Is a dual-clutch transmission right for you? (10,000km test - part 2) | Auto Expert John Cadogan

Here are the three key positives and three key negatives you need to know before paying that deposit and driving off into the sunset with a DCT.
POSITIVES
The big one is fuel economy. There’s a six-to-10 per cent fuel saving attributable to the DCT. And while that’s not a lot of money in terms of annual fuel budgets for you and me, perhaps, it’s a potentially huge saving overall.
Look at it this way - if you spend $100 a week on fuel, the annual saving is $300-$500. But if this kind of transmission were widely deployed, there’s an immense amount of fuel saved.
Australia drinks about 20 billion litres of gasoline annually. A six per cent saving there equates to 1.2 billion litres saved. The benefits are: Better national energy security because: less dependency on foreign oil, extension of a finite, non-renewable resource (gasoline) and less CO2 emission and pollution for any given amount of driving. And it saves you money.
The second big benefit is acceleration. If you look at 0-100km/h (0-60 miles per hour in ‘Murica) you’re 4-6 per cent faster. That’s without any engine tweaks. Same engine performance - 4-6 per cent reduction in time 0-100.
The last big positive is the shift quality for engaged, sporty driving. It’s incredibly positive, fast and seamless. That’s because the computer already has the next gear engaged and ready to drive. All a shift really is, is the disengagement of the clutch on the geartrain driving now, and the engagement of the other clutch.
Shifts occur in less than one-tenth of a second, and they’re ultra smooth. This is when you’re in ‘D’ and also when you’re shifting manually, with the paddles - nothing shifts as well as a DCT.
NEGATIVES
The unfortunate thing about engineering is that there’s no solely ‘good news’ story. There’s always feedback. If you make a car better it costs more. If you improve the off-road performance, on-road performance suffers. If you increase outright dynamic performance, refinement takes a hit.
It’s always a balancing act.
The first negative is the transmission’s computational challenge of predicting the future. In some situations this is straightforward. Unfortunately though, there are plenty of situations in traffic where the future is entirely difficult to predict, and the computer pre-selects (say) fourth with the gearbox driving in third. Then there’s a rapid change in the conditions, and second is in fact suddenly required.
There’s a slight but noticeable lag while the computer reassesses things and switches from fourth to second and swaps geartrains. This typically happens in these dithering driving situations in traffic, at relatively low speed.
This is a slight negative operational characteristic, not a glaring flaw.
The next negative is a big one - but only for some potential owners, and unlike what I just spoke about, this is a reason not to own a dual-clutch transmission - but only for some few number of people.
You have to be aware of the danger of slipping the clutch under load. This is something that only happens at low speed, like less than jogging pace. Remember, a dual-clutch transmission is like a manual transmission, and this problem is just like riding the clutch in a manual.
You need to be wary of low speed crawling under load. Both those things - low speed and under load. Let’s say you’re in a traffic jam, uphill. Lots of inching forward against the load imposed by gravity, tugging you backwards.
If you inch forward at speeds lower than those which allow full clutch engagement in first gear, the clutch will slip to stop the engine from stalling. Significant heat will be generated (just like riding the clutch in a manual). In the short term, the car will tolerate that - because the clutch is not especially fragile.
But if you keep doing it, you’ll damage the clutch. The same sort of creeping under load clutch abuse is easy to do if you need to (say) reverse a trailer up a steep driveway. It’s hard to do that without slipping the clutch - so I’d be re-thinking whether a dual-clutch is appropriate for you in that situation. Or maybe you can just drive up, de-couple the trailer, swing it around and drive out.
I did not just say: never do a hill start in a DCT. Normal driving, hill starts, a bit of stop-start traffic, having a steep driveway - all completely compatible with DCT ownership. Slipping the clutch under load - not OK. OK?
The final negative is about steep hill-starts and low-speed maneuvering. Because the clutch is automated, you’re essentially driving a car with a clutch take-up algorithm instead of a pedal. Sometimes that take-up response is a little non-linear - and this is more apparent, the steeper the hill you’re on, especially if you roll back.