Air conditioning light

[The Natural Philosopher]

7.5KW? I dont think so.

[Dave Plowman (News)]

Yup - remember seeing the spec for the AC in the then new Rolls Silver Shadow. Said at full belt it took approximately the same power as a 850 Mini could produce. ;-)

[Dave Plowman (News)]

Yes - you of course can reduce the output of the AC if you wish maximum performance from the engine to actually drive the car. Which may or may not matter much in practice. Who needs AC when grinding up a long hill? ;-)

[John Rumm]

Even a basic system will take 3kW, but two to three times that is not unheard of.

[bert]

In article , "Dave Plowman (News)" writes

No noticeable difference to the driver pedant.

Stating the bloody obvious again. But s I said I have had several (7) small engined cars with air con and one didn't notice any sudden need to floor the throttle when it was switched on.

[bert]

All my systems large and small have coped in hot UK conditions.

[bert]

In article , "Dave Plowman (News)" writes

And what was the engine output in said car?

[bert]

Well with aircon my experience ranges from engines less than 1 litre to

4 litre v8s and straight sixes. But it is obvious you like to think of yourself as an expert on the subject and quote numbers out of any context to try to prove so.

[Dave Plowman (News)]

Not surprised at your constant 25 mph.

[Dave Plowman (News)]

All you're proving is you are simply too mechanically insensitive to notice it.

[John Rumm]

I think all bar one of ours have as well. SWMBO had a Honda Prelude that could not really cope on a really hot humid day - it would run for 15 mins, and then trip out with a "compressor" light lit if you tried to run it too hard. If you set it to half fan speed and put it in recirculate mode then it would cope, but performance was not exceptional.

I have been in others cars where they system runs fine, but doesn't really have the power to shift the heat fast enough.

[John Rumm]

The first car I had AC in had a 2L injection engine (probably producing about 130bhp), but the AC system was fairly powerful @ around 11 HP maximum consumption. While it was not a problem, you did feel it take the edge off the acceleration. It also made quite a noticeable change in load when it cycled in and out - so if you were creeping along in traffic - you would feel the jerk as the engine adjusted to the step change in load.

However my current car has a equally powerful but more sophisticated AC system, but you don't really notice any step in and out effects at all (probably helped by being an auto - so a less "rigid" connection through the transmission at traffic jam speeds). Its far less of a lump out of the available 280 bhp anyway so you don't tend to notice it on acceleration either.

[Dave Plowman (News)]

The most powerful system I've had on a car was the old Rover. Judged by how long it took to cool the inside from being parked in the sun. And you can clearly feel that cycle even with a 3.5 litre engine.

Of course you can control things in software to make any load from the AC less obvious. All my newer cars have done. But you can still notice the difference in performance to a certain extent. And certainly to the MPG.