rpm vs. speed question

laocmo · 2006-04-20T13:13:29+00:00

I've recently acquired a 05 MazdaSpeed Turbo, 6-speed, a retirementgift for myself. Love it so far. It's been 40 years since as a singleguy I drove a '64 Vette 4-speed. My driver for the last 13 years hasbeen a 6-cyl '93 T-Bird auto transmission. Now the questions. At 60mphmy Mazda is turning exactly 3000 rpm in 6th gear. My old T-Bird loafsalong at 1750. Both have roughly the same hp. My 300 hp V-8 Corvette,with a 308 rear end turned about 2750 in 4th if I remember right.Anyone know a good source for the relationship between rpm, highwayspeed, horse power, number of gear speeds, etc. How can that old Fordengine cruise along at 1750 when it takes the MX-5 3000 rpm? Why do Ineed 6 gears in the Mazda when 4 worked fine in the Corvette? Iprobably knew all these answers 40 years ago, but I need a refresher.

Apr 20, 2006 21 Replies

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Mal Osborne 20 years ago

No it's not!

Imagine you are in your Miata, doing 60Mph in 5th, on a flat road, throttle at say 60%, cruise control engaged. You change upon a slight hill, whereby you remain in 5th, but the CC increases throttle to 95%. RPM remains constant. Are you saying that fuel consumption would not increase?

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BRUCE HASKIN 20 years ago

No ! That is not what I said. Go back and read the part about a "flat freeway" !!

Bruce Bing '03 LE

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