Higher Performance and MPG
 

I am getting a seems to be stock '91 FC soon so i started reading around, looking up specs and performance parts for it. As iSurfed the web i ran over an article that said this about the rotary engines. "They typically consume more fuel than a piston engine because the thermodynamic efficiency of the engine is reduced by the long combustion-chamber shape and low compression ratio." If that is so, then would putting nice sized super- or turbocharger give the car better fuel efficiency and more horsepower????

:scratch:

no, a turbo does not increase compression ratio. It only increases the amount of air you can cram in the chamber, thus requiring more fuel to utilize that air and giving more power.

I'm saying that since the engine isn't burning all the fuel because of a low temperature. Wouldn't putting a turbo on it give you better fuel mileage or at least keep it the same since the air heats up when it's compressed in the turbo before it is mixed with the fuel.

when air heats up, you lose density, which equals losing air mass, which equals less combustion per volume. The engine is burning all the fuel, it's just thermally inefficient, a lot of energy escapes as heat.

if my understanding is correct you want your cake and eat it too.

with the exception of the last couple years efficiency and power were almost mutually exclusive. you could have one but not the other. (The new C6 Z06 with 28MPG Hwy is the most notable exception.) typically the higher milage cars like the Geo metro and the Honda crx had LOWER compression engines. Im not sure why that got better fuel economy.

I do know that when you boost the compression of the Honda's either through higher compression pistons or a turbo the engine required more fuel to run smoothly thus killing its gas mileage. If you want a more efficient rotary my theory would be to take the turbo off a turbo motor and run it as an NA and swap out to smaller injectors.

I certainly wouldn't expect you to be able to maintain hwy speeds going up hill though.

yes, rotary engines are not as efficient as piston engines. Its the truth. Look at the mods in my sig. I get about 12 mpg. It sucks but the car is a blast to drive

No.
The turbo gives you more power versus displacement due to the turbo being able to utilize the exhaust gases to create more power.
"Supercharging" an engine runs into the problem with detonation.
Most engines run really close to pre-ignition.
To combat pre-ignition, MORE fuel is "wasted" just to keep the engine from pinging.


-Ted

You can still make good power with a turbo and not completely kill your mileage. It should only drop your fuel economy big time when you are actually in boost. Since rebuilding my motor I have well over the 300rwhp the last motor put down (no dyno yet but very noticeably faster) and still manage 23mpg highway and around 16-17 in town.