Fuel injection plugs

Howard Wilkinson owly at mcn.net
Sat May 1 06:12:20 GMT 1999


James:
    BMEP is an acronym for Brake Mean Effective Pressure...... It may
be considered to mean the pressure developed in the cylinder by the
combusion process.  At low throttle settings BMEP is low, at WOT in
the max torque range BMEP is max....... Actual BMEP values vary
between engines as a result of compression ratio, boosting, camming,
etc.  The max torque developed by an engine per cubic inch
displacement is a direct relation to max BMEP.  Thus at high RPM BMEP
values are lower than at low RPM due to lower induction efficiency,
although the power output BHP is greater.  In general engines live
longer operating at lower BMEP.....    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 7:40 PM
Subject: Re: Fuel injection plugs


>
>
>Howard Wilkinson wrote:
>
>> 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.
>
>I am not familiar with the max bmep term, could you explain?  One
this to
>consider is the changes that could be made if this were the case
though.
>At max ve, we could optimize the ignition timing/cam duration/timing
to
>make max power at this specific point.  By doing so we could
significantly
>reduce advance and therefore negative torque on the engine btdc.  We
would
>also have less wear because the engine rpm would be constant and
would not
>experience varying loads on the bearings and such.  Though temps
would be
>greater as you mentioned.  Load would not be an issue because the
>transmission would compensate, always giving the engine some load.
The
>magnitude of the load would be in the engineers hands.  At this point
it
>seems as though we would be dealing more with transmission
reliability
>than engine reliability.
>
>James Ballenger
>
>




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