MAF

[Greg Hermann]

>>
>> Sorry--spaced out showing the VE calc--so here it is:
>>
>> (7)  3.8 liters x 61 cubic inches/liter = 232 cubic inches
>>
>> (8) 232 cubic inches/revolution / 2 revolutions/cycle x 5300
>> revolutions/minute = 614800 cubic inches/minute.
>>
>> (9) 614800 cubic inches/minute / 1728 cubic inches/cubic foot = 356 cubic
>> feet/minute (theoretical swept intake volume)
>>
>> (10) 299.6 cfm/356 cfm = 84.2% VE (actual intake air volume/theoretical
>> swept intake volume) ((3)/(9))
>
>except max VE occurs at ( or very near) max torque
>not at the max flow rate of the injectors if porperly sized
>real VE for this setup would be in the 95-100% range if the torque peak is in
>the 3500 range
>
>also you are relating the VE to the size of the injectors
>this really has nothing to do with it
>just supplies a number that is the max VE that the FI could support
>with these injectors
>increasing size 17% or fuel pressure 35% would allow the same injector to
>support 100% VE at your indicated 5300 RPM
>
>Clive

All I was doing was calculating the VE for the particular operating
conditions which were stated---170 gr./sec. @ 5300 RPM on a 3.8 liter  4
stroke engine , as an example of how to do the calculation.

Of COURSE maximum injector duty cycle % will occur at maximum VE (which
occurs at maximum bmep, and at a lower engine speed, one which is fairly
near the brake torque peak, if we are going to be truly rigorous about our
semantics.) But the same calculation would apply had the data at that
engine speed been given. Anyone who wanted to develop a VE vs. Rpm curve
could do so by data logging the output from the MAF vs. RPM. Pretty simple
thing to plug into a spread sheet from there. Could tell a person a whole
lot about cam profiles----

And YES, peak bmep DOES happen at a DIFFERENT engine speed from brake
torque peak, because friction losses vary with engine speed also!

Regards, Greg