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Author Topic: 4-2-4 Power Boost  (Read 605 times)

Online Peter Germann

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4-2-4 Power Boost
« on: December 25, 2010, 03:37:54 AM »
Dear Friends

Running at governed 8'600 RPM, the attached graph displays power (watts) vs. time (sec) when doing a single wingover manoeuvre. How does the power modulation shown (525 - 740 -525 W  = 1.4 x) compare to the change of power of a 4-2-4 IC power train?

Kind regards and a happy new Year!
Peter Germann

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Peter Germann

Online Dennis Toth

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Re: 4-2-4 Power Boost
« Reply #1 on: December 25, 2010, 06:09:05 AM »
Peter,

This is very interesting to see just one maneuver and how the Watts vary, it looks very much like what one would expect to see from a 4-2-4. The thing that comes to mind is could we govern our rpm off a Watts load. Maybe Will H or Igor can develop a timer that would have rpm set points that would sense the Watts and add or reduce rpm based on how it varies. Looking at your data for instance, you would set a an rpm band or say 500 - 600W as level flight rpm at 8600, then a band of 600 - 900W at say 8800 rpm and then a <500 W set to 8750 rpm. There could be several smaller steps and initial setup would require several flights with a data logger (like the CC ICE ESC's) to find the correct transion Watts load points for  a particular ship.

This would follow the power needs through the pattern adding power and brake at the load points like a good 4-2-4. How about it Will and Igor?

Best,              DennisT
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Online Peter Germann

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Re: 4-2-4 Power Boost
« Reply #2 on: December 25, 2010, 09:07:59 AM »
Dennis,

the point I am interested in first, is whether a 4-2-4 IC setup does increase/decrease power by the same, quite substantial amount (+/- 40%) when I fly a single wingover? At this point in time I suspect (without knowing, of course) that the IC power train does not change power as much, which might be one of the reasons why flying electric seems to be so effortless...

Peter Germann
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Peter Germann

Offline Igor Burger

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Re: 4-2-4 Power Boost
« Reply #3 on: December 25, 2010, 09:21:24 AM »
No problem with me Dennis, it is actually 4 years old thing ... http://stunthanger.com/smf/index.php?topic=12673.0

 VD~
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Offline Igor Burger

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Re: 4-2-4 Power Boost
« Reply #4 on: December 25, 2010, 09:33:17 AM »
Quote from: Peter Germann on December 25, 2010, 09:07:59 AM
the point I am interested in first, is whether a 4-2-4 IC setup does increase/decrease power by the same, quite substantial amount (+/- 40%) when I fly a single wingover? At this point in time I suspect (without knowing, of course) that the IC power train does not change power as much, which might be one of the reasons why flying electric seems to be so effortless...

I do not think so. I would say the IC power train (I mean classic 4-2-4 setup) can add more or less. All depends on ventury, prop, tank, fuel, cooling ... etc etc etc ... while electric setup depends only on prop ... means that the advantage of the electric power train, is, that I can send setup by mail to opposite side of the globe, and it will run exactly as mine. And it is not only from this hemisphere to that hemisphere, but also from today to tomorrow. There is typically only one thing which gives properties of the power train, and it is the prop. Nothing else. The rest (ESC, motor, battery, timer) work or not, and if they work properly, they do not come to the formula. Larger prop will give you more boost, smaller will give you less. Clear and simple.  :)

All only to the point when you start to use something more clever that just 4-2-4 in IC (pipes) or active control instead of constant rpm ... that is the point where true fun begins  VD~
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Online Dennis Toth

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Re: 4-2-4 Power Boost
« Reply #5 on: December 26, 2010, 10:28:29 AM »
Igor,
Thanks for the path, does the timer add power based on watts or just amps? Is it adding throttle between limits or holding rpm?

Peter,
Most of the IC 4-2-4 setups will add only about 500-800 rpm depending on how sensitive the engine is to tank height (i.e. nose vertical fuel draw) and the pressure system used (this would be roughly 5 - 10% increase in HP). The straight uniflow will give more boost than the pipe or muffler pressure system and both are adjusted by the size of the venturi (i.e large venturi, lower suction - engine leans more - rpm increases more. Small venturi - slightly stronger suction less rpm change). Other tricks used are length of fuel line - further back, longer length fuel line requires more fuel draw thus is more sensitive to nose up / nose down position and  is used to add more lean break.

Best,         DennisT
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Offline Igor Burger

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Re: 4-2-4 Power Boost
« Reply #6 on: December 26, 2010, 01:45:17 PM »
It has only current sensor, but I use A123 batteries, which has flat voltage curve during discharge. And it does exactly you wanted - it adds rpm depending on current (or power if we count that the voltage is more or less constant) ... so the result is that it can cancel slippage to some extent ... or acts like a larger prop ... or as an IC 4-2-4 break ... and that is why I do not like it :- ))))))))))))))))))))))) ... but works well in gym (read in calm  VD~ )
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