does torque affect gas mileage

[Opliko]

Okay, I assumed the amount of torque a car has would affect its gas mileage, but someone of my other forums seems to think otherwise. I really don't know, but if anyone does that would be sweet.

 

[JNasty4G63]

In theory, more torque from an engine means that it will work less to get the car moving, thus not using as much gas from the lighter load. A big V8 will get a car moving fine without even getting above 2000 rpms, whereas an S2000 won't do much below 6000 rpms. Thus, you have to spin the S2K motor much higher, and more revs mean more fuel used. But also, the bigger engine uses more fuel than the smaller engine regardless of speed, with twice as much engine to feed. So, I guess, in theory more torue is better. But, there are many more factors than just torque that need to be evaluated.

Hilg

 

[Jmac279]

Torque is the product of a Force applied to a Lever ...

The length of the lever in an engine is called Stroke ...

The force in an engine is created by the combustion of fuel ...

If you apply 1000 lbs of force to a 3" stroke, the result is 250 ft-lbs of torque ... If you apply the same amount of force to a 4" stroke, the result is 333 ft-lbs of torque ...

However, the force caused by of combustion dependent on many, many things such as the amount of fuel in the cylinder, the air/fuel ratio, the compression ratio, the amount of friction within the cylinder, the quality of seals in the cylinder, etc.

So, to get to the point, an engine with more torque won't necessarily get better fuel economy ... Even if you look at the amount of torque made vs. the stroke, you still have very little idea about the force was achieved ...

Generally, the amount of fuel used is based on the Displacement, Engine Speed (RPM) and the Air/Fuel Ratio ...

 

[Jmac279]

Fuel Consumed (mL/s) = 1000*(ED/1000)*(RPM/240)*(1-((AFR/AD)/((AFR/AD)+1/737.22)))

ED = Engine Displacement in cc
RPM = Engine RPM
AFR = Air:Fuel Ratio by weight
AD = Air Density in kg/m^3