Baiting eco-mentalists in the grauniad
Discussion
Got a bit peeved by an article and comments in the Guardian, so now have great fun baiting the eco-mentalists!
http://www.guardian.co.uk/money/2011/mar/12/cut-yo...
http://www.guardian.co.uk/money/2011/mar/12/cut-yo...
If you have any concept of how a modern petrol fuel injection engine works, then you'll know it's better to be in higher revs and have your foot only slightly on the pedal than to be in low revs and have your foot flat on the pedal.
I've always felt the best engine size for economy is a 1.4 or 1.6. 1 litres have to strain to much, and 2 litres tend to get a bit hungry. But 1.4 is great for city and 1.6 is better for the motorway as you can put longer gearing in.
I've always felt the best engine size for economy is a 1.4 or 1.6. 1 litres have to strain to much, and 2 litres tend to get a bit hungry. But 1.4 is great for city and 1.6 is better for the motorway as you can put longer gearing in.
bozmandb9 said:
Got a bit peeved by an article and comments in the Guardian, so now have great fun baiting the eco-mentalists!
http://www.guardian.co.uk/money/2011/mar/12/cut-yo...
Excellent work. Champagne socialists get on my tits.http://www.guardian.co.uk/money/2011/mar/12/cut-yo...
Someone say that they have been getting better mpgs by reducing their driving time by driving as fast as possible before the petrol runs out.
preferably mention it's in a RR 4.6HSE too, and say how hard it is getting a big vehicle around congested city roads these days.
(then move back to a safe distance)
preferably mention it's in a RR 4.6HSE too, and say how hard it is getting a big vehicle around congested city roads these days.
(then move back to a safe distance)
maniac0796 said:
If you have any concept of how a modern petrol fuel injection engine works, then you'll know it's better to be in higher revs and have your foot only slightly on the pedal than to be in low revs and have your foot flat on the pedal.
Very wrong. A petrol engine has the best thermodynamic efficiency at low revs, as it allows for complete burning of the fuel/air charge. So low revs are best for economy.I don't know if it's on their website, but today's Guardian came with an electric car supplement. It was actually quite good, and only one bit really annoyed me, one of the interviews with electric car owners where an American patent lawyer said (about his Nissan Leaf) "It accelerates like a video game, not a laggy old combustion engine".
First of all, I really hate how cars are becoming like video games and it upsets me that a lot of people think it's a good thing. Secondly, I took the comment 'laggy old combusion engines' to mean that his previous cars have been underpowered with bad automatic boxes and he shouldn't be damning an entire technology on that basis.
First of all, I really hate how cars are becoming like video games and it upsets me that a lot of people think it's a good thing. Secondly, I took the comment 'laggy old combusion engines' to mean that his previous cars have been underpowered with bad automatic boxes and he shouldn't be damning an entire technology on that basis.
maniac0796 said:
Sort of 30mph. 5th gear will use more fuel than 4th, even though 4th is revving higher.
Erm...no.Most cars will pull in top gear at 30 mph without labouring and get better mpg.
Petrol cars waste energy pumping air against a closed throttle plate. The higher the gear the more open the throttle plate for any given torque.
Seriously, try it in a car with a computer. Higher gear equals better economy.
In general terms, and ignoring things like VTEC to which a whole different set of generalities apply 
The trough of the BSFC curve at WOT is at pretty much the same rpm as the peak of the torque curve.
At less than WOT the BSFC is worse overall, the curve has a less well defined trough and the trough moves away from the WOT peak torque rpm, usually towards higher rpm.
At very low throttle settings the overall BSFC is at its worst and the curve is not that far off flat.
If you draw the family of BSFC curves for different throttle settings, then draw a line through all the troughs, you get a sort of J shape.
The trough of the BSFC curve at WOT is at pretty much the same rpm as the peak of the torque curve.
At less than WOT the BSFC is worse overall, the curve has a less well defined trough and the trough moves away from the WOT peak torque rpm, usually towards higher rpm.
At very low throttle settings the overall BSFC is at its worst and the curve is not that far off flat.
If you draw the family of BSFC curves for different throttle settings, then draw a line through all the troughs, you get a sort of J shape.
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