It's Monday again and the DT Saturday edition has penetrated deepest rural France.
I read in DT Motoring that the latest Lexus - described as unmemorable - has an eight-speed autobox and spends its life changing up and down for no apparent good reason.
I see many recent cars have six manual gears.
Just how many ratios do we need?
My present Hondas have: 1, a four-speed auto with lock-up overdrive and sport mode which I don't use because it works perfectly well without; 2, a four-speed auto with lock-up overdrive and 'sequential sport mode' for manual use, which i don't bother with very often. It, too, works well.
My first automatic had a Hondamatic box with low, 'star' - in which it would do 0-100mph without apparent stress - and a selectable overdrive.
Do we really need all this complication? Surely it would be better to have lots of torque - or a good torque converter - and just a few gears to make life easier?
We don't all need to pretend we are F1 drivers do we?
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M
deadright. I think it's "I can so I will". I have no idea why my Passat has 6 speeds with a diesel engine. I should probably block change more.
JH
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Real reason is MB has seven so Lexus has eight.
However, the engine's torque also comes at relatively high revs so that is also a factor. But 8 vs. 7 that MB has must be a factor.
I like the fact it will park itself! And yes I can park but that is cool.
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R
jacking itself up on a set of castors and going sideways into a gap 2 inches longer than the car - that would be cool.
JH
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I liked the old Daf Variomatic - an infinite number of gears. The things always sounded as if the clutch was slipping though - in a hurry and the engine sits at maximum revs as the rest of the car caught up with it.
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Why is torque so fashonable. I drive a 1.1 petrol P reg clio and I have driven a 1.9 diesel fiat doublo. The clio is so free reving and I block change often since it has such a felxible engine. For me I have found the doublo so diffrent. Block changing is not an option I would like for normal driving.
Remember power and refinement is what we are after so it's a balancing act. Force (that is torque) muliplied by distance moves (revolutions) = power ( The get up and go of a car). However refinement seems to be the inverse of revolutions. If so on a purely objective test their will be constant refinement across all rev. and torque possibilies keeping power (the end product that we seek from an engine) constant. Some people prefer lower rev. and so like diesel and some like revs. and so like petrol. I prefer petrol myself, but that is because of bad experiances with white van man type cars.
On topic I feel that gears are deemed to muliply throughout this century. Prehapps a better way to thing of it is in 2050 the average family car will have 8 gears or so and to only have 6 will be seen as not letting the engine display it's full potential. I was amazed when I heard cars had forward gear. My dads old auto renault 5 only had 3 gears. What I am trying to say is it is all relative. Who said truck drivers need anymore that 10 gears for instance?
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I liked the old Daf Variomatic - an infinite number of gears. >>
It had a finite number of gears.
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The gap has to be big enough to park it of course ;-)
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15 years ago or more HGVs were fitted with 16 or more ratios however the likes of high pressure CR and electronic control etc have improved the spread of power and torque so trucks with more than 7 or 8 ratios are less common.
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There was a five-bladed gilette advertised on tv this week.
There'll probably be a six bladed wilkinson sword next week.
I'm gonna sellotape two together for the first V12 wet shave.
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Dave, that time is now............
cgi.ebay.com/NEW-Gillette-FUSION-6-Blade-Razor_W0Q...m
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I don't know what to say. The world's gone mad.
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Dave, that time is now............ cgi.ebay.com/NEW-Gillette-FUSION-6-Blade-
>>
only problem is, it is still only 5 blades! (despite the headline).
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no - it has a secret 6th blade for trimming.,
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TourVanMan TM < Ex RF >
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There was a five-bladed gilette advertised on tv this week. There'll probably be a six bladed wilkinson sword next week.
I said the exact same thing to SWMBO when I first saw that advert too!
It's rather worrying that we seem to think alike. ;-)
I'm gonna sellotape two together for the first V12 wet shave.
Be careful not to nick your legs.
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In a life imitating art moment, the Onion covered this story back in early 2004.
www.theonion.com/content/node/33930?issue=4228&spe...4
Article contains swearing, but is funny!
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Soupytwist !
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Nigel Tufnel's amp went up to eleven: i wonder if they've been watching Spinal Tap at Lexus?
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I can see it now - around 2015 we will have an engine governed precisely to its most economical revs and a CVT for speed control.
Unless of course we finally have the jetpacks those '60s science mags all said we would use by the year 2000.
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More gears is OK for the block changers - I'm not sure I could cope (as a passenger) with 7 snatched gear changes up /down the box. Engines are getting more flexible so why do we need more gears ?
Gearboxes are now more expensive to repair than engines and getting less reliable it seems.
We have a 70 MPH speed limit - we have motorcycles that can get you banned in first gear :-)
When I tried the new Golf, I was put off by it having six gears - my last two VW boxes had failed with only 5 gears. I can't imagine they would be more reliable with six, or cheaper to fix.
Just give me a nice reliable 5 speed with an overdrive 5th with a decent gear change please.
But I'd still like six close ratios on my motorcycle, thank you
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I thought oldman would be here by now with his first,second and top!
Steve.
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Xantia HDi.
Buy a Citroen and get to know the local GSF staff better...
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Three is for cissies! My Morgan Super Aero has two - and no reverse ether.
Eight gears implies a power band about 2" wide, or a shed load of gears you'll never need.
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My mums Hyundai Coupe V6 has 6 gears and its just too many. Instead they should put the 6-speed box in the 1.6 and 2.0 models.
My Mazda 323 ( old one ) has a 5-speed box of which the top gear is an overdrive 5th. It works very well although in top gear, it slows quickly at hills, but change back to 4th and its fine.
I think CVTs are great but 8 speeds is just plain silly unless the changes are so smooth and quiet, that your not aware of it.
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Just like the 7-litre Ford Galaxie of the 60s, 2-speed auto. They raced successfully in Europe too, sometimes beating 3.8 Jaguars and the like. Of course the suspension had to be modified or at least chained down to lower and harden it.
I suppose the Super Aero can be turned round by lifting the tail off the ground and walking about with it? Is there a throttle control on the steering wheel with a bowden cable running to the carb(s)? A true vintage classic, and one of the very few cyclecars that were any use... Lucky man SlidingPillar, clearly a Morganisto through and through judging by yr handle... who used sliding pillar ifs other than Morgan and Lancia?
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When I tried the new Golf, I was put off by it having six gears
That's why I went for the DSG - 6 speed manual involved far too many gear changes, especially in a diesel with a relatively narrow powerband. A friend with the 6 speed 2.0TDi was commenting how useless first gear was resulting in the requirement for an immediate 1-2 change as soon as the car starts moving. DSG takes care of this without fuss.
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Yup, Super aero, the back can indeed be picked up and car turned that way although for most people it is better described as bouncable round as it is not that light on the back wheel.
Yes it's hand throttle, along with air and advance and retard levers on the steering wheel. Actually quite nice as it is only 270 degrees lock to lock.
As for other users of sliding pillars, Darmont (French) would be one as they started of building Morgans under licence, but always badged as Darmonts. Sandford (also sort of French) may have used them but here I'm not so sure. Oh and some Alta racing cars...
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6 gears is great on my friends seat ibiza 130 hp. 90 mph and about 2500 rpm.
Much more economical than my honda which is doing about 4500 in 5th at the same speed.
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6 gears is enough and just about perfect.
Renault had it just right with the goona and 1.9 dci. 1st had the turbo kicking in for fast step aways at junctions and roundabouts, going to a useful speed that didnt get a lorry up your bum when you hit the rev limiter and pullng for second, 6th gear was a lazy 2000 revs at 70mph, just at the start of turbo to accelerate if required.
The other 4 filled up the gaps nicely.
The ran has 6, nicely matched up to 4 but 5th and 6th are too low. 6 is 2500 revs at 70 and needs to come down to 2000, there is plenty of torque for it not to be a problem.
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TourVanMan TM < Ex RF >
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My Honda 2.2 diesel has 5 perfectly spaced gears, with 5th pulling about 2100 at 70, perfect for high speed cruising. Loads of torque, so relaxed easy hard accelleration in most gears.
I had a 307 SW hire car with the 1.6 diesel the other week. 5 gears weren't enough, the power band was too narrow and kept running out of puff. Having said that, three up with about 200 kg of luggage on mountain roads probably wasn't what it was designed for!
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My Honda 2.2 diesel has 5 perfectly spaced gears, with 5th pulling about 2100 at 70, perfect for high speed cruising. Loads of torque, so relaxed easy hard accelleration in most gears.
They soon changed it for a 6 speeder though - I assume purely for marketing reasons.
I thought it was fine with 5 gears - in fact as long as it could be kept rolling, then 3rd on its own was adequate for all around town use.
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Quite happy with five gears in my car.
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"They soon changed it for a 6 speeder though"
Yep, and a friend of a mate of mine was forced by company policy to 'upgrade' as his car went over mileage. He hates the 6 speed box.
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SWMBO only uses 4 gears up to 45mph... the thought of six seems excessive.
I thought modern designs were to make things simpler for the driver?
What about bringing back overdrives? Much simpler...
I could not be bothered with 6 gears...
madf
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What about bringing back overdrives? Much simpler...
Hear, hear. Clutchless changes at the touch of a button. Extremely reliable. Both my cars have overdrives and they have done hundreds of thousands of miles. Why were they ever dropped?
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Current cars are 'overdrive' in most gears e.g. VAG 2.0TDI 6 speed is overdrive in 4th, 5th and 6th gears.
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Current cars are 'overdrive' in most gears e.g. VAG 2.0TDI 6 speed is overdrive in 4th, 5th and 6th gears.
If you simply define overdrive as having ratios greater than 1:1 then perhaps so though the guys are referring to electrohydraulic overdrive systems as fitted to my old Dolomite Sprint, excellent though expensive to manufacture, much more cost effect to make a 5 speed or 6 speed box.
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I take overdrive to be higher gearing than required for maximum speed.
With no overdrive ratios in the box, then top gear would give maximum speed at max BHP
On old style gearboxes then top would equate to a 1:1 ratio and all reduction would be at the differential. Bolting on an 'overdrive' unit - essentially a 2nd gearbox - allows lower revs for the same road speed - it has a less than 1:1 ratio. This has a significant weight penalty - it's much better to have these ratios in the one gearbox.
So typically on a 5 speed box, I would expect maximum speed to be reached in 4th, with top gear optimised for relaxed cruising - i.e. an Overdrive ratio.
I don't understand what an overdive 4th, 5th and 6th gear means.
Do you meam that these ratios are all less than 1:1 - or do you mean that max speed is achieved in 3rd (surely not !)
I do understand what overdrive on 2nd 3rd and 4th gear means with the old overdrive units (meaning you can enable the 2nd gearbox in these gears) - but what does it mean on the VAG box ?
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The reason we need more gears is because from an engineering point of view the therodynamic efficiency of engines has gone about as far as it can. There are some minor improvements of say a few percent that can be made but not huge leaps like we saw with direct injection diesel and fuel injected petrol. Most of the time when cruising at 70 in the average 2.0TDI car you spend your time with a very light throttle application. Now that is seemingly good for economy but actually not. The engine is running at a very low load factor which means although a low amount of power is being drawn from the engine it makes that power very inefficiently. By using more gears we can force the engine to run where it is most efficient, producing a low amount of power still but at high load. The accelerator ceases to be a direct link to the engine but instead becomes a true speed control device where the gearbox and engine work together to deliver the performance the driver wants. To achieve that high load when cruising a very high gear is needed, one which basically offers no acceleration without a downshift hence the need for a multigear automatic. How big are the fuel savings of this kind of thing? Well theoretically driven on the same journey with the same power demand, about 10-40% with bigger savings on bigger engines. This is the same reason why driving hard doesn't make a huge difference to fuel consumption, because as you drive harder the engine works more efficiently.
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I am sorry, but I fundamentaly disagree with this
"This is the same reason why driving hard doesn't make a huge difference to fuel consumption, because as you drive harder the engine works more efficiently."
Wrong, work the engine harder and you burn more fuel.
Most of the time when cruising at 70 in the average 2.0TDI car you spend your time with a very light throttle application. Now that is seemingly good for economy but actually not.
Wrong, come out with me and I will prove to you that 60 mph at 2000 revs in 6th is burning less fuel than 60 mph at 2500 revs in 5th,
The only reason that cars now have 5th and 6th gears is to aid fuel economy. A direct correlation to reducing revs for a given gear = decrease in fuel consumption.
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TourVanMan TM < Ex RF >
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I think he is thinking on the right lines in that fuel economy is greatest at wherever peak torque is (1800rpm on my engine I believe), so I always use 3rd for 30mph and 4th for 40 as these are geared to be bang on 1800rpm. This can't be a coincidence as the Peugeot did these speeds at 1900rpm - again, peak torque figure for that engine.
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I agree that maximum fuel economy is somewhere in that band where torque is in its highest releative to the rest of the band, rarely at peak torque tho.
All these things have to be considered on the flat at a constant speed tho otherwise we are into too many vaeriables to have a meaningfull "heated debate"
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TourVanMan TM < Ex RF >
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half agree, more gears are there are an aid to fuel economy but also mask the narrowness of power bands and IMHO make it too easy to get caught "off boost" in a Tdi.
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The only reason that cars now have 5th and 6th gears is to aid fuel economy. A direct correlation to reducing revs for a given gear = decrease in fuel consumption. ------------------------------ TourVanMan TM < Ex RF >
I broadly agree with you RF but for that last statement, I think the real reason is a combination of marketing (ooh it has 6 gears!) and "official" consumption / CO2 figures and hence BiK. Many 6 speed TD's are over geared in 6th giving a relaxed cruise and good MPG / CO2 figures at cruise though make it too easy to drop out of the efficient peak torque area thus requiring a change down.
I.e. 35mph per 1000 rpm gives 2000 rpm at 70 mph which is fine until the road speed drops below 55 or 60 when a change to 5th is needed however a top gear of 30mph per 1000 = still less than 2350 rpm at 70mph though is also over 1600 rpm at 50 mph, just wher the torque in building nicely.
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Dont get me wrong. I dont disagree that power bands have gotten too narrow, and as a result gearboxes have to have too many gears to make use of it.
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TourVanMan TM < Ex RF >
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Dont get me wrong. I dont disagree that power bands have gotten too narrow, and as a result gearboxes have to have too many gears to make use of it. ------------------------------ TourVanMan TM < Ex RF >
Again I dont disagree but to say that power band have not got narrower, early 90's mainstream TD's produced nothing below 2000 and were out of puff at 4000, it is simply a matter of the gearing being appropriate and IMO a top gear of around 30 - 32 mph / 100 is ideal for a engine that pulls strongly from 1500 and produces around 250il/ft torque at around 1800 however if the the gearing is a little higher and perhaps the torque peak is also a little higher in the range then too much stirring the gearbox is required rather than being able to make use of the generous torque.
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I agree, the only way that a large number of ratios in a box (to improve efficiency) is beneficial is if these ratios are automatically not manually controlled. It would not be practical to have a manual gearbox with enough ratios to always keep the engine at maximum efficiency.
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"This is the same reason why driving hard doesn't make a huge difference to fuel consumption, because as you drive harder the engine works more efficiently." Wrong, work the engine harder and you burn more fuel.
If I deliver a set number of kW of energy over a period of time (say one hour) then if I produce that energy burning on average 240g/kWh of fuel (typical high efficiency diesel) I will burn less fuel than I produce them with the engine lighter loaded at 300g/kWh average.
Wrong, come out with me and I will prove to you that 60 mph at 2000 revs in 6th is burning less fuel than 60 mph at 2500 revs in 5th,
I know it does. That is precisely because the engine is loaded more heavily and running at a more efficient point in the fuel map. At 2500rpm in 5th the power produced is a function of torque and speed to provide an arbitary amount of power. At 2000rpm to produce the same arbitary amount of power (because the vehicle is no lighter or slower) the amount of power coming as a result of enigne speed is less hence the load on the engine is greater, making it more efficient.
I'm trying desperately to find a link to an engine map online to explain this rather better than I have here
Regards
Chris
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Hi All,
My wife learnt to drive many years ago in a car with a four speed box. To this day I have to gently cough to remind her that both our cars now have five gears!
I dread to think how she'd drive a six-speeder....
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Chris,
I share your frustrations about not being able to get this point across without the aid of an engine map - I take it you mean rpm vs BMEP, with contours of equal BSFC - where you obtain maximum efficiency by being near the "centre of the onion"? If so, there are some examples of these maps in books like Heywood - I haven't seen any online, and I certainly don't have the time to create any!! If I can find a decent sized one in my stash of info, I'll scan it, and post it in a photo-bucket type site.
To be fair, I think that the insensitivity to load is more true of a throttled petrol engine than an unthrottled diesel.
In the case of the throttled petrol engine, part load inefficiency effectively due to pumping losses mean that the penalty you get by loading the engine (and reducing the pumping losses by opening the throttle) isn't as harsh as you might expect.
Because there isn't this interplay between pumping losses and the extra fuel required under higher load operation, the effect of load on a diesel is greater.
Number_Cruncher
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Actually, I found this isn't a bad graph of an economy/performance map
me.queensu.ca/courses/MECH435/
Pick on item 2
Look at page 31 of the presentation.
It also makes the point that specific fuel consumption is worse at low speed because the heat energy input from the fuel has more time available to transfer into the engine components, rather than producing useful work.
The main thing to note is that the best BSFC **isn't** obtained at the lowest engine speed - also it isn't obtained at the lowest load (or bmep on this map), but somewhere mid range.
The problem with the map is that it shows BSFC, i.e. how much fuel you burn per BHP. How you choose to drive your car, and turn this into a mpg figure isn't always obvious. Among the strategies which are used in CVTs, keeping towards the "centre of the onion", as the sweet spot of this map is known as is among them.
Number_Cruncher
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8 speeds? Is that all? ;-)
Suzuki were building vehicles with 14 speed gearboxes in the 1960s. Sequential box with a stick shifter and a proper clutch is good fun (paddles or buttons is cheating), just hit the lever and touch the clutch for the next gear, but don't forget which way is up :-0
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Happy memories of my Fifties childhood, when my father's Austin A40 was greatly superior to most of the opposition in that it had four gears while equivalent Fords and Vauxhalls had only three.
I think there was a very early Vauxhall automatic which had only two speeds - slow and slightly less slow.
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If you missus struggles with a 5-speed box - she'll definitely struggle with a 6-speed box.
She'll either stick it in reverse at 90mph or try and reverse in 6th.
(speaking from personal experience.....)
Greetings to Mike Hannon (I assume of West Buckland fame!)
I think the whole efficiency thing is confusing the issue. As a % efficiency measure, of course an engine at low rev's producing a low power output will lose proportionately more power through heat loss than running at peak power and so will be less efficient if just measuring net power output from calorific input. It may be more efficient at peak power but it will still be using more fuel.
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In my youth I drove a Ford Prefect 100E which had just 3 gears. In comparison to a Morris Minor, which had 4, the Ford's gears corresponded roughly 1st, 2nd and 4th. - So in the Prefect you got into top (3rd) at 20-25 mph and stayed there!
Also used to drive a Leyland Super Comet 16 tonner that had 10 speeds (5-speed non-synchromesh main gearbox and 2-speed diff).
But my mountain bike's got 18 gears although some combinations are redundant like chainwheel 1st / sprocket 6th!
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