Freewheeling

daveza

daveza

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So I've taken to freewheeling downhill in order to save fuel.

On Plattekloof bend I can almost get to the NI City turn off without dropping below 110.

On a trip to Paarl about a quarter of the trip is downhill so lots of savings there.

Anyone else doing crazy stuff while every kilo costs you a rand or more ?

PS: If I turn the engine off at a red traffic light does it use more to restart it ?
 
By freewheeling do you mean having the clutch in and the car literally rolling, or having the car in gear but not accelerating at all?
 
daveza said:
PS: If I turn the engine off at a red traffic light does it use more to restart it ?
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I don't know if you'll save anything doing that, but I've been told it's a bad idea to turn your engine on and off too much - something about the water in the radiator not circulating properly and the engine temperature going up and down. ;)

I do know an engine should maintain as steady a temperature as possible, otherwise it wears it down faster..
 
By running the car in 5th gear you actually don't use any petrol or minimal amounts as the car is running itself itself due to the revolutions of the engine. Where as if you put the car in neutral the car can't pick up its revolutions and not support itself.

Tested this myself where I can have a look at the petrol usage on my cars information panel.
 
Rahl said:
By running the car in 5th gear you actually don't use any petrol or minimal amounts as the car is running itself itself due to the revolutions of the engine. Where as if you put the car in neutral the car can't pick up its revolutions and not support itself.

Tested this myself where I can have a look at the petrol usage on my cars information panel.
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That is just what I was trying to say, but you have put it much more eloquently :)

5th gear FTW :D
 
Good to know. :D

Another question - what is the minimum speed at which one can put the car in to 5th gear?
 
modern cars have an automatic fuel cutoff, so when you coast, clutch out, there is no petrol going into the cylinders to burn.

older stuff doesnt..

so , before deciding what to do, find out if your car has an automatic fuel cutoff on overrun. if it does, then just lift off the accelerator on a downhill and you will be fine (but engine braking will limit how long you can coast for)

if your car doesnt have automatic fuel cutoff on overrun, then pushing in the clutch and freewheeling will save a heck of a lot of petrol on downhills.
 
werner said:
modern cars have an automatic fuel cutoff, so when you coast, clutch out, there is no petrol going into the cylinders to burn.

older stuff doesnt..

so , before deciding what to do, find out if your car has an automatic fuel cutoff on overrun. if it does, then just lift off the accelerator on a downhill and you will be fine (but engine braking will limit how long you can coast for)

if your car doesnt have automatic fuel cutoff on overrun, then pushing in the clutch and freewheeling will save a heck of a lot of petrol on downhills.
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How old is old though? Like does my 2005 velociti count as old or new considering the design has not changed for 25 years? I hope the engine has changed at least a bit in that time :o
 
redarrow said:
I don't know if you'll save anything doing that, but I've been told it's a bad idea to turn your engine on and off too much - something about the water in the radiator not circulating properly and the engine temperature going up and down. ;)
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Not when the engine is warm. The engine will take hours to cool down when turned off. A few minutes won't make any difference.

PostmanPot said:
Another question - what is the minimum speed at which one can put the car in to 5th gear?
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0 kph. Try it yourself. Even works when the car is off. :)

werner said:
modern cars have an automatic fuel cutoff, so when you coast, clutch out, there is no petrol going into the cylinders to burn.
Click to expand...

That's only the case if the car is in gear, when the wheels and drivetrain can keep the engine turning. In neutral, or with the clutch in, the engine is not connected to the drivetrain, so the engine needs to be powered to keep it turning.
 
Claymore said:
That's only the case if the car is in gear, when the wheels and drivetrain can keep the engine turning. In neutral, or with the clutch in, the engine is not connected to the drivetrain, so the engine needs to be powered to keep it turning.
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yes, that is what i said. read it again, hence the "clutch out" part of my sentence. it is obvious you didnt read my whole post

did you have learning difficulties as a child or something? :-)

some more info re: switching engine off when stationary....."The new bmw 1 Series also comes with Auto Start-Stop function to cut fuel consumption. The system automatically switches the engine off when the vehicle is stationary and the driver puts the car into neutral. To restart the driver only need engage the clutch again before pulling away in the normal manner."
older european mark2 golf's had a similar system, read about it in the bentley manual. i dont know (and dont care) how they worked around the heatsoak pronblems, but if it saves fuel it is a good thing in my book.
 
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I think he means the minimum speed before the engine starts to labour because of it being in the incorrect gear.
 
werner said:
yes, that is what i said. read it again, hence the "clutch out" part of my sentence. it is obvious you didnt read my whole post
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I beg your pardon, I was looking at it at the technical level: clutch out = disengaged from flywheel, clutch in = engaged.

did you have learning difficulties as a child or something? :-)
Click to expand...

Yes, I did, thanks for asking.

(Though that may have been more due to never learning to study...)
 
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