Small/Medium/Large Automatics - edisdead {P}
I've heard various blokes in various pubs profess that automatic transmission is a variably desirable option, depending on the capacity of the engine driving it (ie. small auto = ok, large auto = fine, medium autos = pants).

Can any BR'ers offer any technical guidance as to why this might be the case?
I'm thinking in terms of power/torque curves, not efficiency.

Ed
Small/Medium/Large Automatics - Mutterer
I am not a technician, but have had several autos over the years, most of which have been 2000cc and up. Auto Boxes love lots of torque, delivered as low in the rev range as posssible, my 8v Cavalier was good because of 135 ft lbs at 2300rpm.

Medium autos are usually fine which the notable exception of the Mk 1/2 Escort which was horrible.

My present Nissan 1600 has poor torque at low revs but the box is matched to the engine's power delivery. This just means that it revs higher in each gear, but the engine response is so good that this dosn't matter.

Small Autos?? Dunno, never driven one, never really want to.

Small CVT Autos seem to work better than the conventional type, until they break at vast expense.
Small/Medium/Large Automatics - SkyMan
I've driven a few autos over my life:

2000 Clio 1.6 - took ages to get to up to speed, lovely cruising

1992 R19 1.8 - Would spin wheels when it wasn't stalling

1995 Toyota Carib 1.8 - Better than Clio, but still needs the gear selector fiddling with to get it moving

1995 Skyline 2.5 - has a 5ps auto box. 190BHP with 170ft lbs. The best auto I've driven because the engine has a lot of power but doesn't redline until 7000 (which it can easily reach). I've never need to pre-select a gear when over taking, just press the throttle harder and the gearbox will change down accordingly (sometimes into 2nd at 60mph - it really flies then!)
Small/Medium/Large Automatics - Dizzy {P}
I have owned quite a lot of autos since my first one in 1970. Small-engined autos used to be a complete waste of time but I feel sure that this doesn't apply today. However, I still think the bigger (and torquier) the better.

What is very clear to me is that some autos are far better than others, even with similar sized engines. As an example, I have recently been comparing the BMW 5-Series with the Rover 75 with a view to buying new, or perhaps nearly-new in the case of the BMW. I would almost certainly have gone for either a diesel or petrol BMW with automatic 'steptronic' gearbox but have in fact ordered a diesel manual Rover.

I've driven a couple of automatic Mercedes C-Class and got on fine with the gearbox (but decided against the car). I have a limited experience with Ford automatics and don't like them at all. One was an almost new Mondeo (this was in 1999) and the changes were neck-jerkingly awful. I don't think GM have ever fitted a bad auto box, most being their own design though a Japanese one is fitted to several current models.

So there's no black-and-white answer to Ed's question in my view. Automatics are brilliant for town work and in slow-moving traffic situations, but you need to be very sure before you buy that it's the right car/gearbox combination.
Small/Medium/Large Automatics - 3500S
Dizzy, you are in for a treat with the 75 diesel, if you can get the 131ps. I test drove three 75s, a 2.5 V6 auto (too heavy on fuel), a 131ps diesel auto (very smooth but I'd had two auto before and wanted a manual) and of course a 131ps Manual which I settled for.

Autos are good for a number of reasons. I've owned two.

Rover 620 with sports auto.
Rover 623

And driven several..

Jag X-type 3.0 auto, very smooth, shame about the gruff engine)
BMW 523 auto, nice engine but disappointing sluggish auto.
Rover 75 diesel auto tourer, only 118ps but the smoothest auto I've driven.

Advantages

1. Never having to balance the clutch on a hill-start, an auto will just sit there.

2. Crawling in traffic, just lift your foot off the brake.

3. Hill decents, drop it a gear or two manually and let the engine brake the descent.

4. Rapid progress, big smiles, great changes, never have to worry about going into the red line.

5. Kickdown, pedal to the metal and the auto supplies the power right on cue, can take a second but it's second nature after a while.

Disadavantages

1. They can be bad for economy.

2. ATF is another fluid to change and check.

3. It goes wrong your bank manager will not like you.
Small/Medium/Large Automatics - Dizzy {P}
3500S,

That's a very good summary of auto v. manual, though I'm sure you'd agree that the economy can be *better* than manual with some cars and driving conditions, i.e. boxes with 'lock-up' in open road journeys.

You could also add that automatics encourage courteous driving as they make it so simple to ease off, to let someone pull out or a pedestrian cross the road, and then accelerate to speed again.

I'm sure I'll miss my automatic box but will indeed have the torquey 131ps Rover (BMW) engine to compensate! I never thought I'd buy a Rover again but they've got so much right with the 75 that I've no doubt I've made the right choice. If the replacements for the 25 and 45 are as good, the rest of Europe and Japan will have lots of catching up to do. About time we led from the front again!
Small/Medium/Large Automatics - 3500S
Wanting to stay on topic, the Jatco auto box in the 75 is very good offering normal, sport and winter settings but it was at the price of 5-8mpg on economy.

It's true when you say they do encourage courteous driving as progress is so much easier in an auto.

As for the 45/25 replacements, they've had problems with TWR going bust but the talk is that they've suffered a three month setback which isn't too bad. The chassis is a winner and development finished early, it's a FWD/RWD cutdown of the 75 chassis. They are expecting to be able to use it as a platform for no less than seven variants. I've heard they have working mock-ups of two 5-dr hatch and 5-dr saloon and whilst a little overweight at the moment they promise to be real belters, they've put the 1.8T into both for now.
Small/Medium/Large Automatics - edisdead {P}
I agree with the "courteous driving" comments - also i think an auto promotes a much more laid back driving style generally, possibly the thought of all those wasted gallons if i'm too enthusiastic?

I drive a 1.5 Civic auto. I think it's smooth and responsive, and i regularly get 44mpg (mainly motorway cruising, lock-up converter). I don't have experience with anything bigger, mainly for cost reasons - and because I don't realistically need any more than 90bhp. Wouldn't mind a try though, perhaps in a turbo-diesel auto. I've driven a CVT Micra, which i didn't like much.

Trying to keep this technical... I guess a torque converter inherently soaks up plenty of torque. If it's not there to be mopped up, then performance suffers. Big torquey engines don't mind so much, as there is plenty on tap. Small motors can be revved harder more easily to get the torque required, hence the popularity of CVT in small cars. So a mid-size engine must be a compromise somewhere between the two?

...But i've just gone and disproved my theory with my 1.5 example. D'oh!

Ed.
Small/Medium/Large Automatics - Malcolm_L
Agree with your summation of automatic v manual, however fuel economy is nearly always worse.

Check out the 'Official CO2 figures' for manual v automatic and
auto's are between 20-30% higher.
Remember the official figures are usually no load, one person and only a couple of gallons on board (let's face it - they are trying to sell a product!).

Rover 75 diesel and auto-box is excellent, combination of high torque at low rpm suits the box very well.
Diesel economy makes extra consumption bearable.

 

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