Slight rant warning : Dad and I.
Discussion
briers said:
Your dad needs to know foot firm down on the throttle to get up to speed as quickly as possible is the most efficient way to drive. Slow acceleration means you take longer moving 2 tonnes of car up to speed.
That also means he needs to anticipate when he can give it full throttle once the car in front is far enough down the road.
Then obviously highest gear lowest rpm without labouring and cruise off throttle to slow down and light loading.
I enjoy my 350bhp and for economy drive my wife's god awful hybrid company car she's been lumbered with. Hopefully for not much longer, it's so dull you may as well play the economy game. No issues achieving 70+ mpg average. Even 62mpg on a 400 mile round trip up the m-way to north Wales. Zzzz
To be fair i love playing the odd economy game now and then. Record for the celica is 38mpg. For the swift i've averaged 60mpg on an 80 mile trip of motorways and A roads (serious lorry slipstreaming going on there) and 36mpg in the TT. That also means he needs to anticipate when he can give it full throttle once the car in front is far enough down the road.
Then obviously highest gear lowest rpm without labouring and cruise off throttle to slow down and light loading.
I enjoy my 350bhp and for economy drive my wife's god awful hybrid company car she's been lumbered with. Hopefully for not much longer, it's so dull you may as well play the economy game. No issues achieving 70+ mpg average. Even 62mpg on a 400 mile round trip up the m-way to north Wales. Zzzz
Edited by briers on Monday 28th May 21:03
briers said:
Your dad needs to know foot firm down on the throttle to get up to speed as quickly as possible is the most efficient way to drive. Slow acceleration means you take longer moving 2 tonnes of car up to speed.
That also means he needs to anticipate when he can give it full throttle once the car in front is far enough down the road.
Then obviously highest gear lowest rpm without labouring and cruise off throttle to slow down and light loading.
I enjoy my 350bhp and for economy drive my wife's god awful hybrid company car she's been lumbered with. Hopefully for not much longer, it's so dull you may as well play the economy game. No issues achieving 70+ mpg average. Even 62mpg on a 400 mile round trip up the m-way to north Wales. Zzzz
That also means he needs to anticipate when he can give it full throttle once the car in front is far enough down the road.
Then obviously highest gear lowest rpm without labouring and cruise off throttle to slow down and light loading.
I enjoy my 350bhp and for economy drive my wife's god awful hybrid company car she's been lumbered with. Hopefully for not much longer, it's so dull you may as well play the economy game. No issues achieving 70+ mpg average. Even 62mpg on a 400 mile round trip up the m-way to north Wales. Zzzz
Edited by briers on Monday 28th May 21:03
I think you'll find thats not the most efficient way to drive. To get the best economy you never fully open the throttle.
Bert
Mr Grayson said:
A previous boss of mine had one of those stupid management books (he even insisted on lending it to me) called "Don't Sweat The Small Stuff" [1]. That's the gist of most of the advice on here.
Seriously if you want uber MPG, you need to drive differently, pump up (or even change) your tyres, fiddle with your engine management, accelerate like an oil tanker, coast down hills, use miles of forward vision to avoid ever having to brake, and completely switch off your brain (apart from the last point).
But you're an advanced driver, and that's not how you do things. You want to be involved with the driving process. You want to make progress. You can still obtain perfectly respectable MPG figures, as you've demonstrated. The other 4 mpg (debatable since it's not even measured in the same car) is the reward for completely spoiling your driving. Don't do it. As others have said, drive your way, don't drive his car, don't enter into discussions about driving, consider leaving home
IMHO block changing up the box will save nothing in mpg terms, most likely, since manufacturers carefully choose the gear ratios in their cars to give smooth acceleration with reasonable economy with all gears in use. Most likely by using 3rd for longer you're wasting the economy you then achieve by using 5th, and you may be using 5th too soon to be economical, even then.
[1] - it was a crap book, don't even bother looking
I disagree, hypermiling if you do it properly can be an involving and fun process, at least if you're nerdy Seriously if you want uber MPG, you need to drive differently, pump up (or even change) your tyres, fiddle with your engine management, accelerate like an oil tanker, coast down hills, use miles of forward vision to avoid ever having to brake, and completely switch off your brain (apart from the last point).
But you're an advanced driver, and that's not how you do things. You want to be involved with the driving process. You want to make progress. You can still obtain perfectly respectable MPG figures, as you've demonstrated. The other 4 mpg (debatable since it's not even measured in the same car) is the reward for completely spoiling your driving. Don't do it. As others have said, drive your way, don't drive his car, don't enter into discussions about driving, consider leaving home
IMHO block changing up the box will save nothing in mpg terms, most likely, since manufacturers carefully choose the gear ratios in their cars to give smooth acceleration with reasonable economy with all gears in use. Most likely by using 3rd for longer you're wasting the economy you then achieve by using 5th, and you may be using 5th too soon to be economical, even then.
[1] - it was a crap book, don't even bother looking
This thread made me start a thread: http://www.pistonheads.com/gassing/topic.asp?h=0&a...
BertBert said:
Perhaps a reference to the engine using less fuel on the over-run than on tickover?
Less fuel - most modern (well, most fuel injected) engines turn off the injectors above a certain rpm (typically 1700-1800) rpm if they are on the over-run. So by using a lower gear and releasing the throttle, one can gently slow down whilst proceeding using no fuel whatsoever. You slow down less when in neutral/clutch down, but the engine needs fuel to idle - although a diesel needs naff-all fuel to tick over.RenesisEvo said:
BertBert said:
Perhaps a reference to the engine using less fuel on the over-run than on tickover?
Less fuel - most modern (well, most fuel injected) engines turn off the injectors above a certain rpm (typically 1700-1800) rpm if they are on the over-run. So by using a lower gear and releasing the throttle, one can gently slow down whilst proceeding using no fuel whatsoever. You slow down less when in neutral/clutch down, but the engine needs fuel to idle - although a diesel needs naff-all fuel to tick over.BertBert said:
briers said:
Your dad needs to know foot firm down on the throttle to get up to speed as quickly as possible is the most efficient way to drive. Slow acceleration means you take longer moving 2 tonnes of car up to speed.
That also means he needs to anticipate when he can give it full throttle once the car in front is far enough down the road.
Then obviously highest gear lowest rpm without labouring and cruise off throttle to slow down and light loading.
I enjoy my 350bhp and for economy drive my wife's god awful hybrid company car she's been lumbered with. Hopefully for not much longer, it's so dull you may as well play the economy game. No issues achieving 70+ mpg average. Even 62mpg on a 400 mile round trip up the m-way to north Wales. Zzzz
That also means he needs to anticipate when he can give it full throttle once the car in front is far enough down the road.
Then obviously highest gear lowest rpm without labouring and cruise off throttle to slow down and light loading.
I enjoy my 350bhp and for economy drive my wife's god awful hybrid company car she's been lumbered with. Hopefully for not much longer, it's so dull you may as well play the economy game. No issues achieving 70+ mpg average. Even 62mpg on a 400 mile round trip up the m-way to north Wales. Zzzz
Edited by briers on Monday 28th May 21:03
I think you'll find thats not the most efficient way to drive. To get the best economy you never fully open the throttle.
Bert
R300will said:
I've also heard an engine is most efficient on full throttle as there isn't a vacuum created in the inlet manifold or something along those lines anyway.
Yes we do hear that quite a lot. I have no idea whether it's true or not. But it certainly doesn't make for the best fuel economy on a journey. I think the hypermilers know how to do that.I know you really want to get some answers here about how to drive economically, but I think even if you drove in a way that took the average higher than your dad's, he still wouldn't be happy. He just has a problem with you driving his car.
Do a Ferris Bueller and put the car's wheels in the air and then run it for an hour so it does 90mpg or whatever, take it back to your dad and see if all is rosy.
Do a Ferris Bueller and put the car's wheels in the air and then run it for an hour so it does 90mpg or whatever, take it back to your dad and see if all is rosy.
BertBert said:
R300will said:
I've also heard an engine is most efficient on full throttle as there isn't a vacuum created in the inlet manifold or something along those lines anyway.
Yes we do hear that quite a lot. I have no idea whether it's true or not. But it certainly doesn't make for the best fuel economy on a journey. I think the hypermilers know how to do that.No-one seems to have picked up on the rev-matching thing. I guess that we all agree that rev-matching is a good driving must, and it is disappointing that your father believes in dragging the clutch.
On economy, we are all clear that unnecessary braking wastes fuel and that braking can be minimised by good observation, anticipation and planning. We have not yet discussed cruising speeds. I am completely clear that the biggest determinant of consumption is chosen cruising speed. If you really want to use less fuel, cruise slower.
Amusingly, in my household it is my children who try to get the best consumption from their cars; I drive the way I want to, and live with the 20 odd mpg which results. When I drive my daughter's car, she does not like it if I let the OBC consumption get below 40. My approach to acceleration to achieve decent consumption is to use a fair amount of throttle, and change up at about 3,000 revs. I believe (but don't know) that changing up at lower revs would improve consumption; my main evidence is the way manufacturers calibrate their autos and their change up lights. However, I don't have the patience, and I dislike the sensation of an engine lugging, which you seem to get with manufacturers modern change up points.
Boring insurance issues generally prevent the children from driving my cars.
I would love to know how the OP betters the official consumption figures for her car. That is exceptionally unusual.
On economy, we are all clear that unnecessary braking wastes fuel and that braking can be minimised by good observation, anticipation and planning. We have not yet discussed cruising speeds. I am completely clear that the biggest determinant of consumption is chosen cruising speed. If you really want to use less fuel, cruise slower.
Amusingly, in my household it is my children who try to get the best consumption from their cars; I drive the way I want to, and live with the 20 odd mpg which results. When I drive my daughter's car, she does not like it if I let the OBC consumption get below 40. My approach to acceleration to achieve decent consumption is to use a fair amount of throttle, and change up at about 3,000 revs. I believe (but don't know) that changing up at lower revs would improve consumption; my main evidence is the way manufacturers calibrate their autos and their change up lights. However, I don't have the patience, and I dislike the sensation of an engine lugging, which you seem to get with manufacturers modern change up points.
Boring insurance issues generally prevent the children from driving my cars.
I would love to know how the OP betters the official consumption figures for her car. That is exceptionally unusual.
I think that this is the normal method
MrLion said:
I get fair economy - drive like there's an egg under the pedal
notR300will said:
Full throttle makes sense because there is much less air resistance at low speed and you're doing it for a shorter peiod of time with high efficiency from the engine. Once you're up to speed then high gear and lower throttle is the better option of course.
BertBert said:
I think that this is the normal method
This graph and accompanying article would seem to support R300will's position. My understanding is that the engine is most efficient at full throttle, but that a higher rate of acceleration increases the effect of air resistance.MrLion said:
I get fair economy - drive like there's an egg under the pedal
notR300will said:
Full throttle makes sense because there is much less air resistance at low speed and you're doing it for a shorter peiod of time with high efficiency from the engine. Once you're up to speed then high gear and lower throttle is the better option of course.
Every car will be different but my gut reaction is that about 75% throttle is likely to be right for an average car, I offer no evidence whatsoever to back that up though.
It ain't so much air resistance, it's that high revs you have a huge amount of drag coming from the engine and all the ancillaries.
It is probably most efficient to have "jabs" of full throttle, but changing up at very low revs.
I wonder what happens if you just put the car in top gear, let it idle, and slowwwwwwwlly engage the clutch. In most cars that would have you doing about 25 to 30 once the clutch was fully engaged.
It is probably most efficient to have "jabs" of full throttle, but changing up at very low revs.
I wonder what happens if you just put the car in top gear, let it idle, and slowwwwwwwlly engage the clutch. In most cars that would have you doing about 25 to 30 once the clutch was fully engaged.
Somewhatfoolish said:
It ain't so much air resistance, it's that high revs you have a huge amount of drag coming from the engine and all the ancillaries.
It is probably most efficient to have "jabs" of full throttle, but changing up at very low revs.
I wonder what happens if you just put the car in top gear, let it idle, and slowwwwwwwlly engage the clutch. In most cars that would have you doing about 25 to 30 once the clutch was fully engaged.
I was thinking more along the lines of not high revs but just full throttle through the gears until you reach your desired speed changing up at say 2500-3500 rpm? That seems the most efficient to me.It is probably most efficient to have "jabs" of full throttle, but changing up at very low revs.
I wonder what happens if you just put the car in top gear, let it idle, and slowwwwwwwlly engage the clutch. In most cars that would have you doing about 25 to 30 once the clutch was fully engaged.
Gentle acceleration - use less fuel, but for longer
Firm acceleration - use more fuel, but for less time
So its not quite as simple as gentle acceleration uses less fuel.
Some time ago, I was trying to get a young lad thrrough the iam test, but couldnt get him to make good progress.
Took him out for a demo drive, good long run of 30ish miles, reset the computer before we left.
Throughout the drive I used mostly firm to hard acceleration, averaged 52 mpg, which was above what I would normally get.
Why, simply because I used the engine efficiently, I have to admit that I was surprised at the result.
M
Firm acceleration - use more fuel, but for less time
So its not quite as simple as gentle acceleration uses less fuel.
Some time ago, I was trying to get a young lad thrrough the iam test, but couldnt get him to make good progress.
Took him out for a demo drive, good long run of 30ish miles, reset the computer before we left.
Throughout the drive I used mostly firm to hard acceleration, averaged 52 mpg, which was above what I would normally get.
Why, simply because I used the engine efficiently, I have to admit that I was surprised at the result.
M
waremark said:
No-one seems to have picked up on the rev-matching thing. I guess that we all agree that rev-matching is a good driving must, and it is disappointing that your father believes in dragging the clutch.
IMO, in normal driving, under braking, you should be changing-down into a gear that closely matches the engine speed at the time you make the down-shift, which negates any need to rev-match. The only exception I can think of to this is when overtaking, when you would need to rev-match on the down-shift.IMO, the most efficient driving style will depend largely on the flow and volume of traffic. The OP said she usually accelerates fairly hard and changes-up at around 4,000rpm with the object ot getting into 5th as quickly as possible. However, this strategy wouldn't work in town traffic; if the average speed of traffic is around 30mph, or less (so too slow for 5th in most cars), surely it wouldn't make any sense to hold onto a lower gear, keeping the revs up? So, in this scenario, you'd be better-off short-shifting and using minimal throttle.
In my experience, many drivers seem to under-estimate when they can change into 5th and a lot of people seem to have fixed speeds where they'll change into 5th. These fixed speeds are often quite high (eg. 50 or 60mph). In actual fact, it's quite possible to change into 5th by 40mph in the vast majority of cars and, in some cars, you can safely change into 5th at 30-35mph depending on the conditions, which is another key point. If you're capable of treating the throttle with some finesse, it's easily possible to use 5th a lot more frequently, but this requires mechanical sympathy and a feel for when the engine is labouring.
In my experience, many drivers seem to under-estimate when they can change into 5th and a lot of people seem to have fixed speeds where they'll change into 5th. These fixed speeds are often quite high (eg. 50 or 60mph). In actual fact, it's quite possible to change into 5th by 40mph in the vast majority of cars and, in some cars, you can safely change into 5th at 30-35mph depending on the conditions, which is another key point. If you're capable of treating the throttle with some finesse, it's easily possible to use 5th a lot more frequently, but this requires mechanical sympathy and a feel for when the engine is labouring.
ian_uk1975 said:
waremark said:
No-one seems to have picked up on the rev-matching thing. I guess that we all agree that rev-matching is a good driving must, and it is disappointing that your father believes in dragging the clutch.
IMO, in normal driving, under braking, you should be changing-down into a gear that closely matches the engine speed at the time you make the down-shift, which negates any need to rev-match.....Gassing Station | Advanced Driving | Top of Page | What's New | My Stuff