LG John

Thats impossible surely - how can a machine be more than 100% efficient?

TonyBurns

iTrader: (3)

You wont notice it if you have a higher power output engine over say a 65bhp engine which will show a noticable effect.
In the hot weather, your car will show a drop off in power to start with (probably missed by a few people ) so its slower anyway, if you actually watch when you turn on the a/c unit, the revs should adjust slightly upwards to compensate, thus the reason you have lower fuel economy with it on.

Tony

jaf01uk

I'm far from an expert on air con but if I read the original post about the inlet, the way I see it was the guy is feeding the cold air into the inlet therefore cooling the charge and as even I am aware the colder the charge the denser the air the more power? I appreciate that there is a power loss to run the air con and whether the power gained would compensate or not I doubt it,

Diesel

Brit in Japan - point taken, but I still reckon pulling 30hp through a rubber band makes for a very very stiff compressor!

Wonder how much the alternator takes for basic systems and then with the headlamps on? There will be a sum there somewhere where the wattage equals XX horsepower versus alternator efficiency. Anyone?

D

ajm

Remember that airconditioning units in cars are not as efficient as electric units that run at a nice constant RPM away from heat sources etc. The compressor in your car accelerates and deccelerates with the engine so while it is on your engine has additional inertia to overcome every time you press the accelerator in addition to the resistance of compressing the refrigerant. Also, as the RPM's climb the work done also increases so more power is used at higher RPMs. At high revs the unit will be consuming more energy than it needs to cool the same amount of air that was going through at half the RPMs. This is why, in real terms, the power used can be significant.

To most people it is hardly noticeable, but to those of us who obsess over a 5hp gain with an aftermarket air filter , the power the aircon uses more significant relatively speaking!

AvalancheS8

Yes, it is impossible for a machine to be more than 100% efficient, but that wouldn't be an example of that. How about turbo and superchargers ? They increase the engine output by more than the power it takes to run them - which can be 100's of bhp on drag car engines.

Not suggesting that feeding your air-con output into the inlet will do the same though, although I'm sure I remember seeing mention of a system on a modified American pickup truck that did something a bit similar - using the aircon to chill either water or air (water I think) that could then be dumped in to lower the charge temperature and recharged once you were off boost again - like a re-chargeable nitrous system.

LG John

Good example with turbo/supercharger - that makes sense