stunthanger.com
Engine basics => Engine set up tips => Topic started by: Steve Helmick on May 19, 2011, 03:15:07 PM
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Like I have posted before, I think a lot of folks have bad runs because they set the NV before the engine is up to temp. Often, this is clearly shown by the engine's rpm increasing as the flier heads for the handle. Don't do that!
With my muffler planes, I temporarily & intermitantly block off the uniflow vent or pinch the muffler pressure hose. The idea is to get the engine leaned out to the peak, to get it heated up faster. When it comes back down to the same rpm twice, it's hot. Once hot, I set the NV with the tach, and I'm ready to launch. It works very well, IMO.
My question is: Can I do this on a piped engine? Will it come back down to its normal launch rpm, or will it stay peaked?
In this case, the uniflow is open to ram air. I have blocked the vent for short periods, but not long enough to get it really lean, just lean-er. :-\ Steve
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Like I have posted before, I think a lot of folks have bad runs because they set the NV before the engine is up to temp. Often, this is clearly shown by the engine's rpm increasing as the flier heads for the handle. Don't do that!
With my muffler planes, I temporarily & intermitantly block off the uniflow vent or pinch the muffler pressure hose. The idea is to get the engine leaned out to the peak, to get it heated up faster. When it comes back down to the same rpm twice, it's hot. Once hot, I set the NV with the tach, and I'm ready to launch. It works very well, IMO.
My question is: Can I do this on a piped engine? Will it come back down to its normal launch rpm, or will it stay peaked?
In this case, the uniflow is open to ram air. I have blocked the vent for short periods, but not long enough to get it really lean, just lean-er. :-\ Steve
Hi Steve
We do this as a routine, just put your finger over the vent and let the motor rev for a couple of seconds, when you move your finger it will drop right back, then set the needle, it is most important for first flight in the day
Randy
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With my muffler planes, I temporarily & intermitantly block off the uniflow vent or pinch the muffler pressure hose. The idea is to get the engine leaned out to the peak, to get it heated up faster. When it comes back down to the same rpm twice, it's hot. Once hot, I set the NV with the tach, and I'm ready to launch. It works very well, IMO.
My question is: Can I do this on a piped engine? Will it come back down to its normal launch rpm, or will it stay peaked?
Of course. If it doesn't come back your pipe length it probably too short. Of course the effect you are trying to get is that the setting changes as a result of warming up.
Brett
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Thanks Randy and Brett. I'm so glad you two agreed on this! Conflicting info makes me, uh...conflicted.
~> Steve
PS: This retirement gig is great. Like being on welfare without the stigma, drugs and munchies.
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Hi Steve
We do this as a routine, just put your finger over the vent and let the motor rev for a couple of seconds, when you move your finger it will drop right back, then set the needle, it is most important for first flight in the day
Randy
It also takes a surprisingly long time to get rid of the after-run oil. Sometimes I can start my engine, set it, get out to the handle, and go a couple of laps, and still be able to smell a bit of it in the exhaust. Warming it up accelerates process.
Brett