[CrAzY dRiVeR]

Originally Posted by fz_rider

Maruti, Tata and Mahindra will be churning out AMT's in near future. Though it won't be a problem on small naturally aspirated engines, due to use of Turbo, I'm a little skeptical how AMT will work with diesel (and turbo petrol) engined cars. Also, C segment onwards deserve conventional automatics.

I think it would suit a diesel better. More torque so it can hold ratios longer rather than shifting down, all the while not compromising on high FE they are known for! Also, a major drawback for diesel automatics have been their high sticker price, and this is solved with AMT.

Turbo petrol- I am not sure. They are meant for having fun. Forget AMT, forget regular slush boxes, a DSG is just what the doctor ordered.

[Mpower]

Originally Posted by amulu10

The article doesnt say that. This is something I got to know with GM being one of our customers. Sure you can do cylinder deactivation with DSG but apparently the torque converter is the best in terms of NVH. Just think about it ? The torque converter would dampen the vibrations that arise due to sudden deactivation of a few cylinders. DSG would probably end up with a lot of reliability complaints especially at the torque produced by a Z06 engine

We are digressing but the Corvette M/T also features AFM so don't think that's the case here. Secondly a V8 running on 4 cylinders is much smoother than a 4 running on 2!
I agree that an unlocked T/C is very effective in absorbing torsionals but its not prudent to employ that strategy anymore in today's efficiency conscious times. Many T/Cs today are using external dampers & CPAs.

Originally Posted by amulu10

This is kind of what I meant. What I meant was while the gears themselves might shift quick , the response i.e lag between you pressing the gas pedal and the vehicle actually moving forward is quite different from a automatic and a manual "clutch based"( includes manual as well as DSG and AMT). It takes a little longer to get the same torque transfer with torque converter as opposed to a clutch.

OK so you are talking about launching from a stop? That's a totally different scenario and involves no shifting because 1st gear is already pre-selected.

Automatics w/ T/Cs have lag because they are tuned to achieve a smooth launch feel. In addition keep in mind any AT will benefit from much faster reaction times.

[amulu10]

Originally Posted by Mpower

We are digressing but the Corvette M/T also features AFM so don't think that's the case here. Secondly a V8 running on 4 cylinders is much smoother than a 4 running on 2!
I agree that an unlocked T/C is very effective in absorbing torsionals but its not prudent to employ that strategy anymore in today's efficiency conscious times. Many T/Cs today are using external dampers & CPAs. BTW, I work in the same field as well
OK so you are talking about launching from a stop? That's a totally different scenario and involves no shifting because 1st gear is already pre-selected.

Automatics w/ T/Cs have lag because they are tuned to achieve a smooth launch feel. In addition keep in mind any AT will benefit from much faster reaction times.

True that it is also there in the manual which happens to be the first manual car with such a technology. I do agree that the V4 mode is certainly "more" smooth than a 2 cylinder mode on a 4 cylinder but I am talking about the transitions between the modes which causes the vibrations.True that the M/T would have the same problem as the DCT with the deactivation technology but at least from the press releases , this seems to be the reasoning for the for T/Cs. This begs the question why did they internally go with this over DCT. I would believe that they had quite a bit of work on the manual transmission to let it work seamlessly.
You can read about it in the article which suggests that one of the reasons for torque converter is the deactivation technology
http://www.roadandtrack.com/go/first...e-stingray-z06

Originally Posted by Mpower

OK so you are talking about launching from a stop? That's a totally different scenario and involves no shifting because 1st gear is already pre-selected.
Automatics w/ T/Cs have lag because they are tuned to achieve a smooth launch feel. In addition keep in mind any AT will benefit from much faster reaction times.

Nope I am not talking about from a stop. Just imagine a scenario , say your are talking a corner or for that matter straight line in 3rd gear at say 4000 rpm and hit the gas. Which one do you think is going to be faster to respond (with everything else being equal) ? In a DCT and a manual the clutch ( all friction clutches) is already engaged and the angular velocity is transferred almost instantaneously( less transient time) whereas in a torque converter there is transient lag before angular velocity of the gearbox tries to catches up with the engine( in reality there is some some % of slip and they will never totally catch up unless it is a locking type converter). I do agree with the tuning but the inherent behavior is not just tuning.
I am not expert in torque converter but when we had to mathematically model transmission( as a simplified spring mass damper) in graduate school, the lag ( not really a lag during modelling but just a analogy) was always taken more for them than friction clutches as suggested in the research papers.
Same industry ? A big hello to a fellow worker ! May I ask which subsystem do you work on ?

[Mpower]

Originally Posted by volkman10

We will see it in Tata's Zest Diesel variant.
Maruti is speculated to have both AMT and regular AT variants for the CIAZ.

Cheers!

With such a strong demand for Celerio's AMT model, I would imagine MM is going to be have a hard time meeting Tata and Mahindra's requirements in the near term.

Originally Posted by amulu10

In a DCT and a manual the clutch ( all friction clutches) is already engaged and the angular velocity is transferred almost instantaneously( less transient time) whereas in a torque converter there is transient lag before angular velocity of the gearbox tries to catches up with the engine( in reality there is some some % of slip and they will never totally catch up unless it is a locking type converter

During a steady cruise, a TC will always be locked. When you floor the gas it may unlock......but it all depends on the calibration so its not really a apples-apples comparison.

[volkman10]

The small little Hatch- Celerio is proving to be a runaway success - the AMT does it all. But again the bookings briings another twist. Though 52% of the 20K Celerio's booked or delivered so far are of the AMT variant, some states like Kerala have preferred the cheaper Manual variant!
The more expensive AMT variant seem to be in demand and Maruti could relook into offereing the ZXI variant of the AMT in the coming days.
But as stated earlier, the demand seems to exceed the expecations and the MM gear box supplies could be a constraint which would affect the deliveries of Celerios.

The automatic Celerio are from metro cities where the stop-and-go congesting traffic demands constant gearshifts and this could now be a game changer and a mandatory variant in all future cars in India.

It is a sign of maturing Indian customers and shows that now the automatics transmissions (read AMT) now are here to stay.

Maruti's upcoming CIAZ, is speculated to be the first in C+ segment to come with the AMT variant.

Cheers!

http://economictimes.indiatimes.com/...w/31061845.cms

[amulu10]

Originally Posted by Mpower

With such a strong demand for Celerio's AMT model, I would imagine MM is going to be have a hard time meeting Tata and Mahindra's requirements in the near term.


During a steady cruise, a TC will always be locked. When you floor the gas it may unlock......but it all depends on the calibration so its not really a apples-apples comparison.

True that ! Calibration does matter to a large extent. I am not generalizing here but I am sure you would agree that a large percentage of the auto boxes (at least the rental/ economy varieties) sold in north america do have a pause in between when you floor the throttle. They are no where as instantaneous as the ones with friction clutch. The Z06 probably doesn't pause and would be just as good as a DCT.
Why do I get the feeling you work for a powertrain department ?

[Sutripta]

Originally Posted by amulu10

that a large percentage of the auto boxes (at least the rental/ economy varieties) sold in north america do have a pause in between when you floor the throttle.

Are you talking of time it takes to kickdown, or something else?

Regards
Sutripta

[a4anurag]

Originally Posted by Sutripta

Are you talking of time it takes to kickdown, or something else?

I guess he is talking of the time taken for power to come on when the throttle is floored.

Anurag.

[Mpower]

Calibration does matter to a large extent. I am not generalizing here but I am sure you would agree that a large percentage of the auto boxes (at least the rental/ economy varieties) sold in north america do have a pause in between when you floor the throttle. They are no where as instantaneous as the ones with friction clutch. The Z06 probably doesn't pause and would be just as good as a DCT.

Yes. Its not so much a pause but more of a slip due to the TC unlocking and gradually locking. If the tip in is agressive, there may be a few seconds of pause before it decides to downshift

[Sutripta]

Originally Posted by a4anurag

I guess he is talking of the time taken for power to come on when the throttle is floored.

Some quantitative figures would be interesting. (Many more questions, but should be part of a thread on the technology of Autos, and torque converters, rather than this thread. Maybe the experts can oblige and start such a thread.)

Originally Posted by Mpower

TC unlocking and gradually locking.

How does one gradually lock a TC?

Can gears be changed with the TC locked?

Regards
Sutripta

[srishiva]

The Pagani Huayra if I am right also uses a single clutch AMT transmission. So I guess like a manual shift, the gear and clutch will have to match the power and hopefully manufacturers will do a great job so as not to kill this much needed tech for Indian traffic conditions

[a4anurag]

Originally Posted by srishiva

The Pagani Huayra if I am right also uses a single clutch AMT transmission.

Quoting from Wikipedia about the transmission used in Pagani Huyara:

The Pagani Huayra uses a seven-speed sequential gearbox and a single disc clutch. The choice not to use a dual-clutch in an oil bath was due to the increase in weight of over 70 kg (154lb), negating the advantage of the faster gear changes in those transmissions. As a result, the entire transmission weighs 96 kg (212lb).

Originally Posted by srishiva

hopefully manufacturers will do a great job so as not to kill this much needed tech for Indian traffic conditions

Would be a highly appreciated technology if given to small cars which will increase the drive comfort in crowded city traffic.

Anurag.

[Mpower]

Originally Posted by Sutripta

How does one gradually lock a TC?

Sorry what I meant was gradually reduce % slip. Locking is more of an on off thing

[Sutripta]

Originally Posted by Mpower

Sorry what I meant was gradually reduce % slip.

Can % slip be actively controlled?

Regards
Sutripta

[justin.das]

Originally Posted by volkman10

Here is the irony, Magneti Marelli is a subsidiary of Fiat Group,( it has 36,900 employees and a turnover of 5.8 billion euro in 2012.) and FIAT lost an opportunity in leading the AMT tech introduction in auto sector in India.

Cheers!

Automotive lightning a subsidiary of magneti marelli supplies lights to almost all major manufacturers. Head lights and tail lights of Audi's, Merc(cla,s class etc),BMW and many more.The infrared vision system in s class is also from marelli.Automotive lightning is a pioneer in automotive light systems with more than 100 year heritage.Many of these light technologies are patented by Al-lightning.