Wren 44 acceleration problem.
#1
Thread Starter
Wren 44 acceleration problem.
Hi Guys, I'm having a problem with an early, manual start 44 accelerating.
The engine will accelerate to about 120,000 RPM then run rough, flame out & belch smoke.
The problem has been getting progressively worse but I have been increasing the accel. delay
to overcome the problem. Now the delay is so long (50) as to be unacceptable.
If I open the throttle verrrry slowly it will run up to full power at 190,000 rpm & decelerate o.k.
Starting is also faultless.
Any ideas? I have a spare engine with all accesories so I can mix & match to fault find. - John.
The engine will accelerate to about 120,000 RPM then run rough, flame out & belch smoke.
The problem has been getting progressively worse but I have been increasing the accel. delay
to overcome the problem. Now the delay is so long (50) as to be unacceptable.
If I open the throttle verrrry slowly it will run up to full power at 190,000 rpm & decelerate o.k.
Starting is also faultless.
Any ideas? I have a spare engine with all accesories so I can mix & match to fault find. - John.
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RE: Wren 44 acceleration problem.
Ron,
In other posts, you mentioned that too much oil (5%) can cause a blocked fuel ring in this engine. Could this be a possible cause? I ask because I have fuel mixed for my Mk III that I plan to use for my 44. If you find out that this is the reason, can you post it here?
Thanks
In other posts, you mentioned that too much oil (5%) can cause a blocked fuel ring in this engine. Could this be a possible cause? I ask because I have fuel mixed for my Mk III that I plan to use for my 44. If you find out that this is the reason, can you post it here?
Thanks
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RE: Wren 44 acceleration problem.
The higher percentage oil usually results in a condition where the bearings seem to be "sticking " after cooldown.
The early 44 motors have a bit smaller needle and are more prone to blockage.
If the motor is on the bench....run some clean kero thru the fuel line, you may get lucky.
It is not a hard job to upgrade the motor...but it should be done at the factory.
The early 44 motors have a bit smaller needle and are more prone to blockage.
If the motor is on the bench....run some clean kero thru the fuel line, you may get lucky.
It is not a hard job to upgrade the motor...but it should be done at the factory.
#6
Thread Starter
RE: Wren 44 acceleration problem.
Hi Ron, thank you for chasing this up.
I am running 5% oil, the reason being my Super Sport's bearings (and other owner's Supersport bearings) sounded noisy to us & Mike suggested upping the oil to 5% to see if it made a difference. Run time on these engines is low.
I questioned if it would cause problems in my 44 & the reply was it may cause slightly more combustion chamber coking with prolonged use but otherwise no problems.
I take it a blocked fuel ring requires a complete strip down & rebalance? - John.
I am running 5% oil, the reason being my Super Sport's bearings (and other owner's Supersport bearings) sounded noisy to us & Mike suggested upping the oil to 5% to see if it made a difference. Run time on these engines is low.
I questioned if it would cause problems in my 44 & the reply was it may cause slightly more combustion chamber coking with prolonged use but otherwise no problems.
I take it a blocked fuel ring requires a complete strip down & rebalance? - John.
#8
Thread Starter
RE: Wren 44 acceleration problem.
Problem solved!
Removing the engine to send it back to Wren for repair I noticed two of the rear screws missing, not the ones that hold the nozzle on but the ones in between that sit nearly flush.
Fitted a couple from my 'spare' engine & it's now running fine.
Now the pieces of the puzzle fall into place. Quite some time ago the engine statred flaming out on acceleration so I increased the acceleration delay to make it accelerate ok. [sm=confused.gif]This may have been when the first screw fell out. It ran, with slower acceration, for a while then after a few succesful flights at Wangaratta jets it all of a sudden had acceleration problems again, when the second screw fell out, I'm assuming letting case pressure escape. [&o]
Can anyone tell me what the factory setting for acceleration delay for the first Wren 44's is? With the screws out it would not accelerate at 50, I had it down as low as 10 today but it stumbled on acceleration, a little less stumble at 15 so it's now at 20 & ruuning smoothly. I can live with that spool up time.
Thanks for your help & put it in your memory bank. - John. [sm=wink_smile.gif]
Removing the engine to send it back to Wren for repair I noticed two of the rear screws missing, not the ones that hold the nozzle on but the ones in between that sit nearly flush.
Fitted a couple from my 'spare' engine & it's now running fine.
Now the pieces of the puzzle fall into place. Quite some time ago the engine statred flaming out on acceleration so I increased the acceleration delay to make it accelerate ok. [sm=confused.gif]This may have been when the first screw fell out. It ran, with slower acceration, for a while then after a few succesful flights at Wangaratta jets it all of a sudden had acceleration problems again, when the second screw fell out, I'm assuming letting case pressure escape. [&o]
Can anyone tell me what the factory setting for acceleration delay for the first Wren 44's is? With the screws out it would not accelerate at 50, I had it down as low as 10 today but it stumbled on acceleration, a little less stumble at 15 so it's now at 20 & ruuning smoothly. I can live with that spool up time.
Thanks for your help & put it in your memory bank. - John. [sm=wink_smile.gif]