Re: Cosworth V8 may be the most powerful in the pitlane?

On Thu, 09 Mar 2006 22:41:32 +0000, Phil Newnham <pnewnham@xxxxxxxxx>
wrote:

The heat comes from the amount of work done. The V8 produces less power,
so it will do less work. IOW, the cars will go slower, in a straight
line, than they used to. Except they won't, because the aerodynamics
have improved - the vehicle weight might be the same, but the dominating
load is the aerodynamic drag, not rolling resistance. So the V8 will be
asked to do less work than the V10 because of the improved rear

I don't think aerodynamics could have improved so much, that 150KW of
power would not be missed. If they could have, they would've done that
before.

engine. The heat equation is simple:

Energy from fuel = useful work + heat rejected through the exhaust +
heat rejected through the radiator

But that is just an "energy" equasion. It has not much to do with how
and where heat occurs, how it travels and how it is dismissed.

You are only thinking about the top end of the engine and the big
bang. If your thesis would be correct, then my 190Bhp engine after
being reworked to 350Bhp, without engine size or radiator change and
something close to triple the fuel flow, should have been running much
hotter. Yet, in equally hard driving, both the oil and coolant temps
were in fact markably down. So much so, i drove the thing with a crack
in the radiator top joint for over a year, including to Perth and back
at some rather high(240 is pretty good) and sustained speeds in 43c
heat.
Same size cylinders, much bigger bang. This engine should have had
much more "rejected heat" and hell, you certainly didn't want to get
your hands near the extractors. But that is "rejected heat" from the
explosion, leaving only some residual heat flushed during the next
couple of strokes.

And this is what i'm trying to say with all this. When the explosion
occurs, heat travels in all directions form a number of sources.
The most obvious is the combustion chamber, once every 2 revolutions.
The chamber of a running engine sits well over 400C no matter what
happens and is very well vented in a race engine. It certainly
contributes greatly to engine heat, but it's not the only thing.
The less obvious sources are the mechanical components. Do you realise
that in a good engine some 50% of mechanical energy is lost in
friction ? Let's say 40% for an F1 engine. That is friction, all under
huge pressures right around not just on the end of the power stroke,
producing a lot of heat, which ends up carried away by the oil, which
in turn needs to be cooled by the water. Since oil plays a vital
partin stabilising the engine temperature, this is just as critical
to get right as coolant flow and quantity.
So if they simply underestimated the pressures on the components with
the new configuration, then it will nicely explain exactly why the V8s
are complaining about being 'uncomfortable'.
Basically this is what i'm trying ot say with this whole thing, that
it's not all "power = heat". Although, i certainly agree with you
that power does determine the amount of friction right through the
engine. So in a way you're right, it's just that i think you are
thinking of it too simplistically.

Your example of the trailer is flawed, because an F1 engine is always
asked to work at maximum load, as opposed to my car, which is only asked
to work at maximum load when I'm feeling rich ;). If the drag
coefficient is reduced for a particular setup, then the car runs at a
higher speed on the straights, and the engine is once again at max load.

No it is not. Maximum throttle or speed is not maximum load.
"Maximum load" is at the time when you floor the pedal, provided
you're on the torque curve. This load will depend on the resistance
your engine has to deal with.

When they switch to V8s they will still run the engine at max load all
the time, but it will be less capable. The load isn't capable of
generating heat (beyond skin friction heating of the car, but they're
not going *that* fast) - all the heat has to come from the fuel. Unless
you're suggesting that the engine's useful power output itself is
reduced by running a higher drag setup, then the specific fuel
consumption will be the same at max load as it always is, so the heat
rejected will be the same.

Um.. no. As i've said, drive up a long hill at a nice steady throttle.
Note temperature readings of oil and coolant.
Now hook on the trailer and using the same throttle setting, do the
same. You'll notice a higher temperature both in oil and water.
Is the engine using more fuel ? No. How could it, when it's getting
the same amount of fuel. So where does the heat come from ?

--

Regards, Frank
.

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