Our long-term 2009 Audi S5 has a manual gearbox. It has cruise control. Those things by themselves are not remarkable.
The way they interact, if not remarkable, is unusual. Once set, the S5's cruise control does not cancel if you decide to downshift. The S5's cruise control resumes your set speed as soon as you've completed the gearchange.
This took me by surprise at first, only because so few manual-gearbox cars allow this. Typically the cruise cancels when you dip the clutch.
Because I'm a geek, I began thinking of what might drive an automaker's decision to adopt this "clutch-resume" strategy (as Audi has) over the usual "clutch-cancel" one.
Pro: On a steep freeway grade that requires you to drop down a gear to maintain your speed, "clutch-resume" allows you to do so without having to hit resume afterwards. One less button-press in this case.
Con: Downshifting for engine braking in a "clutch-resume" car requires you to hit cancel first, else you're in for a surprise when the car tries to re-accelerate to your set speed! One more button-press in this case, or use the brakes.
Any geeks out there that can think of other pros or cons to either approach?
Jason Kavanagh, Engineering Editor
jederino says:
01:25 PM, 10/ 9/09
I don't like the setup described here. For steady-state drive, I like cruise control. If I hit the clutch or break, I want control back! It's so easy to press "resume" if you needed to grab the lower gear.
alex4515 says:
01:28 PM, 10/ 9/09
Con: Most drivers are used to "clutch=cancel" so they had better beware if using cruise in this car...
bimmerjay says:
01:29 PM, 10/ 9/09
BMW also has this feature. The system does deactivate if you hold the clutch for too long, however - I think it gives you maybe 2 seconds to complete your down or up-shift. I love it though - it shows that in Europe, enough cars are equipped with manual gearboxes that systems like this are built around them. Unlike in the automatic transmission-centric U.S. where most American or Japanese automakers wouldn't bother with details like this on manual-equipped cars, and just have clutch-cancel.
nealibob says:
02:17 PM, 10/ 9/09
Personal preference. As such, it would be nice if it were configurable. It would be nice if you could buy an option on cars like this that gives you a screen full of preferences that you can adjust. Think of how much fun that would be!
spaceywilly says:
02:31 PM, 10/ 9/09
I feel like if I added up the times I've pressed the clutch when using cruise control I would end up with cancel as the intended result 10 times more than resume. This is overengineering if I've ever seen it.
kjmiller1 says:
03:28 PM, 10/ 9/09
Clutch cancel would be my preference. What kind of grade would it take to warrant a step down in a car as powerful as the S5?
I think it might be more for dealing with slower traffic ahead of you on the highway. Picture a dummy pulls in front of you, you push the clutch in to give you more time before you rear end them to look over so you can change lanes, put it back in gear and you are off.
bimmerjay says:
06:52 PM, 10/ 9/09
The other reason this function is present is the Audi can be equipped with active cruise control, which may command dramatic speed variations. In those cases, the driver obviously would have to downshift/upshift or the car will give a warning that engine speed is too low/too high and will cancel the cruise control.
bimmerjay says:
06:57 PM, 10/ 9/09
@kjmiller1, as I stated above, if you hold down the clutch for more than the normal amount of time it would take to complete a shift the cruise will cancel itself. With dynamic systems a tap or two of the stalk will apply the brakes and slow the car as needed. Clutching for a momentary slowdown would be more work. A couple taps back on the stalk would take you right back up to speed.
clarkma5 says:
07:40 PM, 10/ 9/09
My GTI does this and I love it. You control the gear you're in and the speed you're at, it's very logical, since the car can't control its ratio like it could with an auto (and frankly, most cruise controls are obnoxious when paired with automatics).
blueguydotcom says:
03:48 AM, 10/11/09
Bimmer has it too. Shrug.
epbrown says:
02:07 AM, 10/12/09
I've only used it a couple of times on my M Coupe, but I'd think it's more useful for passing, since the system doesn't disengage for acceleration. You can downshift, pass, resume previous speed, upshift again, all without having to fiddle with cruise control. I've never had to use this capability, at the speeds our roads are limited to and my driving style, it's rare I have to downshift to pass someone.