I am going to get a transmission from a Mazda 626 with taller final gears (4.111:1 instead of my 4.388:1), and it has a taller 5th, so I will lower my 65mph rpm by a little over 400. With that, and running lean, I should be able to get into the 40mpg range!
I imagine that most people can find taller junkyard gears for their cars. I know it's not a DIY thing, unless you have the time, and tools, but it can make a big difference. I have to change my clutch anyway, so I'm doing it all at once. The standard mileage for this car is 28HWY with a 1.8L, and this one has a 2.5L.
The "and it has a taller 5th" part is hiding after the ratios . I don't remember what the ratio was for 5th, though. It's a bit of a jump from 4th to 5th, but with variable resonance induction, the engine has a good long torque curve. The gearing was made small with this car for "more fun", so 60mph is about 3,100 rpm. For the first 6 months of driving an MX-3 GS people try to change out of 5th on the freeway, and remember that that's it.
There's a guy that's figuring out a way to mate a G6 6 speed tranny to this engine. That would be awesome.
when you've got high rpms to start with, small gear changes make a big difference.
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
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