Cars that are economical at 80-90mph? Hypothetically ;)
Discussion
My 3.0 CDI gives me 42mpg on drives to Germany. I average about 70mph and to do that means upping the speed on the Continent.
Funny but I don't see much of a drop of in average consumption at the higher speeds.
My experience has led me to believe that bigger engines are more economical for higher speed motorway driving. The ngine doesnt have to work so hard to deliver the same amount of power to maintain the speed.
Funny but I don't see much of a drop of in average consumption at the higher speeds.
My experience has led me to believe that bigger engines are more economical for higher speed motorway driving. The ngine doesnt have to work so hard to deliver the same amount of power to maintain the speed.
Herman Toothrot said:
My 325i seems to be more efficient at 80 mph rather than 70mph, I assumed it's mapped with a hole in the fueling for autobahn / 80mph EU speed limit efficiency.
Same here. I bought a 3.0 325i expecting to have to be careful with my right foot but it's more efficient at 70-80 than at 60.Another factor which hasn't been mentioned is that motorways are rarely flat. Stretches of for example the A1M constantly rise and fall and will affect the consumption of a low powered car at 90mph as it will be at wide open throttle when going up hill, versus a big diesel with the throttle opened just a little bit more. If you're even more analytical about it you can look at how cruise control works too - arguably in this instance a bigger engine won't need managing as much by the cruise control either which will improve efficiency and reduce the benefit of having a smaller engine.
rsv696 said:
Same here. I bought a 3.0 325i expecting to have to be careful with my right foot but it's more efficient at 70-80 than at 60.
were these autos or manuals? 2 people with the same makes this seem plausible, but it is still very suprising.
My suspicion is that these are both autos and at around 60 the transmission selects top gear despite not being at a high enough rpm for the lock up to engage but at 70-80 the lock up engages and the transmission is much more efficient.
Bigger engined diesel cars in my experience are less affected as the speed rises but use more fuel all the time anyhow , so the difference between 70 and 85mph might be a drop in economy on a 3.0l diesel of 10% on a 1.9l it might be 15% but they 1.9 will already be significantly better on fuel anyhow so can afford a bigger drop.
A 6 speed box matters as well , in 6th on the continent I can still get over 50mpg in my 2.0CR 170 Superb with the cruise set to 87mph indicated
A 6 speed box matters as well , in 6th on the continent I can still get over 50mpg in my 2.0CR 170 Superb with the cruise set to 87mph indicated
ging84 said:
were these autos or manuals?
2 people with the same makes this seem plausible, but it is still very suprising.
My suspicion is that these are both autos and at around 60 the transmission selects top gear despite not being at a high enough rpm for the lock up to engage but at 70-80 the lock up engages and the transmission is much more efficient.
Mines an Auto2 people with the same makes this seem plausible, but it is still very suprising.
My suspicion is that these are both autos and at around 60 the transmission selects top gear despite not being at a high enough rpm for the lock up to engage but at 70-80 the lock up engages and the transmission is much more efficient.
Welshbeef said:
What do you mean - without really trying? If you tried harder at 90mph could you get more MPG/what would you be doing harder to achieve this?
Well I've done similar to you recently and gone from a performance car to a sensible diesel. To make up for that I never drive this with economy in mind. I check the average MPG reading from time to time and those are the sort of figures I'm seeing! I would imagine I could achieve higher by for example turning the AC off and not accelerating as hard. 
I started looking into drag coefficient of cars to find the 'slipperiest' 
I was surprised to find that some of the cars with the lowest drag (0.26cd) are a Mazda 3 and 'boxy' Mercedes B Class (see this link: http://motorburn.com/2014/01/12-of-the-most-aerody...
My rather chunky Seat Leon 1.9TDi has 0.33cd.
Sooo....
How the hell can a car as 'slippy' looking as the Peugeot RCZ have such a high cd as 0.32/0.33??
I was surprised to find that some of the cars with the lowest drag (0.26cd) are a Mazda 3 and 'boxy' Mercedes B Class (see this link: http://motorburn.com/2014/01/12-of-the-most-aerody...
My rather chunky Seat Leon 1.9TDi has 0.33cd.
Sooo....
How the hell can a car as 'slippy' looking as the Peugeot RCZ have such a high cd as 0.32/0.33??
mrrossi said:
I started looking into drag coefficient of cars to find the 'slipperiest'
I was surprised to find that some of the cars with the lowest drag (0.26cd) are a Mazda 3 and 'boxy' Mercedes B Class (see this link: http://motorburn.com/2014/01/12-of-the-most-aerody...
My rather chunky Seat Leon 1.9TDi has 0.33cd.
Sooo....
How the hell can a car as 'slippy' looking as the Peugeot RCZ have such a high cd as 0.32/0.33??
cd is the coefficient of drag. I was surprised to find that some of the cars with the lowest drag (0.26cd) are a Mazda 3 and 'boxy' Mercedes B Class (see this link: http://motorburn.com/2014/01/12-of-the-most-aerody...
My rather chunky Seat Leon 1.9TDi has 0.33cd.
Sooo....
How the hell can a car as 'slippy' looking as the Peugeot RCZ have such a high cd as 0.32/0.33??
AIUI - its the actual amount of drag divided by the frontal area, so cars with a low frontal area have to be more streamlined to achieve the same low cd as more upright cars.
Remember that a proportion of the drag is created in places where the cars probably look very similar, e.g. the underside and the wheelarches ( where the tops of the tyres are going completely against the direction of travel)
So a lower car can have less actual drag than a MPV, yet still have a higher coefficient of drag.
Warning: PH analogy coming up.....
I am 6'3", and my missus is 5'5", If I drank a bottle of wine, and my missus drank half a bottle, she would still be more pissed than me, because her coefficient of pissedness is greater than mine
sparkyhx said:
underphil said:
The effect of higher speed of different types of cars' economy can be quite varied:
the merc (Blue line) has a pretty flat line - quite impressive.talksthetorque said:
mrrossi said:
I started looking into drag coefficient of cars to find the 'slipperiest'
I was surprised to find that some of the cars with the lowest drag (0.26cd) are a Mazda 3 and 'boxy' Mercedes B Class (see this link: http://motorburn.com/2014/01/12-of-the-most-aerody...
My rather chunky Seat Leon 1.9TDi has 0.33cd.
Sooo....
How the hell can a car as 'slippy' looking as the Peugeot RCZ have such a high cd as 0.32/0.33??
cd is the coefficient of drag. I was surprised to find that some of the cars with the lowest drag (0.26cd) are a Mazda 3 and 'boxy' Mercedes B Class (see this link: http://motorburn.com/2014/01/12-of-the-most-aerody...
My rather chunky Seat Leon 1.9TDi has 0.33cd.
Sooo....
How the hell can a car as 'slippy' looking as the Peugeot RCZ have such a high cd as 0.32/0.33??
AIUI - its the actual amount of drag divided by the frontal area, so cars with a low frontal area have to be more streamlined to achieve the same low cd as more upright cars.
Remember that a proportion of the drag is created in places where the cars probably look very similar, e.g. the underside and the wheelarches ( where the tops of the tyres are going completely against the direction of travel)
So a lower car can have less actual drag than a MPV, yet still have a higher coefficient of drag.
Warning: PH analogy coming up.....
I am 6'3", and my missus is 5'5", If I drank a bottle of wine, and my missus drank half a bottle, she would still be more pissed than me, because her coefficient of pissedness is greater than mine
Tries to find a list of cars measured by Cda.....
cptsideways said:
talksthetorque said:
mrrossi said:
I started looking into drag coefficient of cars to find the 'slipperiest'
I was surprised to find that some of the cars with the lowest drag (0.26cd) are a Mazda 3 and 'boxy' Mercedes B Class (see this link: http://motorburn.com/2014/01/12-of-the-most-aerody...
My rather chunky Seat Leon 1.9TDi has 0.33cd.
Sooo....
How the hell can a car as 'slippy' looking as the Peugeot RCZ have such a high cd as 0.32/0.33??
cd is the coefficient of drag. I was surprised to find that some of the cars with the lowest drag (0.26cd) are a Mazda 3 and 'boxy' Mercedes B Class (see this link: http://motorburn.com/2014/01/12-of-the-most-aerody...
My rather chunky Seat Leon 1.9TDi has 0.33cd.
Sooo....
How the hell can a car as 'slippy' looking as the Peugeot RCZ have such a high cd as 0.32/0.33??
AIUI - its the actual amount of drag divided by the frontal area, so cars with a low frontal area have to be more streamlined to achieve the same low cd as more upright cars.
Remember that a proportion of the drag is created in places where the cars probably look very similar, e.g. the underside and the wheelarches ( where the tops of the tyres are going completely against the direction of travel)
So a lower car can have less actual drag than a MPV, yet still have a higher coefficient of drag.
Warning: PH analogy coming up.....
I am 6'3", and my missus is 5'5", If I drank a bottle of wine, and my missus drank half a bottle, she would still be more pissed than me, because her coefficient of pissedness is greater than mine
Tries to find a list of cars measured by Cda.....
CdA is just another way of stating the force needed to overcome the absolute drag the car produces - assuming that the air is the same density and the speed is the same for comparisons.
It could be called F if the air density and speed are known constants.
Cd divides absolute drag by frontal area, CdA just multiplies the area back in again.
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