Quote:
Originally Posted by MetroMPG
I also find it funny that automakers almost never made a manual transmission (at least in the North American market) with a truly "tall" top gear (meaning: one that would satisfy an ecomodder). In other words, something analagous to the very tall top gears in some modern automatics for extra highway fuel savings.
I recently drove a Chrysler 9-speed automatic, and top gear didn't even engage until somewhere around 90 km/h (55 mph) on level ground.
Apparently a manual "economy" top gear that might require downshifting for any reason once at highway speeds is verboten by the product planners.
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The 1984- 1987 CRX HF had three overdrive gears. Top speed was achieved in 3rd-gear, as shifting to 4th dropped rpm so drastically that all power and torque was lost.
On the flat, the car could cruise effortlessly at 55-mph,in 5th, but throw a headwind or any grade at it, and you'd be back down in third-gear just to maintain speed.
According to Sergio Pininfarina, these 'tall' gears were a form of speed governor.
If allowed to accelerate to a horsepower-limited terminal velocity, the brakes would be inadequate, requiring a weight gain to brakes, suspension, and chassis, in order to beef everything up, safety wise; defeating mpg gains.
Robert Cumberford reported that engineers at a major European auto manufacturer had presented a producible Cd 0.15 design to their top brass in 1963. The CEO rejected it wholesale, on account of the top-speed implications and braking issues, etc.. The company chose to just keep making 750cc, softened 'bricks,' like always.