Fellow Europaphiles,
Update as of this morning, 2009 09 06.
Over the last two days, I have checked all the areas recommended by
you folks. Lots of good ideas! Thanks to those who took the time to
call. I appreciate all the help.
Everything checks out so far without tearing down the carbs. I've
reached the point where I need a better check of the airbox/fuel
differential pressure. It could very well be that there was
insufficient fuel pressure at full boost to over come that level of
boost. The UMA gage and sender I have installed seem to be binary,
either 0 or 1. And that's not right. It should read between 2 and 5
PSI. Tomorrow I'll be evaluating why the differential pressure isn't
reading properly.
I have completed six full power run-ups. Three yesterday and three
today. The engine performed perfectly at all times.
Engine started before three blades went by. Maintained idle in the
2000 - 2100 RPM to warm up.
Once the engine warmed up and all temperatures were in the normal
operating range I confirmed that the prop was in Auto and T/O.
Advanced the throttle slowly, watching RPM and MP.
At full throttle the engine was turning 5750 RPM and 39 in MP. Fuel
flow was 8.1 to 8.2 GPH (roughly 32 L/H for you folks in Europe).
Right on the chart numbers.
The engine was very smooth, no surging, no missing, no hesitations, no
sign of stopping.
I held it at full throttle for about 30 seconds and then brought it
back gently to idle. Allowed it to idle for a minute or so before the
next run to full power.
Yesterday and today, the final full power run was held for a full
minute.
After the final run, the throttle was gently returned to idle (1900
RPM) and the engine allowed to idle for at least 1 minute to allow the
turbo to cool down.
And the engine was shut down with the Ignition switches.
Tomorrow I will be looking at the differential pressure gage package
to see what's wrong with it. The 914 really needs an accurate
differential pressure indication.
I'll keep you posted,
Bob Borger
Europa Kit #A221 N914XL, XS Mono, Intercooled 914, Airmaster C/S
http://www.europaowners.org/N914XL
Aircraft Flying!
3705 Lynchburg Dr.
Corinth, TX 76208
Home: 940-497-2123
Cel: 817-992-1117
On Sep 4, 2009, at 16:29, Robert Borger wrote:
>
> Fellow Europaphiles:
>
> I'm at 10.5 hrs on my XS Monowheel. (Just getting the hang of
> landing it on pavement) As you can see from the signature block it
> has a Rotax 914 and Airmaster C/S prop. On the last flight the
> engine developed a surge and a miss at full throttle at about 500'
> on takeoff. When I retarded the throttle and surge stopped and miss
> went away. After immediate RTB, pulled the upper cowl and began an
> inspection. 1st thing noticed was that it was not really obtaining
> full throttle. Only about 37.5 in MP. Full throttle is 39 in MP
> and 37 - 38 in MP is in the unstable range for the turbo
> controller. That explained the surging. Located the reason the
> throttle wasn't going to max and fixed it. Also checked both fuel
> filters. Secondary was fine. Main was had considerable crud so it
> was replaced. I can now get full throttle. Re-synched the carbs.
> Runs nice and smooth.
>
> Now here's what happened today on a full-power, chocks-in, tail tied
> down, run-up test.
>
> Engine starts immediately. I kept the idle at 2000 - 2100 RPM to
> warm up.
> Engine warmed up, all temps and pressures in the green. Prop
> controller set Auto and T/O. Main and Boost pumps are both on,
> Advance throttle. Everything is OK up to engine RPM 5790 & MP 36 in.
> When the throttle is advanced beyond 37.5 in MP the engine quits.
> Like fuel starved or ignition cuts out. It just quits.
> Retard throttle back below 37.5 in MP and it re-starts and runs
> smoothly.
> Throttled back to 4000 RPM and did a "mag" check. Left-Off drop is
> about 275 RPM, Right-Off drop is 305 - 310 RPM.
> Throttle back to idle and shut off ignition, the engine stops and
> after about 15 seconds there was a large backfire through the
> exhaust (first time for that!).
> Engine has only run on 100LL with appropriate amounts of Decalin TCP
> & Marvel Mystery Oil to help with the lead situation. Oil is still
> nice and clear.
>
> Do any of you Rotax Gurus have a suggestion as to why the engine
> cuts out when full throttle is applied? Any suggestion for things
> to check and/or fix?
>
> Thanks in advance for your help,
> Bob Borger
> Europa Kit #A221 N914XL, XS Mono, Intercooled 914, Airmaster C/S
> http://www.europaowners.org/N914XL
> Aircraft Flying!
> 3705 Lynchburg Dr.
> Corinth, TX 76208
> Home: 940-497-2123
> Cel: 817-992-1117
>
>
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