How much does aircon affect performance?

[yky]

Does anyone know by how much %tage does the aircon compressor saps up engine power and affect car's performance?
Does BMW cars come with the function that automatically cuts off the compressor clutch when the engine is under load, eg. during acceleration ( like the simple vaccuum triggered devices that I used to install in my previous Jap cars )?

 

[Mockngbrd]

Re: How much does aircon affect performance?

for mine, switching off the engine does help considerably.
must better response... cos mine is a 1.6

 

[achtung]

Re: How much does aircon affect performance?

for mine, switching off the engine does help considerably.
must better response... cos mine is a 1.6

Hi Mockngbrd.... switch off engine? ;-) It helps with consumption but not sure about better response

 

[Mockngbrd]

Re: How much does aircon affect performance?

haha....woops.. type... switch off aircon i mean

 

[achtung]

Re: How much does aircon affect performance?

haha....woops.. type... switch off aircon i mean

I kinda figured but just wanna pull a fast one.... have not seen you posting pics of replicas (minatures) in AROC since they move to the new forum....

 

[mistraele]

Re: How much does aircon affect performance?

i think most modern compressors, the power loss is probably equivalent to around 2-3hp, not more than 5 i would say.

of course the lower your engine BHP output, the more likely you notice the power loss as it comprises a bigger percentage of your engines power.

 

[Mockngbrd]

Re: How much does aircon affect performance?

I kinda figured but just wanna pull a fast one.... have not seen you posting pics of replicas (minatures) in AROC since they move to the new forum....

Yup. actually i stopped posting when they implemented the rule that only "paid-members" can post.
And everyone else just kinda left after that.

 

[totoseow]

Re: How much does aircon affect performance?

i read somewhere its about 5hp of engine power....

for me trying to outrun a van no differnce. trying to chase an EVO. alot!

 

[TripleM]

Re: How much does aircon affect performance?

i read somewhere its about 5% of engine power....

for me trying to outrun a van no differnce. trying to chase an EVO. alot!

You are already chasing Evo in your 5-er
I dunno wot u will chase if you have a porky or gs :juggle:

 

[totoseow]

Re: How much does aircon affect performance?

jackie...chase only...doesnt mean can catch...

 

[piggyboyz]

Re: How much does aircon affect performance?

Generally it should be around 5hp and don forget together with the compressor cutting in, the engine fan will also be activated as well and for those with the magnetic fan clutch that draw power from the engine, it will be pretty significant.

For the later cars like the E60 and E90, where they do away with the magnetic fan cluch and went with a complete electric fan, the loss is slightly reduced.

For our cars, the air-con compressor will cut off momentarily when we activate the kick down button or when we do WOT acceleration beyond 5000rpm to protect the compressor.

 

[CGT]

Re: How much does aircon affect performance?

Less than 0.1 HP.

If you were to read into the DME manual, at WOT (wide-open-throttle) the AC is automatically switched off.

Unless you remove the AC altogether, like what they did to the factory racecars, you'll gain some % of hp, because of lesser drag at the crank pulley. Then again, racecars are not equipped with AC because of weight consideration not power.

 

[SFW]

Re: How much does aircon affect performance?

To me, switching off the air-con gives me a more spirital drive. It rev up more easily. But of course you have to withstand the noise and dust from outside.

 

[yky]

Re: How much does aircon affect performance?

OK. The compressor cuts off at WOT. But most of the time in real life, we don't drive at WOT but at partial throttle. So, it seems that there is still a place for aftermarket devices like the 'passmaster' or other adjustable compressor cutoff devices isn't it?

I had such a vaccuum operated device fitted to my previous Jap cars and its sensitivity can be adjusted, so that it can cut off the compressor even during mild acceleration ( a few seconds ). The compressor will be back online once stable speed is reached so there is no discernable lack of cold air from the vents.

 

[CGT]

Re: How much does aircon affect performance?

OK. The compressor cuts off at WOT. But most of the time in real life, we don't drive at WOT but at partial throttle. So, it seems that there is still a place for aftermarket devices like the 'passmaster' or other adjustable compressor cutoff devices isn't it?

I had such a vaccuum operated device fitted to my previous Jap cars and its sensitivity can be adjusted, so that it can cut off the compressor even during mild acceleration ( a few seconds ). The compressor will be back online once stable speed is reached so there is no discernable lack of cold air from the vents.

Agreed. There are basically 3 Maps in our DME: idle, part-throtle and WOT. Only at WOT the compressor is cut off. I agree that there is a place for such device as it helps part throttle acceleration. But I felt the HP-increase claims are way over the hill.

Take for example: A 2000cc NA engine at 50% throttle, sucks in 50% less air and therefore behaves like a 1000cc at 100% throttle. And if the same 2000cc churns out 100bhp at 4000rpm (WOT), so it should be doing 50bhp at 50% throttle (AC off). Now switch on the AC, are we going to get only 45 bhp?

A domestic AC with 3KW (4 HP) compressor does enough to cool a 5 room HDB flat.