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ValgardForkbeard

smart shifting

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A number of articles and reviews I have read all comment about the shifting in the smart cars. "...unlike the annoyingly jerky sequential six-speed in the Smart." Toronto Star about the Insight

I have had my smart since May, and have driven about 12000km in it, and don't really see the problem with the shifting. At times, I wish it would downshift a bit faster, but the upshifting is no worse than a manual with a clutch, and is less jerky than the automatic transmission in my Plymouth Voyager.

I will admit that it did seem to smooth out quite a bit after 5000km, so is it just that the reviewers are all driving low mileage cars, or am I just too easy to please.

Comments, anyone.

MG

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Ever driven it in automatic mode? It is the very definition of "jerky".

Even in manual mode, the transmission does seem to take it's sweet time with shifts. Jeremy Clarkson on Top Gear made some funny comments on it... at the end of this clip he called it "the Hugh Grant of gearboxes" (in reference to the one in the Roadster, which certainly can't be an worse than ours)... you have to watch the clip to get it.

darren.

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It's true; only the clumsiest driver of a manual gearbox would shift as poorly as the smart fortwo does. It's one of the car's quirks, and I love it. ;)

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A lot of people find it jerky. I think us drivers can get used to it pretty easily though.

The auto on 2005s seemed to be jerkier than the 2006 models. (Or at least between the two demos we test drove)

Sometimes when I drive the car shifts really smooth, but most times it does lunge forward a little bit. Makes me wonder if it has anything to do with how far the accelerator is towards the floor.

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I don't have the auto (soft-touch?) mode, so other than the demo I drove, I haven't any experience with the car shifting itself. I let up a bit on the throttle when I shift, and it seems fairly smooth. Maybe sometime I will arrange to ride with someone else, and compare.

MG

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is the schmart gearbox really smart? when i drive aggresively the computer shifts just before the redline and i think it actually does a better job than me?

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is the schmart gearbox really smart? when i drive aggresively the computer shifts just before the redline and i think it actually does a better job than me?

My contention is that the auto-shift map appears to be designed for the higher-revving petrol engine and is not suitable at all for our higher-torque, lower-rpm cdi. Smart just never bothered to tailor a second map for the Diesel - it's just a lazy copy-and-paste.

My opinion, FWIW.

Bil :sun:

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It's quirky, and not to be taken for a drive sloppily. If you drive the smart sloppily, the car performance suffers. I still cannot claim I drive the car 100% correctly, and I have 90,000 kms chalked up.

I was asked to give an impression of the car for a Wisconsin newspaper. I spoke of the quirky transmission.

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I really like the smart 6-speed transmission... my Pulse (paddle-shifter) is easy to compare to the Porsche Tiptronic and Subaru 4EAT boxes (both of which I have considerable experience with), and the smart does just fine, at a fraction of the price.

Compared to the latest Audi DSG box, the smart tranny is a clunker, but then it is a 'way older design, and a sliver of the price of the Audi bit.

I agree that the 'soft-touch' auto-box in a smart does deliver abrupt shifts that detract from the pleasure of driving the car.

:drive:

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The funny thing is that Getrag is famous for it's gearboxes. I wonder why they settled for an imperfect setup on the smart?

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I don't think it's necessarily the gearbox itself that's slow, but the software that controls it.

A gearbox is just a box of gears... i'm not sure how it could be "slow" unless the hardware for actuating each gear is poorly designed. And since ours is electronically controlled, my guess is that the lag between sending the signal to change gears and the actual engagement of the selected gear is due to a lag in the electronics.

Though i could be wrong.

darren.

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The funny thing is that Getrag is famous for it's gearboxes. I wonder why they settled for an imperfect setup on the smart?

I remember (hey that's really authoritative, eh?) reading that Getrag was constrained by a tight budget from smart. Like, "Here's what we want from Getrag but you only have [this much] money to build it."

B:sun:

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I don't think it's necessarily the gearbox itself that's slow, but the software that controls it.

A gearbox is just a box of gears... i'm not sure how it could be "slow" unless the hardware for actuating each gear is poorly designed. And since ours is electronically controlled, my guess is that the lag between sending the signal to change gears and the actual engagement of the selected gear is due to a lag in the electronics.

Though i could be wrong.

darren.

I don't think it's to do with the electronics. The mechanical design of the gear change function will always have a limitation - the speed of the gearmotor which drives the shifting cam drum, and the profile on that cam drum.

The gears are selected by three arms which have a cam follower that rides in three slots on a drum. The drum has profiles milled into it (cam profile)... as the drum rotates, the arms follow a predefined pattern. The arms engage or disengage sliding clutches between the various gear pairs. The selector drum itself is driven by a small gearmotor with a pot on the end for position feedback (not quite a true servo). The speed of that motor is always going to be limited... but software tweaks to when the clutch opens and closes etc. I think are how some of the remaps are removing the "The whole world stops! I forgot I'm a gearbox!" effect. Steeper profiles on the cam (or a faster motor) would mean slightly faster gear changes but you'd need a bigger motor. So I totally buy the fact that Getrag was working with a limited budget and this is what they came up with. I really like it. When I don't like it is when I'm in the middle of an intersection and I hammer it and get no power for 8 years while it tries to remember what it was in the middle of doing. :)

I have a 21 page document from Getrag in German that I started to translate a while back using an online translator, but it was taking forever and I hate word processors. If I had somewhere to upload some HTML I'd consider posting it that way...

-Iain

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Getrag makes poor manual gearboxes too; the 6 speed manual in the RWD Mercedes C-Classes are crap.

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Getrag makes poor manual gearboxes too; the 6 speed manual in the RWD Mercedes C-Classes are crap.

What specifically gives this box an "crap" rating?

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OK

The Smart changes are a characteristic of the car. But I have just noticed something after I have been driving her for a year. I never could get really comfortable with the Forward for gear up and so have almost exclusively used the paddles which I love. My little finger has the power! The other night just for kicks I tried out the floor shift and I imediately noticed that the shifting seemed smoother! My passanger also commented on this. Has anyone else witnessed this? Try it for yourselves and tell me if I'm full of it or is there some different sequence involved here.

2seat

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Gang...

I'm heard this a lot about rough shifting, but I'm not actually convinced the shifting is any worse in auto mode than in manual mode. In fact I think it's indentical.

Try this. Have another person drive your car, cover your eyes and have them use both soft tip and soft touch. (works better with paddles so you don't hear the shifter) To be fair, have them shift at about the same points manually as soft touch would, including reving it too high and downshifting too early, etc. What I found is I couldn't tell if it was the car shifting or the human, even though the human driving thought the car shifted more abruptly in auto mode than they did.

I think it's just a) the car is shifting when you don't expect it to because you aren't controlling it and B) the shift points programmed into the auto mode are poor, causing it to shift up at a high RPM (or not at all) and down shift earlier than a human, and the high RPM causes it to be less smooth. I guess you could argue the choice of shift points make the car change gears rougher in auto mode, but what I mean is if you manually change gears the same way the auto mode does, the car shifts the same. This makes sense if you think about it, and also means if they (smart themselves or some smart aftermarket guy) could reprogramme the shift points it could make the auto mode actually useful.

I'd be curious for some one else to try the same experiment to see if they think the same.

Later!

Dang

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In my car, the automatic mode shifts at much higher RPM than i do when shifting manually. The result is a pronounced "lurch" with each shift.

darren.

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Rough shifting is getting a bad rap.

Smooth shifting is all in the right foot of the driver.

A light foot and some practice is all it takes to let the transmission shift as smooth as silk.

When in softouch, watch the rpm and as you approach the shift point for an upshift, ease off on the fuel.

When is softtip, use your right foot to ease off or blip it slightly on a down shift.

With a bit of practice and getting rid of the heavy foot, you will be shifting smoothly and most of the time won't even know it has shifted.

Learn to be is sync with your car.

Get the feel for the transmission.

Learn to help it ease into gear changes rather than fight it.

In a very short time anyone can make shifts so smooth that a passenger wouldn't even know you had shifted.

There is nothing wrong with the transmission when driven relaxed and don't expect or try to make it perform like a hot rod.

Lurching and diving is only in how you drive the car.

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The lurch is largely the fault of the soft suspension. I purchased one of the stiffest suspensions available for the car before I got the remap done, and that made a huge difference in my enjoyment of the car. Hard shifting at high RPM became very smooth as the rocking horse motion was minimized.

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And what Fred says is true as well - you can 'learn' to drive the car effectively, but I find it does take quite a bit of effort... ie: you cannot be sloppy.

I suppose my own sloppiness is the real issue, not the way the tranny behaves...

The other issue I find I struggle with is gearing down while coasting, and ending up in the correct gear when rounding the corner or advancing on the green or stop sign.

As a typically low revver, I often find myself coming to a turn in 5th, and needing 2nd around the corner... but three taps on the paddle or shifter DOESN'T always do the trick.

The car may have autoshifted one gear on me on top of my three, or my light tapping on the paddle may have only set off two gear changes, or even yet, it may still be in-between gears when I try to accelerate.

In one case I'm lugging, in another I'm revving too high for my liking, and in the last instance, I have no power, and then the car can really be a nuisance at that point.

It is a quirky transmission IMO, but I don't hate it. I accept that my style of driving will result in some additional quirkiness...

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Gotsmart.....

Right, I agree with you that the automatic program does shift too high, and shifting at a high RPM tends to make the lurching worse, but still don't think there is anything in the automatic mode that makes it worse. In other words, if you manually shifted at the same high rpm it would be just as bad.

As Fred J says you can make it shift smoothly. In fact I don't mind the way the automatic mode shifts at all. What I don't like is the fact it won't shift until such a high rpm. It will happily go down the road at 3,000rpm all day and never try to shift. I'd probably use it if someone could change that so it worked more like a normal automatic, and shifted to the next higher gear whenever the load dictated it could. I'm sure smart was trying to get around the driver letting off the throttle, the car shifting, then the driver stepping on the throttle again and having to wait while the car downshifted. There should be a compromise between the two. I have Eibach springs, so the rocking motion is all but gone, but it never bothered me that much with the regular springs.

Also, I don't like the way the car downshifts in auto mode. As you are stopping for a light, it attempts to downshift through each lower gear to a higher RPM which makes the process very jerky. In manual mode it will let the rpm's drop much further, and there isn't really any jerkiness unless you are slowing down very gradually.

Here's hoping some brilliant remap guy can figure out how to reprogram the transmission!

Later!

Dang

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In a related matter, the smartarse company has put out a performance clutch for the 600 and 700 cc models. Looks like they increased the spring strength and made the friction plates more "grabby". The end result is shorter shift time.

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Duck, I think I have the same German Getrag PDF file.

Here are some of the pictures from it...

post-74-1162424368.jpg

post-1-1162424368_thumb.jpg

post-1-1162424369.jpg

post-1-1162424370_thumb.jpg

post-1-1162424371.jpg

post-1-1162424372.jpg

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Yeah - I just didn't post them because I didn't want to get into trouble with copyright issues or whatever. :P

-Iain

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