As I reported to you last week, I am in my new truck and headed for the Walcott Trucker’s Jamboree to be held on July 9, 10 and 11. This new 2015 Cascadia Evolution is powered by the new downsped version of the Detroit DD15. On this truck, the drivetrain is completely integrated with the Detroit DD12 transmission coupled with a Detroit 6x2 rear axle configurations outfitted with 2.28 final gear ratio.
I left out on this trip two days ago and have not filled the tank as of yet. I’ve traveled 889 miles from Charlotte, NC to Davenport, IA in order to prepare for the Jamboree. On Sunday, I was on the highway traveling along with the July 4th holiday traffic. Leaving North Carolina, I went over mountains on I-40 enroute for my destination. In Tennessee, I was caught up in an hour traffic jam as the road became filtered down into one lane. I stopped for the night in Greensburg, Indiana and my fuel mileage was a respectable 9.2 mpg accordingly to the dashboard read out. The following day, with a brisk crosswind, I continued on to Walcott along I-74 onto I-80. The mileage climbed to over 11 mpg before hitting torrential downpours of rain and wind. The rainstorms managed to pull the mileage down to 10.2 mpg before days end. The shipment weight for this segment of the trip has been 35,000 lbs.
The new downsped version on this truck is an example of how less can sometimes be more. One might look at the specs of this engine and feel that it only offers 400 horsepower. However, it actually has more horsepower than the standard DD15 engine at the RPM where you actually operate the engine. What Detroit has done is to downsped the engine and shifts the useable torque range to lower RPM’s. This all reduces parasitic loss as there is less frictional resistance at lower RPM’s. What all of this means is that every moving component in the engine moves slower which contributes to better fuel economy. When I think of all the parts that are moving slower, such as: the crank shaft, pistons, connecting rod, camshaft, rocker arms, valves, gear train and even the fuel pump all become contributing factors to parasitic loss. In theory, it also seems as though the downsped technology could also increase the service life of the DD15 engine.
Driving this truck seems much different than earlier versions of this engine. In fact, this engine seems different than any engine that I have operated in the past. I found myself at times cruising along at 45-50 mph in 12th gear and the tachometer was only reading between 850 – 900 RPM’s. The truck pulls along just fine at these low RPM’s although it does not feel or sound like its making power. As I traveled on the highway, I kept pace with the other trucks around me which showed that the engine was pulling even though the audible tones emitted from the engine would tell you otherwise.
I have included the horsepower and torque curves of this engine as well as the previous engine for you to review. You’ll notice there is more horsepower and torque at the RPM’s in which the engine is operating than in the past. The funny thing is… this engine makes more horsepower and torque just above idle than the first truck which I drove in the beginning of my career at any RPM.
I will be reporting on more of this trucks performance in the upcoming blogs. Next, I’ll share the results of how the Detroit Intelligent Power Train Management is performing.
