Jerry Springer wrote in message link.net...

Jim, while this is notexacetly the same situation you have here is a web page
with some good prop testing done by a local RV-8 builder in my area.

http://www.rv-8.com/Prop.htm


Jerry (slow flying RV-6 and love it) Springer

To you, Jerry, and Corky, the plot thickens, and you may well have the
right of it. We went through the airplane today and found:

1. The mechanical timing (valve timing) was fine.
2. The fuel system was clean. No junk anywhere. There is a military
fuel filter which seemed to be obstructive, so we removed it for a
test flight. Fixed the fluctuations in fuel pressure. No increase in
speed. We are replacing that with a known unit capable of 30ghp flows
before further flights.
3. Magneto is timed appropriately. Will likely time the lightspeed
unit in a day or two. It was in good time when installed, so is likely
not an issue.
4. Prop is an aerocomposites constant speed prop. The best rpm we
could get was 2650, so we adjusted it and took one further test
flight. ROC went up from around 900 (on a hot day in Georgia) at gross
to around 1300...and rpm was up to 2700. We're gonna get another 50
rpm or so.
5. We fixed the fuel flow sensor. At climb we are running around 20
gph. At high speed cruise (still not fast enough) we are burning
around 11.5, 12 gph. This is right on Van's book speed. This also
suggests that we are producing the hp, just not getting the speed.

We are going, as I said, to adjust the prop to get 2750 and then run a
series of tests. I still don't understand how this will effect cruise
(I would think it wouldn't...unless I cruise at 2750 rpm) but perhaps
it will help. Looks like we will get the climb performance we should.

Next step is going to be to talk to the aerocomposites folks. Now,
turns out that aerocomposites are agressively courting the RV-8 crowd.
I am sublimely confident that I can work with them and figure this
out. Oh, I am not writing all that I am thinking...If we are producing
the power, and climb and fuel flow...and the fact that the engine is
working fine...are right on, then the limitations to speed are
airframe or prop. RV's are pretty much all of a kind. Little place for
large variations. So gonna rule out the prop as a problem next.

That doesn't help, going to be thinking on a different cowling, I
guess. After I make sure the airframe is dead straight. Seems to be,
but perhaps there is some improvement available there.

I'll keep you posted and thank you for the input to date!

Jim