Why so many gears?
Discussion
gvij said:
Tickle said:
Drop a cog then?
Sounds like hard work. Engineering is all about making complex things simple to get the best result. 6 speeders take away from that vs 5.The 1.8turbo 225 engine puts up a very impressive show of power for what it is but it is no naturally aspirated V12 with high torque and power throughout the revband.
I can understand that most people haven't got the cash for fuel,co2 taxes and large purchase costs for 6,8, and 12 cylinders hence the push to 4 cylinder turbos petrol and diesel.
Roll on the days if I become wealthy and can pick and choose my chariot.
The problem is the ratios. I've had the pleasure of using a 6-speed box which had ratios selected only for the best driving performance. The ratios in a road car are quite different- 1st has to be short enough to get the car off the line easily even when towing the car's maximum towing load up a gradient. Few people do this, and it means the cars get lumbered with a frustratingly short first gear. The rest of the ratios are selected only to bring the engine into it's most efficient operating window during EU tests. Thus you get an awkward set of ratios which aren't enjoyable to use at all. 6th is often so long that even at 70mph it isn't really usable as the engine is practically idling at this speed and is well short of it's power band. Change down? Yes it's an option. Better still, buy a car with a proper set of ratios and it won't matter if it has five or six speeds.
I have the use of a corsa which has 1.4l engine mated to a 5 speed manual gearbox, in 5th and 3,000 rpm it cruises at 70ish. it really could do with a taller 6th gear but I surmise that it doesn't have sufficient torque to propel its mass efficiently with a higher gearing, i.e. fuel economy would suffer due to higher loading but lower rpm
On the other hand my 3.0l V6 diesel thumps out so much torque that in 7th and 70 it is pulling just over 1500 rpm. Diesels develop lots of torque but have limited rpm, so if you have lots of ratios you can exploit the torque and minimise the impact of low rpm.
So why do cars have more gears, because it better utilises the torque on diesels, it's not worth developing two gearboxes so petrol engines get the same. The byproduct of more gears though is better acceleration, as long as you can change them quick enough that is
On the other hand my 3.0l V6 diesel thumps out so much torque that in 7th and 70 it is pulling just over 1500 rpm. Diesels develop lots of torque but have limited rpm, so if you have lots of ratios you can exploit the torque and minimise the impact of low rpm.
So why do cars have more gears, because it better utilises the torque on diesels, it's not worth developing two gearboxes so petrol engines get the same. The byproduct of more gears though is better acceleration, as long as you can change them quick enough that is
sars said:
Diesels develop lots of torque but have limited rpm, so if you have lots of ratios you can exploit the torque and minimise the impact of low rpm.
Exactly.Many years ago CVT transmissions were thought to be the holy grail, but turned out to be an automotive dead-end. Multi-ratio automatics are essentially the same solution delivered with older technology but strapped to a big computer. What does the computer do? As well as choosing the ratios it has access to engine power, enabling clever torque management during gear-shifts. This in turn enables the swiss watch internals of an 8-speed auto to be protected from the ape at the wheel....
gvij said:
My TT has 6 forward gears and I think it is too much. When you boot it in 6th nothing happens as its out of the turbo range. Obviously its to save fuel which is a compromise.
Give me a 5.9l v12 Aston Martin then I wont care how many gears it has!
Find that hard to believe, unless you're 'booting it in 6th' at 40mph.Give me a 5.9l v12 Aston Martin then I wont care how many gears it has!
veevee said:
Find that hard to believe, unless you're 'booting it in 6th' at 40mph.
Of course it responds with power, but somewhat slowly (probably quicker than most cars though)until the turbo kicks in and then it rockets off with a vengeance. Its perfectly safe if annoying. Yes I could leave it in 5th fair point by a poster above.
veevee said:
gvij said:
My TT has 6 forward gears and I think it is too much. When you boot it in 6th nothing happens as its out of the turbo range. Obviously its to save fuel which is a compromise.
Give me a 5.9l v12 Aston Martin then I wont care how many gears it has!
Find that hard to believe, unless you're 'booting it in 6th' at 40mph.Give me a 5.9l v12 Aston Martin then I wont care how many gears it has!
veevee said:
gvij said:
My TT has 6 forward gears and I think it is too much. When you boot it in 6th nothing happens as its out of the turbo range. Obviously its to save fuel which is a compromise.
Give me a 5.9l v12 Aston Martin then I wont care how many gears it has!
Find that hard to believe, unless you're 'booting it in 6th' at 40mph.Give me a 5.9l v12 Aston Martin then I wont care how many gears it has!
gvij said:
Sounds like hard work. Engineering is all about making complex things simple to get the best result. 6 speeders take away from that vs 5.
You find dropping from 5th to 6th occasionally too difficult, so you'd rather have a lower top gear ratio and live with poorer fuel economy? Why not get an auto and save yourself fro all that terrible exertion?ScoobyChris said:
I think I've only owned a couple of 5-speed cars where the reverse was where 6th is (Micra and Scooby) and you could argue that it's equally dangerous because you may be downshifting from 5th and attempt to go into reverse (complete with lots of mechanical graunching) rather than 4th. All the other cars were next to 1st.
Chris
No no!!!! The reverse leg is blocked out once you've selected 5th. You need to return the lever to the central position to unblock reverse.Chris
Edited by ScoobyChris on Sunday 2nd February 12:40
(that's in a proper car anyway, (i.e. most Mazdas and Fords (not the older Fiesta)) maybe not in Scoobys
)I have seen several cars with reverse next to 1st with drivers selecting reverse to pull away forwards.
(Polo, & in fact most VWs except the Up, some Hyundais, many Vauxhalls, older Clios, etc)
sars said:
So why do cars have more gears, because it better utilises the torque on diesels, it's not worth developing two gearboxes so petrol engines get the same.
Diesels get different final drive ratios to compensate for the lower engine speeds, they're also specified by torque so petrol and diesel gearboxes are very seldom the same. peterbredde said:
Am I doing and damage in skipping gears?
No. They're your gears aren't they? They were put in the car for you to use and that means that when you have finished with whichever one you are using right now, you are perfectly entitled to use whichever of the other five is most appropriate next.Ozzie Osmond said:
Exactly.
Many years ago CVT transmissions were thought to be the holy grail, but turned out to be an automotive dead-end. Multi-ratio automatics are essentially the same solution delivered with older technology but strapped to a big computer. What does the computer do? As well as choosing the ratios it has access to engine power, enabling clever torque management during gear-shifts. This in turn enables the swiss watch internals of an 8-speed auto to be protected from the ape at the wheel....
My company vehicle has a hydro-mechanical CVT and it is the best transmission I've used bar none. You have to pay quite a premium for it, but it's worth it, totally transforms the machine. Many years ago CVT transmissions were thought to be the holy grail, but turned out to be an automotive dead-end. Multi-ratio automatics are essentially the same solution delivered with older technology but strapped to a big computer. What does the computer do? As well as choosing the ratios it has access to engine power, enabling clever torque management during gear-shifts. This in turn enables the swiss watch internals of an 8-speed auto to be protected from the ape at the wheel....
Willy Nilly said:
My company vehicle has a hydro-mechanical CVT and it is the best transmission I've used bar none. You have to pay quite a premium for it, but it's worth it, totally transforms the machine.
Somehow my super-sensitive antennae tell me it's not a car....Agriculture perhaps?
"Stick shift" American V8s tend to have 6-speed double-overdrive gearboxes with a huge 6th gear ratio so that the manufacturer can meet the NHTSA/EPA CAFE standards.
http://en.wikipedia.org/wiki/Corporate_Average_Fue...
There may be 6 gears, but you aren't actually obliged to use all of them.
http://en.wikipedia.org/wiki/Corporate_Average_Fue...
There may be 6 gears, but you aren't actually obliged to use all of them.
Edited by gareth_r on Monday 3rd February 00:53
I don't really care. If it's for cruising then a taller ratio is nice. I agree that a tall ratio on a manual can discourage its use however as it's useless for small speed adjustments. On an auto, even the fastest of gearboxes have a faff-factor as they drop cogs before it'll move but it's only really an issue when I'm driving south of the Midlands in the congestion.
For an enthusiastic drive, extra ratios are irrelevant and I'll probably only ever use 3rd with fleeting moments in 2nd or 4th.
I'm not really keen on the imperceptable gearchanges as a selling point personally. I enjoy a car which obviously works through its gears. I think it's more something born from diesels which I still despise absolutely everything about - exceptionally blunt throttle response, far too lethargic to rev, contemptable sound regardless of whether it's quiet or loud (like one of those people with a voice so grating you just want to pan their face with a shovel whenever they speak) and nauseous torque curve.
For an enthusiastic drive, extra ratios are irrelevant and I'll probably only ever use 3rd with fleeting moments in 2nd or 4th.
I'm not really keen on the imperceptable gearchanges as a selling point personally. I enjoy a car which obviously works through its gears. I think it's more something born from diesels which I still despise absolutely everything about - exceptionally blunt throttle response, far too lethargic to rev, contemptable sound regardless of whether it's quiet or loud (like one of those people with a voice so grating you just want to pan their face with a shovel whenever they speak) and nauseous torque curve.
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