Steep driveways, reversing a trailer, and: Will you kill the new eight-speed dual clutch transmission in the new Santa Fe and Sorento diesel AWD models?
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Here's a question from Larry the landscaper:
"I’m thinking of replacing my Ford Territory with another SUV. I had decided on a Kia Sorento until I saw your article on DCTs, specifically the issue of reversing a box trailer up a steep driveway. Guess what I do every afternoon? Is there a way of mitigating this issue with the use of handbrake, etc., or should I simply discount the Kia and go instead for the Mazda CX-9?" - Larry Watt
Good question - and at the time I did so wish I had a good answer, but alas, my crystal ball was down for the count on this one, and the lapsed engineer in me still recoils at the prospect of making stuff up. So I stalled for time and asked for more info from Landscaping Lazza...
...who deployed his protractor and tape measure. As you can see, it’s a pretty steep driveway, but not that long. I can empathize. About 20 degrees, 21 metres, and the trailer might weigh 400 kilos on a heavy day. And Larry reverses in at the end of the day, five days a week, after toiling hard, turning busted-arse Sydney scrub into the cover of Home Beautiful, repeat.
So - because I had no idea about the duty cycle for this new transmission, I reached out to Kia’s top engineering dude in 'Straya, Roland River and he reached up to the 37.88th Parallel, where the R&D brainiacs hang out, in a very cool place called Namyang.
Everyone should go to a place like Namyang, once in their lives - just for the test tracks and the wind tunnels and the anechoic chamber and the rooms where they bake, freeze and break various parts - and whole cars - with great precision. They take this stuff very seriously.
I’m sure there was some brow-furrowing up there on this. Like: ‘He wants to do what?’ Anywho, Namyang dudes give Lazza’s driveway and trailer due consideration, then they go (I’m paraphrasing):
That should be fine, dude. Just make sure he does it one-up. Like, get the passengers (if any) out. Pro tip, do try to avoid hill-holding using the throttle and slipping the clutch - because in the domain of transmission good things and transmission bad things, that’s generally bad.
They also go (agin, paraphrasing): this is a relatively severe operating condition, because of the low speed and low airflow and high load from gravity and therefore high input heat and low forced convective cooling effect - even though the clutch system is wet and features a dedicated cooling system.
Furthermore, the clutch system features self-protection. And if that triggers, the clutch is programmed to release at a pre-set temperature, to prevent serious damage. In other words, we did our best to idiot-proof things - even though humanity always invents a better idiot when we do that.
And if that happens (the thermal protection clutch release trigger) you will lose tractive effort, so wait a couple of minutes, dude, and leave the engine running (presumably to maintain oil circulation through the cooler). Then you can go again.
I must say, this all seems quite reasonable to me. But the variables are, obviously, how often you do it, how steep and long is your driveway, how heavy is your trailer, and how capable/mechanically sympathetic are you, as the driver.
Негізгі бет Dual clutch transmissions, towing & heavy-duty uphill reversing | Auto Expert John Cadogan
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