Was it the restrictive air filter? No. Was it tuning? No. Was it
a restrictive exhaust? No. Was it the stupid $@%^& spring that I
used to pull the throttle open in case of a broken  cable? Uh
-huh!  Re-configured it, now, instead of getting 4400 RPM and
- 100 hp, I get 5600 and 190 hp on a static ground run. The
- brakes can barely hold the plane back at full throttle on
- pavement.


Next flight should be on Tuesday.


Brian Trubee

Is this the spring Brian?
How are you determining the HP?

Paul Lamar

--

Brian,

Congratulations.   Glad you found the detail.  Say what is the
length of your intake runners?

Cheers


Doug in Japan

I'm determining the HP soley by the readout on Tracy's EM2. It's
supposedly based on fuel flow, and it reads 188-190 HP at 5600
rpm on the ground. The prop is a Catto 74 dia x 88 pitch. So,
although the HP number is really just a number, I have nothing
else to go on, and there's no doubt it's got some umph- the
brakes can hardly hold it at 5600 RPM.

The spring is a 20 LB spring set up so that it would pull the
throttle lever open in case of cable failure. when all the slack
was taken out, it served as a throttle stop, thereby limiting
throttle opening. I changed the configuration so that the spring
parallels the cable pull.

I'll report back after the next flight tomorrow.

Brian Trubee

It all depends on what BSFC number Tracy used. If he is using
the leaned number it should be .47 pounds of fuel per HP per hour.
200 HP would be 94 pounds per hour or 15 GPH at a BSFC of .47.

For full power the BSFC is more like .55.
So for 200 HP that would be 110 pounds per hour or  17.6 GPH.

These numbers assume the temperature is 72 F and gas weighs
6.25 pounds per gallon.

Please note the GPH  on Tuesday and the mixture if you have
that info. A good test pilot should be able to do this :)

Paul Lamar

Paul,

Keep in mind that the GPH computed by the EM-2 must be calibrated over a
number of fill-ups.  I doubt he has had time to do that yet.  It may be very
close if he's using the same size injectors as Tracy used as a baseline.

Mark S.

That correlates the injector pulse width with the gallons per hour
read out.

Paul Lamar