Folks who remember me will know that I have an ol' beater of an 1980 RX-7. Well, that beater is about beaten out. The motor is limping along on cold days (though it runs just fine when it's nice and warm outside). It's difficult to keep started when first starting it, and takes 5 minutes to warm up to the point where it'll run without stalling. It's leaking oil out of both rotors, and is burning coolant. It has 219100 miles on the engine.

I think it's time to retire the 12A.

So, I'm in the process of shopping around, and there's a beautiful 1994 Montego Blue FD33, all stock, and in decent condition. I'll be taking it for a test spin in the coming week or so. But there's something I wanted to ask that got the better of my curiosity:

If the 100HP 12A got 17/24 MPG, why does a 255HP 13B only get 17/24 MPG under the same driving conditions? (e.g., it takes my car 15 seconds to go from 0-60; if I were to accelerate to 60MPH with the 13B in 15 seconds, why am I still getting the same milage?) I would think that the 255HP would give it better fuel economy than the 12A, because it takes less gas to get the same amount of torque.

Any ideas on why this would be?

Thanks.

 

well, the 12a would work harder to bring your car up to 60, and that's the reason why

why is it easy for a domestic to pull outta corners in higher gear? more torque, where does that torque come from? burning more gas per rev

pretty much, if there wasn't a dramatic improvement in the thermodynamics of the rotary engine between the 12a and the 13b, then the fuel consumption wouldnt change

 

Fuel economy on the highway is mostly related to the car, not the engine. It takes a certain amount of power to punch a hole in the atmosphere, SA's and FD's are pretty similar as far as that is concerned (what the FD gains in aerodynamics it loses in tire losses). After that you look into how efficient the engine is as pumping air and using the heat of combustion to make power instead of losing it to the atmosphere (exhaust ot radiator).

In the end it takes about the same amount of fuel to make the same amount of power, and it takes about the same amount of power to move each vehicle, so MPG will be about the same.