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I have been away from the UK for some time and upon my return I am making observations that puzzle me a lot - they are things I didn't see before I left. My latest one is drivers habits when it comes to clutch use.
As a passenger in friends cars I have noticed many of them dip the clutch and hold it down when going around a corner or negotiating a junction. I even see them de-clutch to go over speed ramps/humps. For me it is the oddest thing to watch.
My mechanical empathy feels for the poor old clutch release bearing in my friends cars and it surprises me they are not in the garage once a year for a clutch job.
If I am driving in the above examples I have the car in gear and "drive" the car over humps or around corners. I hate having to take a car out of gear because it means I just have to put it back in again, and it also gives more control. In traffic I crawl in first gear and rarely use the clutch by allowing the engine to idle along. It actually takes a lot for an engine to stall so long as there is some vehicle inertia. Dribbling a car along at idle or even slightly below is quite possible.
I did ask once why they did the "clutch thing" when going around a bend and I was told it stops the engine stalling. I didn't pursue the discussion. So for some reason they believe the engine will stop when going around a corner or passing over a speed ramp. Go figure.
What the hell is going on? Is it just me?
Regards
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Just inexperience. I used to do it as a learner too! You fall into a mantra of thinking that if you fall outside of the 'right speed' for a particular gear, then it will stall. Total baloney of course!
Mind you, some diesels will stall very sharply if the RPM dips below governed idle speed in order to protect the DMF.
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"What the hell is going on? Is it just me?"
Just you.. There are lots of UK drivers who drive in strange ways with zero mechanical sympathy.
Watch them reversing. Always good for a laugh.
Edited by madf on 05/01/2012 at 09:27
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Other clutch horrors that I've seen:
1.) Clutch being used as a handbrake (on the grounds that 'there's not much torque needed to stop the car rolling back, so it'll be ok')
2.) Leaving the car in gear with the clutch 'in' for ages while sitting at lights. Tiring and pointless!
And don't get me started on the quality of downshifting...
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"Riding" the clutch, i.e. keeping ones foot on the clutch pedal at all times "just in case"
Again I have observed this surprisingly often, when a passenger
I did explain to one exponent of this particular behaviour that if one needed to cover the clutch "just in case" one should not be driving.
I fear he did not see what I was driving at?
Me:, I got a hole worn in the carpet covering the side of the transmission housing (as was) from smartly removing my foot sideways from the clutch pedal.
But the clutch is still good at over 240,000 miles of mixed driving incl towing & this with very little Motorway work, and a fair high percentage of town driving.
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I'm not sure that modern drivers can tell the difference between riding the clutch and covering the clutch - nor do they know when to use either - ie never ride the clutch and only cover it approaching a hazard.
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Some of the hydraulically operated clutches have a ridiculously light resistance meaning that even very light pressure could cause the clutch to start slipping.
I like a heavy clutch pedal-dissuades one from using it unless one really has to!
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The people who have no mechanical sympathy are the first to moan when this results in a warranty claim being rejected. My father who has been driving for over 60 years still insists that once you are in 4th or 5th gear you should stay in it all day, he never changes down untill he stops again. Car vibrates and shakes terribly, feel sorry for next owner. He used to constantly critisise me for changing down unnessarily and damaging the engine, never had an engine break on me in 37 years but dad has had many a car with incredibly high oil consumption, wonder how he damaged the rings.
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Driver perception of engine labouring isn't always accurate.
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Have to admit that I dip the clutch when going over a couple of severe speed bumps in a car park near me. The only reason is that even in 1st with no throttle, its too fast, and my 2litre HDi diesel does have a tendency to stall without warning.
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That's the fault of a badly designed bump-not you!
I prefer neutral for the bump-then roll into second between them.
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Speed humps? Less worry at 40mph...
You take them at speed surely..? Hence the name.
Edited by madf on 05/01/2012 at 14:34
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Back in the day, this behaviour was governed by the driver's background.
Those who used to drive Fords, Vauxhalls and such would happily sit at lights in gear with the clutch out and do all the other things you mentioned too.
Those who grew up driving BMC vehicles with their graphite release bearings didn't. We all learned that the clutch pedal had to be touched as little as possible if you wanted the thing to last more then 20,000 miles.
I remember explaining this to an MG specialist who wanted to know why my 'B (used for daily commuting around London) only required a complete clutch every few years, whereas a young lady's car he looked after was chewing a release bearing every six months.
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unthrottled, '
2.) Leaving the car in gear with the clutch 'in' for ages while sitting at lights. Tiring and pointless!
This reminds me of all the people too lazy to put on the handbrake at traffic lights. Surely it's easier than sitting with you foot on the footbrake, all the time. It's particularly annoying when it's dark and raining. There's no point in hopping out of the car to tell them..................we'll only get abuse or worse still, a knifing.
If only drivers could be a little more thoughtful. I think most are just plain ignorant or worse still day dreaming!
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Thunderbird, 'He used to constantly critisise me for changing down unnessarily and damaging the engine',
Sadly mine was the same, accusing me of over revving the engine if I changed down, or if he thought I should change up sooner than I did.. He would sometimes let the engine labour. I think he was so obsessed with economy having lived through the war. In a way you can't really blame him.
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The driver's perception of NVH is not necesarily a good indication of mechanical stress inside the engine.
I used to worry about labouring every time the engine started vibrating at low speed-but I have since realised that this is largely a perception.
I wouldn't lug a diesel down low, but a petrol shouldn't have any problems.
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For me it isn't a question of whether the engine is stressed at 1200rpm going up a hill, more that I have no means of quickly accelerating if I need to.
I drive around town in second or third -- it drives my father, an ex-police driver no less, nuts.
But oh look, my Primera managed 265,000 miles, and his Laguna is a wreck at 95,000, hmmm.
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unthrottled, '
2.) Leaving the car in gear with the clutch 'in' for ages while sitting at lights. Tiring and pointless!
This reminds me of all the people too lazy to put on the handbrake at traffic lights. Surely it's easier than sitting with you foot on the footbrake, all the time. It's particularly annoying when it's dark and raining. There's no point in hopping out of the car to tell them..................we'll only get abuse or worse still, a knifing.
If only drivers could be a little more thoughtful. I think most are just plain ignorant or worse still day dreaming!
This drives me insane. I always let the clutch out and sit in neutral with my handbrake on. I hate having to stop behind someone hovering on their footbrake on a hill.....oh the visions of it rolling backwards into my car....!! Also, at lights on a really long cycle; dead leg much..?! Give your foot a rest!
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If you disengaged the clutch while rounding a corner when I was learning to drive in 1963/1964 on a test , you would have failed, deemed not to be in control of the car.
D
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There's a lot of stigma attached to coasting, but it's so out of date. It comes from the days of front axle drum brakes that would quickly overheat. The lack of control argument doesn't hold much water either since being in top gear gives sod all engine braking or acceleration either. Just easy mantras to remember.
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Another 'clutching' oddity:
Some people like to boast that they double-declutch when changing gear, which seems completely pointless in modern cars. All it does is to put more wear and tear on the clutch mechanism!
Re. coasting: Most automatics coast on the over-run. Although I'm not in the habit of coasting I can't see that it's that much of a sin in a modern car.
Edited by Sofa Spud on 05/01/2012 at 22:18
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With a synchro box double declutching is indeed pointless - good drivers will automatically adjust the revs using the throttle to ensure a smooth change - indeed I used to play around and not use the clutch at all, it soon teaches you how to synchronize the gears yourself.
Automatics don't coast on the overrun - they'll remain in top gear which gives little or no engine braking but that's very different to declutching a manual and coasting.
Edited by RT on 06/01/2012 at 08:20
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The throttle is the key to good downshifts. It's good fun playing around with clutchless shifting-but no one could pretend that it is a good habit! The dogs are toothed rather differently on a synchronised box than to an unsynchronised one making clean engagement less likely.
Being in a tall gear is very similar to overrun as far as driver perception is concerned as both engine braking and potential acceleration are minimal.
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The question I still have is, where did this de-clutching to go round a bend technique come from? I am 100% certain it doesn't get taught.
My theory is that there are many drivers who have no idea what is actually going on mechanically and subsequently imagine all sorts of things. I repair computers and I see the same thing there. People say they can use a computer but that doesn't mean they know how it works, and the same goes for cars.
Most people I see regarding their computers I would like to recommend they unplug it, and I fear the same goes for many car drivers. Without doubt if you understand how something works you will be a better operator of it.
Incidentally knowing that the yellow coloured bits under the bonnet are essential fluids does not qualify you as a car mechanic.
Regards
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Automatics don't coast on the overrun - they'll remain in top gear which gives little or no engine braking but that's very different to declutching a manual and coasting.
Totally agree, glad to see someone with knowledge of how cars operate.
De-clutching or putting car in neutral has no place while driving on the highway. It is dangerous since you have no engine braking for starters. Do it on your test and you will fail.
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Glad to see you agree thundbird.
Putting a car in neutral or de-clutching while moving, was no no in 1963 and is a no no now.
D
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Putting a car in neutral or de-clutching while moving, was no no in 1963 and is a no no now.
What did drivers of Saab two strokes use the freewheel for then?In fact, aren't motorcyclists taught to use the clutch while braking?
An automatic with a loose torque converter provides so little engine braking at low engine speeds that it is effectively in neutral as far as car handling is concerned, even though it is mechanically "in gear". I remember saying this to my driving instructor who admonished me for coasting. He agreed.
Same applies to manuals if the chosen gear puts the revs at little above idle speed.
Just keep sticking to the simple cliches Thunderbird
"Horespower sells cars"
"torque wins races"
"De-clutching is dangerous"
When is "there's no replacement for displacement" going to rear its head?
Edited by unthrottled on 06/01/2012 at 13:09
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>>What did drivers of Saab two strokes use the freewheel for then?
I bought a 1976 Saab 96 V4 four stroke, which still had the freewheel, for my wife. Although intended for a different purpose (to stop the 2 stroke being underlubricated on the overrun) it sounded like a good economy feature.
We lived at the time in a hilly area and it was terrifying. After a brief test it was never used again. The sensation of launching down a steep hill while freewheeling felt like falling out of a window.
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There are times when some engine braking is a welcome feature!
I would still like one fitted to my car though. I came down the Cat & Fiddle the other week-coasted from the top down into Macclesfield. Pretty twisty but no problems. Just annoying when the vacuum servo ran out...
[That'll get the frosty aunts to suck a few lemons]
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Link to the highway code page on freewheeling (coasting as they refer to it), rule 122. But what do they know, our tap room expert will just say its all nonsense. And he admits he coased whilst he was learing and despite being told not to by his instructer he still does it. Some people will never listen.
www.direct.gov.uk/en/TravelAndTransport/Highwaycod...4
Edited by thunderbird on 07/01/2012 at 13:15
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The tap room expert notes the comments regarding coasting in the highway code but cannot find any violation of law (indicated by a MUST NOT).
I will repeat this one more time: virtually any modern CVT or torque converter coupled automatic will have mimimal engine braking during overrun-meaning that as far as driver perception is concerned, the vehicle is coasting, even if it is technically in gear.
Thunderbird: you simply don't read your source material properly. Scanning for phrases that appear to support your hypotheses doesn't work!
My driving instructor's job is to get the general public up to the required standard to pass the drving test. Do you use the handbrake during 3 point turns-as your driving instructor taught you to? Thought not.
Edited by unthrottled on 07/01/2012 at 13:30
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Tap room expert will now advance some safety advantages of using neutral judiciously:
1.) Cleaner downhifts. Much easier to rev match when starting from neutral than a higher gear. This avoids the typical nose dive resulting from a poorly executed downshift.
2.) Whilst in neutral the the right foot can continuously cover the brake pedal instead of maintaining throttle pressure. This makes a significant difference in braking reaction time and hence total stopping distance.
3.) No risk of stalling the engine during an emergency stop, ensuring that the car is in a state ready to pull away again.
No one is suggesting that coasting is always appropriate, but neither should the practice be dismissed out of hand on the grounds of ignorance.
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I had a 1946 Rover 16 with optional freewheel. It was great for clutchless gearchanges. Not so good for long fast downhills as the drum brakes - rod operated - faded and smoked badly (and that's without the freewheel operating!)
Bu then anyone who freewhells down a 1 in 3 hill in a car like that with poor brakes is nuts.
Modern hybrids have limited engione braking when the battery is recharged ad the system stops regen braking..
Most modern car brakes are so good, coasting is not a problem. Of course, if neglected... :-(
A problem of 40 years ago unless you have zero maintenance.
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Diesels often have very little meaningful engine braking, unless in a lower-than-usual gear. My Outlander is a case in point. Normal rpm is about 1500 (about 35 in 5th, or 45mp in 6th, and you are prompted to change up at 1500 unless you are in 6th) and engine braking is as good as non-existent.
I put this down partly to low rpm, but mainly to the absence of a throttle plate which I imagine accounts for most of the retardation on a petrol engine.
Happily, the Outlander has much better brakes than a Saab 96.
Edited by Manatee on 07/01/2012 at 16:59
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Specially for the ludites who don't believe a word I have said here is Honest Johns answer about fuel cut offs and saving fuel. Don't suppose you will believe him either but ther may be hope for some readers.
www.honestjohn.co.uk/askhj/answer/14514/cost-to-co...t
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Well, we ludites (sic) can spell. Not all of HJ's ideas are correct. If he thinks coasting is archaic, what about 3000 mile oil change intervals. Ridiculous!!!
You will yield the best overall fuel consumption by covering a given distance with the smallest possible number of engine revolutions. This is incontrovertible. That is how coasting works.
Edited by Avant on 08/01/2012 at 14:39
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(Comment which caused this deleted)
Edited by Avant on 08/01/2012 at 14:42
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(Comment whch caused this deleted)
Edited by Avant on 08/01/2012 at 14:43
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Sorry unthrottled.
Reading your posts on your driving techniques leaves a lot to be desired.
How did you pass your test?.
Can i suggest you take the advanced drivers test.
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Sorry you had to delete my post Avant. The remark was personal and inappropriate and I apologise.
Xtrailman. Driving techniques are a matter of personal choice. I passed the test by singing to the DSA hymn sheet, then reverted to my own style of driving once I had passed the test. With regards to 'leaving a lot to be desired' my driving techniques have yielded the following:
1.) Zero claims
2.) Zero accidents
3.) Zero stoppages in snow
4.) 10% better than combined quoted fuel economy inspite of only a 7 mile average commute.
All without any namby pamby electronics designed to protect drivers from themselves. Not an earth shattering record, but better than a lot of drivers.
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Such expertise as I have is in words rather than engineering. In exchange for showing you how to spell Luddite, can you answer my question? If it's been answered in the posts above, apologies, but I haven't seen it.
I'm driving down a hill steep enough to make me engage a lower gear (or hold an automatic in low gear - no difference surely?). The car is being put in motion through the wheels and not the engine, and my foot is off the accelerator, but the RPM are about 2,000.
Question - leaving aside any safety advantage of engine braking, am I using more fuel than if I coasted in neutral with the engine at idling speed?
Edited by Avant on 08/01/2012 at 14:50
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Is the answer not in the link to Honest John above.
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I have put a link above to an Honest John answer that confirms no fuel is used when you have no throttle applied, simples.
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Yes it is, and it's what I've always believed: but there are some people on here with engineering experience who seem to disagree. Hence the open question.
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My mechanical engineering experience goes little beyond filling the washer bottle up but i struggle to see how an engine only uses fuel when the throttle is applied. Even if you're coasting, the engine is running and working so how is it doing that with zero fuel?
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From the Honest John Website
"If you drive down the incline with your foot off the accelerator, the wheels turn the engine and all its ancillaries without any fuel being used at all. This is the case for all modern fuel injected engines whether petrol or diesel"
Its because the engine sensors/ECU stop the injectors injecting fuel into the engine when a certain set of criteria are met i.e. throttle closed and revs above 1200 approx. This applies regardless of whether you are decelerating up to a juction or going downhill in gear.
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So it operates similar to a windup toy car then? Wind its wheels up and the energy carries it forward?
Edited by jamie745 on 08/01/2012 at 15:46
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Avant:
It depends on whether you want to maintain your momentum-which is universally regarded as the key to obtaining good fuel economy.
If you wish to slow down-leave the car in gear. But if you don't want to slow down, coast!
Another way of putting it is that you can coast much further in neutral than you will in gear. Therefore, whilst leaving the car in gear uses no fuel whilst in overrun, you will have to re-apply the accelerator more frequently than if you coasted. The aggregate effect is that you use more fuel over a long distance. The instantaneous fuel ecocomy is irrelevant . In fact, it tends to lead to cause drivers to use more fuel than if they ignored it.
I'm very pleased when the real time mpg meter reads 10mpg. It means that I'm going to get better economy! ;-)
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Many thanks - very helpful. I now understand the point.
Edited by Avant on 08/01/2012 at 20:13
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