Team-BHP - View Single Post - Why diesel engines are revved before switching ignition off?

sumitkalindi · 8th May 2006, 17:52

Hi guys, I have an answere to this question.

See most of the trucks and busses have a battery built by the freindly neighbourhood electritian. While building a battery the main concern is how many plates are giong to be in the battery more no of plate better the amper hour rating. As such there is no quality controll over the battery. So after whole day, especially the whole evening with soo many lights on the battery is already under strain.

So the Drivers just rev the engine at a constant high RPM, putting off all the lights trying to add that extra bit of juice in them.

Now the second and more important reason. These vehicles use air pressure to use the brake. The parking brake is just a valve that applies the air pressure or releases it making the brakes to work.

If you can, try to check what meter the driver checks while revving the truck/bus before cutting off the engine. It is the air pressure meter. As soon he has enough air pressuer, he is going to cut off the engine and head home. Battery charged or not charged.
Hope this cleared out some of your doubts.

8th May 2006, 17:52	#31 (permalink)
sumitkalindi BHPian Join Date: May 2006 Location: Shillong Posts: 276	Hi guys, I have an answere to this question. See most of the trucks and busses have a battery built by the freindly neighbourhood electritian. While building a battery the main concern is how many plates are giong to be in the battery more no of plate better the amper hour rating. As such there is no quality controll over the battery. So after whole day, especially the whole evening with soo many lights on the battery is already under strain. So the Drivers just rev the engine at a constant high RPM, putting off all the lights trying to add that extra bit of juice in them. Now the second and more important reason. These vehicles use air pressure to use the brake. The parking brake is just a valve that applies the air pressure or releases it making the brakes to work. If you can, try to check what meter the driver checks while revving the truck/bus before cutting off the engine. It is the air pressure meter. As soon he has enough air pressuer, he is going to cut off the engine and head home. Battery charged or not charged. Hope this cleared out some of your doubts.