Immediate difference between C5 and Xantia

[wheeler]

some cars used to have a switch to turn off the air-con when you fully opened the throttle.....

On the C5 the A/C pressure sensor is directly linked to the injection ECU (surprisingly not the A/C control unit) for this exact reason. if it needs to it will drop the A/C compressor under load,accelerating heavily or any other time it thinks it needs to.

[nick]

It does this on my Xsara HDi too. I notice it sometimes when accelerating away from a junction, you don't tend to hear it cut out, but can hear a definite click when it cuts back in again as you build up speed and ease off the throttle.

I think some HDis even have a similar clutch setup to cut drive to the alternator under heavy acceleration.

[AndersDK]

I think some HDis even have a similar clutch setup to cut drive to the alternator under heavy acceleration.

That would be much simpler just using an electronic control signal to the charge module, telling the alternator not to charge.

[nick]

Yes that would seem more sensible, I'm trying to remember which PSA car I was told had this setup, I don't think Citroens ever did. Could have been bollox of course . . .

Edit: Looks like what they were referring to was actually a freewheel pulley on the alternator, designed to reduce the load on the crank as the engine slows.

[frenchcarnut]

Oh and the electric windows are a pain on the C5 - great if the wife's stuck in traffic and a carjacker comes up to her, NOT.

Basically they are too sensitive to obstructions such that when winding up to close they almost always stop at 75% and pull back a little. I have cleared out the tracks which helps a bit, but it soon falls back into failure mode.

Grrrrrr

[frenchcarnut]

aircon is on (which is rare due to green issues)

Why?

This is being referred to in the latest green article from the BBC. See here

However, they do offset this to a degree with the drag caused by open windows which according to one report in The independent, and alluded to on here, comes into effect from 40 mph

[nexarius]

Just thought I'd introduce some common sense to this... debate.


YES, powering a compressor will lead to the consumption of more fuel than not powering one because there is more load on the engine.

YES, air conditioning is a heat pump and will lead to more HEAT being pumped out of the vehicle, even if the temperature of the radiators is the same. Heat and temperature are not the same thing.

BUT:

YES, driving with the windows open at high speed also puts more load on the engine which also leads to the consumption of more fuel and the output of more HEAT from the car.

AND:

The heat being pumped out of the vehicle by the heat pump is NOT BEING GENERATED BY THE ENGINE, it is being generated by the sun because it's a hot day which is why you have the air conditioning on in the first place.

Air conditioning is simply pumping the heat out of your vehicle. Heat pumps are MORE EFFICIENT THAN HEATERS, so maybe when it's freezing cold in the winter we should just put up with it because we're saving energy by not using our heaters?




Besides, the effect on the environment of not using A/C is negligable compared to what you could achieve by fitting energy saving lightbulbs to your house, or using public transport or cycling or walking instead of using a car!

The amount of ENERGY used to cool you down is still nothing compared to the amaount of energy you're using to continuously accelerate/deccelerate a huge lump of car every day!



Excuse my 'shouting', but it's really frustrating watching people arguing about something without the proper context.


In conclusion:

Frenchcarnut is right to say that in certain conditions, energy is saved by air conditioning not being used.

The opposition is right to say that the difference is usually negligable, and that in some conditions energy can in face be saved by using air conditioning.

[frenchcarnut]

In conclusion:[/u]

Frenchcarnut is right to say that in certain conditions, energy is saved by air conditioning not being used.

The opposition is right to say that the difference is usually negligable, and that in some conditions energy can in face be saved by using air conditioning.

I think there's some merit in this and my conclusions on current theory suggest a) That in urban traffic I will use open windows, b) On motorways and trunk roads I will use air vents and c) on the odd occasion when the UK is simmeringly hot and I'm in slow moving traffic where the neighbourhood is, in known criminal terms, less than salubrious , I will use air-con.