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RCV-91CD Tuning

Old 07-06-2007, 10:20 AM
  #1  
Scotsman
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Default RCV-91CD Tuning

I have read many of the posts here, but didn't find one similar to my problem. I have an RCV-91CD in a Hanger-9 Spitfire. The engine is mounted inverted. Using Cool Power 10% fuel, APC 14-6 prop. The engine does not start real easily, but requires about 5 seconds of cranking with an electric starter. It requires the throttle trim all the way up to start. Once started it requires the battery to stay on the glow-plug for about 20 seconds as it warms up. After it is warmed up, full throttle runs are good at 9200 RPM. After warm-up I remove the glow clip and the idle RPM drops 800 RPM. If I transition quickly from wide open throttle to idle the engine backfires or pops once, twice at most. For other 4-strokes this typically means the idel setting is to lean. I have richened the idle to 5 1/2 turns open. This setting gives a reasonabel transition from idle to high speed, but the acceleration is slower than the throttle movement, so it takes an extra second to reach top speed after the throttle is already at wide open. When I do throttle down from wide open with a smooth throttle movement, all is fine except the idle will stay high at around 2500 RPM and then slowly decrease to around 2000 RPM. The idle is reliable at 2000 RPM, below that and it will quit after about 15 seconds of idling. The engine has 1 1/2 gallons of fuel through it with 2 hours of running time. The signs that seem contradictory to me is the large drop in RPM when removing the glow clip, this makes me think the idle setting is rich, yet the bakfiring makes me think the idle is lean, am I reading the symptoms correctly? Do you have any ideas for a tuning procedure form here. The engine has performed well with only one incidence of quiting in the air which was after 1 gallon of fuel through the engine. I richened the high speed needle one click after that it has not quit yet. I'm guessing and hoping my problems are in tuning and not the engine..... Any ideas or help are appreciated. Thanks,

Scot
Old 07-09-2007, 08:41 AM
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Default RE: RCV-91CD Tuning

Dear Scot

Thank you for your query. Before we can advise any further we need to know your engine serial number for the 91CD.

Thank you and kind regards

Stephanie
Old 07-09-2007, 01:59 PM
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Scotsman
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Default RE: RCV-91CD Tuning

Stephanie,

The engine serial number is 1651 as stamped on the mounting lug. Purchased at the WRAMS show in NYC this winter, 2/24/2007. The Warranty registration should be on file from your web site.

Scot
Old 07-10-2007, 06:23 AM
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Default RE: RCV-91CD Tuning

Hi Scot

Thank you for coming back to me with your serial number.

We have checked our records and can advise that this engine was tested at 2200 - 9300 rpm range orginally. The setting for the needle gap should be to 0.70mm as a base setting - 5 1/2 turns out is really too rich a setting. Approximately 3 turns would be a more suitable setting.

I hope this helps, however please come back to me if this does not solve the problem.

Best regards

Stephanie
Old 07-10-2007, 02:16 PM
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n9331v
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Default RE: RCV-91CD Tuning

I have just run my two new 90CD's for my B25 in for around two hours in 15 minute cycles, they started right up and I adjusted per the manual. After an hour or so I re-adjusted my high idle 1 1/4 turns out and my low idle 4 1/2 tuns out, the low idle is very touchy and I used very small adjustment 1/8th or less while the engine is running. My idle withought the remote glow system connected will settle in at 2022 rpm I had it idle at this rpm for 15min per engine. Remember if you adjust the low idle you will need to re-adjust the high side. I know you may have done this already, I read on another thread that one guy could not keep it running very well because he left the plug on the breather.

When these are tuned they sure run very nice and the sound is great.
I hope this is of some help.

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