Fuel injection plugs

[Raymond C Drouillard]

On Thu, 29 Apr 1999 22:47:49 -0400 James Ballenger <jballeng at vt.edu>
writes:
>
>
>Howard Wilkinson wrote:
>
>>     The most reasonable way to control engine power output is by
>> gearing so that RPM is controlled by load.  A continuously variable
>> transmission system could allow an engine to operate at full throttle
>> all the time except at idle when it would need to be throttled.
>> Allowing the engine to always operate at WOT would greatly increase
>> efficiency.           H.W.
>
>    Ok, I know this isnt right.  If we had continously variable
transmissions,
>we would be running them at peak torque not at wot.  VE is greatest at
peak
>torque, the reason we rev engines higher to acheive high horsepower is
to combat
>inefficient gearing.  At wot, there is significantly reduced ve and not
enough
>time to get good mixture and combustion, therefore lower torque.  The
reason
>this is an asset is because it produces more torque per unit time, ie
power.
>With a continuously variable transmission we could run the engine all
day long
>at peak torque and get double or triple the gas mileage, more power, and
reduced
>wear.  Again, im just a student so tell me where i goofed but I have
discussed
>this with others before and feel somehat confident that this is right.
>
>James Ballenger
>

Don't make the mistake of getting volumetric efficiency mixed up with
engine efficiency.  Engine efficiency is work in / work out.  VE is air
in / (.5 * displacement)   (for a four-cycle engine).  Torque is highest
at the highest VE because you can get more fuel in for each revolution of
the crank.  Power is highest at the point where you can get the most fuel
per unit time.

If you are running at the highest torque point (max VE), you have to
throttle it down to reduce power.  This throttling, of course, reduces VE
to the point where you get the desired power level.  Of course, this
increases pumping losses.

A more efficient way to reduce the power level is to reduce the engine
speed to below max torque.  You will have about the same amount of air
per unit time, but more air per revolution.  Actually, you will have a
little less air per unit time because it'll be running more efficiently. 
It won't have to do as much pumping.

Other benefits are less wear and tear, lower windage losses in the
crankcase, lower losses at the oil pump, etc.

Ray Drouillard

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