The Big Three's New Diesels put on a Dyno

CumminsDriver wrote:


The GM Truck ran the hill in third gear, same as the other two. My DMax/Allison won't downshift until right at 2000 rpms.

Rich

I can't completely see the exact speeds they are going, but guesstimating it and plugging it into the rpm formula(RPM=(Axle Ratio x Vehicle Speed x Transmission Ratio x 336.13) / Tire Diameter) it looks as if they were in 2nd. I plugged in 33 inch tires. If they are actually 32 then it could have been third.
Although, I was just using 3rd as my example to explain to travelnutz what I was talking about.

The Ram was in 4th most of the way and did got into 3rd at the very end. You can tell by the gear number right next to the "D" on the dash with the Rams. The Ford was also in 4th most of the way until the very end. The gear they are in is shown in the tack.

If the GM was in third like you say, then that would mean that the GM actually had more torque multiplication versus the other two.

Ram
4th 1.00x4.10= 4.10

Ford
4th 1.14x4.10= 4.67

GM
3rd 1.41x3.73= 5.26

ShinerBock wrote:
To continue what I said above, here is the mph that each truck can stay in gear. I don't know the max engine speed of the GM so I am just going to assume it is 3,000 like the Ram. If it is higher then it tilts this in favor of GM being first up the Ike even more.

Ram Aisin
1st 3.75: 0 mph-19mph @ 3,000
2nd 2.00: 19 mph @ 1,650 - 35 mph @ 3,000
3rd 1.34: 35 mph @ 1,950 - 53 mph @ 3,000


GM Allison
1st 3.10: 0 mph - 25 mph @ 3,000
2nd 1.81: 25 mph @ 1,800 - 43 mph @ 3,000
3rd 1.41: 43 mph @ 2,300 - 56 mph @ 3,000

So as you can see, due to the taller rear gear and the Allison's better gearing spread(which is almost identical to Ram's 68RFE). The GM truck was not only able to stay in a lower gear (with more torque multiplication) at higher speeds, but it also started the next gear at a much higher rpm pitting it closer to peak horsepower.

In contrast, the steep 2nd to 3rd spreed on the Aisin along with the shorter gear ratio forced it to shift up to 3rd at a lower mph and put it at a much lower rpm making less horsepower.

The GM Truck ran the hill in third gear, same as the other two. My DMax/Allison won't downshift until right at 2000 rpms.

Rich

Wild Card wrote:
No brainer that the inline engine produces more torque. Hp is derived by the RPM the engines can spin to...again no brainer that the V engines spin faster thus produce more HP.

Lets take a look at the spes.

Ram 6.7 385 hp @ 2800 rpm
900 ft/lbs @ 1700 rpm

Ford 6.7 440 hp @ 2800 rpm
925 ft/lbs @ 1800 rpm

Duramax 445 hp @2800 rpm
910 ft/lbs @1600 rpm.

I'd prefer a test of all three with no emissions and good tuning.

justafordguy wrote:
I agree, all three trucks should have been tested with the same rear gear.

But different transmission ratios perform better with different rear axle ratios. I'm not sure how or why they picked the trucks they did... but they should have approached all 3 manufacturers, told them EXACTLY what they were testing and measuring and allowed the manufacturer to provide their best product for the test. That way we can't say that they hate the Fords, so they picked a Ford with the worst ratio... or they loved the GM, so they picked the GM with the best ratio.

Explain the tests, explain the measurements they would compare and allow the manufacturer to decide the best combo for those tests. Ford might have stuck with the 3.73 regardless, because they were more worried about mileage. We don't know why the chose what they chose.

At the end of the day, all three trucks are remarkable in their abilities, their efficiencies and honestly their reliability (look at trucks 20 years ago). Its all a measuring contest at this point. All 3 trucks are capable of impressive tow ratings, payload ratings, fuel economy, comfort and convenience. Any of the 3 will be an excellent choice. We should be celebrating the choices, rather than bashing someone else for the choice that they made.

Its always the same 2 or 3 people going on and on about brand loyal nonsense... Grow up people.

NJRVer wrote:
I didn't watch the video.
Which transmission was in the Ram?

Aisin

I didn't watch the video.
Which transmission was in the Ram?

What kind of mileage are they getting when towing. And which one isn't going to be rusting away after 5 years?!!! I don't care about which one made 3 more HP or which one is 30 seconds faster up a hill. I want longevity for the entire vehicle.

I agree, all three trucks should have been tested with the same rear gear.

To continue what I said above, here is the mph that each truck can stay in gear. I don't know the max engine speed of the GM so I am just going to assume it is 3,000 like the Ram. If it is higher then it tilts this in favor of GM being first up the Ike even more.

Ram Aisin
1st 3.75: 0 mph-19mph @ 3,000
2nd 2.00: 19 mph @ 1,650 - 35 mph @ 3,000
3rd 1.34: 35 mph @ 1,950 - 53 mph @ 3,000


GM Allison
1st 3.10: 0 mph - 25 mph @ 3,000
2nd 1.81: 25 mph @ 1,800 - 43 mph @ 3,000
3rd 1.41: 43 mph @ 2,300 - 56 mph @ 3,000

So as you can see, due to the taller rear gear and the Allison's better gearing spread(which is almost identical to Ram's 68RFE). The GM truck was not only able to stay in a lower gear (with more torque multiplication) at higher speeds, but it also started the next gear at a much higher rpm pitting it closer to peak horsepower.

In contrast, the steep 2nd to 3rd spreed on the Aisin along with the shorter gear ratio forced it to shift up to 3rd at a lower mph and put it at a much lower rpm making less horsepower.