Big Three road tests

RCMAN

Alpar has it as 1.84 second. Diesel hub has it that way also. Don't no where I got the 3.27 from. I may have been cross eyed.

Yea, I got the Aisin and Alison mixed up I guess. That is a big drop. But that isn't the transmission that was tested.

buddyIam wrote:


Boy, Alison sure takes a big jump from 1st to 2nd

The Ram Aisin and the 68RFE both have a larger jump from 1st to 2nd than the Alison.

Alison change is 1.7127
Aisin change is 1.875
68RFE is 1.765

Bottom line the Alison probably matches the Duramax HP curve better than the Ram transmissions match the Cummins HP curve.

buddyIam wrote:
I found it. The 68RFE is:
3.27
1.84
1.41
1.00
.82
.63
reverse is 4.44

I found the 68RFE to be
3.23
1.83
1.41
1.00
.81
.62
R 4.44
68RFE

Turtle,

This is what stinks

Dang, Ford has torque converter lock up down to 900 RPM, (I like that) and by fare the lowest 1st gear.

3.97
2.32
1.82
1.15
0.86
0.67

It also had the highest torque 860 and HP 440.

This stuff doesn't make sense.

Then also why did they choose to test the lower power version of the Cummins with lower rated 68RFE?

I found it. The 68RFE is:
3.27
1.84
1.41
1.00
.82
.63
reverse is 4.44

No, the ford has the most power, the ram the most torque in the high horsepower version. But ford was also higher in torque than the ram that was tested

Boy, Alison sure takes a big jump from 1st to 2nd

Wonder what the gears are in the tansmission the ram was tested with. The one in the truck they tested was the 6-Speed Automatic 68RFE Transmission.

Something seems amiss. First the fact that there was a quarter mile test. And then looking at the results, the two with the highest power ratings score near equal times. Yet the Lowest rated truck bests the other two by 3/4 second empty and .9 seconds loaded

Then why do you think something is amiss? The Chevy had the most "power" and won going up hill. Ford is overrated (as I said in my first post) and many tests have proven it.

BTW the Allison has a:

3.10 1st gear.
1.81 2nd gear.
1.41 33rd gear.
1.00 4th gear.
0.71 5th gear.
0.61 6th gear.

The Aisin has a:

3.75 1st gear.
2.00 2nd gear.
1.34 3rd gear.
1.00 4th gear.
0.74 5th gear.
0.63 6th gear.

Both in the test had 3.73 rear. So much for the gear advantage. :E

Turtle

You just made my argument. Go to the point on the chart where the PRODUCT of RPM, times torque, is the greatest.

For this chart it is about 3200 RPM just like you said. Torque dropped off slowly up until that point, but the rise in RPM meant the product of RPM and torque continued to increase.

If torque only drops slowly as RPM increases. POWER goes up. Because POWER is the product of RPM and Torque.

You notice I don't argue with the term power. Just HP. That is because HP is only a salesman pitch.

For instance, tell me the size of the horses Watt used to come up with his constant of 5252? Were they Shetland Pony's or Clydesdales?

It's fine to compare an engine using Power as long as you understand that power is just a product of torque and RPM.

HP=RPM*torque/5252

I will say this again. A engine makes it's greatest power at the point of a graph where the product of Torque and rpm is the greatest.

You can say it all you want but it's still totally wrong.



Look at this chart. Lets look at the Dmax (yellow line). It makes the most torque around 1600 RPM. The Dmax does not make it's most power at 1600 RPM. It makes it around 3200.

buddyIam wrote:
Basically HP is acceleration, torque is twisting power, Your highest HP will be at the point of a curve where the product of RPM and torque is the greatest.

A dyno can not measure HP. It only measures torque and RPM.

Torque times rpm equals power. To compare that to a real horses power you have to divide by the constant 5252.

To rate yourself in elephant power you would have to make an estimate of how much power a elephant makes, make the calculations the same as Watt did, and replace the 5252 constant with your new elephant constant.

The 5252 number is not exact. It's just a number that is used in all HP calculations. It was a steam engine salesman's pitch to sell steam engines.

And that is why the Cummins with almost 100 more ft of torque got waxed towing up a hill and at the drag strip. The Chevy put out more HP so it was faster up the hill.

Nothing amiss at all. The math works. The Chevy had the most HP and beat the Ram up the hill.