This weekend I went on a nice 900 mile round trip flight. It was my longest
trip to-date with the Subaru. Our Quickie group had a little fly-in in
Mattoon, IL so I decided to give it a shot (from Minneapolis). Since I'm
still trying to figure out how to run this engine, I did a fair amount of
playing around and am looking for input.
In case anyone doesn't know, I have:
1) EA-81 Direct Drive
2) EA-82 Turbo with stock wastegate actuator fixed to a manual on/off
mechanism (remember this actuator is relative to atmospheric pressure)
3) Weber Carburetor
4) Q2 (typical cruise with 75HP Revmaster is about 140mph)
5) VERY draggy radiator/cowling setup.
6) Warp Drive 3 blade prop, paddle blades reprofiled by Gary Hunter
I started the trip cruising at 6500'. I tried a variety of power settings
but it seemed most happy with 3400 rpm and 2" boost (2" of boost at 6500'
MSL is still less than sea level pressure). This was ok except I burned a
ton of fuel - something around 8 gph!! Ouch! It ran about 180 degree oil,
190 degree coolant, about 1250-1300 EGT, and 120mph IAS.
Another leg was run at 3500', 3500 rpm, 3" boost, and 130mph IAS. It now
ran about 190 degree oil, 210 coolant, and about the same EGT. Still had
high fuel burn.
Yet another leg was run at 3500', 3500 rpm, 0-.5" boost and 125mph IAS.
STILL high fuel burn.
There were a couple other legs with similar numbers.
Here are my questions/ramblings:
1) Why such high fuel burn?? Is it the Weber carb? Several people warned
me that it would result in high fuel burn. Let's say for a minute that it
is the carb. The plugs currently show that the mixture is not overly rich.
2) When I run the turbo at 3-4" boost there is some vibration, any ideas
why? At full boost 7.5" it feels pretty smooth.
3) My speed sucks - am I using the right prop blades? Now I fully admit that
my cowling and radiator installations are very draggy and even that my total
airplane isn't all that clean compared to some of the other Q2's but with
the Revmaster it would high cruise at 140mph. Warp Drive told me to use the
paddle blades with Gary doing the reprofiling. Others have said that I
should be using the taper tip blades on a high rpm, high speed plane. How
would I know (other than experiment)? Am I underestimating the speed
penalty from the draggy radiator/cowling??
4) What will running at "high" boost levels (7.5 pounds - relative to
atmospheric) for extended periods do to an engine. Seems to me that I
should be able to run at 6500' MSL at around 3500 rpm and 7.5 lbs of boost
and the engine should think it is running at about 100% power at sea level,
right? Obviously there are intake air temperature considerations
N54JF - Quickie - 1835CC VW - 450 Hrs.
N90MG - Q2 - EA81 Turbo Subaru - 440 Hrs.
Apple Valley, MN