Pros/Cons of a fully auto tranny

[Keef]

I've driven a number of new Mazdas with electronic power steering and electronic throttles. I've driven a number of them after they've had quite a few miles and have improved response also. None of them are as satisfying to drive as my 1991 Mazda and I'm not sure they ever will be.

Fact is, the days of being connected to the car and physically controlling it are coming to an end. I can't afford to restore a classic sports car and drive it every day, so I own what I can. It may not be as convenient as anything on the market today, it may have some rattles and harshness, and the throttle might be tough to operate smoothly in a parking lot, but it is definitely a better driver's car than anything on the market now.

 

[Eric.]

As McLaren said, this is not the point of a rev limiter.



I suppose you don't have power steering.

No. The same analogy you're aiming for would be the same as taking a Logitech G25 steering wheel and pedals and having the steering send a signal to an electric motor which then steers as if you had a normal mechanical linkage to the steering rack. And then you don't have feedback, or maybe you have some artificial feedback where the steering system can also send a signal to the wheel to turn to match where the steering really is. So maybe it would feel close to right. Maybe.

The throttle part of the equation is easy. My Civic does it currently. Drive by wire throttle is becoming really common as the ECU can control emissions better. The cost is slower throttle response (isn't bad in my car, especially with a tune), and some unexpected side effects like rev hang and dulled response at a stop/low speed, which I assume is to make the throttle less touchy to take off. I dunno. Tunes do wonderful things though...

Drive-by-wire brakes scare me. Without any sort of redundant system to stop the car, brakes need to stay hydromechanical. There's no real benefits for it anyway apart from easier packaging.

And the clutch...I would assume there'd be some latency and would be hard to get used to, but I don't know for sure.



--------------------------------------------


Regarding miss-shifting.

I'm surprised no manufacturers have come up with a simple system that blocks out certains gears under whatever situations. Say I'm in sixth gear, cruising at 60mph in my Civic. That's somewhere around 2500rpm. I intend to shift to 4th to bring the rpm to about 5000, but I miss and get 2nd gear instead, and release the clutch. Valves, meet pistons (maybe, it'd be very close anyway...probably low 9000 rpms). But if there was a system that blocked shift gates that would cause an overrev, I'd have just saved myself some head work. That system would have only left 3rd and higher gears open.

 

[niky]

GM had "skip shift" for the Corvette. Admittedly, it was meant for something else, but a similar system would help prevent catastrophic 5th -> 2nd downshifts.

I've driven a number of new Mazdas with electronic power steering and electronic throttles. I've driven a number of them after they've had quite a few miles and have improved response also. None of them are as satisfying to drive as my 1991 Mazda and I'm not sure they ever will be.

I think Mazda is one of the few that actually gets e-throttles right.

As for steering, they're getting better. I think the electric rack in the Mazda3 was absolutely horrid. The first NC MX-5 was a little better... the Mazda6 was better than that, and the new NC MX-5 better than that...

The Mazda2 has brought it to the point where I honestly wouldn't mind trading in my Protege for one. Of course, it has to be on the right wheel package to pull it off.

 

[Keef]

I would have to try the newer applications. The Mazda 3's throttle I eventually got used to, though I prefer a cable. The steering was always a tad awkward but nowhere near as terrible as any GM application I drove, or my family's current Toyota.

 

[McLaren]

Actually, all a DSG can do is prime whichever gear (one higher or one lower) it thinks you might want next. So if you're accelerating gently, the next gear up is primed and it won't be able to shift down one as quickly. Especially if you're cruising, and it's shifting up as quickly as possible to save gas.

It can do that, yes. But it will also make sure you do not try to downshift into a gear you shouldn't.

I can sit there doing 35Mph, and try to shift down into 1st, my TL will stop itself, and remain in 2nd at most.

And a DSG will never be able to shift two down at once without some difficulty. And it will do it much slower than an average user. The one solution to this is "sports mode", where the DSG always resorts to the lowest gear possible.[/B][/COLOR]

A DSG may not. A DCT can with the right car, though it'll technically be doing it 1 at time. But, using the PDK in the Cayman S to downshift from 3rd to 1st, would take a good driver to beat. It's very quick.

 

[niky]

RE: Mazda3: the steering was one of the biggest complaints of owners upgrading from the Protege. Didn't help that Protege steering is near-perfect. But yes, the first-gen 3 was probably the worst of Mazda's EPS boxes.

A DSG may not. A DCT can with the right car, though it'll technically be doing it 1 at time. But, using the PDK in the Cayman S to downshift from 3rd to 1st, would take a good driver to beat. It's very quick.

I'll have to take your word for it on the PDK. The most performance oriented dual-clutch box I've driven so far is Mitsubishi's TC-SST. It can get the double downshifts right in "sports" mode, where it's primed to downshift every chance it gets, but in "normal", it's about as bad as most of the DSG/DCT boxes out there.

 

[homeforsummer]

Worth mentioning at this point that you should never change down to first anyway while you're moving so talking about the speed of 3-2-1 downshifts isn't really relevant? I expect even dual-clutch gearboxes only change down to first at literally a couple of miles per hour.

What they call them isn't the issue. It's that they don't understand how to yield to people. AFAIK, the person in the circle has the right of way, not you coming off the side street.

Correct. It's a fairly simple right-of-way system, no different than you'd get at a four-way intersection over there. Essentially, whoever gets there first has right of way, though on a roundabout you only really need to concentrate on the car coming towards you rather than the exits themselves.

Unless you're going around the notorious Arc de Triomph one in Paris of course, which like many other French intersections offers right-of-way to those driving onto the roundabout so cars on it have to slow down and let people on...

 

[eiriksmil]

Can I do a clutch dump in a DSG equipped car?

 

[Eric.]

GM had "skip shift" for the Corvette. Admittedly, it was meant for something else, but a similar system would help prevent catastrophic 5th -> 2nd downshifts.

And I hate it. My friend owns a C5 Corvette and I was driving it around town. At the speed I'd usually shift to 2nd in my car, the skip shift kicked in and would force me to go to 4th if I didn't pay attention and let it pass. Really, if I intentionally want to skip to 4th gear, I can do it myself, thanks.

 

[McLaren]

I'll have to take your word for it on the PDK. The most performance oriented dual-clutch box I've driven so far is Mitsubishi's TC-SST. It can get the double downshifts right in "sports" mode, where it's primed to downshift every chance it gets, but in "normal", it's about as bad as most of the DSG/DCT boxes out there.

I will be honest and say the PDK isn't too different in regular driving mode. And if you're ever trying to do some spirited driving in it, I would suggest never taking it out of sport mode. I had one instance during a test drive where the car actually downshifted during a turn (a nasty habit I'm sure you know if in autos), and the car started to lift-off oversteer when it did so. In sport mode thankfully, it held the gear.

Can I do a clutch dump in a DSG equipped car?

As long as the car is a CLK GTR?

 

[niky]

I will be honest and say the PDK isn't too different in regular driving mode. And if you're ever trying to do some spirited driving in it, I would suggest never taking it out of sport mode. I had one instance during a test drive where the car actually downshifted during a turn (a nasty habit I'm sure you know if in autos), and the car started to lift-off oversteer when it did so. In sport mode thankfully, it held the gear.

Ouch.

Can I do a clutch dump in a DSG equipped car?

Most won't allow it. Some will allow it with "launch control" or with ESC deactivated, but most won't. It allows manufacturers to claim a longer service life for dual clutch boxes versus regular manuals or automatics. Though whether this holds true remains to be seen.

 

[homeforsummer]

Most won't allow it. Some will allow it with "launch control" or with ESC deactivated, but most won't. It allows manufacturers to claim a longer service life for dual clutch boxes versus regular manuals or automatics. Though whether this holds true remains to be seen.

I expect that they're better, because releasing one clutch and engaging another in one swift move seems like a very unstressful process on a drivetrain, plus the fact that you can't dump the clutch, mis-shift or anything else that causes drivetrain stress.

I did wonder about clutch use in slow traffic though. Since most DSGs have a creep function, it's surely slipping the clutch to allow for this. Very low revs obviously so it won't be causing loads of wear, but I reckon the clutch-slipping thing is one of the reasons the Smart doesn't have a creep and why shifts are so tardy, to keep clutch stress to a minimum.

 

[Eric.]

I'd guess eiriksmil is meaning that in any gear can he rev the car up and dump the clutch, which the answer (and he knows it) is "No.".

 

[Keef]

I did wonder about clutch use in slow traffic though. Since most DSGs have a creep function, it's surely slipping the clutch to allow for this. Very low revs obviously so it won't be causing loads of wear, but I reckon the clutch-slipping thing is one of the reasons the Smart doesn't have a creep and why shifts are so tardy, to keep clutch stress to a minimum.

I have my own "creep" mode. It's called idle in first and breath on the brakes. No clutch slip. As long as you don't take it below 300 or so rpm it won't stall and will keep creeping at half the usual speed. That way I can go as slow as all the people in their automatics riding their brakes.

 

[niky]

I expect that they're better, because releasing one clutch and engaging another in one swift move seems like a very unstressful process on a drivetrain, plus the fact that you can't dump the clutch, mis-shift or anything else that causes drivetrain stress.

I did wonder about clutch use in slow traffic though. Since most DSGs have a creep function, it's surely slipping the clutch to allow for this. Very low revs obviously so it won't be causing loads of wear, but I reckon the clutch-slipping thing is one of the reasons the Smart doesn't have a creep and why shifts are so tardy, to keep clutch stress to a minimum.

They should technically be better... but complicated electro-mechanical systems tend to develop issues over time... I'm waiting to see where this latest generation goes...

About the creep... most tend to disengage the clutches completely when the revs and speed get low enough, and clutch engagement doesn't seem to include a lot of slip (electronic throttles help mediate this, also), but I must admit, I don't really pay that much attention when I drive them.