RCU Forums - View Single Post - Tapered-Bore Engine Break-in

09-04-2011, 09:16 AM

#379

DarZeelon

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RE: Tapered-Bore Engine Break-in - Upgraded

Quote:

ORIGINAL: WMB

Hey Dar, I may have all this wrong. The piston is pushed down by a force. The force is from the expanding air trapped above the piston. The air is expanding due to the massive temperature increase. The temp increase is caused by the burning of the fuel. If this is true, then the heat is the needed product to make the piston go down. So, does the energy in fuel itself do the work, expanding air due to heat, a combination of the two, something else?

Oil content? The car guys use less and there engines are run harder. Are we airplane guys ungrounded in engine tuning or is there another reason for more oil in our plane fuel? Never did understand this.

Thanks, MikeB

That is correct, Mike.

It is through heat (and expansion) that an engine makes its power, but it is only between 20% and 26% of that heat; that is actually used by the engine to spin the prop.
The remainder of that heat is just excess that the engine needs to get rid of...

Getting rid of the heat is apparently not the reason plane engines need more oil.
After all, gas guys easily get away with just 2-3%, or even less.

Brian,

Because I also sometimes err in this, i.e. not reading entire posts, I can comment to others that do....

Aren't most iron-steel engines built with a parallel sleeve? I supposed this before hand.

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