I'm guessing 95/5? Any idea?

 

It varies from one engine to another, but here are some general valves of where the energy contained in the gasoline is used.

Crankshaft output 25-35%
Coolant 10-15%
Exhaust 40-55%
Friction 5 - 8 %
Accessories 3 - 5 % (water pump, power steering, AC)

 

I know that friction does play a huge role in heat. How much? I have no idea. I do know that one of the Miata's that was on the T25 team that I was on ran amazingly cool. For reference, a 120hp spec Miata will often have issues with running slightly hotter than you would like with an aftermarket radiator. This car had different internals that were lower friction, it made 150hp easily, (could have been much higher, but it was limited by tune for classing reasons) and with the stock radiator half blocked and a very fine mesh screen it was still running cooler than we would have liked.

We were all scratching out heads trying to figure out how to get it to run hotter... Granted the actual race too place in Northern CA in December, but even in much warmer weather testing it still ran very cool. Friction should have a large factor with heat and MPG, but I would guess that the heat from the combustion cycle is still much greater.

 

I'm not 100% sure on this, but I think you should take into account that most of the heat from combustion escapes through the exhaust pipes which means it has to convect from the combusted gas to the engine, whereas friction heats up the engine directly...

 

Not really arguing the point, but most engines run on oil surfaces, not metal to metal bearing surfaces. Even the rings are designed to float on the fine layer of oil held to the cylinder walls by the cross-hatching machined on the cylinder walls. There is an oil ring that serves to keep oil out of the combustion chamber but that just scrapes any excess, it cannot leave the cylinder walls completely bare of the stuff.

When Ford went with the iron block in the 2003-2004 Cobras the popular idea was the iron block was stronger, but in reality Ford's AL blocks were actually their strongest blocks - at no point would one of their AL blocks crack before one of their iron blocks from pure power production. But the iron block made a few more horsepower, apparently because iron has more capacity to absorb energy without increasing in temp, i.e. why we use iron brake rotors instead of AL rotors even though AL would be lighter and cool faster. I'm not going to argue why the capacity for absorbing heat matters in making power, beyond my knowledge. But the capacity for an iron block to maintain a consistent temp and generate a couple more horsepower during operation was cited as a deciding factor in that block choice. The point being that if friction heat was a relevant concern the block material and combustion chamber temps wouldn't be the issue. Crank, rod, and piston materials would. And those are steel in any Cobra.

My point is that while the heat generated in combustion might mostly go out the tailpipe, a very large amount of that energy is still transferred to the pistons, head, and block. That's why we have designs that squirt oil from the crank up through the rod to squirt on the bottom of the piston to carry that heat away, and squirt fuel on the backs of valves to cool them between combustion events. And reverse-flow designs that run coolant through the head before entering the block.

I don't think the heat from friction in an engine is a significant value compared to the heat generated by combustion. Heat from friction in transmissions and rear ends is definitely a significant issue but not really related to the question - "in an ICE..."

 

It would be interesting to take for example an f20c motor and spin it via crank by another power source and simulate different driving conditions just to see what the motor oil temp does.

 

No no, don't get me wrong I totally understand the point you're trying to make. I was just noting that its not as easy as it looks to quantify these numbers themselves due to the complexity of the mechanism- as you pointed out, friction is bearing friction...etc. I'm sure heat generated by friction is very small compared to the combustion.

 

and geeze could we harness the heat going out the tailpipe and turn it into steam or something? If youve ever stood behind a car on a dyno, damn!