Question about A/C and engine power

doogiefish · #1 (**permalink**) 07-18-2006, 04:50 PM

Ordered a BOM Sport MT last month. Test drove a base model with AT. I didn't seem to notice that when the A/C was on, the engine power didn't seem to be affected like many other vehicles I've driven. Has anyone else noticed much power difference when A/C is on or off? Difference in power with it on with MT? Just curious.

motordad · #2 (**permalink**) 07-18-2006, 05:14 PM

I don't notice any difference between A/C on or A/C off.

VBP Sport 5MT

MotorDad in Milwaukee

IBTG81 · #3 (**permalink**) 07-18-2006, 05:17 PM

Quote:

Originally Posted by motordad

I don't notice any difference between A/C on or A/C off.

VBP Sport 5MT

MotorDad in Milwaukee

I do. I have a Sport AT. I definately think it's slower and less powerful when the AC is on.

gimme · #4 (**permalink**) 07-18-2006, 05:30 PM

I TOTALLY notice a difference. NHBP Man Sport

Fray Adjacent · #5 (**permalink**) 07-18-2006, 06:07 PM

I kinda wished Honda would go with an electric compressor for the AC system.

Still waiting for the industry to go to 48v DC system to pretty much accomplish that. From what I recall, the industry will be going to 48v DC systems to run more things electric/electronically in automobiles. The batteries would be 48v (more cranking power), but most legacy electronics (radios and lamps and stuff) would still be run off of 12v.

At least it has electric power steering.

bluemeanie · #6 (**permalink**) 07-18-2006, 07:36 PM

Yeah, I also notice a lost in "zip" when the AC is on. At least it's not as bad as my old 1994 Toyota Tercel, where I had to turn off the AC every time to get enough power to get to highway speed. Does anyone notice any mileage/gas loss due to AC use with their Fits?

switchbrdopr · #7 (**permalink**) 07-18-2006, 08:12 PM

It's a Honda thing. I've had the same problem with all three Hondas I've owned. You turn on the air and the power gets sucked right out of the car. It's not a big thing to me though; I still wouldn't drive anything else.

gettinafit · #8 (**permalink**) 07-18-2006, 11:16 PM

Definately there is a difference! And the reason is that the drive belt, (connected to the crankshaft of the motor) has to now spin the compressor b/c the clutch on the compressor is engaged and that basically takes extra strength! It's like throwing 1-2 extra people in the car!

Jetydosa · #9 (**permalink**) 07-19-2006, 12:51 AM

Its not a Honda thing, pretty much any 4cyl car that will happen. You definitely notice the difference when A/C is on but I have been in other vehicles that felt more power sapped.

Flyboybob · #10 (**permalink**) 07-19-2006, 02:29 AM

Anything that the engine has to turn, will steal power from the engine and reduce gas milage. If you drive your car at highway speeds with the windows rolled down and the air-conditioning turned off, the extra aerodynamic drag will reduce your gas milage more than the power required to run the air-conditioning compressor. There is no free lunch! It takes energy to compress the vapor (freon) in the air-conditioning system. Electric motors also will reduce power from the engine by increasing the load on the alternator. The engineers have to figure out which is a bigger draw of energy.

All of today's airliners rob their jet engine's compressor section of air to run air cycle machines for pressurization and air-conditioning. The Boeing 787 Dreamliner, which is still on the drawing board, will use electric motor driven compressors for cabin pressurization and air-conditioning. This will give them an estimated 20% increase in fuel economy.

hiroko12 · #11 (**permalink**) 07-19-2006, 02:36 AM

This is only a 109 hp car. You definitely notice when AC comes on. But you still have enough power.

jazz_honda · #12 (**permalink**) 07-19-2006, 02:57 AM

yup theres a difference....so when i need more power...i turn off the aircon...

trowpa · #13 (**permalink**) 07-19-2006, 07:52 AM

A difference - sure. But not huge. Now - my 2.3 L saab 900 - that car, I had to turn the AC off before climbing hills or getting on the highway! The fit? No issues...

BlipOnTheRadar · #14 (**permalink**) 07-19-2006, 08:53 AM

Yeah, I notice it too. I have a 61KW (no idea how many HP) 1.3 litre iDSI Jazz (Australia) and it does tend to lose a bit of power. That said, it doesn't lose as much as I thought it might. The motor still spins beautifully, and I just adjust the revs up by a couple of hundred before gear changes to compensate.

It brings the fuel economy down a little, but I came from a V6 motor, so no complaints....

Jonniedee · #15 (**permalink**) 07-19-2006, 09:56 AM

Two words - "Parasitic drag"

fits2000 · #16 (**permalink**) 07-19-2006, 04:40 PM

I drive the MT and yes I notice a change when the A/C is on. I actually stalled a couple times with the A/C on b/c the change in power and feel.

tcousins · #17 (**permalink**) 07-19-2006, 05:26 PM

Sure there's a loss of horse power... But it has to be the smallest I've experienced, enough so that I made a mental note... and find it interesting others have as well.

dancingsun · #18 (**permalink**) 07-19-2006, 05:31 PM

The A/C shuts off when the computer thinks you'll need that extra power for acceleration, usually from a full stop.

So it really isn't that big of a deal.

MikeB · #19 (**permalink**) 08-07-2006, 04:57 PM

i think ac does make a difference on at models

tubaman · #20 (**permalink**) 08-07-2006, 07:04 PM

Power (kW) = Power (HP) x 0.7457
Power (HP) = Power (kW) x 1.341

I didn't remember that from school - I found it on the Interweb Thingy
http://www.wentec.com/unipower/calculators/kw_hp.asp