Prop size and Engine Tunning
11-10-2016 | 06:26 PM
#1
Thread Starter
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Prop size and Engine Tunning
I have have two questions . I have a DLE 35 RA , runs great in all respects it runs a 20x6 prop . Engine tune is perfect running at factory settings
1) If I went to a higher pitch prop ( 20x8, 20 x10) what would happen to the engine "tune" ? Would it be too rich or too lean? What would happen if I went a lower pitch prop , ( 19x8, 19x6, etc.) again too rich or too lean ? Also is no change at all possible.?Assume nothing else changes.
2) Does anybody have any knowledge about some thing called the " Prop Rule"? It is explained the following way- 2 times the prop diameter plus the pitch results in a number for that prop. Any other prop with different dimensions adding to the same number will have equivalent performance.
For example a 20 x6 and 19 x8 will both by the " Prop Rule " generate the same number - 46. Thus they are equivalent in all respects including how they load the engine , power developed and performance.
Anybody have thoughts or insights about this ? It seems like it should be true.
1) If I went to a higher pitch prop ( 20x8, 20 x10) what would happen to the engine "tune" ? Would it be too rich or too lean? What would happen if I went a lower pitch prop , ( 19x8, 19x6, etc.) again too rich or too lean ? Also is no change at all possible.?Assume nothing else changes.
2) Does anybody have any knowledge about some thing called the " Prop Rule"? It is explained the following way- 2 times the prop diameter plus the pitch results in a number for that prop. Any other prop with different dimensions adding to the same number will have equivalent performance.
For example a 20 x6 and 19 x8 will both by the " Prop Rule " generate the same number - 46. Thus they are equivalent in all respects including how they load the engine , power developed and performance.
Anybody have thoughts or insights about this ? It seems like it should be true.
11-10-2016 | 07:01 PM
#2
My Feedback: (2)
Regarding tune, just a theoretical WAG (I would encourage you to start your tune over again) but I'd guess the low speed wouldn't change much, while the high speed could go either way - but not much. Maybe a screwdriver blade width.
Your "prop rule" is one I haven't seen. It sounds close - but only as regarding engine load. When you change the propeller's pitch there will be an associated change in the planes performance envelope. 6" props will generally result in better braking, lower top speeds, better vertical, and shorter take off runs. If you know the plane well, all of those attributes will change with an 8" prop - faster top speed, less available braking on down lines and while on final, etc. Basically, going to an 8" prop is like shifting the plane into a higher gear if that makes any sense.
I know they don't give away props, but you really don't know which you'll like better until you try them (6" vs. 8"). Another WAG - 6" will usually work out best for most sport flyers....
Your "prop rule" is one I haven't seen. It sounds close - but only as regarding engine load. When you change the propeller's pitch there will be an associated change in the planes performance envelope. 6" props will generally result in better braking, lower top speeds, better vertical, and shorter take off runs. If you know the plane well, all of those attributes will change with an 8" prop - faster top speed, less available braking on down lines and while on final, etc. Basically, going to an 8" prop is like shifting the plane into a higher gear if that makes any sense.
I know they don't give away props, but you really don't know which you'll like better until you try them (6" vs. 8"). Another WAG - 6" will usually work out best for most sport flyers....
