ROTAX 582 Loss of power
Frank Garofalo
approx 20 seconds at full power? THe rpm's will drop from 6000 to 5000.
If I come off the throttle the RPM's come back to 6000.
This problem can easily be duplicated. I know since I attempted two
takeoffs before deciding it wasnt my imagination! Further tie down
runups produced the same results.
Any help is appreciated.
Thanks
--
Frank
fra...@panix.com
[ your ad here ]
Richard Van Der Pryt
>Does anyone have any experience with the ROTAX 582 loosing power after
>approx 20 seconds at full power? THe rpm's will drop from 6000 to 5000.
>If I come off the throttle the RPM's come back to 6000.
I've had a similar occurence when going down the long straights of both Portland and
Seattle International Raceways on my motorcycle. It came down to fuel starvation
caused by small ID fuel lines. I modified the fuel tank petcock and used larger
fuel lines and the problem disappeared. Another place to check is the fuel level in
the float bowl. If it is lower than the spec, it could create the same symptoms.
Hope this helps
jgraham
>
> Does anyone have any experience with the ROTAX 582 loosing power after
> approx 20 seconds at full power? THe rpm's will drop from 6000 to 5000.
> If I come off the throttle the RPM's come back to 6000.
>
> takeoffs before deciding it wasnt my imagination! Further tie down
> runups produced the same results.
>
> Any help is appreciated.
> Thanks
>
> --
> Frank
> fra...@panix.com
> [ your ad here ]
starvation. The most likely point of fuel flow resistance is the
fuel shutoff/fuel flow "on" valve. Fuel flow in tubing is governed
by physical laws that are best described by the Poiseuille-Hagen
equation. This equation basically states that flow is directly
proportional to the radius raised to the fourth power. Therefore,
flow in a fuel line can be doubled by a 19 % increase in the radius
of the fuel line. Fuel flow restriction can likely cause engine
damage and/or failure if an excessively lean condition occurs. There
is some protection against highly undesirable and unintended fuel/air
mixture leaning if you have CONSTANT VELOCITY carburetors. It is
simple and easy to change to fuel valves with much larger fuel
passages and fuel lines with greater diameters.
Poiseuille-Hagen formula from the viewpoint of resistance to flow:
R = 8nL R = resistance
_______ Pi = 3.14
4 L = length of tube
Pi r n = viscosity
r = radius
Sincerely yours, jgraham
Graham Edward Laucht
> Does anyone have any experience with the ROTAX 582 loosing power after
> approx 20 seconds at full power? THe rpm's will drop from 6000 to 5000.
> If I come off the throttle the RPM's come back to 6000.
Are you seeing a corresponding rise in EGT temperatures? if so you have either
a fuel flow problem or air leaks on the induction side of the carbs.
Have a good look at the rubber carb connecters for splitting.
Can you measure fuel pressure during full bore static tests? If it's dropping
below 0.3 bar (4.2psi) then it might suggest a constriction in the fuel system
before the pump or the Mikuni pump is strangling, check the pulse line for
blockage/kinking/leaks. 0.7 bar 9.8psi is normal for a good full power setup.
Also check the small breath hole on the pump backside is clear.
Best, and most dangerous method, is to place a T piece in one feed
pipe to a carb, attach a pressure guage and a tap leading to a measured
container. Run full bore and open the tap until fuel pressure drops no lower
than 0.15 bar (2.1psi) and measure the amount of fuel collected from the
bypass over time. A good set up should show at least 1.5 times maximum full
power consumption which is around 28 l/h. Dangerous because you end up very
close to the prop and the fire risk is high.
Check every fuel line joint especially before the pump for air leaks, these
may not show up as fuel leaks. Inserting a short section of clear plastic line
just ahead of the pump will show the presence of air bubbles in the fuel.
Drop the float needle valves out of the carbs and look for tiny fragments of
debris which might be blocking the float seats but not passing into the float
chamber.
Are you using Mogas which is vapourising somewhere and causing vapour locks?
Vapour locks in unvented header tanks and gascolators will resist gravity flow
from even high wing tanks. Is your tank filler cap vent clear?
The fact that you are only reaching 6000 on static suggest the prop is either
overpitched slightly, or there is a difference between individual blade
settings. Aim for better than 0.5 degree difference. Is the prop balanced?
Peak torque comes around 6050-6150 and if the prop is either overpitched or
maladjusted you won't spin fast enough to hit peak power around 6300
Bad prop balance shakes the carbs up and foams the fuel.
Have you had a mini seizure and picked up aluminium off the pistons onto the
bores. If this is the case frictional losses rise more quickly reducing
available power. Glaze bust the bores and check the pistons for galling.
Have you well bled the coolant supply, small entrapped air bubbles around the
jackets cause hot spotting and distortion of the barrels again increasing
friction losses.
Odd ball possibles, is the area around the magneto housing unconfined and
running reasonably cool? Excessive expansion of the aft end of the engine
casting through poor ventilation causes the Hall sensors to "move" away from the
flywheel retarding the sparks slightly.
Is the crankcase base evenly ventilated? the main bearings can get to run
too hot and cause friction losses to increase.
Substitute your kill switches for known good ones to eliminate contact arcing.
Check the ignition coil earth returns for vibration induced high impedance
circuits.
Check the DC side of the regulator for abnormal voltages, short circuited
triacs inside the regulator brick muck up the sparks department and reduce the
available HT voltage across the plugs.
I assume that the test conditions were nearly ISA day.
--
Graham Edward Laucht
Birmingham UK