2008 Lexus IS-F
Instead of reinventing the wheel, Lexus engineers got smart and took the compact 8-speed planetary gear transmission from the Lexus LS460 and placed it into the IS-F super sedan. The transmission works like a conventional automatic transmission, but has been tweaked to shift like a performance car. The secret is the torque converter, which is now programmed to fully lock in every gear except for first and reverse. This allows the car to start and stop like an automatic, but once past first gear, there is a direct connection between the throttle and the wheels. This gives it a very connected "manual" feeling, like the SMG, while still having lightning fast shifts. The IS-F also doesn't lurch from a start or when coming to a stop, as the transmission doesn't have to decide when to disengage from 1st gear to neutral like the SMG. The large number of gears and close gear spacing also allow for faster shifts, as the rpm drop between gears is smaller. The drawback is that, during manual shifting, a driver can get lost in all the gears. Regardless, it is an amazing evolution of the automatic transmission, but still, on occasion, has a delay between the shift input and the actual shift occuring.
2009 Mitsubishi Lancer Evolution X MR
Among all these semi-automatic transmissions, the Evo X's Twin Clutch Sport Shift Transmission (TC-SST) mechanically shares the most in common with the original Audi/VW design. It's a transverse mounted transmission with six gears, designed for all-wheel drive applications. But the software integration and intelligence is highly evolved when compared to VW's first-generation DSG. The TC-SST is integrated into Mitsubishi's Super All Wheel Control (S-AWC) system, which looks at all the vehicle dynamics sensors so that automatic gear selection depends not only on what the engine's doing, but also if the car is setting up for a corner or powering out of one. The more intelligent transmission control software and superb calibration make this dual-clutch transmission stand out in terms of smoothness and its ability to time and anticipate shifts as well as seasoned racers when on track.
Mitsubishi avoided the inflexibility of earlier DSG transmissions by providing three different shift modes, instead of two. Drive Mode is again for commuting and fuel economy but seems to be intelligent enough to keep the engine in its powerband when necessary, instead of instantly up-shifting at a set RPM point. Sports Mode is ideal for driving an Evo as it's meant to be on the streets. Shift points are above 4000rpm, which allow for positive engine braking and keeping the turbo spooled. S-Sport mode is a track-only mode, which changes gears only at peak power near 6500 rpm.
One main advantage of the dual-clutch concept on the Evo X is the fast shifting, which prevents its single turbocharger from falling off boost. Mitsubishi's detailed calibration of the transmission software makes manual shifting a futile exercise when on the track. The smoothness of the shifts is also a great advantage on track. The downside comes with tuning. While the TC-SST has a maximum safe torque load rating (according to our sources) of 330 lb-ft (which is more than Evo manual and automatic transmissions) and can still operate with additional power, the stock transmission calibration for automatic shifting becomes less effective since engine torque changes with tuning. This affects the time required to shift and the hydraulic pressure controlling the clutch engagement and torque exchange timing.
2009 Nissan GT-R
Of the cars tested, the GT-R's dual clutch transmission is the best fit for our tastes in terms of positive shift feel, speed of shifts, and overall intelligence. Whether driven as a manual or automatic, the GR-6 Dual Clutch transaxle offers the best of both worlds, immediate feedback, like the SMG and Lexus IS-F, but without the delay, as well as silky smooth shifts for commutes, like Mitsubishi's TC-SST.
In terms of technology, Nissan's Dual Clutch transmission operates the same as other dual-clutch-type transmissions. But the much higher power and torque output of the GT-R makes the Transmission Control Module (TCM) calibration very different from other cars. Because the GT-R has a relatively flat and high torque curve, the car can be operated in relatively lower engine speeds, while still offering good acceleration response from a cruise. The transmission does not need to downshift for mild bursts of acceleration like the DSG or TC-SST, which helps save gas.
More torque also allowed Nissan engineers to use only two levels of aggressiveness for the transmission shifting, normal and R. A third mode is only used in snow. Under both manual and automatic modes, the transmission controls shift intensity and timing, based again on engine performance (torque) and vehicle dynamics. While the automatic shifting in R mode is geared for track use, it is not nearly as intolerable as the TC-SST S-Sport mode when driven on the street. Just like in manual transmissions, matching power delivery to gearing and gear changes has a huge effect on overall driveability.