When I first started tuning ECMs and making high performance programs I road tested almost every job that I did. I wanted to make sure every program I did was doing its job. I was also hungry for engine performance data and collected as much as I could. Road testing takes a while. You have to hook up to a loaded trailer and find a nice hill with some dry pavement if you were to have a shot at getting a good test. Traffic, snow and construction all make road testing a real pain. If there were no loaded trailers to pull or the weather was bad going to full load wasn’t an option. On an average day I’d go on around 4 to 6 road tests and that ended up being the limit on how many jobs I could take on. The engine performance data wasn’t easy to interpret but the road test almost always ended with the driver smiling. When we pulled back into the shop I’d give a thumbs up so the techs could see the job was a success. We really didn’t know how much power we were making but when the owner of the truck was smiling and telling us we did a good job that number didn’t seem to matter.
Then came the dynamometers. Testing with a chassis dynamometer became fast and efficient. A single tech can test a truck in less than 10 minutes before testing another. This meant more ECM tuning jobs per day and a flood of engine performance data to study. Still I couldn’t help feeling something had been lost. As the programs I made became more developed I saw the second half of the throttle became more like an on/off switch because most of the new data I had was based on power pulls under full load. Once I recognized this I started to see the same problem in ECM programs from other tuning shops that rely too much on their dynos. The dyno operators hold the throttle to the floor then pull the engine rpm down never letting up until engine rpm is below 1200. This kind of ECM tuning doesn’t make a good usable program. Programs like this hit their marks at full load but can be erratic and unpredictable at fractional throttle values. A sudden wild surge of power from an engine isn’t something that should happen unless the operator just went to full throttle. Power like that can get scary and unpredictable. Initially these early dynamometer crafted programs would get sent back because they became hard to control unless they were at full load. It wasn’t until after I went out on a road test that I knew what had been lost. Proportional throttle control. This also caused a loss in fuel mileage. When an ECM program is making your power hard to control it’s also making your fuel consumption hard to control. The guys who only care about dyno numbers and turning up the fuel almost never consider this.
A throttle is a control and should feel controllable. The throttle is the most important link between you and your ECM. Together your ECM, your throttle, and you are part of trucks control system. All three need to be predictable and work together to be safe and efficient.
Written by Fernando DeMoura, Diesel Control Service LLC. Website: www.dieselcontrolservice.com Phone 412-327-9400