra]

OK heres the latest. Bolted the tubo on and got another 350 revs. But a pressure gauge on the inlet manifold and at idle it is showing -20psi and at full revs it is around 5psi. Does this mean I have 25pound boost or 5psi boost. Haven"t gone for a fly yet but will put a bit more pitch on my prop to get my revs back down.

[Russell]

You got 5 psi................hardly working. Mine was 12psi boost max............cruised at 2psi. ( was direct drive tho, wooden 2 blade 56" diam )Up the boost to around 10 max.............then hang on.

[Tim]

G"day Baz,Manifold pressure in automotive terms is mostly measured as vacuum, and as such idle or de-accelerate gives you the highest reading. In many aircraft terms negative manifold pressure was expressed as a "positive", considerably confusing the issue. The best way and the least confusing is to use the most common dedicated turbo gauge which shows both positive and negative readings, with zero in the middle. One side of zero is normally called Vacuum, and the other side called Boost. It sounds as though you have the right gauge and that you are running up to 5 lbs boost, which is a good maximum for a standard compression EA 81.