General accelleration query

[Arnold]

if you accellerate quickly, and accellerate slowly (up to the same rpm). does it use the same amount of fuel?

Just wondering!
Cheers

 

[59 bhp is more than enough]

nah coz if you accelerate quickly you put more throttle on, hence use more fuel, there is more too it than that though bt im lazy and that is the basic answer

 

[Retepetsir]

Research was carried out, and apparently its most economical when you accelerate as quickly to your cruising speed as possible, as you'll then be cruising at this steady speed for longer......!

 

[Ian]

yeah accelerating quickly uses less fuel

 

[59 bhp is more than enough]

yeah but he didnt ask that he asked that if acceleratin quicker than normal uses more fuel, didnt say anythin out cruising speed afterwards. im sorry but putting you foot down to the same revs as you would do if you was accelerating slower would use more fuel FACT

 

[kristian]

simpilest terms

Accellerating faster takes more power!
Hence more fuel..

 

[Allan]

Yeh this has confused me reading this as it was a bit of a contradiction.

I get the theory that the quicker you get to your cruising speed the better.

However if it's around town and your starting and stopping a lot, quick acceleration will use more fuel because you are pressing the accelerator further down releasing more fuel.

Ok it's all sorted in my head now!

 

[Ian]

so accellerating fast can use more or less fuel depending on situation

 

[Alienfish360]

no..... fast acceleration uses more fuel regardless of situation. However, if you accelerate quickly then cruise, the constant cruising distance extra, more than compensates for the heavy acceleration

 

[masterbiker]

just to complicate things further, keep in mind there will be more wear on componets, tyres etc with the faster acceleration. You get good saving on fuel if you slow down when comming up to junctions/roundabouts without using your breaks, but you get the best saving in fuel if you go in somone elses car!

 

[scottish-sr]

If you press the pedal down further and harder then it is obviously going to use more fuel than if you press it gently. Thats why the car would accelerate faster as there is more fuel/air mix into the engine to bigger bang!

 

[RIK]

just drive to the conditions

i say make the most of it before it all runs out

 

[Jim]

My question about acceleration is, although a Ferrari would reach 60mph a lot quicker than a micra, would both reach 60mph at the same place if they set off from the same place?

 

[greg_k12]

If i remember correctly:

distance travelled = average velocity x time.

I think their average velocity will be the same as they are accelerating to the same speed, therefore if it takes a longer time, it will also be a longer
distance

 

[Andrew]

My question about acceleration is, although a Ferrari would reach 60mph a lot quicker than a micra, would both reach 60mph at the same place if they set off from the same place?

This one is easy. No. The distance travelled accelerating to the same speed is proprotional to the time taken. So if a Ferrari takes 4 seconds and the Micra 12, it will take 3 times the distance to get there.

 

[Andrew]

if you accellerate quickly, and accellerate slowly (up to the same rpm). does it use the same amount of fuel?

This one isn't easy to answer.

Conventional wisdom states that driving gently you get better MPG. Totally true. That isn't what the question asks though.

A theoretical petrol engine is most fuel efficient (amount of fuel burnt to power produced) when the throttle is wide open. This is because pumping loses are reduced. This is true across the rev range.

You can otherwise use a large amount of power to accelerate quickly, or a small amount of power to accelerate slowly. The change in kinetic energy is the same, so the amount of energy the engine produces is the same whatever. If 100bhp takes 5s, 50bhp will take 10s.

The amount of energy an engine makes is related to the amount of fuel it burns, and then you take into account efficiency. Both types of acceleration use the same amount of fuel before you take throttle position into account. But the quicker acceleration has a wider throttle opening, so is working more efficiently.

Hence, accelerating quickly uses less fuel during that period of acceleration. This ISN'T MPG. You will have travelled less distance for the same amount of fuel - but that wasn't the original question.

In the real world, in actual driving, it is different. Hard acceleration will generally cause greater fuel enrichment. Hard acceleration is normally accompanied by changing gear at higher rpm. Hard acceleration normally means stop-start driving (constant speed uses less fuel). Hard acceleration means wheel spin and slipping clutch.