Duramax 6600 Performance Pull-Off - Reprint from October 1999
Duramax 6600 Performance Pull-Off
By Jim Bigley
What follows is a reprint from an article that appeared here shortly after October of 1999.
By now, those of you watching the Duramax story unfold here in TheDieselPage.com have probably guessed that we ran the Duramax trucks right along with the 6.5TD Project truck and Ford & Dodge during the recent Pull-Off competition.
The Diesel Page was given an opportunity to test-drive both a new Duramax Chevy and GMC here in Montana a full year before any Duramax powered pickup trucks would become available at dealerships. Not only were we able to get a feel for how the trucks handled on the highway in a variety of empty and loaded configurations, but we also ran these trucks against a 1999 Ford F250 Super-Duty 7.3L Powerstroke and a 1999 Dodge 24-valve 5.9L Cummins in an ultimate test of power we call the "Pull-Off".
The Duramax performance is impressive. After you read what these new Duramax diesel prototype trucks can do, I'm sure you'll want to share with as many people as possible just what Ford and Dodge are up against. I don't blame you, I do too. But, please honor our copyright, and don't re-post the images and text. Simply post the link to this page.
I was skeptical of the early Duramax performance rumors, but after having an opportunity to drive these trucks, I can say that if anything, GM is underplaying the performance of their new diesel. In my opinion, the Duramax/Allison powertrain was designed not to compete with Ford and Dodge, but to dominate the light-truck diesel market.
During two days of driving, we ran 0-60 after 0-60, and loaded hill climb after grueling hill-climb, comparing the Duramax performance to Ford & Dodge. GM's new 6600 is a real killer. The power and performance is so far ahead of the new Ford and Dodge trucks that it'll be a long time before they become a threat to the Duramax superiority.
To make this strictly a test of diesel engine power, all the trucks were "weight-matched" with sand bags before any runs were made. I initially disagreed with this philosophy. I felt that if a truck manufacturer produced a heavy truck, they should pay for it in reduced performance and payload capacity. The majority out-voted me though, and all the trucks weighed exactly the same for each of the performance runs. The Ford Super-Duty (at 6820 pounds) turned out to be the porker of the bunch, weighing fully 500 pounds more than the quad-cab Duramax Chevy at 6320. Even the Dodge with its heavy I-6 Cummins was 180 pounds lighter than Ford.
Ford and Chevy were both equipped with 3.73 gearing, while the Dodge carried 4.10 gears. Chevy and Dodge were both equipped with an automatic transmission, but the only Ford we had access to came with a six-speed manual. And finally, all three trucks were quad-cab shortbox ¾-ton 4x4's. This was as close a match as we could have hoped for.
First in the series of tests was a direct comparison in 0-60 mph acceleration. We ran all the trucks on the same track, under the same conditions and with the same driver. For this portion of the performance test, Willie Worthy (Four Wheeler magazine tech editor) performed the driving duties. Willie did his best to treat each truck fairly in launching method and driving style, and I rode shotgun, operating two G-Tech performance meters in tandem.
Here we are at the track (an undeveloped industrial park) used for the 0-60 acceleration runs. Aside from the gas Suburban, this is one impressive lineup of diesel trucks. The Duramax Chevy is just behind the Suburban and the Duramax GMC is bringing up the rear. The 6.5TD Project truck and the new Dodge are just behind the enclosed trailer hooked to the Ford.
Empty acceleration performance is a test of horsepower. Even with 500 lbs of sand bags added to the bed, the Duramax Chevy easily outran both Ford & Dodge. The 300 horsepower Duramax clearly had the advantage.
Keep in mind that these numbers were generated under less than ideal conditions, due to a rain-slicked track. Willy just mashed the throttle at the beginning of each run, to keep the engines from developing too much power from a standing start. A turbo diesel needs a couple seconds for the turbo to spool up before real power can be generated, and to produce the quickest elapsed times.
We also planned to perform a series of 0-60 runs with the 9,700 lb trailer, but had to give it up. The Powerstroke wouldn't accelerate fast enough through a loaded 0-60 to trigger the G-Tech performance meters. The Duramax, on the other hand would trigger the G-Tech meters every time, and produced a 26.08 second average. Since the Powerstroke couldn't do it, we didn't try it with the Dodge.
With a flat torque curve that peaks at an advertised 520 lb-ft, the Duramax Chevy stunned us with a run of just 83 seconds, reaching a top speed of 55 mph from a dead stop on a 6% grade while pulling a 9,700 lb trailer. The Ford Powerstroke (with an advertised 500+ lb-ft of torque) finished a distant 2nd in the mile-long hill-climb, producing a run of 113 seconds and a top speed of 50 mph. The Dodge 24V Cummins came in last at 122 seconds, with a low top speed of just 40 mph.
Nine seconds separated Ford and Dodge, but the Duramax finished the mile-long loaded hill-climb a full 30 seconds ahead of Ford, and 39 seconds ahead of Dodge. The Duramax performance is in a class by itself.
Next up, was a loaded hill-climb. Many people buy a diesel to pull trailers; sometimes really big trailers. The mighty Powerstroke has always excelled at this game because of its torque advantage. Torque is what pulls heavy trailers up steep grades, and the heavier the trailer, the more torque plays in deciding the winner. Our 9,700 lb trailer was heavy enough to clearly show which truck was developing the most torque.
When the Pull-Off was still in the planning phase, I wanted to use a 7500 lb travel-trailer for the loaded performance runs. The GM team "suggested" we use a trailer that weighed as close as possible to 9,800 lbs, which is the limit in some states, above which the driver must have a commercial license. So, we loaded our trailer to 9,700 lbs. They knew the Duramax would have the advantage with a heavier trailer.
Evaro hill, a few miles Northwest of Missoula Montana on US93 provided the site for the hill-climb. This hill is infamous among diesel truckers for its 25-35 mph grind in the slow lane. To make the hill-climb even more demanding, each truck was required to pull the same 9,700 lb enclosed trailer up this 6% grade from a dead stop. Each run was then timed for exactly one mile using the conveniently located mile markers. A more brutal hill-climbing power test would be hard to find.
Besides spending a lot of time driving the GM trucks, we also spent a nearly equal amount of time in the new Ford and Dodge. Having driven several other Dodge diesels over the years, I couldn't help but notice the Cummins has come a long way since the early days. Aside from a few minor issues, I actually enjoyed driving the Dodge, even if it didn't do well in our performance tests. The Cummins was quieter than the Powerstroke, and I liked the open engine bay. The ISB 24V engine revved willingly to 3000 rpm, and once under load, the diesel clatter became almost tolerable. Dodge has a long way to go to stay competitive, but I'm sure the "industrial" nature of the Cummins will continue to appeal to lots of folks, regardless.
Even while trying to remain objective, I found the new Ford Super-Duty Powerstroke to be the most objectionable truck to drive. The PSD was noisier than even the Dodge Cummins, and road noise transmitted through the chassis quickly became a nuisance. After spending an hour in this truck I was asking myself why it was so popular.
Continued...
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