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HelicopterEngines Plugs Mufflers Fuel › OS .50 powerband
06-03-2010 12:48 AM  7 years agoPost 21
Gearhead

rrMaster

Vt

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""this still dosnt tell me how a different size pipe can make the "optimum" powerband range of 17000 go higher than the range that OS has set for it""

SIMPLE,, the shape of it !!

http://www.pmbmodelboats.com/tunedpipetheory.htm

http://www.motorcycle.com/how-to/ho...-care-3423.html

Jim
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06-03-2010 01:50 AM  7 years agoPost 22
Chuckie

rrKey Veteran

Crofton Maryland

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Someone needs to learn how to read
first off we do not know what Pipe OS uses on their 50 & 55 Heli Engines to set Power Ratings, for all we know OS uses a stock 46 Plane Muffler, or no Pipe at all, so with that a well Tuned Pipe/Muffler most likely will increase RPMs a bit over Stock Ratings,,
Good points. In the past motor manufactures have reported OPEN exhaust power and torque ratings. This means no exhaust or tuned pipe was used to determine the power ratings.

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06-03-2010 03:49 AM  7 years agoPost 23
jasonrusso

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Haverhill, Massachusetts

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Guys, I think we are arguing two different points here. I don't think anyone can argue that different pipes make the same engine run different. The question is/was: WHERE is max power made? If the engine is rated at 1.9hp at 17000 rpm, then pipe "x" will make 1.95hp at 17000 rpm, then pipe "y" will make 1.98hp at 17000 rpm. I don't see how a pipe will change WHERE the max power is made, just how much.

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06-03-2010 12:11 PM  7 years agoPost 24
Chuckie

rrKey Veteran

Crofton Maryland

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Pipes affect where and how much HP and torque are made.

First horse power is not the only consideration, torque is also and even more important than hp. Hp and torque curves over the usable rpm range of the motor differs with different pipes. I'm sure you have seen graphs for 6 and 8 cylinder car motor power/torque curves. The exhaust/pipe design affects the shape of the curves (how fast the values rise) and when (rpm) the max torque and power are reached, they also affect how fast the curves drop off after max values.

For the most part the pipes we use today are wide band tuned pipes. Narrow band tuned pipes will produce more power and torque but the curves rise and fall more quickly. The diagram and text I referenced shows how tuned pipes work where fuel and air that are drawn into the pipe is pushed back into the motor by the pressure wave. This in affect is increasing the engine size, bigger engines make more power because they have more fuel and air to burn; turbo charging does the same thing. The problem is narrow band pipes are hard to tune and once the motor is out of the ideal rpm range the hp/torque falls off rapidly. Wide band tuned pipes produce less hp/torque but they are much easier to tune and operate over a wider band.

A few years back an rc magazine published an article testing different pipes on the YS91 ST motor. They showed torque and power curves for the motor without an exhaust and with 6 or so narrow and wide band tuned pipes. I still have the article but don't have a scanner. I'll look for an example and post it later. A graph may help in seeing why different pipes change where and how much hp and torque are made.

Regards

Charles

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