Differential pressure test
I've just done the tests on my engine (permit to fly aircraft) and the results have come out similar to those for the last 3 years - 64,68,76,74 respectively.
Normally low 60s would be a bit of a worry.
But reading AC43-13 it states that the orifice for testing bores over 5" diameter should be 0.060", my tester has the smaller 0.040" orifice.
The engine is an O-320 with 5.125" diameter bores.
So presumably the larger orifice would give "better" compressions.
My questions are:
How much difference is changing the orifice likely to make?
Should I be concerned about the consistent low readings on the front pots?
The engine runs very well and performance is spot-on.
Thanks for any advice.