I just bought a 2018 Hyundai Sonata Limited sedan. It has an eight-speed automatic transmission. The owner’s manual says that it has a “dual clutch” rather than a torque converter.

Given modern electronic control, an electrically operated clutch is no surprise. But why a “dual clutch”? Seems as though a single clutch to connect/disconnect the engine and transmission would suffice. The explanations that I’ve found on the Internet don’t really explain. This one, for example:

https://www.autotrader.com/car...-transmission-245373

Shifts are crisp, but smooth, regardless of the mode I select: Comfort, Sport, or Economy. I’m guessing that “Economy” up-shifts at a lower RPM.

Someone can correct me if I'm wrong, but it sounds like one clutch is for gears 1,3,5,7 and the other is for 2,4,6,8. When shifting from first to second, one clutch disengages while the other engages, making shifts faster and smoother. There's no need to disengage, then shift, then re-engage.

One clutch locks up one set of gears, (odd numbered) the other clutch locks up another set (even numbered).

This provides more efficient power management.

Think of it like this. First clutch allows coupling of on gear number, then the second handles the next gear.

Think of it like hopping, vs walking.

Hopping forward, on one leg, and compare it to one foot in front of the other. The first moves you the same distance over time, but is less "optimal/efficient" then the one foot in front of the other.

So, your car's transmission is "walking" odd/even/odd/even (first clutch/second clutch) and it can do so mechanically faster.

I'm familiar a little of what Luk clutch is doing with them. With these 8 speed plus gear boxes for efficiency the OE's are using a dual clutch in lieu of a conventional automatic transmission. They way it works is one clutch does half the gears and the other the other half. They switch back and forth so that when in drive the engine and transmission are never uncoupled. One clutch does first, the next second, back to the first one for third etc.

The other trend is the CVT types for efficiency.

Either way, the dual clutch multi speed or the CVT are lighter and more efficient than what we are accustomed to in an automatic transmission.

There are some informative videos on YouTube. This is one that may be worth considering:

https://www.youtube.com/watch?v=W42zsFYjZvM

Thanks guys. One clutch for odd-number gears and the other for even-number gears makes sense.

It takes getting used to. Drove my brother's M4 with a DCT. If you let go of the brake, there's no forward motion like a regular automatic so if you're stopped on a hill, make sure your foot is on the brake, like a manual.

DCT’s are making headway in the motorcycle industry. Honda seems to be pushing them pretty hard.

quote:

Originally posted by Phelen_Kell:
It takes getting used to. Drove my brother's M4 with a DCT. If you let go of the brake, there's no forward motion like a regular automatic so if you're stopped on a hill, make sure your foot is on the brake, like a manual.

My new Sonata has an “auto-hold feature. When it’s enabled, the brakes are automatically applied whenever the car comes to a complete stop, and remain fully applied until I give it a bit of gas. Perfectly smooth release. The wonders of modern technology. The car has no manually controlled parking brake at all.

quote:

Originally posted by Pipe Smoker:
My new Sonata has an “auto-hold feature. When it’s enabled, the brakes are automatically applied whenever the car comes to a complete stop, and remain fully applied until I give it a bit of gas. Perfectly smooth release. The wonders of modern technology. The car has no manually controlled parking brake at all.

That technology isn't that "modern". When I was a kid my family had a 1951 Studebaker with a three speed manual transmission and it had a "hill holder" feature. You stepped on the brake
and once the car came to a complete stop the brakes stayed on until the car rolled forward a slight amount. You didn't have to jump the clutch to keep it from rolling back on an uphill.

It was a real benefit in our hilly area and I never understood why it disappeared for so long.

VW has been using them for a while.. They get better MPG with the DSG then with the manual. Also quicker in the quarter mile.

quote:

Originally posted by Zecpull:
VW has been using them for a while.. They get better MPG with the DSG then with the manual. Also quicker in the quarter mile.

And fun as hell in my wife's Golf

The wife's GTi has the DSG dual clutch gearbox.
As a diehard manual kinda' guy...it's really impressing me. The lightning-fast downshifts in sport mode (when coming to a stop, etc.) are soooo fun.

I have an Audi TT with the DSG dual-clutch transmission and it works very well. Extremely fast and smooth shifts.

We make additives for dual clutch transmission lubricants. There are many interrelated requirements.

quote:

Originally posted by VictimNoMore:
The wife's GTi has the DSG dual clutch gearbox.
As a diehard manual kinda' guy...it's really impressing me. The lightning-fast downshifts in sport mode (when coming to a stop, etc.) are soooo fun.

Re: “As a diehard manual kinda' guy...”

I was too. I bought my first automatic (on my 2012 Sonata) when I could no longer get a manual-shift mid priced sedan with anything better than the tacky base trim, features, and engine.

Now, the DCT on my 2018 Sonata Limited gives me the best of both worlds. A no-torque-converter gear box that’s fully automatic, or fully manual – my option.

watch this.

Currently I drive a stick. If I was going to get a car with an automatic, I'd want it to be a dual clutch manumatic, not a slushbox or CVT.

quote:

Originally posted by Pipe Smoker:
Thanks guys. One clutch for odd-number gears and the other for even-number gears makes sense.

Yep, the monkey described it well. The advantage, in performance cars, is that the software anticipates what your next gear will be (up or down depending on a lot of parameters) and pre-engages that. The shifts are just releasing the one clutch at the same time the other/next gear is engaged, hydraulically.

I'll admit I'm surprised they've gotten to the point where they can be affordably put in cars in that range. Cool, if so, but I suspect that Hyundai may be taking some liberty with the phrase over what it means in a Porsche, BMW, etc.

For example, the DCT in a Porsche Cayman is a sealed, non-serviceable lifetime unit. If you are unlucky enough to grenade one somehow, out of warranty, the last prices I saw were in the $12-14K range, plus install.

Even for a three-pedal fan like me, they are amazing pieces of technology and, in the right configuration, the sub-100ms shifts are freakin' awesome!

Re: “I'll admit I'm surprised they've gotten to the point where they can be affordably put in cars in that range. Cool, if so, but I suspect that Hyundai may be taking some liberty with the phrase over what it means in a Porsche, BMW, etc.”

You might be right. I can’t say since I have experience only with the dual clutch transmission of my Sonata Limited. But after two weeks I can report that it shifts quickly and crisply, yet smoothly – don’t see how it could be much better.

Also there’s a neat “auto-hold” feature – when enabled, the brakes are automatically applied when the car comes to a complete stop. The brakes smoothly release when a bit of throttle is applied.

Its engine is quite sophisticated too. 16 valves, dual overhead cams with dual-continuous variable valve timing. Fuel is injected directly into the chamber, rather than the intake manifold.

Like most turbocharged engines, peak torque is achieved at relatively low engine speed (1350 RPM), and remains at that peak through 4000 RPM.

The engine comes up to operating temperature very quickly. I attribute that to two things. First, the engine is light aluminum, including the heads. Second, sensitive knock detectors allow the mixture to be leaned as much as possible.