307 HDi DTurbo Cruise Control

Although I've owned a 307 Dturbo since January, I've only just got round to trying out the Cruise Control, and only for brief periods owing to the congested state of British roads. On a longish trip, mainly on motorways, I accelerated up to 90MPH (to keep up with the flow of traffic) and set the cruise control. After only a short distance I came up behind slower moving traffic and had to slow down to about 50MPH. When the congestion had cleared I re-engaged cruise and was amazed by how quickly the car accelerated up to the memorised speed, seemingly much faster than flooring the accelerator.

At first I put this down to imagination but my wife who also drives the car got the same impression. It's as though there's an extra boost from the turbo. Is this a possibility? Anyone care to comment?

-- "Once in a while, I'm standing here, doing something. And I think, What in the world am I doing here? It's a big surprise."

Reply to
Crazy Aizy
Loading thread data ...

I get the same on my C5 when letting the cruise control resume the speed. Nice isn't it?

What is more suprising is when you forget what your last speed was, say

70mph, then when you doing 30ish in 4th and hit the resume button you will get there very quickly indeed!

Nice cars

Ben

Reply to
Ben Cowell

On Sun, 4 Jul 2004 12:39:25 +0100, a particular chimpanzee named "Crazy Aizy" randomly hit the keyboard and produced:

I've the same model. At first I thought the cruise control would be a novelty, but I couldn't do without it now, especially on long journeys. Even on congested roads, it's helpful to drive with it on to even out the 'speed-up-brake' mentality of the likes of the BMW drivers. I use the c/c to accelerate and decelerate rather than the pedal.

I don't think there's a 'boost' in the output; it's just that the electronics reacts a lot faster to the changing engine speed than your right foot can. After all, you shouldn't just floor the pedal when you want to increase your speed; you should allow the revs to build to prevent wasting fuel.

Reply to
Hugo Nebula

Very nice indeed. I now realise what I've been missing for the last 6 months!

I must try that!

Reply to
Crazy Aizy

I was of the same opinion - a novelty - until I used it. It's nice to show a clean pair of heels to a tailgating BMW!

Perhaps the ECU uses a different program rather than a turbo boost? Normally I never floor the throttle for economy reasons but did so as an experiment in this case. Another thing that impressed me was the absence of wind and engine noise - seems to reduce above 70MPH. I really like my 307!

Reply to
Crazy Aizy

Interested to hear someone else noticed this. I thought I was going mad but swore it is a lot quicker.

If anyone knows the real technical reasons for this I'd love to hear them. Surely with all the electronics in the car if you put your foot right down on the accelerator it should do its best to go as fast as possible - the accelerator is not mechanical on the 307?

Reply to
HDIdriver

I have noticed the same effect in dad's Volvo (don't have CC in my 206). I put it down to psychology. In the volvo the CC is electro-mechanical (it presses the accellerator for you) so there is certainly no trick going on.

Maybe the fact that you are not directly in control of the car enhances the experience, making it seem that little more scary/fast. Try sitting in the passenger seat and do the experiment with CC and driver and see if you notice a difference?

Gerd.

Reply to
Gerd Busker

Probably not necessary to mention but noticed a couple of posts regarding peeps using CC for the first time here. Please be advised not to use this on wet surfaces as any loss of traction to the wheels in wet conditions with the CC turned on can lead to a very scary experience.

Found this out personally last year when Aqua-planing due to having CC engaged in the middle of a down-pour. Car was quite happy on motorway until it hit a patch of standing water, the wheels lost traction and the CC tried to get the car back to memorised speed. When the tyres got some purchase back the resulting skid was terrifying, fortunately no-one was hurt and managed to have the sense of mind to apply gentle braking and got car under control again.

Just thought I'd share it, as wouldn't recommend the above to anyone but adrenalin junkies!

Reply to
Longshot

I agree that it could be all down to imagination from not being in direct control of the car but during my experiments with CC when my wife was a passenger, she also commented on the apparent faster rate of acceleration. One thing I haven't mentioned is the 'kick' when CC is engaged, similar to 'kick down' in an automatic. This is especially noticeable when engaging CC from say 60mph in 5th gear upto a memorised speed of 90mph.

Reply to
Crazy Aizy

Thanks for the warning! On the 307 Dturbo, traction control and ESP are standard equipment. Just wondering how they would cope with such a situation.

Reply to
Crazy Aizy

The fact that the CC is controled electronically means that the sensation of speed is more instantaneous. I don't know if its true of Pugs but a lot of CC systems are controlled by and actuator which is independent of the normal accelerator set-up. The CC system is designed to get you to your chosen speed quickly without overshooting it.

So for those people having set the CC speed to 70mph and who then re-engage the last memorised speed from a relayively low speed e.g 30mph will notice a seemingly aggresive accelereation back up to your desired cruise speed. As such the 'flooring' of the accelerator pedal won't recreate the same experience as CC controlled acceleration because all your doing there is opening the throttle and adding more combustible material to the mix which eventually leads to greater acceleration.

There isn't a 'kick-down' as such just a more efficient and faster electronically controlled acceleration of the combustion process.

Reply to
Longshot

Has anyone noticed whether fuel economy is better or worse when using CC? I don't actually use mine that much so can't really comment.

Reply to
HDIdriver

It says in the C5 manual that the CC will disengage when the ESP is triggered.

Reply to
Ben Cowell

That's comforting to know!

Reply to
Crazy Aizy

Not doing a great deal of motorway driving myself, I find CC more useful when driving through 30 or 40 mph zones. Assuming there isn't much other traffic around. I can set it to say 33 mph (!), then not have to worry about continually checking my speed, especially with so many speed cameras in my area.

Robin

Reply to
Robin Bendall

Agreed

Reply to
Ben Cowell

You can add it to most new HDI engines (the ones with the radio controls on a big stalk)

Ask your dealer if they can do it.

The procedure is as follows:

1, Fit CC stalk. 2, Ensure brake and clutch switches are present, fit if they aren't (I didnt have a brake switch) 3, Tell the ECU it has CC.

Total cost at a UK main Citroen dealer: £125.

Reply to
Ben Cowell

The 307 HDi solded down under are Not fitted with Cruise Control.

Keith

Reply to
Keith Holley

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.