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HelicopterEngines Plugs Mufflers Fuel › MP2 - how does it operate?
04-28-2004 06:24 AM  13 years agoPost 1
Ninjak2k

rrApprentice

Centreville, VA

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This is kind of related to the "Governors with pipes" thread, but a slightly different question, so I thought a new thread would be better.

I've read posts stating that the MP2 likes to run with engines at 17000 RPM or so, giving head speeds in most helicopters near 1900+. Will it tend to pull engines to this, or is that still setup via throttle curves or a governor? Similarily, once the engine is at the speed, will it tend to keep it there, or is that again controlled by curves/governor? Will it still overspeed if you don't throttle back in descents or will the pipe keep it there?

If you want lower headspeeds, say 1700 or so, can you lower the curves to get there, and is this a bad thing in terms of how the pipe operates?

Thanks,
Dan

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04-30-2004 01:19 AM  13 years agoPost 2
Wisdom-Seeker

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Danville, CA

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The thing about a pipe is that you are either operating in its tuned range or you are not. If you are not, then the pipe is nothing more or less than a muffler. However, when you are operating in the pipe's tuned range, you get a boost in performance, and a corresponding change in fuel requirements. If you adjust your fuel mixture to the tuned range of the pipe, then it will tend to be on the rich side when operating at other speeds. So, once on the tune, the engine tends to stay at that speed. Running off of the tune and you might as well have a tin can on your engine for all of the benefit you get.

--

Wisdom-Seeker
Protest letter to insurance co.: What do you mean "Act of God"?

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04-30-2004 01:45 AM  13 years agoPost 3
Ninjak2k

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Centreville, VA

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So there is a tendency for the engine to stay on the pipe on its own? You still have to help it along with a good throttle curve or governor, though, right? Else, it would fall off at some point, correct?

Thanks for the insight.

~Dan

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04-30-2004 02:06 AM  13 years agoPost 4
DS 8717

rrProfessor

Here wishing i was somewhere else

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There are other variables to consider,compression has a huge effect on how a motor comes on pipe. if the compression is high or too high it will come on sooner and hang if it's too high. I use a Hatori 60 size tune pipe and header on my OS 50 with a 8.63 gear ratio and a 1850 headspeed and it works very well,i used to run 9.6 ratio but did not like that,the 8.63 is much smother and the motor handles it just fine for 3-D.
I use a 2 speed set up 1700 in normal mode and 1850 in stunt mode,it is really smooth in hover in the 1700,i like this lower headspeed because i can easily tell if i am in normal or stunt mode.
Having said that the OS 50 has fairly high compression,being as i use 30% nitro i lowered the compression by making the combustion chamber bowl shaped instead if the stock flat top around the glow plug.
I also raised the exhaust port 5 degrees which also lowers the compression and gives a little more mid and top end power. DOUG

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04-30-2004 07:39 AM  13 years agoPost 5
Unbalanced

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Melbourne, Australia

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Interesting question - there are quite a few MP2 models in the range btw - for different engines/gearing.

If the pipe is really peaky, like a full wave or the MP1, then the governing is very effective. You just have to ensure that the throttle is opened enough to keep the RPMs in band and it is very insensitive to load or minor throttle changes. If you use a full pipe then I'd say a governor is optional if you are at least prepared to hit the hold switch rather than going for full down collective powered descents for example.

I've only used the 90 sized MP2 and it isn't particularily peaky, easy to overspeed for example. From what I understand it is more focussed on generating strong torque then max power anyway - to suit lower engine RPMs/quieter operation - so it isn't a classic b?lls and all pipe. Haven't played with the 50 sized pipes.

Jeff

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HelicopterEngines Plugs Mufflers Fuel › MP2 - how does it operate?
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