Why are Audi RS and BMW M ditching DCTs in favour of torque converters?

Jason · Feb 16, 2021 01:00 PM

With the recent launch of the Audi RS6 and RS7, plus the BMW M3 and BMW M4 performance cars on our shores, it seems that there is a shift in direction towards the torque converter transmission (TCT) on core performance models. More importantly, manufacturers like Audi were - up until this point in time - massive proponents of the dual clutch transmission (DCT). Other performance-oriented brands have also followed suit.

It wasn't that long ago when the dual-clutch transmission (DCT) was hailed as a revolution in transmission technology. Carmakers couldn't launch cars equipped with one fast enough. The narrative has changed somewhat now, where DCTs are slowly dwindling in numbers. Which begs the question, why?

Cost

The one inescapable notion is that, in a world of mass production, the shift is partly driven by the need to spread costs. Yes, halo models are nice to have in any carmaker's line up, but they constitute a rather small amount towards the bottom line. Moan about bean counters all you want, but carmakers run a business, not a charity.

E92 M3, the first in the M3 lineage to receive a V8 and DCT 

Using a common component across many products is a tried and trusted way to keep costs down. It's all about economies of scale. The higher the volume order for a certain component, the lower prices become. Gone are the days where carmakers spend money developing one specific transmission for just one specific model line up. It just isn't justifiable financially. 

BMW's M DCT 7-speed transmission

For example, previously BMW only deployed the 7-speed DCT in its M cars, while the majority of its regular cars employed the ZF 8-speed TCT. It was almost a certainty that the returns of investment on the ZF TCT was far higher than the DCT, simply due to the economies of scale. 

Emissions and efficiency

Emissions and efficiency compliance is another spill-over effect of component sharing. This is not to say that DCTs are inferior in these metrics. What you must know is, the process for emissions and efficiency testing is very tedious. What more a performance model that uses a specific powertrain combo? If they can shorten the process by using only one transmission option, why wouldn't they?

With ever-tightening emissions and efficiency regulations, it simply makes more sense to deploy the TCT transmission even in performance models. Instead of having to do testing on separate transmissions, now there is only need to concentrate on one, with varying parameters.

It's pretty capable

ZF's 8HP 8-speed torque converter, the best of its kind in the world

Whilst cost, emissions and efficiency are major driving forces, it's not like carmakers are plonking in an inferior transmission in their performance models. In my previous column, I have outlined what both types of transmissions bring to the table. It's worth mentioning again, TCTs are every bit as good as DCTs, and then some.

Inherently, TCTs are the smoother transmission of the two. Plus, it gives very little away in shift speeds, swiftness and power losses. Think about it, 90% (even more, I'd argue) of the DCT's capabilities, while suffering none of the foibles that are common to the DCT. Talk about having your cake and eating it. 

Is the DCT head and shoulders above the TCT from a performance perspective? That would be a resounding 'no'. It's not just all talk. Look Audi, long purveyors of the DCT, run TCTs in majority of its RS models now. The same can be said for other performance brands like Mercedes-AMG and also BMW M.

It can handle the big numbers

Any way you look at it, TCTs are very capable of handling big power and torque figures. Early DCTs had a lower maximum torque rating compared to its TCT counterparts. DCTs have improved in this aspect since, but TCTs - out of the box - are just effortlessly good at coping with such large firepower. This is especially important in the performance car sphere, where power and torque wars are never-ending.

Yes, you'd argue that Ferrari, McLaren, and Porsche run DCTs that can handle big figures. But remember, that is a DCT tailored to a very specific purpose, in a very specific model line up. TCTs can be deployed across many models, with varying power and torque applications.

Conclusion

Expect to see more and more performance models equipped with TCT transmissions in the near future. Again, this isn't to say DCTs will go extinct. Objectively, the DCT is still a fine transmission. But whatever advantage the DCT use to have over the TCT has been wiped out, or rendered neglible.

Even BMW M's Sales & Marketing boss, Peter Quintus admitted that TCTs are the better choice. Bold statement from a man whose company was advocating DCTs just a generation ago in their core M cars.

Comments