How to drive most economically? - Chicken Madras
Hi,

I've been driving since 1985 and am having a mid-life crisis regarding my driving style.

What I'd value your opinions on is this: Is it more economical to accelerate slowly and gently, or accelerate more quickly (not in a boy-racer, tyre squealing style of course) to reach your desired speed? I appreciate that it depends on a multitude of factors, but generally what does everyone think?

Also, I rarely drive with a front seat passenger and was appalled recently to see a friend I gave a lift to pitching back and forth in the passenger seat when I was changing up the gears. How do you change gear smoothly? I seem to either slip the clutch too much ("comfort" mode..) or snatch it ("sport" mode!). I never notice any movement because I'm holding onto the steering wheel. God help me if I'd got a tank of red water on the roof as in Britain's Worst Driver..!

All comments gratefully received,

Regards,
CM
How to drive most economically? - Sooty Tailpipes
Driving gently accelerating is much more economical I'm afraid, get a car with instant consumption guage or computer and you will see a stark difference, but also anticipate the road ahead, have the traffic lights been green ages? then they're likely to change, so lift off the throttle and slowly glide to them instead of heavy breaking. There are many pages on the net with economical driving tips.

Smooth gearchanges are easy to learn, as you drive, learn the way the gine sounds, when you change up and let the clutch out, you will hear the engine suddenly changes to a much slower speed, and as you change up, the engine with be forced to go faster as you let the clutch out, and you may even feel the car slow and your passenger is thrown forward until you accelerate, This is bad.
What you need to do, is initially is slow the gear changes right down and think them through.

yor accelerate in first and then ease off so that your speed is no longer rising before you press the clutch, ie your speed must flatten for a second (less if you can, but that is something you will brush up on later)
This means there is no load on the transmission, the engine is not trying to haul the car, when you press the clutch, this will stop the occupants going forward.

Now gently move the gear shifter to 2nd, don't force it, feed it through, and let the synchromeshes and cones do their job.

Now, as you are changing up, the engine will be spinning slower once the clutch is released, do you let the car do this by force, or so you ease off the throttle slightly so that the revs are a perfect match for the gear and road speed and the gearchange is seamless and undectectable?

Go up through the gears, now, when shifting down, you need to put reves on during the neutral, so that they are faster and match the lower gear and road speed, without the car being forced to do this its self by suddenly losing a few mph and jerking the occupants.

practice these skills at all times, think about every gearchange. Try missing a gear, such as change 2nd to fourth, these should be seamless too.

Soon you will be as good or better than an automatic, and a good chaeuffer for your friends.
How to drive most economically? - Dynamic Dave
What I\'d value your opinions on is this: Is it more
economical to accelerate slowly and gently, or accelerate more quickly



www.honestjohn.co.uk/forum/post/index.htm?t=9008&v...f

How to drive most economically? - Chicken Madras
Many thanks for your replies joosisiqu and Dynamic Dave. Time for some practice methinks. I did search the forum first (honest DD!) but was clearly looking for the wrong thing.

All the best,
CM
How to drive most economically? - Vin {P}
It\'s important to realise that what you see on the \"instant fuel consumption\" gauge is not a guide to your overall economy.

For a proof, imagine an extreme case where you have a car that cruises at 30mpg. If you accelerate at full whack, this drops to 1mpg. If you accelerate gently enough, it will only drop to 29mpg. Sounds like gentle acceleration is the answer.

The problem is that you don\'t know how long you will be accelerating, so if the full on gets you to cruising speed in, say, one second, while the other takes 20 minutes (see, I told you I was looking at the extreme case) then it would make sense to accelerate hard.

The research shown at tinyurl.com/oalj

shows that overall consumption is lower with a bit more acceleration. The reference to 2/3 full power revs is (I believe) a rough reference to peak torque. Find out where your car delivers peak torque - a five minute web search should give you the revs at which it develops peak torque - and try to keep around that range when accelerating.

Do, however, try to keep your eyes on the road.

V
How to drive most economically? - waterboy
I tend to use full throttle getting full compression, up to cruise, and vary my rate of acceleration by opting from changing up as soon as may be, up to going to just short of rev limiter in each gear, depending on demand, or mood. I would imagine the first limit will be reasonably economical; I venture an analogy, somewhat loose, between notching up a steam locomotive (shutting off the steam early, to take full advantage of the expansion of steam in the cylinder) for most efficient operation while reducing power as opposed to just closing the throttle a bit.

As to a 3-litre automatic twin turbo, I can affirm that all bets are off.

Tomo as was!
How to drive most economically? - Obsolete
I'm not sure a concensus was reached in the thread referred to by DD though I tend to hold with TrevorP who favours rapid acceleration. I understand that the IAM also favour rapid acceleration up to cruising speed, and I suspect this is in part to ensure rapid progress and not annoy others.

I find that rapid acceleration helps get smooth gear changes, something I was not good at. Make sure there is a good amount of revs and then change up a gear, making sure the clutch is not released too quickly. It can also help to miss a gear e.g. 3rd direct to 5th to avoid unnecessary fiddling with the gear knob. Of course rapid acceleration does not mean a racing start.

Where I have more trouble is slowing and changing down smoothly ready to take a sharp corner slowly though I am improving. I find that braking, changing down to 2nd (from 3rd or 4th), then braking a bit more seems to do the trick. Here it can help to feather the gear change. This means that you release the clutch slowly when at the biting point, so as to allow the engine to match the wheels. Also brake gear overlap is said to be bad and best avoided. (I am not sure why. It might be something to do with the car weight distribution and hence grip changing under braking?)

Regarding improved fuel economy, probably the best way to achieve this is using improved forward observation and planning to reduce unnecessary braking. I am sure this far outweighs the loss from too rapid acceleration. Increasing your distance from the car in front will reduce the need to 'comfort brake' and hence reduce fuel wastage. Not hurtling up to a stationary car and then slamming on the anchors at the last minute, but approaching gently, by which time he might be moving again, can also help. Approaching a roundabout smoothly at a reduced speed can improve safety and aid slotting in without having to stop.

Sorry if this is all obvious. Just my sixpence worth anyway.
How to drive most economically? - arnold2
My Corolla has a neat fuel consumption gauge; since I bought the car it has helped keep my driving much more economical !

Here's what I have found (35K driving/year): Accelerate briskly (not foot-to-the-floor, though) to cruising speed, changing gear at around 2.5-3K RPM (don't let the engine scream to the limiter!). This really does use less fuel then accelerating slowly - I tried both as an experiment ! Drive at a constant speed too - so many drivers shunt their speed up and down on A roads, unaware that doing so really hurts your fuel consumption - makes me wonder if some drivers have terminally bald tyres that can't handle any corners...
How to drive most economically? - Vagelis
Hi CM,

My opinions:

Re economical acceleration: My experience says use your engine's torque, as rightly noted by others. This is the rev range where your engine accelerates most efficiently, ie burning less fuel. For example, accelerate from 50 to 70 with 4th instead of 5th. You will find out that you can achieve swift acceleration without "flooring" it.

Re gear changes: During a gear change the engine revs fall. Each engine lets its revs fall at a different rate. Each gear change upwards means the revs will need to fall by roughly 1000 ~ 1500rpm. Observe the time your engine needs to lower its revs by such an amount, and you have the time-window in which you should perform your gear changes. Do that, and when you re-engage the clutch the engine revs will be about those needed for your selected gear and speed.

For gear-down changes I use the following method: When pressing the clutch, right at the point where it's starting to disengage, I push the acceleration pedal to raise the revs by roughly 1500rpm. That way I get faster and smoother changes.

Some people might say that this is a very complicated way of doing a very simple thing like a gear change. Well, that's me ;-)

Vagelis.
 

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