> I also thought that long stroke engines developed more low end
> torque for their size.
>
> Blake
Blake you're right, they do. Or more specifically their torque peak comes
earlier in the RPM band. The area under the torque curve (when plotted) is
the same for either long stroke/short rod and short stroke/long rod. The
shorter stroke/longer rod combination will have a lower torque peak... but
it's curve will be more flat through the RPM band and taper off less quickly
(once engine speed passes the torque peak).
Note though, that much of what has been discussed I tried to keep in direct
relation to the rod/stroke ratios. Things like torque generated are also
subject to intake system design, port shape, EFI vs. Carb and many other
factors. Larry Hoy and I were further discussing some things, and I brought
up Rick Lindsay's post a few weeks ago about using long intake runners on
BMW motors. This is one of the ways BMW manages to increase its bottom end
torque since they're torque and power peaks typically come at higher engine
speeds.
Here is an excellent article on tuned intake runners, explaining about
intake runner lengths, port velocities, resonance, and well just about
everything:
http://www.autospeed.com/A_0122/P_1/article.html
The Auto Speed website is a good one, with MANY easy to read and well
written technical articles.
The point about intake runner length in relation to connecting rod length
(or stroke length), is that a short coming of one area can be engineered out
of the system with modifications to other areas. Since you really aren't
losing torque with a short stroke engine, since it is spread out more evenly
and for longer than a long stroke motor, I wouldn't see too much of a need
for everyone to run into their garages and measure the intake runner lengths
on their MGs and then calculate the optimum length.
Kai
///
/// mgs@autox.team.net mailing list
/// or try http://www.team.net/cgi-bin/majorcool
///
|