no 100% power

skykay

skykay

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skykay
Hi, my Mooney M20J MSE io360 200 hp does not deliver 100% power at takeoff. I have installed a EDM900 from JPI. Everything is correct callibrated and some comunication with JPI has been done to confirm that all is installed and callibrated the right way. At 45 to 75% hp in cruise all values are shown correct and are equaly to the poh. But at takeoff EDM shows max 90%. FF18gph rpm 2700 full Map at sealevel all values above isa. Could it be that the engine has lost 10% power after 1500 hrs?
 
Full rich or leaned to best power? Seems rich at 18 gph. ISA + means higher than 0 MSL DA so you arent "really" at sea level.
 
DA was below sealevel. I know that when DA is above sealevel that power decreases. Mix was full rich as instructed by poh.
 
EdFred said:
Full rich != full power.
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Lol, try that with a super high DA.


To the OP, I'd go off of your RPM and manifold pressure first.

Also how does the plane preform against the book?
 
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I agree, the engine monitor only uses the MP and RPM to approximate it and YOU have to calibrate it using the fudge factor (similar to how you set the fuel flow k factor) given some experimentation at known power settings.
 
skykay said:
Hi, my Mooney M20J MSE io360 200 hp does not deliver 100% power at takeoff. I have installed a EDM900 from JPI. Everything is correct callibrated and some comunication with JPI has been done to confirm that all is installed and callibrated the right way. At 45 to 75% hp in cruise all values are shown correct and are equaly to the poh. But at takeoff EDM shows max 90%. FF18gph rpm 2700 full Map at sealevel all values above isa. Could it be that the engine has lost 10% power after 1500 hrs?
Click to expand...

The JPI does not know how much power you're actually developing, and there is no way for it to know unless you were to install a torque sensor of some sort on the crank. The JPI's percent power value is a calculation based on what it does know - Manifold pressure, RPM, and fuel flow.

Can you download the logs from your JPI and post them here? That should help to determine what exactly is going on.

I wouldn't be overly worried about it, though. Pull out your performance charts and calculate your expected takeoff distance, and then go out and see if that's accurate. If you're only developing 90% power, your takeoff distance will be 23% longer than book value I think, which should be noticeable.
 
What does the aircrafts original mechanical tach and manifold pressure say?
 
Many aircraft have their prop governors set to give a max static RPM somewhat lower than redline. The engine should reach redline by the time the airplane is off the ground. If the governor is set for redline on the ground the prop might overspeed in the takeoff roll.

A few RPM short of redline means a bit short of max power.

All these engine monitors give so much information that they scare some owners. These old engines have significant differences in EGT/CHT, for instance, but the owner of a new monitor wants to see all the numbers looking the same.

Things were a lot simpler with the stuff that was popular when I was your age........:)
 
kgruber said:
Unreliable for determining power. An engine failure in flight will indicate RPM and MP.
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We're we taking about engine failures?

I'm talking there should be a RPM setting and manifold for takeoff in the POH/AFM
 
Depends on the unit. In talking to EI they run the horsepower calculation on CHT/EGT in addition to manifold pressure and prop speed.
 
I can tell you the JPI 800/830 series (I've had both) don't have any "absolute" knowledge of the power setting. YOU have to calibrate them. Essentially, I took my plane up and set a known book value (say 2300 at 23" at 3000 on a standard day which is 65%) and adjust the fudge factor until the instrument read 65.
 
So if you have a fixed pitch prop, does the percent power mean anything?
 
Hang 4 said:
So if you have a fixed pitch prop, does the percent power mean anything?
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I would imagine that they still put an MP sensor in and still take that into account for the calculation, so you'll know how much power you're losing as you climb.
 
At that fuel flow with a healthy engine you should be producing 207hp. Give a little error and 200hp seems likely. I’d say some value in your instrument is incorrect.
 
Does your plane's performance match the POH? Do a climb test and see if you can match or exceed the POH numbers.
 
ok I will try the climbtest next time...
 
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