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High Performance Diesel Engines

By Bruce Mallinson

January, 2018

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On November 30, 2017, John Walko, Pittsburgh Power’s technical director and I were invited to tour the Paccar test center in Mount Vernon, Washington. The invitation was for us to introduce and explain the “Dorothy” (EGR soot separator) to the Paccar Engineering Group. At the beginning of the meeting they were skeptical. About 1 hour into the meeting it turned into a brainstorm session, and we left with an assignment. The Paccar engineers asked us to generate more data, such as the flow through the Dorothy and temperature drop, which was very important to them because it lowers the combustion temperature thus lowering the know emissions. Currently the Dorothy is dropping the temperature of the EGR flow by 70 degrees.

During our tour we witnessed a T-880 tandem dump truck on a controlled environment chassis dyno. The temperature was 22 degrees below zero, the wind tunnel in front of the truck can generate 75 mph wind, and the altitude can be changed. Think about that, how do you change the altitude in a dyno room that is at sea level? Other tests we witnessed were the turning on and off of the turn headlights and turn signals to see how long the bulbs will last. We saw the rear section of a truck frame being twisted; they will twist it until failure. A shaker rig was being set up to shake an entire truck until failure. Actuators working dash switches until failure, and Paccar engines, transmissions and differential equipped with disc brakes running on engine dynos simulating actual driving experiences. Paccar was testing their own front axle, placing different torques and twisting of the axle and kingpins. John and I also had the opportunity to go for a ride on their test track, which is a banked oval of 1.5 miles, an off-road course with many types of pot holes, low bridge expansion joints, speed bumps and two hills to do dead stop start outs of 20 and 30 degrees. The Paccar engine and automatic transmission (12 speed) will start out on the 30-degree hill, once the brake is released, without touching the throttle while pulling a gross weight of 80,000 pounds. WOW, automatics have come a long way and that transmission is a joint effort between Eaton and Paccar.

John and I would like to thank the employees of the Paccar testing facility for sharing their time and beautiful facility with us.

Mike Lane, owner-operator with Tramcor out of Ogden, Utah and a member of the Owner-Operators Snowmobile Group, is in my office and sharing his driving thoughts and techniques for the remainder of this article. Mike owns a Western Star Low Max powered by a Pittsburgh Power DD5 Detroit, 840,000 miles on the engine producing 720 horsepower to the ground through an 18 speed Eaton transmission. He has one of the most powerful trucks in the fleet of 100. Mike is a true gear head, a former mud bog racer with a 1954 Willis pick up powered by a 400 small block Chevy, Edelbrock intake manifold, Holley 750 double pumper carburetor, Brodix heads, and a wild Crower camshaft. Now he rides a 2016 Axys Polaris 800 mountain sled.

Mike Lane says: “Listen to your truck, it will talk to you”. Sounds, pitches, vibrations, how altitude and ambient temperatures affects turbo boost, exhaust gas temperature, available power that can be used, and of course fuel mileage.

Sounds - Different pitches in the turbo will give you an idea of where the turbo boost should be. Naturally, you must have a truck equipped with a turbo boost gauge and a pyrometer (exhaust gas temperature gauge). When you are driving the truck, cruise control turned off, the pitch of the turbocharger and the position of your foot on the throttle along with the tachometer reading (RPM) gauge, your mind should know about how much turbo boost the engine is using and what the pyrometer reading should be. You should play mind games with yourself, knowing where your foot is on the throttle, and the sound of the engine telling you the RPM, you should then know the turbo boost being used and the exhaust gas temperature. And it goes the other way also, the boost being used and your foot on the throttle should tell you the RPM and exhaust gas temperature. If you play these mind games with yourself you will also learn how altitude affects turbo boost, exhaust gas temperatures and horsepower. Please keep in mind at 10,000 feet there is ½ the molecules of oxygen available for the engine to burn.

Vibrations - Vibrations change as parts wear out; however it’s a slow process and our bodies adapt, and our bodies don’t realize it. If you allow your friend or a good mechanic to take it for a ride he will feel the vibrations. The torsional damper, which should be replaced every 500,000 miles, is an item you don’t realize is failing. After all, it takes several years to wear out. The torsional vibrations will travel through the pedals, shifter, steering wheel and the door locks. If they shake, the torsional damper is worn out.

Driveshafts should be replaced or rebuilt every 500,000 miles; however most owner-operators do not do it. Carrier bearings, U-joints, slip yoke, and the shaft can twist, bend and go out of balance. Sometimes it’s a slow process, other times it can happen quickly. A shock load or a bind can destroy the shaft instantly, or start the bending process. When taking the drive shaft to a driveline shop, always have the tubes straightened, and then balanced along with new U-joints, carrier bearing and possibly the slip joint.

Tires - As tires wear they go out of balance, the Balance Masters, Centramatic, Counteract, or Equal will balance the tire as it wears and goes out of balance. If the tire has strange wear patterns and wears out of round, it may not be possible to balance it. Different road conditions can change the vibrations, so when driving on new asphalt pay close attention to the sound and feel of the tires.

Steel wheels, being the wheel is welded and not turned on a lathe; the wheel cannot be perfectly round. If your truck is equipped with steel wheels, chances are you will have a vibration.

Engine Mounts, they are rubber and will wear, it takes thousands of miles, however it’s another gradual item and when the wear is so bad and there is metal on metal, you will hear it and feel it.

All rubber mounts, such as the radiator and charge air cooler mounts, cab mounts, hood mounts, and exhaust piping mounts can cause vibrations. As an owner-operator you need to spend time working on your truck and changing these small items. The rubber around the door and the felt in the window tracks will eliminate squeaks and eliminate air leaks.

We have run out of space, so Mike Lane and I must say good-bye until next month.

Written by Bruce Mallinson, Pittsburgh Power, Inc.,

3600 South Noah Dr., Saxonburg, PA 16056

Phone 724-360-4080