Its physics.

W=f*d

Where f is Force and D is Distance.

Where the wheel spin is the W.

More teeth = less force but more distance traveled to produce the same amount of Work.

To go the same speed, your engine needs to spin faster with a gear that has more teeth......

I really don't understand the confusion. Your wheels are not bolted on your crankshaft.....

I was talking about from tooth to tooth of the 4.667 FD vs the stock 4.1 FD, not total work done. W not Wnet lol. work is more complicated than just F*D :lol: :cry:

Its all miniscule though in retrospect.

4.1-4.667 = .567
.567/4.100= .138
so a 13.8% increase over stock. So every RPM you cruise at, add 13.8% to it. Im assuming subtract 13.8% from the normal MPG, given all conditions are the same.

But it's a 13.8% increase in thrust at a given speed, which means faster acceleration. Also depending on the course/track it could put you in a better rpm range, like say instead of constantly shifting between 1st and 2nd, you can stay in second and still be where you want in terms of rpms. That increase can make a big difference on a track. As far as cost mpg wise it's not as simple as taking off 13.8% and there's too many variables to really say with any certainty. As far as top speed that's a really simple problem assuming you have enough power to top out sixth gear.

Gear display on the dash can be out. I know it was with the 5.1. It can be fixed via a tune. Everything else is fine.

BTW, driving from California to the SCCA Nationals in NE with a full set of race tires and wheels in the car as well as tools, jacks, luggage, popup, etc...I got at least 30MPG on the highway at 70MPH on cruse control, supercharged with the 4.556 final drive.

Neither, other than what wparsons had stated, the following part is completely false. 1 revolution is 1 revolution, the speedometer won't change, but the actual distance travelled and consequently the actual speed is different due to the circumference.

I assume he meant that at a given speed, small wheels will be rotating faster, so it sounds like you're both on the same page.

Yeah OK.
Totally makes sense, he was absolutely right.

i have a 4.56 i thought i would have affected my speedo but it didnt, still accurate to my gps. so im assuming speed isnt taken from the driveshaft. fuel econ isnt a noticeable difference, 6th gear at 70 is like a 600 rpm difference i think.

I have a 4.67. GPS is dead-on against the speedo at a +1MPH delta at 60MPH with stock tires at 32F/35R PSI (61MPH indicated / 60MPH GPS). That number didn't change with the FD, only after changing wheels/tires.

FWIW, there is a table for gear determination thresholds in the map; I'm assuming that's specifically dealing with the gear indicator on the dash for manual cars, because it doesn't seem to do anything on my A/T.

Theoretically you could just calculate the percent increase between your new final drive ratio and the stock 4.1, then increase the values by that percentage. Someone with a manual should test that out to see if it actually works that way. :)

It does.