Comments on: why do Automobile engines have a drag when we decrease acceleration. Is it not a waste on fuel?

By: Hamph

Hamph — Wed, 19 May 2010 17:56:39 +0000

I have been wondering why that happens too. Great answers Hamph

By: shasikant t

shasikant t — Tue, 18 May 2010 19:31:42 +0000

i agrreed with tweak. shasikant t

By: Chevy-man

Chevy-man — Sun, 16 May 2010 05:31:00 +0000

The drag effect under de-accelerate is caused by things: friction within the engine and transmission Chevy-man

By: A U M

A U M — Sat, 15 May 2010 20:14:07 +0000

When you accelerate, engine drives the wheel via transmission.But when you decelerate engine speed, the wheel rotates engine via transmission. This is called engine brake. Its the principle of neutralisation, where engine and wheels neutrals the speeds of each other. A U M

By: Twiggy

Twiggy — Sat, 15 May 2010 11:13:30 +0000

The drag effect under de-celeration is caused by a number of things: friction within the engine and transmission, air resistance, friction between the tyres and road, gravity if you are going uphill, and the compression of the engine when it is being turned by the wheels.

If you want to stop this compression resistance, you could de-clutch as soon as you take your foot off the accelerator. If you do that, you will put extra stress and strain on the clutch.

Many modern vehicles have a device within the E.C.U. which senses when the vehicle is on the over run, and automatically cuts off the fuel supply to the engine,so saving fuel. It`s only operative under certain conditions: on my vehicle, it works oly in 5th gear when the revs are above 1500 r.p.m. Twiggy

By: Manusha W

Manusha W — Wed, 12 May 2010 05:30:37 +0000

in that mode, vehicle kinetic energy is used to rotate the engine instead of engine powering wheels, thats why it de-accelerate.

only the fuel needed to run the engine in idle is used in this mode, so there is no waste on fuel… Manusha W