# Hp

#1
01-28-04, 08:13 PM
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Hp

Cheese...

What is the easiest way to increase HP on all 4cycle engines from 8HP up to 20HP??? I know there has to be a way to do it without getting inside the engine and doing alot of pisten or valves work. I have still of yet done some extra work on this machine, but I was just wondering. I am talking manly on B&S engine.

#2
01-29-04, 09:45 PM
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I think the easiest single way to boost power is to put a straight pipe on it. Have you looked at the thread Dennis G started about increasing hp on 8hp engines? The same stuff would apply to all engines, not just 8hp.

#3
01-29-04, 10:28 PM
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Ya might get 20 HP from an 8 HP engine but ya won't get it for long.

Last edited by jughead; 01-30-04 at 02:33 AM.
#4
01-30-04, 12:31 PM
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#5
01-30-04, 04:33 PM
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The first law of thermodynamics and/or the second law of thermodynamics and/or Newton's 2nd law.

The first law of thermodynamics says that you can't get something out if it wasn't put in first or wasn't there to start with. This applies to heat engines (which all internal combustion engines are). Simply put, in order to get 20 HP out you have to burn at least 20 HP worth of fuel. This would assume 100 percent energy conversion and no other losses. The second law of thermodynamics says that such a thing can't happen. Sadi Carnot had some very significant things to say about the thermal efficiency of heat engines. The amazing thing about his discovery is that heat engine thermal efficiency ONLY depends on the temperature of the heat source and the temperature of the heat sink. Those words apply as well today as they did over 100 years ago when he wrote them. On a reasonable engine you would probably be required to burn closer to 30HP worth of fuel to get 20HP at the output shaft. That much fuel burned in a small space (dictated by the smaller size of an engine origionally designed to be an 8HP model) would mean very high temperatures inside the engine. Metals loose strength at high temperatures. If you were to dump that much heat into the combustion chamber the engine components will quickly soften and fail.

You could try turning the engine faster and burn less fuel per stoke but Newton's second law says that running the engine faster will require the moving components to be stronger to stand the acceleration forces on the parts. Perhaps you think you can compensate for the requirements of stronger parts by using lighter parts, thereby cutting down on the acceleration forces; but, to get light you have to get thin or use different materials. While you can burn less fuel per stroke ,by going faster, you will still be required to burn 30HP worth of fuel per unit time. This would be bad news for your lighter, thiner parts. They would quickly fail.

Getting increased HP from any engine is a balancing act between expense, lightness, reliability, utility, cost of maintance, and a whole bunch of other things.

If you wish to get 20 HP from an engine that came into life as a 8HP model think of the famous words of Scotty on Star Trek "Captain she won't take it much longer, she's gonna blow!!"

Last edited by jughead; 01-31-04 at 01:18 AM.
#6
01-30-04, 08:57 PM
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Thankyou for clerifying that to me jughead. You taught me something today that will help me down the rode.

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