There was a time when “Please remove Optimized idle!” was written on almost every work order that came across my desk. Once I learned how to disable the optimized idle feature in a DDEC that was all I did with it. I’d listen to stories from frustrated techs, service managers, and owner operators who tried to keep optimized idle systems working but always seemed to end up staring at a check engine light that wouldn’t turn off and can’t be cleared. By the time they got to me they didn’t want to fix it, they just wanted it gone. An optimized idle system on a 20 year old truck is finicky at best. Optimized idle monitors all the inputs that cruise control does plus it initiates self-checks on its outputs making it the DDEC III/IV function with the greatest number of activation requirements.
I didn’t fully appreciate optimized idle until recently. An owner operator send me in a DDEC IV powering an MK60 that needed set up for a 2001 International. He also wanted some custom programming work done to the optimized idle system. I told him his request was a little unusual but as I would soon find out, there are some owner operators who love optimized idle. He ended up making a compelling argument so I upgraded my test bench to support the most common optimized idle outputs then I got to tinkering with it. A few weeks later I convinced the optimized idle function in one of my DDECs to attempt an automated startup. First by sounding the startup alarm followed by two cranking attempts. If after two attempts the crank doesn’t stay spinning then the optimized idle system shuts off.
Anyways my MK60 guy wanted to cut back on how frequently his optimized idle system was starting the MK60. The optimized idle system will restart the engine when the engine oil temperature drops below 60 degrees Fahrenheit. He wanted it to automatically restart at 32 degrees F. Here’s the thing…nearly all DDEC factory programs raise minimum ide speed when oil temperature is low. When oil temp is down to 32 degrees F minimum idle speed is almost 900 rpm. So a 32 degree restart will go up to almost 900 rpm. Some engine guys like this and some don’t. This can be programmed out so minimum rpm is 600regardless of oil temperature but unless it’s my truck I prefer to stand on the sidelines and let the techs hash these things out.
The most common programming mistake I see that cripples optimized idle is when someone disables the idle shutdown timer. Like it or not the idle shutdown timer must be enabled in order for optimized idle to work. Optimized idle won’t activate unless the idle shutdown timer shuts down the engine. If you touch the key everything resets. The DDEC can be programmed to ignore the idle shutdown timer and run continuously if the oil temperature or battery voltage is low, if the idle has been bumped up or if the thermostat in the optimized idle module in the bunk is reading a temperature that is out of the desired range.
You don’t need me to tell you idling is hard on these engines. If a truck doesn’t have an APU, Optimized idle could be the next best thing to maintain the truck’s batteries, put some heat in the oil, save fuel, and improve engine life.
Fernando DeMoura, Diesel Control Service LLC., Website: www.dieselcontrolservice.com, Phone 412-327-9400