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Author Topic: engine efficiency ?
Cougyr
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Babbler # 3336

posted 28 January 2006 06:14 PM      Profile for Cougyr     Send New Private Message      Edit/Delete Post  Reply With Quote 
Does anyone know how I can find the optimum rpm for my car engine? What rpm gives the best fuel economy? Power? When should I shift gears? The owner's manual deals with mph in rather simplistic terms, which is stupid, because nothing could be simpler than watching the tach. Oh, the car is a Mazda 3 Sport.

Are there any web sites for this stuff?


From: over the mountain | Registered: Nov 2002  |  IP: Logged
DrConway
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Babbler # 490

posted 28 January 2006 06:31 PM      Profile for DrConway     Send New Private Message      Edit/Delete Post  Reply With Quote 
The rule of thumb I've had car guys tell me is that theoretical mileage is generally at between 80 and 100 km/h for older cars and newer ones generally between 90 and 110.

From practical experience I can tell you this is a true effect; I once made a 500-kilometer drive at 110 km/h most of the way and ended up with a quarter tank left instead of the usual eighth of a tank when I did the same drive at speeds in excess of 120 km/h; you get vastly diminishing returns at higher velocities partly because drag resistance becomes an important factor.

Try googling these terms: dyno curve Mazda 3 Sport. A dyno curve is a plot made by a very expensive piece of equipment wherein you drive your car on rollers, and a computer does magic juju and spits out what your car's performance characteristics look like. In the case of a car that's bone stock, unmodded, the dyno curve for a stock Mazda 3 Sport will essentially be the one for yours.


From: You shall not side with the great against the powerless. | Registered: May 2001  |  IP: Logged
Cougyr
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posted 28 January 2006 07:50 PM      Profile for Cougyr     Send New Private Message      Edit/Delete Post  Reply With Quote 
Thanks, but I couldn't find anything useful to me by Googling. (I'm not good at Search functions.) One would think that the owners manual would tell which rpm range is the most fuel efficient. Come to think of it, one would think that info would be on the dealer's sticker. Why they have an rpm counter (tach to me) and not give this is puzzling; they must be catering to the lowest common denominator.

Actually, I did find one chart by someone who must be a racer because he's shifting at 7000rpm!

[ 28 January 2006: Message edited by: Cougyr ]


From: over the mountain | Registered: Nov 2002  |  IP: Logged

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