Bob, actually the program does show that the long stroke combinations
make more low end torque. The difference was small in the cases I tried
last night but when I exaggerate the stroke spreads you can clearly see
that the longer cases are best down low. I just tried these three
bore/stroke combinations for a 306CID engine;
Bore/stroke TQ@2000 TQ@2500 TQ@3000 TQ@3500 TQ@4000
4.414/2.5 357 365 381
396 406
4.030/3.0 364 370 385
398 407
3.730/3.5 367 372 385
397 405
It is interesting to note that the long stroke did not really make
significantly more TQ than the medium stroke but both the medium and the
long made a few percent more TQ than the short case.
If you graph the IMEP (indicated mean effective pressure, cylinder) you
can see the longer stroke configurations making more cylinder pressure
up to a point between the TQ and HP peaks, then the IMEP converges for
all three cases and the configurations are basically equal with respect
to IMEP. The BMEP (brake mean effective pressure, cylinder) looks to be
mostly a result of subtracting FMEP (friction mean effective pressure,
cylinder) from IMEP, the BMEP looks to be directly related to TQ. The
FMEP component seems to be responsible for reducing the difference in TQ
of the long and short stroke cases in the low RPM end of the plots and
also for creating a divergence in the TQ curves in the high end of the
plot where the short stroke configurations are shown to make more TQ.
Frank
> -----Original Message-----
> From: Bob Palmer [mailto:rpalmer@ucsd.edu]
> It's interesting too that the
> program puts the lie to the old notion that long stroke
> engines produce more low-end torque.
> Bob Palmer
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