"The problem is, every car in front of me wants to go 1mph slower than me, and every car behind me wants to go 1mph faster."
That makes me wonder how the Americans manage on their freeways. I guess each driver must set his/her cruise to match the speed of the car in front, but, with speedo variation of up to 10%, how does the cruise control and the ECU know that? Would work with perimeter defence radar systems as can be bought on Jags and Mercs, but not for every car. So how do the Americans do it on a croweded freeway?
HJ
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>>.... I guess each driver must set his/her cruise to match thespeed of the car in front, but, with speedo variation of up to 10%, how does the cruise control and the ECU know that? ....
HJ, you've lost me there - if the driver sets the cruise speed according to the speed of the car in front, as judged, I presume by a constant and hopefully safe, distance between them, then it doesn't matter what the speed is according to there speedo/ECUs, only that the relative speed is zero.
Or have I missed something?
Chad.
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Should've added that this obviously needs both cars to be on cruise .... otherwise it obviously doesn't!
Chad.
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"HJ, you've lost me there - if the driver sets the cruise speed according to the speed of the car in front, as judged, I presume by a constant and hopefully safe, distance between them, then it doesn't matter what the speed is according to there speedo/ECUs, only that the relative speed is zero."
Yes, get your point that if the inaccuracy is constant then the speed difference should be constant. But it won't be, because cruise control accelerates and decellerates in an attempt to keep very close to a constant speed but doesn't actually keep perfectly to that constant speed.
HJ
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HJ,
What happens is you're travelling across the Nevada Desert, side by side with the same car you've been next too for the last 10 miles inching past it. And nobody cares - what else is there to do ?
Seriously though, on longer journeys is happens a lot.
And as for whoever suggested not using the CC, silly idea. I use it a lot and it makes life a whole lot more pleasant. You don't think I *really* care about having to change my speed by a a couple of mile an hour, do you ?
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I use my CC a lot, too.
Motorway roadworks.
Set to 40, or whatever, and divert more attention to reading unfolding events than specifically trying to control speed and look for the Scameras.
Free running motorways.
With a car as wonderfully quiet and refined as the one I drive, with tall gearing and truck loads of torque, it is very easy to fall in to the trap of cruising faster and faster. I now routinely set cruise to something appropriate for the traffic volume, and relax. Relax doesn't me go all dozy. It means relax from the pressures of breaking the speed limit, and divert more attention to what's going on around, including what's evolving in front (is that juggernaut catching the one in front? Is there a car sandwiched between the pair of them?), and coming up behind. It's usually simple and safe to merge in and out of lanes without touching the cruise control or impeding anyone, but if a gross speed merchant is tanking up behind, I simply knock off the CC and allow speed to bleed away in good time. When safe to do so, hit the resume switch, and then pull out to overtake. This gives a nice smooth surge of acceleration back up to the set speed. Alternatively, I need to, I can accelerate with the pedal to sprint past something, knowing that when I lift off, the set speed will again prevail. No need to touch the CC. All very easy and unruffled.
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Mark, my 'silly' suggestion of not using CC was only (as stated) for busy roads. No doubt your definition of 'busy' might differ from mine, but there comes a point when constantly disengaging and re-engaging CC is more hassle than doing without for a while. This certainly isn't helped by my Volvo, where the CC controls must be located by Braille in the dark!
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LHM,
I wasn't being particularly serious. Actually on/off-ing the CC isn't difficult with cancel/resume buttons but, as you say, I don't use it unless a reasonably constant speed is likely.
And on the Landcruiser they're behind the steering wheel by your fingertips, so no braille required.
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Would be interested to know which Volvo requires braille.
I drive a 2003 V70, and the buttons are well placed, and illuminated, on the left hand side of the steering wheel hub.
When I go to Sweden with my work, I often drive a previous generation V40 2.0T, where the CC controls (same as S40 and I believe the older 800 and 900 series) are located on a stalk with a slider.
Of the two, I prefer the V70, but both systems are extremely intuitive to use, with fingers quickly falling to the required place without needing to look.
I do find however that the system on my V70 (electronically controlled throttle) is far faster to react, and holds a beautifully constant speed at all times, whereas the older S40/V40 system allows speed on a hill to drop before reacting and requires some anticipation to set a specific speed. For example, when pressing 'minus' (or 'disengage') to bleed away speed, the button must be released (or resume pressed) just before the speed wanted, as the car will continue to decelerate for a short time afterwards.
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Hi SjB,
I'd guess my S80 CC buttons are similar to your V70's. I'm being a little harsh with the 'Braille' bit, but the buttons are non-illuminated (1999 model) and identically-shaped, making the 'O' button awkward to find in a hurry at night. I try to avoid disengaging the CC with the brake pedal (so as not to precipitate braking behind me), and hitting the 'CRUISE' button (easier to find) means re-setting the CC afterwards.
Having said all that, I agree that the CC works very well - the 'fly by wire' throttle being far easier to incorporate into the control loop than the 'strings and pulley' variety previously employed!
BTW, have you found the 'resume' funtion to be a bit 'severe' in some situations?
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Yes, LHM, you are correct in that they are almost identical. The steering wheel hub shape being the only real difference between these two Volvo models. The S60 has a different configuration to your car and mine, with a slimmer hub, and the CC buttons arranged at an oblique angle across the left hand 'thumb spoke', rather than on the hub itself. Although I find the S80/V70 controls easy to operate, I do prefer the S60 wheel cosmetically, but was not prepared to pay the £££s to specify is as an option.
I personally don't have a problem with finding the 'O' button, but one trick I do use when needing to reliably disengage CC (i.e. with no missed buttons risk) in a hurry, without pressing the brake, is to slightly depress the clutch pedal. This pedal also has a CC switch, so pressing it just enough to trigger has the effect of smoothly, but instantaneously, disengaging CC. If your S80 is an auto, sorry this doesn't help!
Regarding your 'resume' question, I guess it depends what you mean by severe. At low speeds, resume is gentle, but yes, if I 'resume', say 70MPH from 50MPH, even in 5th gear I get a very strong surge of torque that then bleeds away with a couple of MPH to go.
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Engaging and disengaging the CC has been mentioned as a way to match the varying speeds on motorways. I found that when CC was engaged, one button would give gentle acceleration to increase the CC set speed, and another would suspend the CC and allow the car to coast, slowly reducing the speed. Releasing either button re-engaged the CC at the new speed. With some anticipation, I found that it enabled easy fine speed adjustment to match the other vehicles. I'm sure all CC systems have this, but at least one other person with a CC-equipped car I mentioned this to had never realised it was possible. With a used car, the owner's manual is usually missing, so how many people never use CC because they don't know how to use it fully?
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