Motoring's 2012 Performance Transmission Test

As emissions standards grow ever stricter, automotive manufacturers have had to balance the demand for constant performance progress with ongoing efficiency improvements.
The upper echelon of aspirational, V8-engined sports sedans (and wagons) stands to lose most here; unable to ignore global emissions issues, but not willing to back off in the class war for power and dynamism.
One key point of the performance/efficiency equation lies in the transmission. For buyers of modern muscle, it’s fascinating space with a wide array of options. Here, we take a look at the latest generation of V8 brutes, each employing a different method of transferring torque to the tarmac, and examine their effectiveness.
BMW M3
BMW has an established fan base with cars such as bmw x1 but now it is offering even more enhanced features. BMW itself refers to its seven-speed, dual-clutch system as “a further enhancement of the previous SMG sequential manual systems”. Though in reality this ’box is far more impressive.
Utilising a pair of oil-cooled wet clutches, the Getrag-built M-DCT with Drivelogic transmission follows standard dual-clutch principles -- one clutch works the odd gears, the other the evens. Drive is essentially uninterrupted, and as a bonus BMW claim the lack of a torque converter means less weight, and improved fuel economy. Interestingly, M-DCT also uses 12 per cent less fuel than its manual equivalent.
Operated via a central shifter, or with paddles mounted behind the wheel, M-DCT can deliver a range of driving modes at the behest of the driver -- 11 in all, with five shift programs in fully automatic ‘D’ mode and six in driver-controlled ‘S’ mode.
Setting off reveals a somewhat jerky creep phase as drive is taken up, but from that point on it is obvious this gearbox was developed specifically to suit the M3’s sparkling naturally-aspirated V8, and its 8300rpm capability.
This combination begs to be driven in manual mode, and although the stubby sequential shifter is a tactile delight, it pales into the background when you select ‘S4’ (or above) and snap whip-crack shifts through the well-shaped and ideally placed paddles. Come the next corner, a tug of the left paddle brings a deliciously audible throttle blip to match revs on the down-change. It’s utterly absorbing.
Detracting from the theatre of driving the M3 is the fact that its 11 transmission modes add unnecessary complexity. In D mode, for example, there is little to discern between the three lower shift programs. ‘D4’ and ‘D5’ bring speed and aggression to the up-shifts, however on our drive loop the lack of programmed automatic downshifting under hard braking is at odds with these ‘performance’ settings.
Overall, though, the addition of M-DCT further enhances what is already a class-defining package.
FPV GT Mark II
Demonstrating a more traditional deployment of power, the FPV GT (one of the first in Mark II guise) on test is fitted with the Tremec TR6060 six-speed manual and its associated clutch pedal -- once de rigeur for a car of this performance potential.
As a guide to this car’s torque delivery, you can lift the clutch progressively and it will take off (though your left-leg muscles won’t thank you), summoning a walking pace without even touching the throttle. For best progress, however, it’s best to feed a little power in as the clutch lifts beyond halfway and through its bite point. Once fully engaged, it isn’t a far press of the throttle before the supercharger does its thing and the revs head quickly towards 6000.
It’s brutish power delivery on-boost, and though the rest of the driveline is willing, the gear-change process requires firmness and confidence from both hands and feet. The shift is notchy, with cross-gate moves in this brand new example feeling stiff and a little tight.
On down-changes this stiffness is exacerbated by the pedal’s positioning, the brake pedal too high to allow comfortable heel-toeing. Despite this, you can make smooth, positive progress if you don’t rush the changes. This is what makes a good manual so endearing; the feeling that your inputs enhance the driving experience.
The selector itself is curious on a couple of levels. When in gear, it suffers from a lack of damping, the car’s loadings transmitted through to the palm of your hand quite abruptly. Secondly, the selection for reverse gear is far-right and up, which is too far away from first gear and can delay slow-speed manoeuvring.
When compared to the ageing (in this company) six-speed ZF auto, the manual is slightly ahead on fuel consumption (13.6 vs 13.7L/100km) and keeps better with the car’s muscle-bound demeanour.
Lexus IS F
An acronym for Intelligent Sport, Lexus’s mid-sized sports sedan range is headed by the 5.0-litre V8-powered F (for Fuji Raceway, where it was developed). It houses a Sports Direct Shift transmission -- a highly advanced traditional automatic gearbox that offers eight forward gears, a lockable torque converter and two drive modes -- ‘D’ for Drive, and ‘M’ for Manual.
Straight away you notice the fuss-free drive take-up the torque converter provides. The transmission constantly adapts to driver inputs in Drive mode, providing imperceptible shifts on light throttle loads as it moves to seventh gear by 70km/h.
When driving in this way, a slight increase of throttle pressure holds the high gear, relying on the 5.0-litre’s torque reserves rather than exciting its occupants with a brazen kick-down. It’s this adaptability that contributes to the Lexus having the best fuel consumption figures of the bunch.
Its Jekyll-like character is dispensed with when the tacho sweeps beyond 3700rpm and the exhaust valves open. From here to redline the V8 finds its voice and the transmission follows suit, holding out for higher revs under sustained acceleration while also being keener to drop cogs for cornering.
For a generation brought up on three- and four-speed automatics, seeing the digital gear display pause while the ‘box moves to one of seven other ratios may feel like overkill, but the result is a ratio for any occasion.
Switch to Manual mode and the IS F is less impressive. On more challenging roads seventh and eighth gears become redundant and the sequential plane of the shifter feels counter-intuitive (pushing forwards for up-shifts while being pressed back into the seat under acceleration). The Lexus’s wheel-mounted paddles are also too thin and far away at a ten-to-two steering position. Up-shifts are quick, matching the 100-milliseconds of the Mercedes-Benz, but overall this car feels more complete when left to its own devices.
Mercedes-Benz C 63 AMG
AMG-Mercedes are currently hedging their bets, offering a Getrag DCT similar to the M3’s in their top-line SLS supercar while the remainder make do with SPEEDSHIFT MCT.
The seven-speed self-shifter as seen on the tested C 63 AMG Estate does without the torque converter of a conventional automatic, favouring a ‘wet’ multi-plate clutch arrangement that contributes to a fuel consumption improvement of 9.5 per cent over the previous model.
A console-mounted rotary dial allows interaction with four shift programs, ranging from ‘C’ for Controlled Efficiency, through ‘S’ and ‘S+’ sporting modes, to ‘M’ for driver-controlled manual shifts.
Moving away from standstill, you feel a brief pause as the revs dip before power is taken up, an eerily similar sensation to smoothly letting up a clutch pedal.
C mode delivers relaxed, comfortable up-shifts, easing into higher gears to assist those headline economy figures. In traffic, however, the lack of gearing down in this mode sees the gearbox jolt back into first when coasting to standstill.
S mode does as you’d expect, holding onto gears and being keener to kick-down, but the change itself isn’t particularly positive, slurring on up-shifts where you really want measured response. That’s found in S+, which trades ease for brutality with 100-millisecond shifts that the whole driveline feels. Under braking, electronically-controlled down-changes are announced by an extroverted throttle blip, accompanied by crackles and pops through the exhausts -- you could well be driving the AMG Formula One Safety Car with these histrionics.
Manual shifting brings the wheel paddles into play, and they are a delight to use... As long as your fingers don’t clash with the multi-function stalk which is mounted too close to the downshift paddle for comfort. The regular shifter can also be used manually, though with its east-west change pattern, it’s best to stick with the paddles.
The Verdict
The image benefits of V8-powered halo models have been known for generations. Thankfully the key players have moved with the times, maintaining high levels of performance with ever-increasing efficiency.
Purists may bemoan the lack of mechanical interactivity (and skill) evident in clutch-less shifting, but the rewards offered by the M3’s ’box, on top of its green gains and ability to go auto, make it compelling; and show where the landscape is headed.
Thanks to such advancements, enthusiasts will still able to enjoy a genre that, without such technology, may well have become redundant sooner than you think.