AFSZ • Idling

Eleven school buses that twice a day idled for as much
as 30 minutes. Passing trucks and cars added to
the congestion. (Left)

The AFSZ worked with local police to change traffic
patterns to stop idling and allow buses for only
10 minutes directly before pick-up and drop-off. (Right)

Idling means running the engine when the vehicle is standing still. The exhaust from idling vehicles have been linked to many environmental and health issues, including asthma. Current NYC Law prohibits any vehicle idling for longer than three minutes. New York State law prohibits the idling of school buses while in school zones.

Article from Bus Conversions Magazine Forum, February 12, 2006:
By Clarke Echols

For gasoline engines (cars, pickups, light trucks), start it. If the weather’s cold, let it idle briefly until it is firing on all cylinders, then ease out into the street and let it warm up while working. Idling a cold engine in cold (Rocky Mountain or Northern States areas) weather until it warms up is murder on the insides. It casues high acid build-up in the oil, and generally destructive. A fuel-injected gas engine will start immediately, even in cold weather (down to zero or ten below — minus 40 might be a bit tougher). As soon as it’s running, get going. Don’t idle. If mama wants a warm car, you may have to compromise, but it’s idling that contributes to pollution because there’s not enough exhaust to get the catalytic converter running properly.

Even a warm/hot engine is damaged by idling. One minute at idle is as bad on most engines as two miles of driving at 60 mph on the interstate, whether gasoline- or diesel-powered.

Diesels pull a full gulp of air on every intake stroke. They have no throttle butterfly like gas engines to restrict air flow for idling. They just change the amount of fuel being fed into the injectors to control speed/torque. If the engine isn’t working hard, it gets a smidgen of fuel, not enough to maintain block temperature, and the intake air is like a big blast of refrigerating (cool) air, especially if the turbo isn’t spinning at full compression. Thus the engine cools to below its design operating temperature and you get the high wear factors again.

Idling wastes fuel. It takes about 0.3-0.4 pounds of fuel per hour to produce on HP of output from a diesel. There are 7 pounds of diesel in a gallon. It takes at least 10-15 HP or more to idle a diesel, depending on size, including alternator, compressor, etc. At 0.3 lb/hr, 10 HP = 1/2 gallon of fuel per hour; 20 HP = 1 gallon per hour. At $3/gallon, that’s a lot of bread to be blowing out the stack for no good reason.

If you’ve been pulling hard down the highway and pull in for a stop, let the turbo cool down, but in most situations, by the time you get from the exit ramp through the traffic signals and into a parking spot, you’ve already burned of 1-3 minutes which is adequate for turbo cooling, so just shut down the engine. When you restart, it will be fully warm and ready to roll immediately, assuming you didn’t park for an extended time of hours, even in cold weather. Especially in cold weather, you really knock the temp down on an idling engine.

So start it, get the air tanks up to an adequate pressure (some air bags don’t air up until a minimum-pressure valve opens at 90 pounds or some similar level), then ease it out. As long as you’re not blowing air off of the brakes faster than the compressor can air the tanks up, you should be fine, and the tanks will fill faster as you are driving down the road at the start of the trip.

Once it’s warming up, don’t be afraid to lean on the throttle if you’re so inclined. But you’ll save fuel if you keep your foot out of it.

If you’re hot-footing it and you’re blowing black smoke, lay off. As soon as it starts smoking, that says it’s getting more fuel than it can burn, and you’re just wasting diesel. You won’t go any faster, because the engine’s already at its peak.

For best engine life, don’t idle, and treat it with respect while not warmed up, and again after it’s fully warmed up as well.