Why don't more cars come with 6 gears as standard?

cornbb

I'm curious. Surely the 6th gear leads to better fuel efficiency on motorways etc and therefore would be a selling point in new cars. Is it just uneconomical for manufacturers to design and make 6 speed gearboxes? Or do they just hold these off as expensive extras, or reserve them for high-performance cars, to retain the "I want one but can't have one" factor? Am I missing something obvious?

Owen

All BMW/MINIs come with 6 speeds, and I remember back in 2002, the Punto having 6 speeds too. All cars should be six speed IMHO, but you wouldn't believe the tripe I hear from people about it ... 'Sure when would I use 6th?', or my personal favourite 'What speed should I be doing before I go to 6th?'.

CrowdedHouse

The Lexus IS 220D has six gears but you can only use 6th if the break the speed limit..about 125 Km/h,otherwise it labours..very useful

Anan1

I dunno. Unless the engine is particularly weedy, I think five should be enough.

Jimbo

If the engine was weedy, it wouldn't cope with 6th

fletch

I was in a 5 door Fiat Stilo 1.2 :eek: once with 6 gears. I personally use my 6th gear every day, even in 60kph zones (provided it's not uphill of course )

Anan1

jimbo78 wrote: »

If the engine was weedy, it wouldn't cope with 6th

You're assuming that a six-speed box is like a five-speed with the addition of another, higher, ratio. That may be true in the odd case, but usually the extra cog is used to tighten up the gaps between gears. The less torque the engine has, the more useful this is. A big V8 might be perfectly usable with only three forward gears, a little 1.0 won't.

Jimbo

@ fletch
Talk about stressing your engine. Why bother?

Anan1

jimbo78 wrote: »

@ fletch
Talk about stressing your engine. Why bother?

As I said in my last post, you're assuming sixth to be higher than fifth would be in a five-speed car. Why?

Jimbo

Ive driven 6 speed cars and never really use sixth because the revs seem to be pretty low in fifth. Therefore it seems that sixth is just an extra higher ratio gear

Duiske

Anan1 wrote: »

You're assuming that a six-speed box is like a five-speed with the addition of another, higher, ratio. That may be true in the odd case, but usually the extra cog is used to tighten up the gaps between gears. The less torque the engine has, the more useful this is. A big V8 might be perfectly usable with only three forward gears, a little 1.0 won't.

Nice explanation Anan. Often wondered about that. I'm driving an '04 Corolla at the mo, and its grand for normal driving. But when I'm on the motorway, doing about 120kph, I often find myself checking if I am actually in 5th gear, and not 4th. Feels like it could use the extra gear.

Guy:Incognito

Renault seem to be going down the 6 gear route. The new Laguna has 6 and some of the current range of Scenics have 6.

mike65

The original Fiat 6 speed was designed for, excuse the term, "baby-boy-racers" who wanted something cheap to insure and run but which could sound and behave all exciting. I belive the ratios were rather short.

Mike.

colm_mcm

the Punto sporting gearbox was very good, it really helped the run to 60mph. ratios were short alright, but great fun.

tossy

Anan1 wrote: »

You're assuming that a six-speed box is like a five-speed with the addition of another, higher, ratio. That may be true in the odd case, but usually the extra cog is used to tighten up the gaps between gears. The less torque the engine has, the more useful this is. A big V8 might be perfectly usable with only three forward gears, a little 1.0 won't.

spot on anan-taking the TDI golf/passat cars of which i have a good bit of experience the length of 1st gear on the 5 speed and 6 speed box is identical and the length of 5th in the 5 spped and 6th in the 6 speed are also identical,the extra cog is in the middle and its quite useful.

smartypantz

Speaking of "weedy" engines !

The 600cc and 700cc (my car) Smart fortwo has a 6th gear, typically selected over 45mph.

Though the new 1.0l Smart only has 5 gears and after having test driven one, IMO it could do with the extra cog. Fuel economy is also not as good on the new model.

Lex Luthor

I never really thought about it until last week when I was driving back from Limerick on the P'Laoise bypass and the passenger commented how high the revs were in 5th gear when I was doing 80mph. I think it was just over 4000.

He said in his car in 6th at that speed he'd probably be just over 3,000

Explained why I needed to fill the car up again after doing a 200 mile round trip.

Jimbo

You shouldn't be speeding. Report yourself into the nearest Garda Station post haste if you have any conscience

colm_mcm

Lex Luthor wrote: »

I never really thought about it until last week when I was driving back from Limerick on the P'Laoise bypass and the passenger commented how high the revs were in 5th gear when I was doing 80mph. I think it was just over 4000.

He said in his car in 6th at that speed he'd probably be just over 3,000

Explained why I needed to fill the car up again after doing a 200 mile round trip.

Is this the Verso?

fletch

jimbo78 wrote: »

@ fletch
Talk about stressing your engine. Why bother?

Not really, I would only do it on a descent and wouldn't apply more than a quarter throttle. Saves fuel. If the road inclined I would drop a gear or two depending.

Timmaay

The new opel vectra comes with 6speed as standard on all the range afaik, Its very handy on long drives. My folks 2.0l diesel vectra will tick over at 2k rpm while doing 120kmh, whereas my 1.9tdi a4 does about 3k revs in 5th at 120kmh.

E92

Timmaay wrote: »

The new opel vectra comes with 6speed as standard on all the range afaik, Its very handy on long drives.

Nope, only the diesels have 6 gears, and the high powered petrols(the ones with a 2.0 or bigger IIRC). The 1.6 and 1.8 definately don't have 6.


What I can never understand is why most oil burners have 6 speed boxes and most petrol equivalents still only have 5?

In the recent thread about the Opel Astra I was told that at 120 km/h the diesel is at 2200 rpm in 6th gear, and I know from being in one that the 1.4 petrol is doing about 3700 rpm in 5th. I don't know about the diesel but I do know that with the petrol you can hear the engine working away and it is noisy and tiresome. So far as I can tell, the main advantage of 6 gears is greater economy and less noise on the Motorway, and the gears are overall less widely spaced out so you should be in the enginer's power band more often and gearchanges. FWIW the Avensis D-4D(2.0 126 bhp) at 120 km/h in 6th is running at 2000 rpm I'm led to believe(IIRC that was what Honest John said it did anyway) while I know from my old man's 1.8 Avensis(129 bhp) its going at around 70 km/h in 5th gear(which is it's top gear) when it's at 2000 rpm. If his car is travelling at 120, the rev counter is at around 3200 rpm, so it doesn't surprise me that the best he can get from it at Motorway driving is 41 mpg(usually more like 38 or 39).

colm_mcm

A lot of petrol Toyotas could do with a 6th gear TBH. the VVT-i is torquey enough to handle lower revs anyway.

Mailman

E92 wrote: »

What I can never understand is why most oil burners have 6 speed boxes and most petrol equivalents still only have 5

Diesels have very short power bands and with a turbo diesel where the turbo is working as intended you would want to running in around 2 or 2.5k rpm where all the oomph is.
with a six speed you are hitting optimum engine speed near all the time especially out on the motorway.
a 7 speed box would be even better but people would get tired changing gears.
with a CVT or DSG auto box you can be in the sweet spot all the time.

Way of the future - smaller and smaller engines or diesels with forced induction and CVT or DSG transmission to keep you in the sweet spot all the time.

TychoCaine

E92 wrote: »

In the recent thread about the Opel Astra I was told that at 120 km/h the diesel is at 2200 rpm in 6th gear, and I know from being in one that the 1.4 petrol is doing about 3700 rpm in 5th.

That's because diesels run at lower RPMs than petrols. My S80 petrol red lines @ 6,500 RPM, and delivers peak BHP @ 5,300 RPM, but the diesel version red lines @ 4,500 RPM and peaks at 2,500 RPM. :rolleyes:

Oilrig

6 gears are an aberration due to the narrow torque bands produced by "modern" torque compromised eco friendly engines. Once the engineers get ahead of the issue we will be back to 5 speed and eventually 4 speed boxes, ie flexible engines.

Less is more.

galwaytt

well my 968 has six - and it's a 1994 car - but only needs.........4 ?

I know this because the torque is such that I 'block change' like the trucks do, and go 1-2-4-6. The car doesn't even notice that I've done it. It's like driving one big elastic band.

Love it

Mind you, I'd like more gears in 1.4 petrol turbo or something - all noise'n'action, dontchaknow.......just 'suits' the things, as ColmMc says.

milltown

galwaytt wrote: »

The car doesn't even notice that I've done it.

If it ever finds out, there could be trouble!

Green Hornet

The new Honda Civic has 6 gears as well. Mine is a 1.8 Vtec and the 6th gear is only really for cruising. Gives great fuel economy for a 1.8 (44mpg) but no torque unless really driving pretty fast. You really need to go down a couple of gears for overtaking.

I'd say at least a 1.8L petrol engine required for efficient use.

mick.fr

the M6 has 7 gears if I am not mistaken, looks like we are gonna hit 8 gears in a couple of years lol

Run_to_da_hills

Anything over 3 or 4 gears is bunk, older engines had great torque and had real power. With these modern high revving engines you spend all day flipping up and down gears, realistically these motors couldn't burst their way out of a wet paper bag!:D .

mick.fr

Run_to_da_hills wrote: »

Anything over 3 or 4 gears is bunk, older engines had great torque and had real power. With these modern high revving engines you spend all day flipping up and down gears, realistically these motors couldn't burst their way out of a wet paper bag!:D .

Mustang GT had a average HP of 250.
A 4 gear alright, but still average power nowadays.
A 6/7 gear is really about the maneuverability of your car at low speed I believe, correct me if I am wrong.
It is pretty easy to hit a mall's wall with a Mustang GT if you are not used to the gearbox.

Run_to_da_hills

mick.fr wrote: »

Mustang GT had a average HP of 250.
A 4 gear alright, but still average power nowadays.
A 6/7 gear is really about the maneuverability of your car at low speed I believe, correct me if I am wrong.
It is pretty easy to hit a mall's wall with a Mustang GT if you are not used to the gearbox.

The Mk 1 Camero was the same, (3 Speed) driving these cars involved more skill, they never made it over here, I suppose the equivilant car would have been the Ford Capri which also origionally came with just a 4 speed box,

-Chris-

As previously said, cogs are added in the middle, rather than at the top - i.e. 5th gear in your 5-speed car is pretty much the same as 6th in someone else's 6-speed car.

Putting more cogs in the middle makes it easier to keep your car within the very narrow powerband that modern cars are now operating with. As rightly pointed out, large capacity engines (like a big old V6 or V8) will have buckets of torque and therefore not need many gears.
The trend for medium and small cars is for the engines to get smaller and more efficient, but the trade off for this is for the powerband to narrow and 6-speeds to be necessary.

Biro

The VW TDi 6-speed means that it's around 400 rpm lower at 100km/h than the 5 speed. (This is the case in the Passat anyway, maybe the Golf etc 6-speeds are different ratios).
I find it only for economy in a turbo diesel, as the engine has more than enough torque not to need the extra cogs in the mid range.
The gen 7 celica would happily sit in 6th from 40mph, not even hinting at labouring.

colm_mcm

mick.fr wrote: »

the M6 has 7 gears if I am not mistaken, looks like we are gonna hit 8 gears in a couple of years lol

The Lexus LS460 has a sequential shift 8 speed auto

AudiChris

AudiChris wrote: »

As previously said, cogs are added in the middle, rather than at the top - i.e. 5th gear in your 5-speed car is pretty much the same as 6th in someone else's 6-speed car.

Putting more cogs in the middle makes it easier to keep your car within the very narrow powerband that modern cars are now operating with. As rightly pointed out, large capacity engines (like a big old V6 or V8) will have buckets of torque and therefore not need many gears.
The trend for medium and small cars is for the engines to get smaller and more efficient, but the trade off for this is for the powerband to narrow and 6-speeds to be necessary.

More cogs... More like cogs with different ratios. Where they are added is a bit of a red herring. The ratios would generally be different on all the cogs in a 5 speed and 6 speed.

colm_mcm

top gear in a 6 speed generally makes the engine rev lower than on a 5 speed. On a very high performance or luxury car, the very top gear would be useful for very high speed cruising, as in the LS.

-Chris-

ronoc wrote: »

More cogs... More like cogs with different ratios. Where they are added is a bit of a red herring. The ratios would generally be different on all the cogs in a 5 speed and 6 speed.

Sorry, that's what I mean. You keep the top ratio the same, but the number of middle ratios increase and the ratios are changed.

There's actually a formula for calculating gear ratios for an engine, using the rpm of max torque and rpm of max power. I can't remember it though, I'm a bit rusty on the aul vehicle engineering.
You then need to take into account the final drive ratio in the differential and the rolling circumference of the wheels to calculate the speed of the car in a given gear at a given rpm.
The principle holds though, that you match the gears to the power and torque characteristics of the engine. It's not as simple as adding an additional 6th gear to an existing 5 speed gearbox to give you a lower rpm at cruising speed.

Onikage

Spot the difference:

Timmaay

I've heard of a good few people with 1.9tdi engines changing the 5th gear ratio (ie, swapping 2 of the cogs in the gearbox), so as the car will rev lower on motorways and save fuel. It's a bit extreme I'll admit, just to get a small mpg improvment, while basically making 5th gear useless for overtaking/accelerating.

colm_mcm

guys, 6 speed gearboxes are useful, e.g I'm driving an Avensis D-4D 6 speed, and the 6th gear is noticibly longer than on the 5 speed model. If the current 6th gear ratio had been used on the 5 speed box, the gears would have to be farther apart, and it'd be hard to keep the engine in its power band. 1st gear is also shorter than on the old Avensis, so taking off from a standstill is quicker and easier.

-Chris-

Onikage wrote: »

Spot the difference:

Best answer yet!