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Old 02-23-2005, 03:23 PM   #1
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Default [REQUEST] Information or links to literature on engines


A friend of mine is studying car mechanics. He's in his last year and he's doing his paper on the loss of energy in engines.

I told him that there are quite a few people on this car forum that know a lot about those things so I said I would ask.

This is a translation of his email:
The purpose of my paper is to calculate the "effectiveness" (I don't know how to translate this properly) of an engine. To put it simply: what goes in and what comes out. I also have to measure the losses myself. You have mecanical loss because of friction, heat loss because of radiation and convection to the environment (or something like that), heat loss because of the cooling system, ...

Especially the measurement of radiation & convection of the mechanical losses are hard to measure. It would be nice if someone on the car forum could give me some tips on information or literature consering the subject. Especially about the practical way of measuring would be interesting.

Thx in advance
It's a rather difficult subject, but I could give it a try!
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Old 02-23-2005, 03:43 PM   #2
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One way would be to calculate the theoretical power/torque excluding losses and then take the measured power/torque which will give you the actual power/torque plus losses.

It's exceedingly difficult to calculate alone frictional losses as there's so many moving parts and even more difficult to calculate heat loss due to various factors.

Good luck to him
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Old 02-23-2005, 04:04 PM   #3
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Ask him if he can do something with a Sankey diagram of an (older) engine. I have it somewhere, but I'll have to look for it.
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Old 02-23-2005, 04:21 PM   #4
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good luck to your friend. As mindgame says, it's extremely difficult to calculate al frictional losses. The most simple way is to study an old engine, the most basic one.
Just imagine the number of calculations he has to do... one cylinder, the rings, the speeds, forces involved, friction when the oil is at certain temperature...omg
then go to the crankshaft. All bearing, conecting rods, bands, chains, gears, etc involve in power losses up to a 10% in certain conditions, and not mentioning all frictional and heat losses.

for some heat losses he can consider the fuel/air ratio in the cylinder, the effectivness of the combustion, the transformation of chemical to kinetic energy....

I'm dizzy just thinking of everything, that's why it's more easy to have the theoretical input power and measure the output power
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Old 02-23-2005, 08:17 PM   #5
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so your trying to measure the efficiency? there is tons of info on this on the net. probably more than he want lol. some basics are--- there is a temperature for your engine to run most efficiently at. ifs not the coolest temperature either. even on a hot day you have to let a car "warm up"
there is a thing called volumetric efficiency, which has to do with getting air/fuel in the cylinders. you have reached 100% VE (you won't have this in a stock naturally asperated car) when the atmospheric pressure inside the cylinder is the same as the outside of the car.
turbos/superchargers assist the engine in become more efficient at producing power and increase the VE to beyond 100%
heres a link with some info

also, iron blocks make more power than aluminum ones because they retain heat. the aluminum cools very quickly in comparison and makes the engine less efficient.

you cannot accurately predict hp loss to friction.
here is a link of a convo i was a little part of
he has measured the power at the rear wheels and flywheel. to you can subtract to get a frictional loss.

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Old 02-24-2005, 07:34 AM   #6
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Theoretical predictions for losses, both heat and friction, although time consuming will be accurate to within 1-2% i should think.
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