Fuel injection plugs

[Raymond C Drouillard]

On Fri, 30 Apr 1999 12:20:44 -0400 James Ballenger <jballeng at vt.edu>
writes:
>
>
>Raymond C Drouillard wrote:
>
>> 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.
>
>At peak ve, you get the closest thing to perfect combustion.  You get a
good
>full charge of, hopefully, stochiomteric mix and can burn it making
maximum
>force and maximum fuel economy.

I don't argue with the above.  What I am saying is that if you run it at
max VE without throttling it, you will generate MUCH more power than you
need.  If you throttle it, you will not have a good VE.  Throttling works
by lowering VE.


  At max power, we are making less torque but
>making it faster.  The problem here is that there are inherent
combustion and
>frictional ineffeciencies.  At max power (hp) we have to advance
ignition and
>now valve timing to try to catch up.  You get an incomplete burn of the
fuel
>and have a very inefficient cycle, its just that you can do this enough
per
>unit time to get more power.  The only reason we do this is because of
>imperfect gearing.  If we have a cvt, as discussed, the point becomes
moot
>because we can have insanely high (numerically) gearing and torque
>multiplication.  In this case we would not have a need for more power
because
>the transmission could be controlled as the throttle, while the engine
>remains at its most efficient state.
>
>> 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.
>
>There is not throttling with a cvt, the transmission is the 
>"throttle."

Agreed.  There is no throttling with a properly used CVT.  You reduce
power by LOWERING THE RPM of the entine to the point where it is
producing the desired power.

The engine is constantly at WOT, and the power output is controlled by
controling the engine speed.

>
>
>> 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.
>
>You won't be receiving more air, below max torque you will be getting
less
>air per revolution because it is not at peak ve.  At peak torque, you
get
>peak ve.  At peak ve, you get the fullest charge of air and fuel
possible
>from the engine and will be running more efficiently than at any other
point
>in the engines range.

I am comparing a throttled engine at the speed of max VE with an
unthrottled engine that has been slowed down enough to reduce the power
to the desired level.  Based on that, my statement is correct.

IF YOU RUN AN ENGINE AT MAXIMUM VE WITHOUT THROTTLING IT, YOU WILL GET
MORE POWER THAN YOU NEED, AND NOTHING YOU CAN DO WITH THE TRANSMISSION
(besides wasting the power through friction) WILL REDUCE THE POWER LEVEL.

>
>
>> Other benefits are less wear and tear, lower windage losses in the
>> crankcase, lower losses at the oil pump, etc.
>
>If the engine is not throttled and remains where it will make peak power
it
>will have significantly less wear on the engine.

If you are cruising at a speed that requires 25 HP to maintain, and your
engine is capable of putting out 200 HP, you have to either throttle it
or run it at a speed where it only generates 25 HP.  You CAN NOT run it
at its peak VE point or its peak power point and only generate 25 HP
unless you throttle it.


>
>James Ballenger
>
>


There, I said the same thing in several different ways.  Hopefully, the
concepts won't be misunderstood.  Please read it carefully before writing
a rebuttal.

Ray Drouillard, BSEE

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