its been real hot these last couple of months and i have th a/c on full blast at 72 degrees when im driving. and the car feels real sluggish too. just wondering if anyone knew how much the a/c on would effect hp?

sidemarker

 

not much and at WOT, none at all ! (could be just 2003 models)... I think its just the hot weather that your engine no likey....

 

On this car, not much. It also does turn off at WOT. Now take my Explorer, the AC robs about 1/2 the HP on that. My moms 85 Accord doesn't seem to be effected by the AC. All depends on the car

 

I've read anywhere between 10 and 20HP at the flywheel on most vehicles...

(Although, I would think us Hondas are on the low side of that range...)

Does the Helms say anything?

 

hmmm

i guess its the hot weather

sidemarker

 

72 degrees is full blast?

 

I believe when your WOT, with the AC on, the compressor stops to give all attn. to the VTEC WOT.......I could be wrong ! This is another neat feature we have ! Come on gear heads, what's the truth to this ?

 

Well WOT may be different but normal driving there's a huge difference in available power - the car has to rev a lot higher for the same amount of GO.

 

The rule of thumb is about 10 gross hp loss when the AC is on. This is especially noticeable with low hp cars. Try it with a Civic. Drive with the AC on, partially floor the pedal and switch off the AC, you will feel a surge of power.

 

sidemarker:
Don't know where in TX you are...but where I am there's a huge difference versus when I was up North earlier...it's the heat man and thus much lower concentration of oxygen per unit volume of air...

Austin519

 

I think that is a bit high....

Forgetting about efficiencies for a minute, let's take an good home window mount or portable A/C unit for some ideas):

http://www.airconditionershack.com/

12000 BTU cooling capacity
1100W power input

I have a 11K BTU unit that cools down an area of around 24' x 15' (360 sq ft). It has a similar power requirement, so its efficiency rating is "close". (There’s less window glass, but that’s a lot more room than a car gets)

So, I'm going to convert the power required to run the unit shown in the link (it would turn a car into a icebox):
1100Watts * 1 HP/746Watts = 1.47HP

So, a pretty nice home or office wall unit would only need 1.5HP to cool a couple of pretty hot rooms.

Also, if the A/C really needed 10HP to run, it would cause the idle to really kick when in cut in and off. There would be a very large change in the amount of idle air that was let in to compensate!

As a rule, the auto units will have lower efficiencies as they do not have "flingers" to take the condensate (water from the condenser inside the car) and fling in on the evaporator coil (in front of the engine's radiator) to help cool it down. (Evaporating water gets rid of a lot of heat from its phase change [liquid to gas]...)

So... If you have a large American “float-a-type”/SUV/land-yacht that can turn your passengers into ice cubes then the following might be applicable (I’ve been in some 1980 Caddies that would freeze my toes off when it was 120-degrees F outside!)

"Refinements to automotive air conditioners continued to be made throughout the 1970s. Units became more efficient, more compact and lighter weight. For example, some of the compressors produced in the early 1950s weighed nearly 60 lbs (27 kg). Design modifications reduced the weight by 80%; they also improved the efficiency, capacity and durability of the units. It is remarkable that an automotive compressor the size of a bread loaf weighing about 12 lbs (5 kg) can provide 3 tons (10.5 kW) of cooling, which can cool an average seven-room home"

LINK: http://www.ashraejournal.org/feature...-feature1c.htm

(That would amount to about 14HP. (Sorry, I don't think the A/C in my Acura is more powerful than the one in my office or in a new some of the bigger American "freeze-mobiles")

And

I found a page for a 30,000 BTU unit for a greyhound bus, that should require about 5HP...

http://www.busair.com/66.htm


The rest of the articles I found indicated that a "typical" car requires an air conditioner to handle about 6000 BTU/HR (back to 1-2HP)

 

well if the a/c dosent rob a lot of hp

then would it be possible to channel some of that "cold air" into the air intake system so that it will lower the temp of the air going into the intake manifold? or will this not work at all?

sidemarker