Fuel Efficient Driving

Looked to me like it took a fair bit longer to stop than the Volvo. Perhaps the speed was different?
 
Phantom Shadow said:
Do you have a diesel or petrol? My wild guess would be that the most fuel efficient way to get up a hill would be with the revs near peak torque for your engine - which for diesel would usually be lower down in the rev range than a petrol.

I don't get instantaneous consumption displayed in my car so can't go test what's best for me unfortunately. I usually go for a gear that will require the accelerator to be around 50% depressed.
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I own a petrol, but I drive both for a living :)

Yes near peak torque is the sweet spot for efficiency I believe.
 
Acme said:
Looked to me like it took a fair bit longer to stop than the Volvo. Perhaps the speed was different?
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Huh?

The Volvo didn't stop and clearly the speed was different otherwise the lorry wouldn't have caught the car!

That was clearly simulating something like a disorientated pensioner doing 20mph on the motorway.
 
Scania said:
The Scania system is equally good....


The brakes on modern trucks are quite something!
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The adaptive cruise on VAG's is similarly impressive, had some tubbin pull out in front of me and brake on the A34 and the brakes reacted so fast I nearly carped myself!

If every vehicle had a similar system then life would be safer for all of us, assuming the moron behind the wheel engaged it haha.

Truckers have a particularly tough job on the roads with impatient car drivers, so anything that helps them out is good by me.
 
Jonnycoupe said:
Huh?

The Volvo didn't stop and clearly the speed was different otherwise the lorry wouldn't have caught the car!

That was clearly simulating something like a disorientated pensioner doing 20mph on the motorway.
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He means the video of the volvo system, those trucks looked to stop quicker but as he mentions, there is no indication of speed or indeed weight in those videos, so difficult to compare.
 
Dr Who said:
Very interested in the results, make sure you let us know.
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Just been and tested this (All figures are averages rounded slighly)

3rd gear (2300rpm, MAP 68Kpa) 13.8% duty cycle.
4th Gear (1800rpm Map 76Kpa) 11.3% Duty Cycle
5th Gear (1400Rpm Map 91Kpa) 10.8% Duty cycle

I'm sure I could have done it a little more scientifically with a longer hill allowing a larger dataset but it does show that lower RPM higher gear is more fuel efficient

Screen shots of logs


3rd Gear

VTXCfcj.png


4th Gear

s2jIFBY.png


5th Gear

Vw7UbWj.png
 
So the injectors are flowing around 28% more fuel in 5th than 3rd even allowing for the motor being out of its favoured torque rpm.
 
Other way around.

13.8% duty cycle equates to roughly 34.5cc/min fuel flow and 10.8% duty cycle is around 27cc/min (edit: Per injector)

So using 5th uses just under 22% less fuel, on an engine that is way off its peak torque which isn't until 5000rpm
 
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Like a few people have already mentioned, I'd favour using peak torque when accelerating to higher speeds, so if I'm joining a motorway or dual-carriageway, then I'll be using the gears to stay at around 3-4k rpm which is peak torque area for my pathetic little 1.25l engine.
 
Frozennova said:
Other way around.

13.8% duty cycle equates to roughly 34.5cc/min fuel flow and 10.8% duty cycle is around 27cc/min (edit: Per injector)

So using 5th uses just under 22% less fuel, on an engine that is way off its peak torque which isn't until 5000rpm
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Sorry yeah, that's what I meant... duh!
 
Frozennova said:
Other way around.

13.8% duty cycle equates to roughly 34.5cc/min fuel flow and 10.8% duty cycle is around 27cc/min (edit: Per injector)

So using 5th uses just under 22% less fuel, on an engine that is way off its peak torque which isn't until 5000rpm
Click to expand...

But there's less vac in the higher gear so more fuel pressure, you haven't accounted for this.
 
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