Axle ratio of 3.27 is lower than 2.73.

Debate:

A. If 3.27 takes more turns of the engine compare to 2.73, than 3.27 would cause the engine to use more gas than 2.73. So it take more revs to crank the same distance.


B. 2.73 is taller, so the engine has to do more work to go the same distance compare to 3.27. Yes, it turns less, but the load is greater. So 2.73 uses more gas than 3.27.

What do you think?

 

B) Not quite true - an engine isn't using its full potential during normal driving, so the horsepower difference required to turn the gears is negligable. Hence the increase in consumption is more than outweighed by the revs/distance change.

 

So would you say A is "more" true than B? Can you think of an exception? Would the weight of the car be the exception?

 

B) Would depend on the amount of work the engine can do (torque). That is why a lot of those V8's run 2 or 3 gear trannies. They have lots of toruqe. So basically, An engine that produces less torque will consume more gas at the same load vs another that produces lots of torque at the same ratio.

 

What ever allows the engine to run at peak torque for a given speed.

 

It takes a certain amount of energy to maintain a certain amount of speed. So theoretically, a car going a certain speed should use the same amount of gas no matter what the gear ratio. Higher revs with less load or lower revs with more load all equal to the same amount of gas burned. However, there is more frictional losses at higher rpms, so that will increase fuel consumption. Other factors come into play, but I think frictional losses have the greatest bearing on gas burned.

 

depends on the engine and how it is tuned/cammed/carbed

For example, say the 2.73 put the engine below it's sweet spot for cruising. It will lug the motor and use MORE fuel.

Also depends on cruise rpm.

I just did a 2.77 to 3.27 conversion in my 86 Trans Am.

A vs. B comes down to tuning the COMBO.