January 2010 - Performance Zone
CHANGE IS GOOD!
By Performance Specialist Bruce C. Mallinson
As the world of diesel engines keeps changing, those of us who specialize in high performance diesel engines must also keep changing. Innovation requires an open mind and breakthroughs can often take some time, but on Thursday, December 10th, we had a breakthrough. Fernando (our resident mechanical engineer), Nathan (one of our diesel engine technicians) and I took advantage of an uncommon opportunity when a Freightliner equipped with a DDEC IV EGR Detroit engine came into our shop. This engine was one of the first Series 60 EGR applications. We have been studying the EGR engines since their implementation in 2003. Our goal is to figure out how to make these engines more efficient, burn cleaner, live longer and eliminate the problems associated with the complex and expensive VGT (variable geometry turbo).
This DDEC IV EGR-powered Freightliner came into our shop to have a turbo boost and pyrometer gauge installed, along with one of our straight-through (but quiet) performance mufflers. This truck was equipped with a 2:64 rear gear ratio and a 10-speed direct transmission. A gutless wonder she was, dropping two gears on most hills, drinking fuel by the gallons because of low power, a clogged muffler and all of the garbage that various dealerships had put into the ECM trying to improve this truck’s fuel mileage and performance. But without performance, there is no efficiency.
After lunch I mentioned to the owner of the Freightliner that we have been studying the DDEC IV EGR and asked if he would be interested in testing some changes we wanted to make to his engine. He had to be in Long Island, NY to deliver his load the next morning, so any changes we made had better work. At 9:00 PM that evening, we went for our test ride – and we were very pleased with the results (35 psi of turbo boost bobtailing and 37 with his loaded trailer grossing 79,000 pounds). Only one minor check engine light came on and we knew how to fix that problem. Later that night I called Brandon, the owner operator of the truck, to see how the engine was running. He answered the phone, “I love this truck! I went over Snowshoe Mountain in 10th gear at 25 to 27 psi of boost and never slowed down!!”
Brandon is fairly new to the wonderful world of owning a truck, but he hated his “gutless wonder” that had no power and no fuel mileage. He was even told by a Detroit Diesel dealership that his engine was worn out (and they had a dyno sheet to prove it). This engine is a crate engine with only 420,000 miles on it and they said it would never run right until it gets rebuilt. This is the second engine in this 2004 truck, but let me tell you, this engine is NOT worn out and is running great. With 585 horsepower, Brandon’s rig can now cruise along at 6 to 8 psi of turbo boost at 60 mph (on level ground). We do not have a fuel mileage report yet because the experimental ECM on the truck will not accurately calculate fuel mileage because it has not been calibrated to his rear gears, but I will let you know in future articles how his mileage is doing.
This Freightliner rig we are testing is equipped with 2:64 rear gears. Now think about this – when we build our “Signature Series” glider kit trucks, we install the 2:64 rear gears so the trucks will run effortlessly across the highways. Many people think a truck with high gear ratios like this will lose power on the hills and mountains, however the opposite is true. The truck will effectively gain horsepower because today’s double overdrive 13- and 18-speed transmissions have higher parasitic losses due to friction in high gear. We also know for a fact that the double overdrive Allison Automatic loses about 40% of its horsepower in the transmission’s highest gear. This Allison is only a 6-speed transmission but the torque converter locks up in 2nd through 6th gear, which means it doesn’t lose any power due to torque converter slippage. So, if the Allison is losing up to 40% of its power, what is your 13- or 18-speed transmission losing?
Many owner operators think that their 13- or 18-speed Eaton transmission is a single overdrive, and when they split down half a gear they think that they are in direct drive. This is not true. You must go down two gears or one full gear to get into direct – which is the work gear – the gear you should be using to pull a hill. All 13- and 18-speed Eaton transmissions today are double overdrive when there is a 3:36 to a 3:73 gear ratio in the rear ends. When you’re pulling in direct gear only about 11% to 12% of the power is lost in the drivetrain, which is why when a truck is on a dyno it’s always run in direct gear.
So, let’s do some calculations and see how much power is lost in 13th or 18th gear, versus direct gear. A 550 Caterpillar with 3:55 gears puts out about 490 hp to the rear wheels in direct gear and has about a 12% loss of power. Now, if 30% of the power is lost in 18th gear, then only 390 hp would be delivered to the rear wheels. That is a difference of approximately 100 hp less when pulling in double overdrive – and that is not good!
The fuel mileage of your truck will improve by at least half a mpg running in direct gear with 2:64 rear gears. Now I’m not saying the 2:64 gears are for everybody – if you’re heavy hauling, logging, pulling a dump trailer or running mostly on two-lane roads, then this combination may not be for you. But, if you’re running across the interstates with 80,000 pounds or less gross weight, you just might want to think about converting to 2:64 gears.
I’ll keep you posted about the progress we are making in regards to the changes we have made to Brandon’s DDEC IV EGR engine as more information becomes available. In the meantime, if you have a performance-related comment or question, I can be contacted at Pittsburgh Power in Saxonburg, PA at (724) 360-4080. I hope you all have a happy and prosperous New Year!