2014 Ultimate 1 Ton Challenge results

AH64ID wrote:

Turtle n Peeps wrote:


Sorry but it doesn't work like that.

The best way I can explain it without writing a book is this:

Chassis dyno a vehicle a with 2.75 gears in it and note the HP.
Then chassis dyno the same vehicle with a 4.56 gear in it.

Or do this. Take a vehicle and dyno it in a 1 to 1 gear or as close to 1 to 1 as you can get. Then take the same vehicle and dyno it in 1st gear.

Which vehicle is going to show the most HP? This will be HP to the wheel which is what counts. From your way of thinking the 1st gear way of dyno'ing should show way more HP. See if it works out that way for you.

If the short gear will not make that much difference in fuel economy why doesn't Ram just have the 4:10 gear and call it good? Think what that would do. Less inventory stock. You could just stock one gear in your dealers for your trucks.

It absolutely works that way, that's what gearing and torque multiplication is.. plain and simple. Do a little research on it, and do not confuse HP with Torque.

Chassis dyno's are not a good example, too hard to load the engine in lower gears. The engine is out of rpms before full power can be made. This is why dyno runs are generally done in 1:1 for NA/super charged motors and OD for turbo motors. The last time I dyno'd I ran 5th and 6th. HP was within 1% but torque was 50 ft/lbs lower on the 5th run because the rpms increase faster than the engine makes power. So a run in 5th didn't get to full power until 2500 rpms plus, but the 6th run gets there around 2000. Neither of the run were as much boost as on the street, meaning that there is actually more power than recorded.

They don't do just 4.10 for the same reason Ford has a lower geared transmission and a higher geared rear end, public perception. I am also not saying it doesn't make any difference, just saying the difference is much smaller than most think with modern engines.

My dad 2006 Dodge has the AD ratio G56, with a .79:1 OD and I have a 2005 with a .73:1 NV5600. Both truck have 3.73's, but his OD is low enough that his final drive is nearly identical to what mine would be with 4.10's and we get pretty much the same mileage on the freeway, close enough that sometimes he is a little better and sometimes I am. Loaded up he can get better mileage in 6th that I do because the engine needs to make less power to get the same torque to the wheel.

You said:

It does not make power, but it does increase or decrease the power depending on the ratio.

Torque is not power. You are just increasing torque and torque is not power as you found out on the dyno.

You said:

HP was within 1% but torque was 50 ft/lbs lower

As you can see, the torque increase was huge but by your own words you did not make anymore power. (1% is within static of most dyno runs)

Power is a timed event. Torque is just twisting.

Next time dyno your car in 2nd or 3rd gear and then 1 to 1 and see which makes more "power" then come back here and tell all of us of your results. Read post #10 if you want to know the story without doing anything.

My point being of all of this is:
In the old days of 3 speed autos and 4 speed manuals with 200 HP at the rear wheels it made a BIG difference in the rear gear we chose. Now days with 6 speeds+ and huge HP, rear end gear picking is almost out of the equation.