Fuel injection plugs

[Howard Wilkinson]

James:
    I must take issue with this statement.... my experience with
engines suggests that this is far from the truth:

>If the engine is not throttled and remains where it will make peak
power it
>will have significantly less wear on the engine.

My experience with numerous gas engines over the years would suggest
that there is a far stronger correlation between % Max BMEP operation
and engine wear.  At WOT (Max BMEP) combustion temps are greater, the
lubrication is less effective, and bottom end stresses and bearing
wear are higher.  Greatest engine life, and minimum wear appear to be
at lower throttle settings, and constant load.  This may not be
correct according to the experts, but this is what I've observed to be
true.       H.W.


-----Original Message-----
From: James Ballenger <jballeng at vt.edu>
To: diy_efi at efi332.eng.ohio-state.edu
<diy_efi at efi332.eng.ohio-state.edu>
Date: Friday, April 30, 1999 2:01 PM
Subject: Re: Fuel injection plugs


>
>
>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.  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 o
f
>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."
>
>
>> 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.
>
>
>> 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.
>
>James Ballenger
>
>
>