[Akshay1234]

Originally Posted by Harbir

I am not an AT expert by any means, but I would conjecture that in the accord, the torque converter is unlocking (by design or failure) in the situation you describe but the BMW's is not. You have to keep in mind that the locking converters are unlocked a portion of the time. The slushy effect is often apparent in cars with locking TQs.

Guess thats probably right, but quite silly of Honda. They still do it.

On another note, check this. I was shocked for a second when I saw SMG. Didn't think non Ms had it. This might be a fun car eh? Not as good as a manual, but still better than a slushbox. What say?

http://classifieds.team-bhp.com/buy-...3-Series.html/

[Harbir]

What a surprise to see that in India!

You're right, non M BMWs did not have SMG. for about a year in 2003 and early 2004 BMW made some E46 non M cars with a transmission called the SSG (sport sequential gearbox) that they labeled SMG on the cars themselves.

Like the true first generation SMG, the SSG was the EXACT SAME manual gearbox used in the manual transmissions version of the cars they were fitted to (the 5speed in the non M and the different 6 speed in the M3) , but with electrohydraulic systems to operate the clutch and the shift forks. (This is very different from later automated manuals from BMWs and others - DCT, DSG, etc - which have been designed with the shifting mechanisms internal to the gearboxes and are very different in design from the manual transmission in the same cars).

The normal D mode (C in this case, for cruise) is the fully automatic and its terrible. this is the first generation automated manual, and the electronics and programming are very simplistic. These are NOT good to drive as full automatics. slow and jerky shifts. They are OK in normal driving if you choose EVERY shift yourself. Unlike the true SMG from the M, the SSG does not have the rapidfire shifting capability so while the SMG is also not very good in full auto modes and normal driving, it is brilliant under hard driving, but the SSG is not.

Really, its not good as an automatic or as a manual. but it was no issue because it was an early effort. But 9 years on, its best to stay away from the SSG cars like this one. As much as I hate slushboxes, in this case, I'd pick one over this.

[sgiitk]

The bottom line is that there are areas where you need a 'slipping clutch' for driving at low speeds, esp stop and go, and also for smooth shifting. You do not want this to increase consumption at higher speeds. There are many ways to bell a cat, each with its own plus and minus points. If one was far superior to the others then everybody will have switched to it.

[d_himan]

Originally Posted by Harbir

the absence of the "jerk" is because of the torque converter. I think lots of people don't understand what exactly that is.

Superb post Harbir. Thanks! Just have a couple of points to make:

a. Once the torque converter 'locks up', I believe the the RPM drops as per engine speed when the foot is completely off the accelerator.

i. In case of my ancient Accord 4AT, this happens only if I drive at 70/80 kmph for a couple of minutes.

ii. In case of my i10 AT, this happens a bit more frequently at lower speeds as well. Not sure why this is so.

b. The ATF is a super critical component of an AT gearbox. The higher the operating temperature, the quicker is the damage to internal components.

I think the service change intervals provided by the manufacturers here are very optimistic. I do a single Drain and Refill every 10K.

[nithi]

Originally Posted by sgiitk

The i10/i20 do with a 3+1 as does the Dzire eCS. The last surprised me since the AStar has a proper 4-speed.

Can you please explain the difference between 3+1 and 4 speed Auto?

+1 refers to overdrive in 3+1 auto. right? Overdrive is only a term that says the engine RPM is less than the wheel's RPM. Please correct me if I'm wrong. So, 4 th gear in 4 speed auto also will be a overdrive. right? So, what is the difference between 3 + 1 and 4 speed auto? Sorry if this has been already discussed.

[sgiitk]

3+1 means that the 4th gear is not fully integrated into the AT but is an add-on to a 3-speed box, while a 4-speed will be properly designed and integrated.

Overdrive traditionally referred to a manual transmission which was not 1:1, today hardly any is? So in principle almost all manual transmissions are overdrive! Normally there is a further gearing of (typically 3:1 to 4:1) to get at the tyre / wheel speed. This is the drive ratio! Also, you could buy an overdrive (normally fixed to the rear axle) which added more gears (typically on 3 & 4 only, so two gears) when switched in, normally with an electric actuator switch.

[Mpower]

Originally Posted by sgiitk

3+1 means that the 4th gear is not fully integrated into the AT but is an add-on to a 3-speed box, while a 4-speed will be properly designed and integrated.

Overdrive traditionally referred to a manual transmission which was not 1:1, today hardly any is?

So in principle almost all manual transmissions are overdrive! Normally there is a further gearing of (typically 3:1 to 4:1) to get at the tyre / wheel speed. This is the drive ratio!

Also, you could buy an overdrive (normally fixed to the rear axle) which added more gears (typically on 3 & 4 only, so two gears) when switched in, normally with an electric actuator switch.

I have not seen any other publication use this 3+1 terminology so I think we should refrain from using it. There is no evidence to suggest that Hyundai started with a 3 speed and added a 4th. Even if they did, functionally there is no difference

Its like saying a Jetta is a Golf with boot attached but a Civic is a sedan from the ground up and therefore Civic is better.

Quanto 3cyl engine is a Mhawk? with once cyl removed. So are we supposed to call it a 4-1? We could and we'd be right but it does not indicate anything thats significant in any way

As long as its transparent to the customer and there are no functional deficiencies, it makes no difference.

Overdrive is used to describe not a transmission but a specific gear like 5th or 6th.

The switch that you are referring to is for a electronic 2 speed transfer-case.

[supremeBaleno]

^^^Yes, I agree. I doubt MSIL will give a proper 4-speed AT in a lower-priced car like A-Star, but give an inferior transmission in the costlier Dzire-AT. IMO both are 4-speed ATs with the Dzire just having a simpler/quicker way to switch off overdrive when needed (for eg. while overtaking).

[Jaggu]

3+1 first time i am hearing this? I thought the GB has a set number of ratios, indicated by 3,4,5,6 etc. The last one or sometime even two (for box with many gears) are mostly OD. If cars have a OD button in the shift system, it just controls how the OD ratio works. Just like a D or 2D position.

In Santro its a 4 speed box, which has the 4 the gear as OD if am not mistaken. The OD button just decides if the vehicle can shift to the 4th gear or not, just like the D and 2D positions below that for low gears?

[sgiitk]

Originally Posted by Jaggu

In Santro its a 4 speed box, which has the 4 the gear as OD if am not mistaken. The OD button just decides if the vehicle can shift to the 4th gear or not, just like the D and 2D positions below that for low gears?

Not exactly. No reverse engine braking on downhill, and also 'hunting' between 3 & 4 in the 60-70kph range (at least in my Santro). I got so fed up I just disabled 4th. So the integration is not good, typical of a grafted on ratio. Never seem hunting on any of the lower three. Remember I have had to car for 7 years so should know. Before that I had a Zen with a three speed AT, never any hunting there either.

The problem may be similar in the Brio, reverse braking may only be available in 1 & 2. I doubt whether they will have put in grade control. Also, whether the torque converter lock is there. But then it is a box derived from the City, so one has to see.

I do not expect the same sophistication in a cheaper box as in the expensive box. Even the Dzire AT has a similar box, even though the AStar has a proper four speed.

[Jaggu]

Originally Posted by sgiitk

Not exactly. No reverse engine braking on downhill, and also 'hunting' between 3 & 4 in the 60-70kph range (at least in my Santro). I got so fed up I just disabled 4th. So the integration is not good, typical of a grafted on ratio. Never seem hunting on any of the lower three.

Absolutely no issues in our car Santro AT, just checked, and i really don't think it takes 60-70 kmph for the box to shift to 4th gear, i feel this happens as low as 40-50 kmph. The sweet spot as indicated in the speedo is also somewhere near 50 kmph, iirc. I think you should get the car checked. EDIT: This is normal driving mode, not toooo sedate nor too aggressive. EDIT 2: Returning 9 kmpl in BLR choco bloc roads and with short trips

Engine braking is less, but this is true in any selector position. Atleast that is what i feel compared to a manual car, be it BMW or Santro.

[sgiitk]

@Jaggu; I am selling it in about 10 days. I get about 9.5 in town with AC and 10.5 or so without. My car does not have a tacho so cannot judge the gear, have tried switching the OD off and on with no change in engine note. So expect that it was in 3. As for the indication (red mark) on the speedo it is the same on the MT and AT.

Engine braking is less, but this is true in any selector position. At least that is what i feel compared to a manual car, be it BMW or Santro.

There is no engine braking unless you are in 2 or 1. Definitely not in D. Even my Civic has no engine braking in D (I hear that Grade Control comes in on slopes, but have not tried that out as yet). Almost all AT boxes have no engine braking in D. The result is a higher brake wear. I remember in my student days the AT versions often came with uprated brakes.

Remember I have owned at least one AT since 1999. Even, before that I have driven hired AT cars.

[Jaggu]

Originally Posted by sgiitk

@Jaggu; I am selling it in about 10 days. I get about 9.5 in town with AC and 10.5 or so without. My car does not have a tacho so cannot judge the gear, have tried switching the OD off and on with no change in engine note. So expect that it was in 3. As for the indication (red mark) on the speedo it is the same on the MT and AT..

Our car also does not have tacho, but one doesn't need tacho to really make out the difference. With the K&N intake the higher rpm note can be easily understood. I guess if you do slightly higher speed with OD off, the engine tone will definitely be different. I have tried this in 2D but not with OD. I will check that and confirm.

Maybe Samurai, the previous owner who has better experience can confirm.

[Harbir]

Originally Posted by sgiitk

3+1 means that the 4th gear is not fully integrated into the AT but is an add-on to a 3-speed box, while a 4-speed will be properly designed and integrated.

respectfully, and regretablly, I must challenge you on this. I have tried repeatedly to get you to clarify your meaning but now I must bluntly say that you are not only spreading misinformation on this point, you continue to do so without acknowledging the questions raised about statements you keep making about 3+1.

• You have not shown that the 4 speeders are in fact 3 speeders with a 4th added but "not fully integrated".

• you have not shown that a 3 speed with a 4th "added" to it is different in behaviour and performance from a box that was designed as a 4 speed.

• You have not shown what "not properly integrated" means in engineering terms.

• You have not shown what mechanical behaviour of an "add on improperly integrated 4th gear" causes it to behave differently on engine braking from a designed in 4th gear.

• You have no shown that the behaviour you attribute to "3+1" gearboxes is not due to the torque converter issues of inexpensive gearboxes as I explained earlier, but due to the "not properly integrated" 4th gear.

I apologize that I am find myself being forced to be so blunt, but since what you are saying is incorrect, and you continue to repeat this wrong information despite the efforts to correctly explain why various ATs behave as they do, I am forced to choose between being respectful on one hand, frankly opposing information that I believe is misguiding this community on the other.

It should also be mentioned that any transmission gear ratio that is 1:1 is a "direct drive" ratio, and any ratio that is taller than 1:1 is an overdrive ratio. The switched in external overdrives are a long obsolete design. Today, a 5 speed manual transmission will typically have a direct drive 4th and an overdrive 5th. 6 speeders can have direct drive on 4th (making 5th and 6th overdrives) or on 5th, making 6th the overdrive. In some cases, there will be no direct drive ratio. 4th will be a little shorter than 1:1 and the higher ratios will be overdrive. To be over driven means the output shaft rotates faster than the input shaft.

And the i10 4 speed AT is a true overdrive. Its 4th gear ratio is 0.71:1. This is a very tall ratio indeed, and explains why the i10 downshifts to third so much at high speeds. the engine just does not have the torque to drive such a tall ratio effectively in high power demand situations, causing the transmission to downshift to 3rd.

The difference from 1st to 4th is so wide that the gaps between adjacent ratios is forced to be large because there are only 4 speeds. This results in the car either being in too low or too high a ratio for many circumstances. This is why I had such high hopes from the 5 speeder in the Brio. But even if its performance is weaker in a straight line, 5 speeds should mean shorter gaps between ratios, leading to a smoother, more efficient operation.

[noopster]

^^ I think we are over complicating things. Which is not surprising, because this is what Wikipedia has to say:

An overdrive (OD) is a mechanism that allows an automobile to cruise at sustained speed with reduced engine RPM, leading to better fuel economy, lower noise, and lower wear.

Use of the term is confused, as it is applied to several different, but related, meanings.

It goes on:

The most fundamental meaning is that of an overall gear ratio between engine and wheels, such that the car is now over-geared and can no longer reach its potential top speed, i.e. the car could travel faster if it were in a lower gear, with the engine turning more quickly.

This is exactly the meaning that I subscribed to, before this talk of 3+1 threw me (and others) in a tizzy.

But then, reading on...

In the era of front-engine, rear-wheel drive layouts, the device for achieving an overdrive transmission was usually a small separate gearbox, attached to the rear of the main gearbox and controlled by its own shift lever or electrical actuation button. These were often an optional extra on some models of the same car. As popular cars became faster relative to legal limits and fuel costs became more important, particularly after the 1973 oil crisis, the use of 5-speed gearboxes became more common in mass-market cars, with the 5th gear being an overdrive, eliminating the need for a separate gearbox.

With the popularity of front wheel drive cars, the separate gearbox and final drive have merged into a single transaxle. However the fundamental meaning, that of an overall ratio higher than the ratio for maximum speed, still applies. Although the deliberate labelling of an overdrive is now rare, the underlying feature is now found across all cars.

Dr. SG, unless there is some evidence that Hyundai uses a different setup for the i10 (the 3+1 theory that you subscribe to), Occam's Razor rules. The i10 AT is a 4-speed gearbox with 4th gear being overdrive.

I drive a 6-speed Vento AT. I believe the 5th and 6th gears are overdrive. Which means accelerating further in these gears is pretty tough. I accept this and downshift to 4 or below when I need a spurt of aceleration: to overtake, for example.

Engine braking is abysmal in my car in D as well. But that is because of the car's inherent tendency to upshift when you ease off the accelerator as opposed to a manual transmission car which slows down when subjected to similar input. This is probably ECU-driven to ensure higher FE figures (I may be wrong here). There are some ways around it:

• Sport (S) mode, which offers the ability to "hold" a gear and avoid upshifts
• Manual mode (tiptronic/paddle shifts) where available.

Over 30,000 km of driving my own AT around, I realised that I was subjecting it to unnecessary brake wear by using D almost all the time especially in city stretches where stopping from speed is required, e.g. between signals. Or on country roads here you need to slow down every time a hamlet appears but cruise otherwise. Hence nowadays I have started using the tiptronic mode to downshift in such situation rather than stomp the brake pedal.

If I'd realised this earlier, maybe I'd have extended my brake pad life beyond the 29,000-odd that I had to have them changed at.

The point is, this is standard AT car behaviour. What does 3+1 versus 4 have to do with it?