stunthanger.com
Engine basics => Engine set up tips => Topic started by: Phillip Kenney on April 03, 2012, 12:49:21 PM
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Outside of the obvious displacement difference, what if any are the advantages and disadvantages of these two engines? Primarily looking to power a Top Flite Tutor kit I'm about to build.
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Well I do have one FP25 and too many to count FP20s. This is because I never want to run out of FP20s! Fit out an FP20 as per the BBTU as preached by Dan Rutherford and you will have the best possible pipe style run out of the many other small bore engine. Without the BBTU, the FP25 probably wins over the FP20 on purely power output.
Dan Rutherford used to convert FP25s to FP 20s so that should tell you something. I have tried the BBTU on an Fp25 and it just doesn't work anywhere near as well as it does on the FP20.
Regards,
Andrew.
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I remember reading Brett's essay on the tuneing of the OS 20 Fp but cant find it now. Do you have either a link to it or a copy of it you could provide me.
Makes sense if people are converting the 25 fp to a 20 fp there must be some magic there.
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It's really complicated:
Use the E2030 muffler that came with most FP 20s (and comes with the LA 25), use an APC 9-4 prop, and the stock FP-20 venturi. Convert to a regular needle valve per your preference: the regular needle valve works better, the remote needle valve survives full-power inverted landings better.
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If you go to Heman Lee's "Aeromaniacs" site and click on "Tips" you will find Brett's instructions on how to set up
FP-20s...and a lot of other good stuff as well. 8)
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If you ask Dan Rutherford very nicely, he will send you his monumental epistle on the FP20 BBTU. It will tell you every last detail of the conversion, plus some things that are not! I like Dan's style of delivery!
Look up Dan Rutherford in the members list and send him an email, that should get you a 12 or 13 page epistle which tells you all!
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If you ask Dan Rutherford very nicely, he will send you his monumental epistle on the FP20 BBTU. It will tell you every last detail of the conversion, plus some things that are not! I like Dan's style of delivery!
Look up Dan Rutherford in the members list and send him an email, that should get you a 12 or 13 page epistle which tells you all!
It's posted here somewhere, too. As far as the engine goes, it's pretty simple - get all the stock parts and bolt it to the airplane, and get an APC 9-4.
The tank is of interest but at long as you keep the uniflow vent (or other pressure reference) no further than an inch outboard of the spraybar, it will work.
Brett
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Question about the setup that I dont recall seeing discussed.
Is it important to seal the muffler-engine flange as is the case with piped engines ?
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Question about the setup that I dont recall seeing discussed.
Is it important to seal the muffler-engine flange as is the case with piped engines ?
Hi Allan,
Nothing other than a good fit between the muffler and flange. If either is damaged, do whatever it takes to ave a good seal, but otherwise, just tighten the muffler down snug. ;D
BIG Bear
RNMM/AMM