It's not just gear ratios, but also the tradeoff between rolling resistance and wind resistance. Obviously the worse the aerodynamics, the lower the optimum speed, no matter if the engine is regeared to operate at optimum efficiency point -- my schoolbus gets much better mileage at 35mph than 60mph because it's a brick. Most modern cars have alot better aerodynamics than ones from the 80's when we had the 55mph limit, so maybe it is higher now.
I know that my VW (1991) is geared such that 55mph is pretty good for 4th gear, but 5th gear is pretty useless till you get to almost 75mph when it starts cruising right along again (which does drop the mileage to low 40's)
Zeke
I know that my VW (1991) is geared such that 55mph is pretty good for 4th gear, but 5th gear is pretty useless till you get to almost 75mph when it starts cruising right along again (which does drop the mileage to low 40's)
Zeke
Jonathan Hardin wrote:
> I'm curious about something. In particular the concept of limiting
> top speed to 55mph. I understand this being important on any car
> build/imported into the US before the speed limit change in the mid
> 90's. However, have car companies not modified their timing/ratios on
> the transmissions of vehicles built after this point in time? (I
> drive a 1990 Camry so the top speed of 55mph is what I try to stick
> with, but I am curious about newer cars). I know the adage about
> 55mph is from before the speed limit change; and it seems simple for
> the car manufacters to change the ratios to move the best ratios up to
> a 60 or 65mph area rather then 55mph. Just curious
> Jonathan
>
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