OT: Hybrid cars

[Oleg Goldshmidt]

guy keren <guy.choo.keren at gmail.com> writes:

> instead of going into theories - does your car have a fuel consumption
> computer?

Yes, it does, that's how I know that it is more efficient at higher
speeds. I made a point to say that I never did systematic observations
or statistical analyses, just watched the numbers occasionally out of
curiousity. In effect it was exactly the kind of experiment you
suggested.

My car is different from yours, that's all. Your Prius, in particular,
may use relatively more battery at lower highway speeds giving you
momentarily better numbers (I don't know that, I am guessing). I assume
it is not a plug-in, so at some point it will consume some fuel to
recharge the battery and your numbers may be momentarily worse. I assume
it is smart enough to do it when the engine is not under load and when
you are in a lousy regime (in a traffic jam, etc.). This would be smart
on two levels: a) charge the battery when you have spare capacity; b)
this regime will improve the average numbers, exactly as I showed in the
previous email.

To emphasize again: all of the above regarding what your Prius may or
may not do is guesswork. Not so unreasonable guesswork, I hope. But even
if it is basically correct, it also may be just a component in the
overall picture. My car has a significantly larger engine, probably uses
a different AFR, definitely a completely different gearbox (and quite
probably lower RPMs at higher speeds), different aerodynamics. It is not
reasonable to expect a particular derived characteristic (optimal speed
for fuel consumption) to be similar for suc different models. Even the
markets for which the cars were designed by the manufacturers are
completely different: Prius's target market is definitely closer to
California than to Europe, while Passats are not very popular in the US
but common in the Old World. Guess what: Americans drive much slower on
average (highway speed limits between 55mph and 65mph). This could
easily affect design decisions. [Again: no, I did not watch over the
shoulders of Toyota or VW engineers.]

-- 
Oleg Goldshmidt | pub at goldshmidt.org