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Engine basics => Engine set up tips => Topic started by: Motorman on August 23, 2016, 10:24:37 PM
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What do you do when your engine has more power than you need and you have to run it rich in a full 4 stroke. I know several ways to get less power but which way is best.
MM
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What do you do when your engine has more power than you need and you have to run it rich in a full 4 stroke. I know several ways to get less power but which way is best.
The typical solution is to reduce the venturi diameter .005" at a time until you get the right setting at the right speed. That will also smooth out the run. An alternative, possibly better, solution is to reduce the pitch to reduce the efficiency in level flight. You can set it leaner to get the same airspeed, then the efficiency will increase dramatically in the corners. A third alternative is to reduce the nitro, which will also let you run leaner but increase the in-flight variation, too
Which of these is best is a matter of experimenting and optimization. To first approximation, you should try each method, and then optimize around that (which may include engine, trim, handle settings, and flying adjustments), then try the next method, repeat, and at the end, decide which works best. With a lot of experience you can short-cut some of it, but overall this is a few weeks worth of flying sessions at least, and you need a wide variation on the weather to really find the best.
Brett
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Consult with Tim Allen on this problem!
Basic rule of stunt is to adjust your airplane speed with propeller pitch. The heat & twist method works if you use a suitable resin. I believe the racer/speed methodology is to use a resin that won't do that. I can't say I'm good at the re-pitching technique, but Howard showed me how he does it, and then I figured out a variation that works for me, with good results so far. y1 Steve
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MM.
For the most part adjusting the pitch and letting the engine run at its happy RPM is the current set up. You didn't mention what prop you were using but lower pitch around 4" gets the RPM up around 11K. If you have a pitch gauge you can easily tweak the pitch up or down in say 1/4" increments to get your desired lap time.
Start by heating the root of the prop (and this works for Carbon, APC and wood props, only the amount of heat varies) then holding the hub (use a glove) give the blade a twist and re-measure. You will get a feel for how much heat and how much twist you need. I am a bit lazy and only pitch at the 70% station out from the hub. Once you do it a few times you can get as detailed as you like but the 70% point works to start.
Best, DennisT