Inside Fiat's Dual Dry Clutch Transmission

Alfa Romeo MiTo DDCT shifter

In April, I reported the Fiat 500 will be getting a version of the new Dual Dry Clutch Transmission (DDCT). Here's more about this transmission.

The 6 speed Dual Dry Clutch C635 transmission debuted this spring in the B segment Alfa Romeo MiTo, with the C segment Alfa Giulietta following. This transmission will eventually show up in the next generation of B, C and D segment Chrysler products coming to showrooms next year. Just recently, Fiat announced the Fiat 500 will receive a smaller version of the Dual Dry Clutch Transmission , this time with seven speeds.

Questions

There are questions concerning this smaller DDCT as far as which model 500 will get it and when. This seven speed DD CT is a natural for the Abarth but it is not exactly clear if it will get it. Curiously, this sporty transmission will initially have a torque capacity up to 140lbs.ft. (190Nm). That is suitable for 500 models with TwinAir, 1.2 liter, 1.4 liter and 1.3 liter MultiJet engines, however, 500 Abarth has a torque rating of between 152lbs.ft. (206Nm) to 170lbs.ft (231Nm), so it is assumed that there will be some changes to allow it to handle the added torque of the turbocharged 1.4 liter Abarth engine.

The New C625 TCT


Or could there be a totally new DDCT for the Abarth? Tucked away in Fiat's Five Year presentation, I discovered a new transmission mentioned. It is called the C625 TCT (Twin Clutch Transmission) and is a DDCT type suitable for power levels between 148-184 lb.-ft. (200-250 Nm), exactly the torque range of the Abarth's 1.4 liter Turbo. There was no mention of this transmission during the presentation and not much is known about it, but, from what I have gathered in Italy, it is a smaller version of the C635 DDCT. We'll watch this one for you.

C625 TCT transmission listed, but not talked about

Another question is when will the 500 receive the DDCT? I mentioned in March there was talk in Italy that the US 500 will use the DDCT as the automatic transmission option and not the Dualogic semi-automatic. However, the smaller DDCT is not in production yet and the 500 is due out in 6 months. The question is will Fiat spend the money certifying the Dualogic for December and then latter next year, certify another transmission for the 500? Remember, each engine/trans combination needs to get certified by the EPA, a time consuming and EXPENSIVE operation.

We'll have to see how this all plays out, but here's what I think: My guess is the DDCT will show up in a US 500 at some point, but it might be in 2012, when a refreshed version of the 500 will make its appearance.

I can't see the 500 Abarth not having the DDCT. As far as time frame, the 500 Abarth is due out around fourth quarter 2011 and thats enough time to get it together for the transmission certification. So I wouldn't be surprised if the 500 Abarth would be the first 500 model to show up in the US with a Dual Dry Clutch Transmission (the C625 TCT).

What do you think? Feel free to post a comment below. In the meantime, let us explore Fiat's DDCT transmission as fitted to the Alfa Romeo Giulietta.

A look at the C635 DDCT

The C635 DDCT mounted to the 1.4liter Turbo of the Alfa Romeo MiTo

Click here to take you to a site that has a great short video on how a dual clutch transmission works.

The C635 DDCT has some notable features. With a torque rating of up to 260ft.lbs (350nm), it currently has the highest torque capacity of any dual dry clutch application on the market. It is also relatively light weight at 178.6lbs (81kg), complete with fluids.

Differential is mounted as close to powertrain centerline as possible

Special steps were taken to make the transmission as short and compact as possible. The center differential was moved closer to the engine. This allows it to fit multiple platforms, from sub-compact platform B cars to larger mid-sized D platforms. Center shaft distance is 197 mm, but there are versions from 181mm (181mm is the same dimension as the C510 transmission used in the 500 Abarth, making the C625 TCT a plausible assumption)

Shared components with manual version

The C635 TCT was developed alongside a manual version and uses some common elements such as the three-shaft layout, the casings, the synchronizers, and even the shift forks. This saves considerable manufacturing costs.

Dual Dry Clutch supplied by LuK GmbH

The C635 TCT uses the Dual Dry Clutch manufactured by LuK GmbH, the premier maker of this type of clutch.

The highlights of using a dual dry clutch is the elimination of the hydraulic support systems and the high efficiency of the dry clutch compared with that of a wet clutch. This enables significant savings in fuel consumption of more than ten percent when compared to the wet clutch and up to six percent in comparison to manual transmissions.

Hydraulic actuation module located in front

Below is the BorgWarner press release explaining their contribution to the C635. Interestingly, they mention three C635 variations, which matches up to a smaller unit for the regular 500, the Abarth's C625 TCT and the larger C635.

BorgWarner will supply the hydraulic actuation module for Fiat Powertrain Technologies' (FPT's) first dry dual-clutch transmission, one of three variants of the C635 family of six-speed gearboxes with 350 Nm maximum torque capacity, launching in late 2009.

Magneti Marelli and BorgWarner were assigned to the industrial development of FPT's innovative transmission control system, which employs a high pressure electrically-driven hydraulic pump and control solenoid valves to actuate the gear selection and engagement as well as the dry dual-clutch unit. Magneti Marelli supplies the control system to FPT, integrating BorgWarner's hydraulic actuation module into its own power and transmission control units. The transmission control strategies remain FPT's responsibility.

Characterized by compactness, speed and efficiency, the FPT transmission control system also uses BorgWarner's solenoid valves, employed for the last 10 years by Magneti Marelli and Fiat in their automated manual transmissions (AMTs).

Alfa Romeo TCT

Alfa Romeo introduced DDCT transmission in the MiTo and later in the just released Giulietta. Alfa Romeo calls this transmission the Twin Clutch Transmission (TCT). Here is Alfa Romeo's official press release on the TCT:

The innovative �Alfa TCT� - the latest automatic dual dry clutch 6-speed transmission - will be debuting in Geneva on the Alfa Romeo MiTo.

Developed and produced by FPT, Fiat Powertrain Technologies, this new device is part of a modern family of 6-speed gearboxes (C635) that was launched - in the mechanical version - on the 170 HP MiTo 1.4 MultiAir Turbo petrol.


Video of Alfa Romeo Giulietta introduction.

Now it's the turn of the �Alfa TCT� teamed with MultiAir engines with Start&Stop system fitted as standard: indeed, the Alfa Romeo MiTo is the first car on the market to combine these three innovative technologies. Available from next spring, visitors to the show will be able to admire a 135 HP MiTo 1.4 MultiAir Turbo petrol with �Alfa TCT� and gear levers incorporated into the steering wheel (optional).



Video of engine and transmission cross section (music warning)

The new device, conceptually, consists of two gearboxes in parallel, each with its own clutch, which allows the selection and engagement of the subsequent gear while the previous one is still engaged. The gear is therefore changed with a simple gradual switch of the corresponding clutches, guaranteeing continuous torque delivery and therefore traction. The result is a driving comfort and sporty feeling well above those offered by conventional automatic transmissions (with torque converter), as proven by greater speed of gear shift, the possibility of selecting between manual or automatic mode and a near-zero power loss during the gear change. In addition, the purchasing, servicing and running costs are limited, while fuel consumption is reduced, thanks also to the implementation of the Start&Stop system, up to 10% less than a traditional automatic hydraulic transmission with torque converter.



Specifically, the �Alfa TCT� features the largest number of interactions with the vehicle's systems available on the market. Indeed, its operation interacts with the steering wheel, the brake and accelerator controls, the Alfa DNA selector, the Start&Stop system, the ABS, the engine and the inclinometer (slope detector to engage the Hill Holder and disable Start&Stop on activation).

Other peculiar features of the new �Alfa TCT� are its flexibility of application, thanks to the compact size of its components, and the fact that it is a dual dry clutch (the type of clutch that guarantees the highest degree of efficiency in terms of fuel consumption among all automatic transmissions). If we compare "Dry" clutches with oil bath ("Wet") ones, we can safely say that the former dissipate energy only during the actual slipping phase of the gear change and on pick-up, whereas wet clutches, which always operate in an oil bath, introduce losses due to viscous friction such as those of conventional automatic transmissions even when they are not in operation.

What's more, they require forced cooling with oil and therefore continuous energy expenditure to drive the dedicated oil pump (absent in the case of "Dry" clutches). Moreover, a "Wet" automatic transmission requires approximately 4.8 litres more oil than the "Dry" version, again for reasons of clutch cooling (in this way, weight is added and losses due to splashing increase). When all these effects are added together, a �Alfa TCT� is found to be approximately 6% more efficient than the corresponding "Wet" one in terms of consumption. Last but not least, the advantages of the "Dry" clutch include the lower cost and the increased ease of installation.



Lastly, it should be remembered that the new �Alfa TCT� boasts a generous 23 public patents split into 3 areas: gearbox control, gearbox mechanics and gearbox actuator.

With thanks to: LuK GmbH & Co, BorgWarner Inc, dctfacts.com,
Fiat Group Press

Fiat 500 coming with 7 speed Dual Dry Clutch Transmission

Fiat announced yesterday during it's Investor Day Five Year Plan presentation, the Fiat 500 will be equipped with the DDCT Dual Dry Clutch Transmission. This will be a new variation of the C635 DDCT that is being installed in the new Alfa Romeo Giulietta and future Chrysler products.

The DDCT transmission going into the Fiat 500 is a new 7 speed design specially created for smaller A and B segment cars.

The advantages of the DDCT transmission is it combines the shifting convenience of an automatic transmission with even greater operating efficiency than a manual transmission.



When you want to relax, you can drive it as an automatic, or when that sporting feeling hits, shift it manually. It delivers a superior sporty feel compared to electrically-actuated manual (MTA) gearboxes because of the greater gear shift speed and a near-zero power loss during gear changes.



An outstanding feature of this 3 shaft transmission is it is modular and can have an electric motor generator attached to one of the transmission input shafts making it the most compact and economical parallel hybrid powertrain on the market.

This is the first in its class and promises to open a huge potential market for Fiat. I've reported on the Fiat Hybrid system previously (you can read more here), but now the DDCT transmission completes the package.


The Fiat Hybrid is really the optimal hybrid propulsion system for city cars. This hybrid drive setup consists of the 900 cc two-cylinder TwinAir engine from the SGE family, combined with an innovative DDCT Dual Dry Clutch Transmission featuring an electric motor coupled to one of its two mainshafts.

The SGE engine�s small size makes it possible to use a simple, efficient transmission architecture, while coupling the motor downstream of the clutches means that all the characteristic functions of a parallel hybrid propulsion system, including electric drive, regenerative braking and torque boost from the two motors, can be provided in a compact, lightweight package: essential for small urban runabouts.

The hybrid propulsion system uses air-cooled lithium ion batteries housed in the car�s trunk. Other features include plug-in traction battery recharging and an HVAC system that can be powered by either the IC engine or the electric motor, using whichever unit provides peak efficiency at any given time.

The great news is this Hybrid Fiat 500 is getting closer to market and there was a running prototype on display for reporters to examine.

We can speculate (guaranty?) that the 7 speed DDCT will likely be a transmission option for the 500 Abarth when it makes it's debut here in the states next year. I'll have more about the DDCT transmission in an upcoming post.

With the help of Fiat Group Auto

Fiat 500 transmissions: 5 or 6 speed, Dualogic or MTA...

The Fiat 500 comes with a wide range of reliable, robust, sophisticated gearboxes: one is a mechanical unit (with 5 speeds for the 1.2 and 1.3, and with 6 speeds for the 1.4), the other is of the sequential robotized type named the Dualogic. The 500 Abarth comes with a heavy duty 5 speed and the 500 Abarth Assetto Corse a 6 speed extreme duty transmission. The 695 Abarth "Tributo Ferrari" has a robotized version of the normal 500 Abarth transmission dubbed the MTA.

Below is a list of the model numbers and technical specifications of the various transmissions fitted to the Fiat 500 and Abarth versions:

Fiat 500 with 6 speed manual

C514: Fiat 500 5 speed (1.2L motor)/6 speed (1.4L motor)
Max Input Torque: 150 Nm
Center Distance: 170, 182 mm
Length: 362 mm (5-sp), 410 mm (6-sp)
Mass: 33 Kg (5-sp), 35 Kg (6-sp)

Fiat 500 with Dualogic transmission

C514 MTA (Manual Transmission Automated): Fiat 500 with Dualogic
Max Input Torque: 145 Nm
Center Distance: 170 mm
Length: 362 mm (5-sp)
Mass: 42,5 Kg
FPT Electro hydraulic add-on, S-Cam

Fiat 500 Abarth with heavy duty 5 speed manual

C510: Fiat 500 Abarth, Fiat 500 Abarth esse esse
Max Input Torque: 206 Nm
Center Distance: 181 mm
Length: 380 - 395 mm
Mass: 36 Kg

695 Abarth "Tributo Ferrari" with paddle shifted 5 speed MTA

C510 MTA (Manual Transmission Automated): 695 Abarth "Tributo Ferrari"
Max Input Torque: 206 Nm
Center Distance: 181 mm
Length: 380 - 395 mm
Mass: 45 Kg
FPT Electro hydraulic add-on, X-Y

Abarth Assetto Corse with extreme duty 6 speed transmission*

M32 6 speed: Abarth Assetto Corse
Max Input Torque: 320 Nm
Center Distance: 197 mm (M32)
Length: 332 mm
Mass: 47 Kg (M32)
Reverse synchronized

The mechanical gearbox is very compact with a lot of attention paid to its shifter feel. This was made possible by the reduced inertia of the driven clutch plate and the introduction of new seals. The gearbox configuration is transverse with two cascade shafts, while the speed control is internal, with four selection levels.

Fiat C514 transmission cutaway view

The external drive is dual hose type, which filters out engine running roughness and vibration transmitted by the engine to the gear lever. The gears have teeth with extra covering, as well as fifth speed and final drive pairs that are given an extra finish after heat treatment (this improves quiet operation). The gearbox housing is light and absorbs noise efficiently, and has been fine tuned using the Finite Element Method.

The mechanical gearbox of the Fiat 500 has a �syringe� mechanism that prevents the involuntary engagement of reverse.

Dualogic

Dualogic shifter

Magneti Marelli Powertrain produces robotized transmission gear or MTA(Manual Transmission Automated), that consist of the transformation of a regular gear box where the manual transmission is replaced by an Actuation kit (plug-in) electronically controlled by a Transmission Control Unit (TCU)

This system allows:
�Automatic gear shift
�Automatic clutch

In this way the driver has the following options:
�Possibility to choose between manual or automatic transmission
�Manual transmission by joystick or at the wheel
�No more clutch pedal
In addition all the information can be displayed on the dash board for a deeper awareness of the driver.

The Dualogic transmission is available on the 1.2 8v and 1.4 16v versions of the Fiat 500. The 695 Abarth "Tributo Ferrari" is equipped with a similar system but is called MTA (Manual Transmission Automated) and is controlled by a race-inspired paddle gearshift.

The Dualogic and the MTA automates the clutch and gear lever controls by means of an electro hydraulic servo, but maintains all the advantages of a dry clutch and a mechanical gearbox (weight, sturdiness and reliability, low energy consumption).

This sophisticated system improves the performance of the manual mechanical transmission components and increases driving safety because it avoids errors by the driver and prevents faulty manoeuvers of the transmission system.

There are two operating modes: semiautomatic and automatic.

The first adopts the most advanced control strategies to guarantee the best performance. Gears are engaged using the lever on the facia. Because there is no clutch pedal, the device is controlled simply by moving the lever: forward to change up (toward the �+� symbol), back to change down (toward the �-� symbol). A simple push is sufficient to ensure the transmission makes a fast, accurate gear change.

Dualogic/MTA controller

This is how the Dualogic transmission functions in semiautomatic mode. Most of the electric signals reach the control unit by CAN (Controller Area Network) and can be grouped in two large subgroups. In one, the data from the gearbox area, which make it possible to identify the engagement position, the selection, the clutch, and the operating pressure of the hydraulic kit, as well as the rotating speed of the clutch.

In the other, all the signals coming in from the control lever on the tunnel or the levers on the steering wheel (which are optional), that let the driver decide when he wants to change gear, and those from the other systems on the Fiat 500 (for example, the engine and braking system), which help to define the gear change precisely and repeatably. For example, coordination with the engine control unit makes it possible to change up without having to release the accelerator pedal or to automatically increase engine speed when changing down (double de-clutch).

Using these two groups of signals, the Dualogic gearbox can manage gear changes in a comfortable or sporty way, in the manual or automatic mode, interpreting the driver�s needs by analyzing the pedal position and the engine speed.

Once the engine on the Fiat 500 is started, any pressure on the brake pedal confirms that the driver is at the wheel, and enables first or reverse to be engaged (on a slippery surface it is also possible to set off in second). And to guarantee safety and prevent incorrect gear engagement, the system engages neutral automatically when a door is open with the engine running. The Dualogic device also prevents errors that might damage the engine or gearbox, by notifying the driver of emergency situations or incorrect maneuvers with warning lights and beeps.

The automatic mode of the Dualogic system offers two settings on the 1.2 version: Normal and Economy.

The Normal setting provides outstanding driving comfort, with brilliant acceleration and gear changes in all conditions. The Economy setting, on the other hand, is used to reduce fuel consumption, while still maintaining outstanding handling and comfort.

On the version for the 1.4 16v engine, the two settings are Normal and Sport (with the Sport button on the facia). The Sport setting activates a faster gear change logic that minimizes the torque gap and thus makes the car more �fun to drive� for the driver.

In automatic mode, the system recognizes the road gradient (by means of a software algorithm) and modifies the gear shift point to ensure the best possible compromise between the driver�s needs, ground conditions and vehicle situation (speed and engine rpm).

Another feature peculiar to the Dualogic gearbox is its ability to measure the vehicle deceleration and adapt gear changes accordingly. For example, in semiautomatic mode, and particularly with a sporty driving style, the system changes down when the driver asks for a lower speed to take a corner with more gusto. In automatic mode, the system anticipates the change down so that the driver has the best speed to maintain the level of comfort or fuel economy.

The Dualogic system is the best compromise for drivers who prefer the enjoyment and entertainment of a manual shift, but like to know they can count on the convenience of an automatic.

With help from Fiat Group Press/Magnetti Marelli

*photo courtesy of Archivio Perini