You make an extremely interesting point here that I have not seen made
before. I only know what bhp the engine in my car makes when I have it run
up on the chassis dyno so all the numbers I see are RPM specific. So, the
bhp the engine produces to drive at 60mph in 3rd gear are in fact much higher
than the bhp the engine produces to drive at 60mph in 4th gear because the
bhp is always rpm specific. I think seeing all my power figures in relation
to dyno testing has blinkered some of my understanding because.........
On that basis your statement below would appear to be incorrect. HOWEVER, as
far as I know the chassis dyno readings are always taken under a full load
which the dyno operator applies to the rollers (I guess this explains why the
power figure as indicated on the dyno station jumps about while the rpm and
speed remain constant (say 5000rpm, 6000rpm, etc). It would also explain why
for any given speed (say a steady 85mph cruising in 5th gear) my car consumes
much more fuel with the softtop roof down than with it up. What is happening
is that because the aerodynamic drag increases the engine is required to burn
more fuel (the max efficiency for any given rpm) to generate optimum power at
that rpm simply because it needs to.
I guess that the chassis dyno power figure for any given rpm is the max rpm
the engine produces is not necessarily what is required to drive the car at
that given speed (as I had previously thought and always puzzled me).
Does all this make sense? Have I seen the light or was I always thick? Any
comment?
Daniel1312
In a message dated 27/09/01 12:50:48 Pacific Daylight Time, TMHEFFRON@aol.com
writes:
<< It doesn't matter what mod's you've made to the
engine, if you need 20 HP to go 60, that's all your engine is called upon to
produce when going 60. >>
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