Quote:
Originally Posted by Deslock
The lower curb weight will improve fuel economy. The engine being mated to RWD and tuned for output and throttle response will hinder it.
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Actually tuning for output doesn't hinder fuel economy for faster cars because the maximum output isn't used in the test. Besides, no engine comes from the factory actually tuned for output, because they always run rich to protect the cats. I'm fairly sure the MX5 won't need to be floored to pass the EPA's acceleration test.
Back in the day of cable throttles, you'd see stuff like the maximum advance on intake cams always activated on Porsche M96 engines for throttle response but nowadays everything is throttle-by-wire and I'd be surprised if they resorted to that kind of method to improve response. With throttle by wire the ECU doesn't have to detect the pedal going down and then shift the cams around, it can open the throttle and change timing at the same time. BMW's solution was to use separate oil pumps to drive the VANOS for better response in the M cars, Toyota's was to use electric motors instead of oil pressure in the higher end Lexus cars.
Quote:
Originally Posted by juliog
True that. I guess convertibles also take a hit in mileage when the top is put down? Does the EPA test convertibles with the top up or down?
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I don't think they actually test the aero, they just take the manufacturer's word for it and enter it into the dyno. The manufacturer tests the drag with top up for obvious reasons. If the EPA actually puts it in a wind tunnel to measure the drag then it would probably test with top up.