This week I flew my RV-4/13BREW from Everett Wa. to Medford Ore. and back.
Headwinds on the way down were brisk- 30 kts at 8500 feet on the way down, but 35 kt
tailwind on the way back. The engine ran flawlessly but the plane is slow- true
airspeed was 110 kts at 19.5 manifold pressure,5600 rpm oil temp 161 and coolant 170,
fuel flow around 8 gpm. My prop is a three blade Catto, 72 dia x 88 pitch.
For one, the plane is over propped. I'm going to have Craig Catto cut it down a
little during the winter maintenance. The other thing is that the cooling scoop is
effective, but way too draggy, so I'm going to re-do it this winter.
Another issue is my left brake line- I"ve melted it twice. It's plastic, and although
it is shielded from the exhaust pipes and insulated with fiberfrax, I think that
heated air from the exhaust pipes is being forced out the opening in the cowl where
the brake line goes to the gear leg. That's where I have found the line melted. I
want to put a reverse scoop near the exhaust pipes to get the heated air out of the
cowl, and to replace the brake line with stainless steel. Everything inside the cowl
except for the brake line looks OK- I wrapped and shielded everything - wires,
coolant, fuel,and oil lines. There are three NACA ducts bringing air into the cowl to
cool the alternator, the coils and exhaust pipes, and an exhaust eductor to suck air
through the cowl and over the muffler.
Comments?
Brian Trubee
Couple of questions.
EGT?
Size of throttle body?
Is the engine ported?
The manifold pressure is very low.
Is the air filter plugged? :)
Are you getting cold air?
8 GPH is 50 pounds per hour at 6.25 pounds per gallon. At a BSFC of .47 leaned that
is only 106 HP. At a fuel burn of .5 that is only 100 HP. If it is really rich and
the BSFC is .55 and that is only 90 HP.
You need a p-port Brian :)
Paul Lamar
Brian, I don't have any pictures of your intake air scoop. What does it look like?
Paul Lamar
-- Remember that this was at 11,500 feet. I"m all for a p-port engine. Do you have
one you'd like to donate to a worthy cause?
Brian Trubee
Take your engine apart. Jeff will port it for you. It only takes 5 minutes on his NC
mill. Maybe a few more for clamping it in his holding fixture. It is called circular
interpolation. You are paying for his NC Mill. Somebody has to do it. The engine will
come apart in 15 minutes. Clean the rotors while Jeff is porting the rotor housings.
If you make a compartmented box to keep track of where the seals go you will not need
new seals. Just O-rings.
Paul Lamar
If you're going to P-Port it, it would seem to be a shame to cut the prop down before
carrying out this mod. You'd then be under propped after changing to P-Port, and
that's harder to correct - you have to buy a new prop.
The difference in power might be 100hp, considering your current low RPM.
Matt-
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