General > General Technical Chat

Full-self-driving needs external infrastructure

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tom66:

--- Quote from: james_s on March 09, 2023, 07:54:48 am ---
--- Quote from: tom66 on March 08, 2023, 11:34:17 pm ---Besides, on my automatic car there exists a manual mode and it behaves much like a manual car. It will even let you hit an electronically limited red line and won't shift up unless you sit at that red line for more than 10 seconds or so (probably just component protection at that point!)  About the only thing it won't let you do is destroy your engine/gearbox by shifting into the wrong gear, but I'm not sure anyone wanted that feature to stay :).

--- End quote ---

A manually shifted automatic is pointless. You have all the mechanical and hydraulic complexity and weight of a slushbox and no clutch pedal so you lose that aspect of control which is hugely beneficial in snow and ice. It's kind of the worst of both worlds, may as well just have an automatic at that point. You'd have to try pretty hard to shift into the wrong gear and destroy something, if you try to for example shift a manual gearbox into 2nd gear at highway speed it won't go in, unless maybe you force the lever really hard and get the synchro to spool up the input shaft. These manual modes are toys for people that want the video game experience, it is totally different than driving a real manual, it's not even close.

--- End quote ---

Nope, it's a dual clutch transmission.  Think of it a bit like two manual gearboxes bolted together with an electronically actuated clutch on each to select the relevant gear.

In general the arrangement is one shaft has R, 2, 4, 6 and the other has 1, 3, 5 and maybe 7.

The gearbox computer preselects the next gear when you are accelerating.  For instance in gear 3, the actuators have selected 4 on the 1st shaft, so all that happens when it changes gear is the next clutch actuates instead.  This also works for downshifting.  You might be cruising in 6th (top gear on my car), in which case 3rd is preloaded on the alternate shaft, and if you gun the go pedal it will jump straight to 3rd.

The DCT can shift faster than even a trained manual driver and on the hybrid models the gear RPM matching is done with the electric motor to further speed up the change.

I can't see why you'd want to slip the clutch in snow and ice.  If you need less torque you can force the car into 2 or 3 and then just press the go pedal less.  I found electric only operation to have the best performance here as the traction control can modulate the torque more quickly and over a wider range.  Obviously not all vehicles have that but the car can modulate the clutches just like any other manual, it does that when you're parking at low speeds if the engine is running.

pcprogrammer:

--- Quote from: james_s on March 09, 2023, 08:19:03 am ---
--- Quote from: pcprogrammer on March 09, 2023, 08:02:27 am ---Unless your gearbox has a lot of wear.  >:D

I had that long long back with an Opel Kadett, I wanted to shift up, but got the reverse.  :-DD  Was easy to fix. Got a second hand gearbox from a scrapyard and replaced it myself.

--- End quote ---

Most of the cars I've spent a significant amount of time driving have been Volvo and Saab. For many years Volvo has a collar you have to pull up in order to shift into reverse and I forget what the Saab had (it's been almost 20 years) but there was some kind of interlock, I have never managed to shift into reverse accidentally but I suppose anything is possible. Reverse on the cars I can think of is way over in the upper-left, so nowhere near any of the gears I'd be using at speed. I know there are some other shift patterns out there though.

--- End quote ---

Can't remember what protection should have been on it, but our new Ford Fiesta has the reverse in the bottom right, but you have to pull up a collar to do so.

Might also have been going down to a to lower gear. It's over 40 years ago, and all I remember is a big bump and bang and no more drive on the wheels. Can't recall how we got it back to my parents house. Do know it was half way between where I lived at the time, and their house. My dad had all the tools needed to do the repair.  :)

nctnico:

--- Quote from: EEVblog on March 08, 2023, 10:27:12 pm ---
--- Quote from: james_s on March 08, 2023, 05:57:00 pm ---What effort? It's like walking, once you know how to do it you don't even think about the mechanical process, it's effortless. It's only when you go and drive an automatic car that it feels so incredibly boring and soul-less, you have less control, you have less engine braking, it feels slushy and mushy, less power, lower fuel economy, with an automatic you're not really driving so much as just aiming. I'm also a big fan of the mechanical simplicity of a manual gearbox. It's much smaller, lighter, simpler, there are no cooling lines or heat exchanger, no clutch packs or valve body, no electronics, it can go hundreds of thousands of miles without so much as a fluid change. When you do have to remove it for something such as to replace the clutch, it's so much easier to handle than a big bulky heavy slushbox.

But like I said, vast numbers of people are in your position and have never driven a manual in their life, they don't know what they're missing.

--- End quote ---

You are projecting your desires onto others, that doesn't work.
Some (most?) people just want to get from A-B

--- End quote ---
I agree. In general I think an automatic gearbox is just more comfortable. But there are some nuances. From my limited experiences with automatic gearboxes in cars I can say some are utterly horrible (like the 2003 VW Passat) and having a manual gearbox definitely is better. More recently I drove around in a nearly new Nissan Rogue (rental) and the automatic gearbox worked just fine. Except when going dowhill; I needed to manually change the gear to get enough engine braking. It shouldn't be hard to add a feature that does that automatically as well?

bdunham7:

--- Quote from: james_s on March 09, 2023, 07:54:48 am ---A manually shifted automatic is pointless. You have all the mechanical and hydraulic complexity and weight of a slushbox and no clutch pedal so you lose that aspect of control which is hugely beneficial in snow and ice.

--- End quote ---

I and many people my age have had plenty of 'exposure' to manual transmissions and most still prefer a good automatic transmission in almost every case.  If you don't get the point of  a 'manumatic' (a feature rarely used but very handy when applicable) I'd have been content to just let you have your opinion until you mentioned snow and ice.  All I'll say is that anyone with snowplowing experience (light duty pickups, not the large dump trucks) wants an automatic, even a crappy one.  And that's not due to lack of exposure, experience or skill.

I do take exception to your worn out 'slushbox' insult.  Yes, if you were comparing the transmissions available on a 1970's Volvo, the 3-speed automatic could fairly be called that.  But if you compare the agricultural 4-speed manual in the old Porsche 930 Turbo with a Tiptronic in a 997, well... :) .  Modern 'good' automatics shift quicker than your left toes can twitch and do it with no loss of torque continuity.  That can be a big deal.

james_s:

--- Quote from: tom66 on March 09, 2023, 08:27:05 am ---Nope, it's a dual clutch transmission.  Think of it a bit like two manual gearboxes bolted together with an electronically actuated clutch on each to select the relevant gear.

In general the arrangement is one shaft has R, 2, 4, 6 and the other has 1, 3, 5 and maybe 7.

The gearbox computer preselects the next gear when you are accelerating.  For instance in gear 3, the actuators have selected 4 on the 1st shaft, so all that happens when it changes gear is the next clutch actuates instead.  This also works for downshifting.  You might be cruising in 6th (top gear on my car), in which case 3rd is preloaded on the alternate shaft, and if you gun the go pedal it will jump straight to 3rd.

The DCT can shift faster than even a trained manual driver and on the hybrid models the gear RPM matching is done with the electric motor to further speed up the change.

I can't see why you'd want to slip the clutch in snow and ice.  If you need less torque you can force the car into 2 or 3 and then just press the go pedal less.  I found electric only operation to have the best performance here as the traction control can modulate the torque more quickly and over a wider range.  Obviously not all vehicles have that but the car can modulate the clutches just like any other manual, it does that when you're parking at low speeds if the engine is running.

--- End quote ---

Yes I'm familiar with the DSG, I've driven a VW that had one. Most of the manually shifted automatics I've driven have been of the conventional type or worse, a CVT. At least the DSG is nice and crisp.

I suspect you've never driven a manual in snow and ice or it would be very obvious why I'd want one. One specific trick I've used quite a few times is when I find myself unable to get over a hump like the snow that has built up in front of my stopped car, or the hump of a curb to get into a driveway is to ride and pulse the clutch such that the car rocks forward and back, the rocking motion gets larger and larger until there is enough movement to crest the hump and then you're off, I'm not aware of any way to do this in an automatic. Another big advantage is in a situation where engine braking causes the wheels to slip and slide, if you push in the clutch the drivetrain is instantly disconnected and the car will straighten right out. This works on wet roads too if the rear end starts to slide out, at least on RWD cars.

I've driven everything, manual, automatic, automatic with lockup torque converter, DSG, CVT, RWD, FWD, AWD, gasoline, diesel, hybrid, several EVs, and everything from subcompact to large commercial trucks, antique to modern and for all of the ICE options the plain manual is far superior to me.

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