On 7/25/2015 10:58 AM, John McCoy wrote:
Leon lcb11211@swbelldotnet wrote in
:

FWIW a small engine putting out extreme hp for its size does need lots
of cooling capacity. I remember when 2.3 liter produced 93 hp. It is
not unusual now to see less than 2 liter producing almost 300 hp.

The size of the engine is irrelevant, it's purely dependant on
the amount of power. Give or take a fraction, about 25% of the
chemical energy in the fuel comes out as mechanical energy (i.e.
horsepower), about 50% goes as heat in the exhaust, and about
25% goes as heat to the radiator.

That was my point, typically all engines are small these days but
produce up to triple HP so the need to cool is greater.
You left out natural heat radiation of the engine itself not counting
the exhaust. ;~) I'm an ex-GM service manager, actually my real jobs
were upper automotive management.
A few things that I could never quite understand and the factory reps
could not explain.

1. The heat extracted by the radiator is blown straight back on to the
source. How does that work? LOL
2. I'm not sure how electric fuel pumps work to day but in the 70's and
80's many were submerged inside the fuel tank. I disassembled an
electric fuel pump and noticed that the fuel travels through the
electric motor including the brushes. How does the vehicle not blow up
when out of fuel but loaded with gas vapors?



With respect to passenger cars, none of them have a radiator
big enough to handle their peak power output. The designers
depend on the fact that drivers rarely ask for full power for
more than a few seconds (passing on a two lane road, stop light
drag races, etc). Semi trucks, which do need to produce peak
power for extended periods, have vastly larger radiators even
tho their power output isn't much more (360-430hp would be
typical).

And hence the extra electric fans that often continue to run after
engine is turned off. I can assure you that engines reach peek
operating temperatures more often when sitting in traffic in summer heat
than when putting out peek power. If it were not for those fans every
vehicle would be over heating when is stop and go traffic.


Yamaha rates my bikes engine at 188hp (from 1 liter). It has
a radiator of 14" x 10". You wouldn't need a much larger
radiator for the typical small car.

Different set up altogether. The engine is more in the open and heat is
not captured by the engine compartment found on most 4 wheel vehicles.
And especially, the engine is not working nearly as hard as a similar HP
car engine lugging around 3000+ pounds and powering AC, which BTY also
contributes heat through the condenser, and vehicles that still have PS
pumps.

But yes in ideal conditions the vehicle is, in varying less degrees,
dependent on radiator capacity.