'83 RX-7 from <30 to 50+

[cosmick]

So my S-10 progress is in the newb introductions part of this site, but yesterday I brought home a cherry '83 RX-7.
Those rotaries are supposed to average mid 20s at best, occasionally spiking to 30. But rotaries carbon-lock, and the cost of gaskets and apex seals exceeds the cost of a used piston engine.
So because my dad had a '96 Bonneville that did 35 MPG with the lockup torque converter not locking, I'm going with one of those engines. It's a 205-HP 3.8L V6, also found in '96-'02 Camaro / Firebird with manual transmissions.
I've talked to a PCM expert, this deal is good.
Classic V8s fit, so this swap will fit.
I see a smaller, lighter car with less drag than the "new" engine ever came in, and stock gearing for those cars gave as low as 1800 RPM at 65 MPH in the 'maro / 'bird, also known as the F-twins.
The five speed has a 0.72:1 OD, the 185/70R13 tires are 23.2" dia., and available axle ratios include 2.286:1, 2.412:1, 2.5625:1, 2.7333:1, 2.929:1, 3.077:1, and up into the mid-4s, because the RX-7 is getting a 7.5" rear axle from my '87 S-10, which is getting a Ford 8.8" rear axle.
I found a decent urethane airdam for $ 136 new, but that will have to wait until the car moves under its own power again. Today I unload it from the trailer, return the trailer, and begin pulling the rotary for disassembly.

[cosmick]

[cosmick]

Just ordered a set of 2.286:1 gears for $ 70 shipped.

[ksa8907]

You could make one heck of a sleeper by supercharging that 3.8

[Fat Charlie]

Pretty, pretty car. It's going to be nice having one back on the road.

[MetroMPG]

Subscribed! If you gear it up, it should return decent top gear cruising economy (at reasonable speeds).

Have you done the math -- what will the cruising RPM be at X mph with that tall gearing?

[cosmick]

Originally Posted by MetroMPG

Subscribed! If you gear it up, it should return decent top gear cruising economy (at reasonable speeds).

Have you done the math -- what will the cruising RPM be at X mph with that tall gearing?

1540 RPM @ 65 MPH, with the 195/55R15 tires I just ordered, because 185/70R13s are getting extremely scarce, and for this odd lug pattern, the best solution for me, after hours of trying to scheme a cheaper alternative, was a new set of Konig 15x7s made for this car, at $ 102.50 ea. The tires are $ 50 ea. Those prices include shipping.

[cosmick]

Originally Posted by Fat Charlie

Pretty, pretty car. It's going to be nice having one back on the road.

Thanks!
As for manual at 98% efficient versus automatic at 86%, the Mustang crowd proved that false on chassis dynos, and the LSx Camaro crowd re-proved it. Manuals are around 86% efficient, while autos are around 78%.

[cosmick]

Originally Posted by ksa8907

You could make one heck of a sleeper by supercharging that 3.8

Rear turbo, in place of the muffler, was thought about. But the factory supercharged ones used very little boost on an engine with different heads because the blower forced relocation of the injectors, plus the pistons and pins were different, the rods probably, the block and crank maybe.
So I'm getting a common L36 instead of the rare L67, which is overpriced, and in high demand by the Fiero guys.

[mcrews]

I raced a 79 RX7 in showroom Stock SCCA many yrs ago.
Had a 4bbl 5 speed.
It LOVED being downshifted!!!!!!!