Best MPG for cruising @ around 100-120mph
Discussion
TheEnd said:
Patrick Bateman said:
8400rpm said:
This thread is brilliant.
The OP is quite clearly taking the piss out of an earlier thread, with a similar question that was running about the same time this one started.
A lot of people in here have gotten carried away.
I thought it was pretty bloody obvious as well but apparently over half a dozen pages say otherwise. The OP is quite clearly taking the piss out of an earlier thread, with a similar question that was running about the same time this one started.
A lot of people in here have gotten carried away.
Ooops..
Hook, line and sinker...
MSTRBKR said:
Sorry, I don't believe you. Your fuel consumption at 120mph WILL be higher than at 70mph, no doubt about it. True, acceleration does kill MPG but so does top speed because the drag on your car is higher at that speed. No practical experience required, that's theoretical fact.
When Clarkson went to Edinburgh and back on a tank of diesel did he travel at 120mph? No he travelled at 65mph because it's the most economical speed for the car, and most other cars are more economical at around that speed. When Audi drove from London to Rome on a single tank in an A4 2.0 Tdi did they travel at 120mph? No.
Are you saying that it doesn't matter how fast you go as long you accelerate to that speed slowly? Why is it that a Veyron can empty its 100L tank in 12.5 minutes at 250mph then? Should he accelerate a bit slower?
Also, 40 million German drivers probably don't give a monkeys about using more fuel and just want to get where they are going faster.
From practical experience the most economical speed for my car is an average of 70mph. Want to dispute what I've seen in practice?
Thanks for writing this. I was going to get into that discussion but I remembered an old quote:When Clarkson went to Edinburgh and back on a tank of diesel did he travel at 120mph? No he travelled at 65mph because it's the most economical speed for the car, and most other cars are more economical at around that speed. When Audi drove from London to Rome on a single tank in an A4 2.0 Tdi did they travel at 120mph? No.
Are you saying that it doesn't matter how fast you go as long you accelerate to that speed slowly? Why is it that a Veyron can empty its 100L tank in 12.5 minutes at 250mph then? Should he accelerate a bit slower?
Also, 40 million German drivers probably don't give a monkeys about using more fuel and just want to get where they are going faster.
From practical experience the most economical speed for my car is an average of 70mph. Want to dispute what I've seen in practice?
"Never argue with an idiot, they will drag you down to their level, then beat you with experience"
C
andoverben said:
MSTRBKR said:
Even between 70mph and 90mph there is a noticeable difference in fuel economy .......
From practical experience the most economical speed for my car is an average of 70mph. Want to dispute what I've seen in practice?
I don't think anyone can realistically suggest that their car is more economical at 120mph there does seem to be a sweetspot where a car is most efficient for example mine seems to be genuinely more economical at 90 than it is at 70 but then it is also very susceptible to the turbo boosting or not. equally if I floor the car at 100mph the MPG needle will drop to about 16mpg while accelerating as I start going past about 130ish it actually starts to creep up until as I mentioned earlier at 150ish with my foot flat on the floor it is showing 24 mpg it is not using any more fuel but is traveling fast enough to counterbalance.From practical experience the most economical speed for my car is an average of 70mph. Want to dispute what I've seen in practice?
Edited by andoverben on Tuesday 14th September 22:51
bobt said:
andoverben said:
MSTRBKR said:
Even between 70mph and 90mph there is a noticeable difference in fuel economy .......
From practical experience the most economical speed for my car is an average of 70mph. Want to dispute what I've seen in practice?
I don't think anyone can realistically suggest that their car is more economical at 120mph there does seem to be a sweetspot where a car is most efficient for example mine seems to be genuinely more economical at 90 than it is at 70 but then it is also very susceptible to the turbo boosting or not. equally if I floor the car at 100mph the MPG needle will drop to about 16mpg while accelerating as I start going past about 130ish it actually starts to creep up until as I mentioned earlier at 150ish with my foot flat on the floor it is showing 24 mpg it is not using any more fuel but is traveling fast enough to counterbalance.From practical experience the most economical speed for my car is an average of 70mph. Want to dispute what I've seen in practice?
Edited by andoverben on Tuesday 14th September 22:51
andoverben said:
150ish with my foot flat on the floor it is showing 24 mpg it is not using any more fuel but is traveling fast enough to counterbalance.
150mph is 2.5 mile a minute, so a gallon used every ~10 mins. I would estimate that travelling at 150 requires around 150-200bhp - say 175bhp. This equates to 130550J, which is 7.83*10^7J - a gallon of diesel is around 18.5*10^7J, which makes your drivetrain over 40% efficient. I think my calcs must be wrong!Edited by andoverben on Tuesday 14th September 22:51
NoelWatson said:
andoverben said:
150ish with my foot flat on the floor it is showing 24 mpg it is not using any more fuel but is traveling fast enough to counterbalance.
150mph is 2.5 mile a minute, so a gallon used every ~10 mins. I would estimate that travelling at 150 requires around 150-200bhp - say 175bhp. This equates to 130550J, which is 7.83*10^7J - a gallon of diesel is around 18.5*10^7J, which makes your drivetrain over 40% efficient. I think my calcs must be wrong!Edited by andoverben on Tuesday 14th September 22:51
C
NoelWatson said:
andoverben said:
150ish with my foot flat on the floor it is showing 24 mpg it is not using any more fuel but is traveling fast enough to counterbalance.
150mph is 2.5 mile a minute, so a gallon used every ~10 mins. I would estimate that travelling at 150 requires around 150-200bhp - say 175bhp. This equates to 130550J, which is 7.83*10^7J - a gallon of diesel is around 18.5*10^7J, which makes your drivetrain over 40% efficient. I think my calcs must be wrong!Edited by andoverben on Tuesday 14th September 22:51
So, astonishingly, it seems the car actually could do about 22mpg at 150mph, assuming it can maintain that with 175bhp.
CraigyMc said:
...I was reading the other day about the top speed of the porsche 917 at le mans in the 70's. Porsche had a problem where it was designed for 250mph, and it would only pull to 243mph or something (I forget the exact number offhand). The German engineers were not pleased.
It turned out that the tyres were expanding at that speed (centripetal force), which meant the car was very slightly taller than it was expected/supposed to be (more draggy due to the height), and very slightly longer geared (due to the bigger circumference).
Lesson:
Anything with slippery aero at 30mph *might* be just as good at 100mph or more, but if it generates a lot of lift, it might actually get less slippery due to a taller ride height. That depends on the lift characteristics.
C
It turned out that the tyres were expanding at that speed (centripetal force), which meant the car was very slightly taller than it was expected/supposed to be (more draggy due to the height), and very slightly longer geared (due to the bigger circumference).
Lesson:
Anything with slippery aero at 30mph *might* be just as good at 100mph or more, but if it generates a lot of lift, it might actually get less slippery due to a taller ride height. That depends on the lift characteristics.
C
bobt said:
I reckon that even 40 years ag othe Porsche engineers would be well aware that a tyre would increase in diameter at 250 mph.
I'm pretty sure I read this in "an unfair advantage" (the book by Mark Donohue, who was central in the development of the 917). I'm not at home this week to be able to look it up to check for you. It's obvious when you think about it, but in 1971 they really went a LOT faster than they had been doing up until that year.C
TuxRacer said:
frosted said:
Actually all engines are most frugal at 0 mph . Doesn't matter if you drive a Clio or a momaro
EFA. Though I've no idea what a momaro is.Iirc , 70 kph is
MSTRBKR said:
andoverben said:
I don't think anyone can realistically suggest that their car is more economical at 120mph there does seem to be a sweetspot where a car is most efficient for example mine seems to be genuinely more economical at 90 than it is at 70 but then it is also very susceptible to the turbo boosting or not. equally if I floor the car at 100mph the MPG needle will drop to about 16mpg while accelerating as I start going past about 130ish it actually starts to creep up until as I mentioned earlier at 150ish with my foot flat on the floor it is showing 24 mpg it is not using any more fuel but is traveling fast enough to counterbalance.
Oh yeah, I understand accelerating will use more fuel and then the mpg will rise as you begin to maintain a constant speed. But as above I don't believe 120mph is economical speed for a BMW 530.Edited by andoverben on Tuesday 14th September 22:51
E.g gallons/minute stays the same, miles/minute increases. Therefore miles/gallon increases.
busta said:
MSTRBKR said:
andoverben said:
I don't think anyone can realistically suggest that their car is more economical at 120mph there does seem to be a sweetspot where a car is most efficient for example mine seems to be genuinely more economical at 90 than it is at 70 but then it is also very susceptible to the turbo boosting or not. equally if I floor the car at 100mph the MPG needle will drop to about 16mpg while accelerating as I start going past about 130ish it actually starts to creep up until as I mentioned earlier at 150ish with my foot flat on the floor it is showing 24 mpg it is not using any more fuel but is traveling fast enough to counterbalance.
Oh yeah, I understand accelerating will use more fuel and then the mpg will rise as you begin to maintain a constant speed. But as above I don't believe 120mph is economical speed for a BMW 530.Edited by andoverben on Tuesday 14th September 22:51
E.g gallons/minute stays the same, miles/minute increases. Therefore miles/gallon increases.
NoelWatson said:
busta said:
MSTRBKR said:
andoverben said:
I don't think anyone can realistically suggest that their car is more economical at 120mph there does seem to be a sweetspot where a car is most efficient for example mine seems to be genuinely more economical at 90 than it is at 70 but then it is also very susceptible to the turbo boosting or not. equally if I floor the car at 100mph the MPG needle will drop to about 16mpg while accelerating as I start going past about 130ish it actually starts to creep up until as I mentioned earlier at 150ish with my foot flat on the floor it is showing 24 mpg it is not using any more fuel but is traveling fast enough to counterbalance.
Oh yeah, I understand accelerating will use more fuel and then the mpg will rise as you begin to maintain a constant speed. But as above I don't believe 120mph is economical speed for a BMW 530.Edited by andoverben on Tuesday 14th September 22:51
E.g gallons/minute stays the same, miles/minute increases. Therefore miles/gallon increases.
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