In the history of performance motoring many a manufacturer has had to chase dollars as hard as dynamic kudos. The natural conclusion drawn is that a slushbox is needed for market share. It’s a point that is hard to argue, but it was in the execution that many were exposed, at least from a driving enthusiast’s standpoint. Inevitably, installing the auto meant the gear ratios grew fewer and longer while weight went up, reducing responsiveness all-round. In more extreme cases, engine power and/or torque were also infected. In applying the auto, many a sportscar lost its sparkle. More recently self-shifting technology has been enhanced to a point where there is little loss in dynamism when compared to a traditional manual shift, however there are still a couple of surprising exceptions, as you’ll discover below.
Mazda RX-8 (2003)
As a manual: Six gears, 170kW at 8200rpm, 211Nm at 5500rpm, 12.9L/100km, 1402kg
Slushbox: Six gears, 158kW at 7500rpm (down 12kW/700rpm), 211Nm at 5500rpm, 12.1L/100km, 1412kg
Introduced for the 2003 model year Mazda’s funky-styled RX-8 ticked all the right boxes on paper. It housed the latest-generation version of the venerable rotary, though it came only in naturally-aspirated form. It was a distinctive, well-balanced sportscar with the trademark smooth ‘revability’ that only a rotary can provide.
With a power peak of 8200rpm in 170kW manual form, it definitely needs revs to keep on the boil, but the wrist-flick manual shift allows you to run between ratios hard, thus keeping the rotary in its power-band. The optional six-speed auto, however, can’t manage the manic engine at full-spec, so makes do with a 158kW version (12kW down on the manual). Its tune means that peak power is reached at 7500rpm, robbing that final zingy surge the rotary is renowned for, without addressing its greatest weakness; a lack of bottom-end torque.
Honda NSX (2002)
As a manual: Six gears, 3.2 litres, 206kW at 7300rpm, 298Nm at 5300rpm, 10.8L/100km, 1390kg
Slushbox: Four gears, 3.0 litres, 188kW at 6800rpm, 284Nm at 5300rpm, 10.6L/100km, 1410kg
For many reasons the NSX sits firmly in our affections. It was Japan’s first true supercar, forcing the Italians to up their game; Ayrton Senna was involved in the chassis development; Gordon Murray used its all-round ability as a source of inspiration for his McLaren F1 road car. And Greg Crick also steered one to outright victory in the first two Targa Tasmanias.
The manual was a true thing of beauty, offering precision, speed and control over an orchestral mid-mounted V6, tightly stacked ratios allowing it to do what it did best: run into the red-line. Handling was keen and sure-footed, standing tall among its contemporaries, while Japanese reliability ensured it would cope with sustained thrashing.
Then there was the auto. From the NSX’s 1989 debut the self-shifter was deemed too weedy to handle the full 201kw output from the early 3.0-litre engine, so it was detuned to 188kW. Worse, when the manual received six gears and a 3.2-litre upgrade, the auto stuck with the old hardware.
Compounding the negatives was the additional 20kg added to the drivetrain when the auto option box was ticked. Dynamically it was still a winner, and the engine’s song remained largely intact, but the harder edge to the NSX was lost.
Toyota Celica ZR (2005)
As a manual: Six gears, 140kW at 7600rpm, 180Nm at 6800rpm, 8.1L/100km, 1138kg
Slushbox: Four gears, same power and torque, 8.6L/100km, 1173kg
There may be a theme developing here, with the Celica being another high-revving Japanese sportscar let down by an inadequate automatic transmission. The power-band of the VVTL-i was paper-thin and really needed rowing, even in six-speed manual form.
One look at the torque figure and peak revs explains how tiresome it could be in traffic. Now add 35kg, remove two ratios and increase fuel consumption by 0.5L/100km. That’s what Toyota did by offering a four-speed auto.
Power and torque didn’t suffer, but usability was reduced even further. In fact, the auto lost on both sides; frustrating in town, it also robbed the driver of fun on the open road, thwarting the VVTL-i engine’s zingy top-end by taking forever to wind up into the cam-change zone.
Subaru Impreza WRX STi (2010)
As a manual: Six gears, 221kW at 6200rpm, 407Nm at 4000rpm, 10.5L/100km, 1515kg
Slushbox: Five gears, 221kW at 6200rpm, 350Nm from 3000-6000rpm, 10.6L/100km, 1525kg
As previously intimated, many a modern automatic sportscar can be as compelling as a three-pedal equivalent. But consider the previous-generation Subaru Impreza WRX STi range, which proves that even the best can get it wrong.
Obviously geared (no pun intended) towards people that favour the kudos of an STi without caring too much about the finer details of driving, it was the first – and so far only – STi to ever provide an automatic option to our market. In this form the STi ran five gears (one less than the manual) and produced the same power as the manual equivalent. Similar fuel consumption and a weight increase of only 10kg appear to further a case that there isn’t much loss of performance regardless of shift option.
Then, you look at the torque figure: 57Nm have been lost in the shuffle to self-shift. Where did they go?
Additionally, and perhaps more frustratingly, the auto loses the helical front and Torsen rear limited-slip differentials featured in the manual, instead using an open front and viscous rear LSD.
Though close enough on paper, on the road the auto sadly dilutes the essential STi driving experience.
Porsche 911 (996) Turbo (2000)
As a manual: Six gears, 306kW at 6000rpm, 560Nm at 2700rpm, 12.9L/100km, 1590kg
Slushbox: Five gears, same power and torque, 13.9L/100km, 1630kg
The 996 range produced a number of firsts for the enduring Porsche 911. It was the first to adopt water cooling, and introduced the five-speed ‘Tiptronic’ auto to the top-of-the-range Turbo model. While the six-speed manual 996 Turbo quite rightly holds its place amongst the very best 911s, the auto version remains a lonely afterthought, never to be mentioned in the same breath.
Power and torque were not affected, but 40kg is significant enough to be noticed, particularly over the back axle. It also slurped a whole litre more fuel for every 100km travelled. The 996TT auto still accelerated ferociously, of course, but it just didn’t seem right to emasculate one of the best all-round 911s ever; even the sound of the flat-six being held back by a torque converter was enough to break your heart.
Continue the conversation
Do you have a slushbox horror story? Have you driven a Ferrari Mondial Valeo? Let us know in the comments!