Is Conventional Automatic Transmission The Best Choice?

[Alberto Michelatti]

I think that nowadays is out of our era that a human being has to think at what gear is better to shift to (an ECU can do this perfectly) and, moreover, having to move directly the clutch pedal that, for me, would haven't to exist. So I would like to explain because for me the conventional automatic transmission with hydraulic torque converter is the best choice:

1) since the birth of the automatic transmissions, there is no power flow interruption during gear shifting, like in the more quick Direct-Shift-Gerabox system of Audi/Volkswagen group; not even a robotized manual transmission like, for example, the BMW SMG (or Ferrari F1) can do this;

2) an ECU always knows exactly the input shaft rpm and the output shaft rpm, matching them perfectly just at the right moment (an human being never could do this so: in my opinion, this is quite impossible);

3) the engine can't never stall, shutting off by its own: with a manual transmission, when you take-off and don't apply sufficient throttle or release too fast the clutch pedal the engine can stall (very dangerous in the road traffic!); also when you have to do an emergency braking, maybe that for the panic you release the clutch pedal wrong and, as well, the engine can stall, leaving you with a much more less efficient braking system just in the wrong moment;

4) the automatic transmissions are electronically and perfectly self-protected against drivers mistakes and, moreover, there isn't to worry about clutch overheat or synchronizers wear;

5) for the life of car, there isn't to worry about the expensive clutch-disc substitution;

6) with a manual transmission, how many burning-wheels dragster-style starts can you do without the clutch overheats? With an automatic transmission, instead, you can do this for the times you want, endlessly;

7) with a manual transmission, when you are at a stop on a uphill, when you have to start you have to release very carefully the clutch pedal, risking to overheat it; with an automatic transmission, instead, you have just to apply trottle, regardless of the weather, grip, slope, car load and anything else;

8) due to the automatic transmission creep feature, at the stops on uphill it's like having a Subaru-like hill holder feature, because the car almost never go reverse;

9) with automatic transmissions there's less wear than on a clutch, and there's less wear on suspensions and crankshaft/lower engine because of lack of transmission snatchs;

10) due to the automatic transmission kick-down feature you can get speed very fast, pulling yourself out fastly from bad and dangerous traffic situations;

11) due to the up-to-3.0x torque multiplication feature of the torque converter, a car has more acceleration when you accelerate out of a stop. Moreover almost all automatic cars today have the torque converter lock-up clutch, that eliminates the slippage between the pump (input power, engine side) and the turbine (output power, transmission side) of the torque converter. This by-pass function is studied to improve fuel economy at constant speed.

12) for the ultimate, the comfort and satisfaction given by an automatic transmission in the city traffic, in my opinion, are really priceless; it's true that the fuel consumption in this condition is higher, but you also have a lot more acceleration and this is undoubtedly a safety factor;

If someone is interested in a very detailed description of an automatic transmission, here there is the explanation for the ZF "4HP18 Q/EH" one (using the Ravigneaux gear train arrangement): http://www.digest.net/alfa/FAQ/164/pb94/pb94-6.htm.

Here there is the description of the state-of-the-art 6 speed "TR-60SN" Aisin AW automatic transmission (using the Lepelletier gear train arrangement), fitted on the Porsche Cayenne and on the Volkswagen Touareg (as well as, for example, as on the Volkswagen New Beetle, Audi TT and Audi A3): 6speedautotranny.zip.

Alberto.

P.S.: please don't say this to anyone, but this is the untold reason why the automatic transmission is absolutely the best choice...

[kingdeacon]

depends how you drive and where, no way is a auto better on the tight b roads when your giving it some

[Johndcfc]

Both have there advantages and disadvantages, after driving an automatic for the last 2 months I'd say I prefer auto.

Do miss revving the nuts off my old car mind!

[Alberto Michelatti]

Maserati GranTurismo 4.2 V8

5_YnHa7GWBs

Maserati GranTurismo 4.2 V8: just one transmission choice, a ZF "6HP26" 6-speed adaptive sequential automatic transmission with hydraulic torque converter, lock-up and paddles behind the steering wheel.

Alberto.

[Karma Supra]

It depends...

I like autos and I hate the fact that most people knock them without trying a proper auto.... For general use I like them... however there are limitations!

Judging that you have an avensis I am gathering that you are talking about auto transmision in a lower power, fwd sense, this is a totally different kettle of fish to driving a bigger power RWD car in a spirited manner ;) For example lets say in full auto mode you are taking a long sweeper in a rwd car and the back end steps out... you lift off slightly to reel it in, the auto box sees it as you reaching the speed you wanted and knocks it up a gear.. Not great idea mid corner!!

For prolonged fast driving, up and down the revs, accelerating hard a lot of heat is generated in the gearbox, This happens in both auto and manual cars, but as you say auto boxes rely on fluid transfer to operate, the fluid being ATF. As we all know oils change viscosity with temperature, excess heat in the system can lead to the box getting a little sloppy and giving a more noticeable feel of slipping/transmission loss, again not ideal for hard driving.

I also find that although you can gear down in auto cars (jerky as you can't match revs/fade in like you can with a clutch) in full auto mode you don't have this effect, again in spirited driving this puts a hell of a lot more stress on the brake componants.

[Guest]

I am looking for fully automatic small car, any good makers and models can you suggest ?

Thanks

Quin

[Cyker]

Bah, autos are for Americans and lazy people who can't drive properly! :P

But seriously, I've yet to drive an auto which responded in the way I wanted it to all the time; They either waste fuel being in too low a gear or are in too high a gear for fast pickup. This is mainly because they are not psychic.

That said, of all the different types, I'd deffo go with either a decent torque-converted box or the HSD eCVT. All the semi-auto clutchless manuals suck donkey balls in real life - I'm sure they're the dog's proverbial on a race track, but in real life with all the different gradients and road conditions I just find them incredibly frustrating. It's a big tell that all the MMT owners who don't hate their MMT drive it in manual mode!

The torque converter and eCVT are nice just because they are smooth and linear; They feel closest to a gear-less transmission (Which is what I hope we'll eventually get with electric motor driven cars!). Biggest downside with the torque converter is it does use up a lot more fuel due to pumping losses. I like the eCVT a lot, although I'd love for them to give it more torque

[MikeSh]

I am looking for fully automatic small car, any good makers and models can you suggest ?

There are several good makes, but to be honest none have yet cracked the answer to a good (reliable, economical, smooth and preferably psychic) auto for small cars. Who'd have thought it so hard, but I suppose when you are building for the low price end of the market you can't really spent a lot on r&d for maybe 10-20% of the cars to be built.

It's a big tell that all the MMT owners who don't hate their MMT drive it in manual mode!

I don't hate the MMT and rarely use it in manual except long downhills. It's not great but I've got used to it. (And it is cheapish to buy and cheap to run.) Bear in mind this forum has a fairly young demographic which will weigh against MMT satisfaction. I'm actually quite surprised that some of the people here have bought an MMT/auto at all.

I like the eCVT a lot, although I'd love for them to give it more torque

CVT's have always been limited in the power/torque they can handle which is why you won't find them on bigger cars. 1.3...1.4 litre is about the top. Some years ago a disc based CVT was developed which was supposed to handle much more power - well into the 2L range if not more. I believe Nissan used it on the Primera but I don't think it took off. Maybe reliability was an issue.

No-one has had a great CVT, except maybe DAF with the original which was surprisingly good (though 70mph in reverse was a bit scary ... ). That also gave you a limited slip diff which made it quite good off-road.

So I will wait a few years before accepting any new version of CVT is actually any 'good'.

[Guest]

I can only drive automatic car because I hold an automatic driving licence and I have never touched a manual car in my life. I had my old Toyota Yaris 2002 fully automatic car which was sold 2 month ago. I was very satisfied with its performance, so I went to Toyota dealership to buy a Toyota Yaris again 3 weeks ago, I was very clear to the salesman that I can only drive Fully Automatic and I only hold auto driving licence. But finally I got an used Toyota Yaris vvi 1.33T Spirit MMT. I don't know about car at all, I just simply want a fully automatic car to help my childrens' school runs. I started to learn about the MMT since I got this car, it is so weird gearbox, I honestly cannot control the car, I remember I wrote an email to the dealership on the same day I took the delivery of the car that I felt the car drives me instead I drive the car, I was jumping and leaping when I was driving on the road. the dealership only can accept Part Exchange because they said the gearbox is fine, and I am qualified to drive this car with my auto driving licence. MMT gearbox maybe supposed to be like that I have experienced: 1,there was a delay before the engine kicks in and I had to immediately brake hard as the car behind me went too close. 2, the gearbox seemsto Chang gear when it feels like it, usually at the most inconvenient times.3, rolling back from hills because it has not got Hill Assist which was the biggest problem for me as I have never driven Manual car before.

[Cyker]

Argh! Nooo! Not a CVT, CVT's suck too - I'm talking about the eCVT in the HSD (Which isn't really a CVT but that's what Mr T calls it ).

The ultimate full-auto would be a gearless full-electric drive train - Totally smooth from 0 to the top, max torque from 0 to the top! Only reason we don't have them right now is that Battery tech is very far behind, but the HSD system is a good compromise; Its gears are always engaged and doesn't use stupid friction belts like a real CVT.

The way it lets the leccy motor and the very efficient but rather pathetic (in torque terms) petrol engine work together to cover each others weaknesses is very clever, and we know it's capable of much more than Toyota have let it do in the Prius and Auris from the spectacular performance of the race-spec version in the Le Mans recently!

On the basis of that, I'd say that the only small current gen car with a decent/pleasant autobox right now is probably the Yaris Hybrid. (Although it's starting to push the meaning of 'small' somewhat ). Isn't cheap tho' :(

[MikeSh]

I can only drive automatic car because I hold an automatic driving licence and I have never touched a manual car in my life.

..................

My wife is the same and has no problem driving our Yaris MMT.

It is not a manual car despite what some people call it. There is no clutch pedal or means for the driver to operate the clutch. There is a facility to encourage the box to go to a particular gear which is referred to as manual, but it does not resemble driving a manual car - because again you don't actually control the gears, you are just telling it which you'd like it to use. (It's closer to a motorbike infact as it's a sequential operation.)

The automatic gear changing does take some getting used to, even for those of us who have driven manual cars. It does feel weird and took me about 6 months to feel comfortable with.

Yes, the change points are sometimes a bit off, but to be fair I've never had an automatic that always got it right. The Borg-Warner type boxes (hydraulic) manage to make this less obvious due to the torque converter (which combines a fluid coupling and CVT effect), but the mechanical boxes don't have the same fluidity (pun intended).

The MMTs are by no means the first automatics not to have 'hill-assist' - certainly the early CVTs were the same. On most autos (incl B-W) this hill-assist is an effect of the 'creep' you get when in gear and it won't hold the car on a steep hill anyway, so you really need to learn how to hill start using either the hand or foot brake. (I'm actually a little surprised you got through your test without that being covered.)

[MikeSh]

On the basis of that, I'd say that the only small current gen car with a decent/pleasant autobox right now is probably the Yaris Hybrid. (Although it's starting to push the meaning of 'small' somewhat). Isn't cheap tho'

That's the catch though. People generally want a small car for economy, but if you take the TCO of a hybrid (given the scary purchase price and possibly new batteries at some point) running something less fuel efficient with a Borg-Warner type box could be cheaper, though possibly less eco friendly :(

Sadly, a really good automatic will never be cheap (though even the lesser ones can do a better job than some human drivers )

[Cyker]

Yeah... as soon as you go automatic there are compromises; Just having the autobox will increase initial purchase and maintenance costs right off the bat so if you're going for cheap it's already off on the wrong foot.

I don't know if people just buy small cars for economy tho'; On the 2nd hand market especially, small cars tend to cost more than larger hatchbacks or salons, at least round here!

I tend to stick to small cars just because I work in a city, and finding parking is so much easier, not to mention the narrowness of the Mk1 Yaris makes it much easier to navigate tight roads safely (One of my fav. shortcuts has a little section that's about 6ft wide for 20m; Everyone has to creep along it but I can go through it at 20mph without missing a beat :P

The biggest problem is the emissions legislation; It's basically killed off most autoboxes, esp. in small cars, apart from the godawful semi-autos like MMT and Tiptronic. The only one of those that doesn't totally suck is the VW DSG, but it's very expensive to maintain and repair (A mate says it cost his dad £6000 to repair when it started slipping on his Jetta! And I thought the £400-odd for my Yaris' clutch was bad ).

Torque converter autoboxs are very rare nowadays, and the only other type are belt-driven CVTs which I've seen more in the far east but seem to slowly be making their way back here.

Bah, gimme a manual any day of the week!