[3/4-Ton 7% Grade]
[1-Ton 7% Grade]
[Diesel v Gas Comparison
[3/4-Ton 15% Grade] [1-Ton
15% Grade] [Diesel v Gas
Comparison 15% Grade]
All Grades] [Summary]
Diesel Pickups - 15%
Grade w/10,500# Trailer:
witnessing the dramatic results of the 15% contest among the gas trucks,
we were even more interested to see what changes or stumbles might
await the diesels on this steep hill.
to space and readability considerations, the bar graphs
below only show the test results from 100-m to 250-m. See the table
at the bottom for full test results from 50-m to 250-m.
times and speeds measured are shown cumulative over the run.
the graphs below: the lower a truck's bar is, relative to the other
two trucks' bars, in the "Time Over 250-Meters" graph the
better it performed. The higher a truck's bar is, relative to the other
two trucks' bars, in the "Speed over 250-Meters" graph, the
better it performed.
shortest time required to cover the 250-meter distance determined the
best performing truck.
Diesel Pickups 15% Grade W/Trailer Summary
Dodge Ram 3500 Quad Cab 6.7-L I6 4x4 DRW 6-speed auto 4.10
Ford F-350 Super Duty Crew Cab 6.4-L V8 4x4 DRW 5-speed auto 3.73
Chevrolet Silverado 3500 Crew Cab 6.6-L V8 4x4 DRW 6-speed auto 3.73
|50-m / 164-ft
|100-m / 328-ft
|200-m / 984-ft
15% Grade Assessment:
we were directing marketing for GM, here's how we'd pitch its diesel
motor. D for Duramax. D for dominant. Check out the how fast the Chevy
finished the hill climb - more than 5-mph faster and over 2 seconds
quicker than either the Ford or Dodge haulers! This time it even beat
the Cummins in the first 50-meters.
the Power Stroke was still slower than the Cummins to the top, the
gap between those two engines narrowed substantially on the 15% grade,
in favor of the Ford. If the F-350 and Ram 3500 both had 3.73 rear
gear ratios, instead of the Ram's 4.10, we think the F-350 almost
certainly would have moved into the second spot.
there was an incredibly interesting reason why the performance
gap between the F-350 and Ram 3500 seemed to close so much. After
two sprints up the hill, the F-350's diesel particulate filter (DPF)
went into regeneration mode. The DPF is a new emissions control device
required to reduce diesel particulate emissions 10-fold from 2006 model
year levels. Regeneration is triggered when the truck senses too much
back pressure from the DPF, because of a large amount of trapped particulates.
To get rid of the soot, the engine injects metered amounts of diesel
fuel into the exhaust stream to incinerate the soot in the filter.
third run, after regenerating, the F-350 ran the hill up to a full
2-kilometers-per-hour (1.2-miles-per-hour) faster than its first two
were very surprised by the apparent power boost the Power Stroke received
from regeneration. It illustrated just how much the new DPFs can restrict
airflow through the exhaust system, and the challenge faced by
all the OEMs to improve engine performance while complying with new
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