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High Performance Diesel Engines

By Bruce Mallinson

April, 2019

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Driving for fuel mileage, the trucking industry says that the driver of the truck is responsible for about 33% of the fuel mileage. I disagree, I think the driver is responsible for about 66% of the fuel mileage. Now let me explain why I feel that way. As many of you know, we at Pittsburgh Power have been specializing in building high performance diesel engines for 42 years and the emphasis has always been on the performance, longevity, and for many years now fuel mileage. We have many performance parts that equate to fuel mileage if properly driven. You can have us install all these specialty parts, but if you don’t change your driving habits you will not see an improvement in fuel mileage. Yes, you will feel the truck having more power and running freer, but if you want to use cruise control on rolling terrain and run 70 to 80 mph, guess what, your fuel mileage will only slightly increase. Cruise control will rob you of ½ mpg, and if you think states such as Ohio, Indiana, Illinois, Iowa, Kansas, Nebraska, and Texas are level, you’re not paying attention to your turbo boost or manifold pressure gauge. The next time you are holding the steering wheel and the cruise control is working the throttle, look at the turbo boost gauge, if it is varying, going up and down, then the terrain is NOT level. Did you ever ride in a car with someone who was up and down on the throttle? It will drive you crazy! Well that is what the cruise control on a loaded semi does, it wants to please you and hold to the exact speed you set it for. Keep this in mind, a diesel engine is most fuel efficient at a given horsepower output, NOT riding the throttle up and down such as what cruise control does. I know you must drive faster because of the ELD’s and the 14-hour rule, however you can drive faster and still get fuel mileage, and it’s called using momentum to roll up the next grade. Cruise control does not use momentum.

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Here is a real-life example, Mikkel Forney, 40 years old, called me last Thursday wanting to install a Dorothy on his new 2019 389 Peterbilt, X-15 Cummins, 18 speed trans, 3:36 rear gears and low pro 22.5 tires. He was Eastbound in Midland Texas with a loaded flatbed, and on cruise control at 69 mph and averaging 6.5 mpg. I asked him what his turbo boost gauge was reading, and he said it was varying several pounds. I said take it off cruise control and hold the pedal steady, at 69 mph the engine was developing 11 psi of turbo boost, and his digital fuel mileage was saying 6.5 mpg. I asked him to drop the turbo boost to 9 psi and the speed came down to 67 mph and as we talked his fuel mileage climbed to 7.1 mpg. I asked him to drive the rest of the day this way, the “Mallinson way” and tomorrow also and he agreed to. I called him Friday afternoon and he confirmed the fuel mileage across Texas driving with his foot was staying at 7.1 mpg. Yes, he was 2 mph slower. When he comes to the rolling hills if he uses the downhill side to accelerate and holds the speed and momentum to climb the next grade and backs out of the throttle when the hill starts to taper off, he will more than gain the 2 mph back. He mentioned he would have to get used to driving the truck that way. Yes, you do have to get used to driving your truck instead of just holding the steering wheel and allowing the cruise control and the ECM to manage the speed and fuel mileage. 

Mikkel Forney was raised in a trucking family. His father, Charles, is still an owner-operator at age 68 and Mikkel’s first experience riding in a semi was his father’s 1974 White Road Commander. Mikkel knew at a young age he was going to be an owner-operator, however, first he wanted to serve his country, so he joined the Army and spent the next 7 ½ years there. He was in the war in Iraq as a communications intelligence officer. After his service his spent the next 3 years in the Army Reserves. 

Mikkel has owned several used semi-trucks and always remembered the smile on his face when his father pulled his new 1987 379 Pete into the driveway. His dream was to be able to follow his father’s lead and purchase a new Peterbilt someday for himself. His dream came true, 4 months ago he took delivery of a 2019 389 Peterbilt painted in the color Firemist. The smile he had on his face back in 1987 when he saw his father’s new Pete was the same smile his father had when Mikkel drove up in his new 389 Pete. Look at the father and son’s Peterbilts, both looking good, and isn’t it amazing how similar they look being 32 years apart. Why change when perfection has been obtained, and it all started with the “359”. Mikkel and his father do most of their mechanical work and maintenance on trucks and trailers and that is why his father still has and drives a 1987. 

Mikkel is a professional dad when not on the road and is proficient at making children and has 6 to prove his proficiency. His children help him clean, change tires, wash and wax his 2 trucks. He is an agent for Ace Doran, is a private carrier for several manufacturers, and driving is what he LOVES to do!

Written by Bruce Mallinson

Pittsburgh Power, Inc

3600 S. Noah Dr., Saxonburg, PA 16056.

Website: Pittsburghpower.com

Phone 724-360-4080.