What determines the duty cycle of the A/C compressor? - Page 2 - Toyota Yaris Forums

cali yaris · 09-08-2009, 03:19 AM

Lafiro, what "engine load" are you scanning exactly?

is this from the OBDII?

IllusionX · 09-08-2009, 01:48 PM

Does the AC on the yaris really cycle? I believe it stays on all the time, untill you turn it off. What you hear kicking on and off is the radiator fan...

Yaris Hilton · 09-08-2009, 02:00 PM

No, the compressor definitely cycles.

As for whether or not you can feel the difference, well, some people wouldn't know the difference if two cylinders weren't firing. If you pay close attention, and particularly if you measure fuel mileage, you can tell the difference even in huge V8 powered vehicles. But it's proportionately a greater effect as you go to smaller engines with less total power.

ddongbap · 09-08-2009, 04:07 PM

Quote:

Originally Posted by Yaris Hilton

No, the compressor definitely cycles.

As for whether or not you can feel the difference, well, some people wouldn't know the difference if two cylinders weren't firing. If you pay close attention, and particularly if you measure fuel mileage, you can tell the difference even in huge V8 powered vehicles. But it's proportionately a greater effect as you go to smaller engines with less total power.

crappp..... i'm missing some pistions.....

Yaris Hilton · 09-08-2009, 05:50 PM

Quote:

Originally Posted by ddongbap

crappp..... i'm missing some pistions.....

Don't you just HATE it when that happens?

IllusionX · 09-08-2009, 07:46 PM

Quote:

Originally Posted by Yaris Hilton

No, the compressor definitely cycles.

As for whether or not you can feel the difference, well, some people wouldn't know the difference if two cylinders weren't firing. If you pay close attention, and particularly if you measure fuel mileage, you can tell the difference even in huge V8 powered vehicles. But it's proportionately a greater effect as you go to smaller engines with less total power.

explain. Actually, i do feel the difference in power when the AC is on, but... when the AC is cycling... ???

ddongbap · 09-09-2009, 05:26 AM

Quote:

Originally Posted by Yaris Hilton

Don't you just HATE it when that happens?

I DO! But I can't tell when it happens.

47_MasoN_47 · 09-09-2009, 01:48 PM

I could tell the difference in power in both my Yaris and my old Ranger if I had the AC on. The difference in my Ranger wasn't as significant as in the Yaris, but that's probably because it had a lot more power than it needed anyway (I had the 4.0 litre V6 in a 2wd). If I'm going uphill I've gotten to where I just turn off the AC no matter the temperature because it seems like I'll never make it if the AC is on.

Lafiro · 09-09-2009, 06:53 PM

Quote:

Originally Posted by cali yaris

Lafiro, what "engine load" are you scanning exactly?

is this from the OBDII?

Hey!

Yes this was with some scanner with a live graph that I borrowed from my friends shop one day to play around with.

But its pretty accurate, I mean I know its just a computer, but when the A?C is ACTIVE I know for a fact that amount of HP is gone because engine load reaches 100% faster, and pressing the pedal faster ot harder to the floor didnt make it faster when it was on. The feeling of lost power was very obvious. And this was done on the same level long stretch of a driveway, so hills have nothing to do with what I felt + the scanner results displayed via OBDII.

IllusionX · 09-09-2009, 10:54 PM

Quote:

Originally Posted by camelll

The AC compressor has a clutch that engages and disengages that is what they are talking about cycling, it engages as needed.

The AC compressor stays engaged, until the AC is turned off....

ddongbap · 09-10-2009, 02:52 AM

This thread is going to be another one of those threads where people just spout out information that they've heard.

I've dyno'd the car, with and without the AC on. 3 whp difference.

Lafiro · 09-10-2009, 11:13 AM

Alright, the clutch is engaged when its ON, hence why cold car comes out the vents, and then its disengaged, meaning its OFF, meaning also NO load on engine, which is why the air gets warmer. You know when its engaged or not, the car either feels faster for a minute, and then it doesn't.

My guess is that ddongbap dyno'd his car just when the compressor disengaged.

Now lets see you argue me wrong on my hypothesis.

cali yaris · 09-10-2009, 12:06 PM

Quote:

some people wouldn't know the difference if two cylinders weren't firing.

unplug one coil and try driving. Anyone would notice that.

Meanwhile, I still don't know what "load" is measured by OBDII. Trying to get educated here, help me out!

CTScott · 09-10-2009, 02:11 PM

Quote:

Originally Posted by cali yaris

unplug one coil and try driving. Anyone would notice that.

Meanwhile, I still don't know what "load" is measured by OBDII. Trying to get educated here, help me out!

Calculated Engine Load
California Air Resource Board (CARB) defines this as airflow divided by peak air flow. Peak air flow may be adjusted for altitude via barometric means if available. For diesel engines, the number is current output torque divided by peak output torque at current rpm. We have noted that vacuum leaks can have dramatic effects on this value.

mikenacarato · 09-10-2009, 02:24 PM

The ac compressor clutch does NOT stay engaged all the time when the ac is on. the thermistor (toyota term), cold control switch, or its also knows as an ac thermostat. it is in the climate unit and should be stuck somewhere in the fins of the evaporator. and as yarishilton said, it measures the temp of the evaporator.

tazrulesny · 09-11-2009, 09:40 PM

Quote:

Originally Posted by camelll

Don't take my word for it, go turn your ac on then actually watch the compressor, you will see and hear when it engages and when it disengages. Just because your ac light on the knob is on does not mean the compressor clutch is engaged.

Hahahahah that cracked me the hell up. Guess when my head lights are on doesn't mean my car engine is still running huh?

ozmdd · 09-11-2009, 10:10 PM

A/c compressor clutch turns on and off as the unit cycles. You still get cold air if the fan is blowing air across the cold coils. When the system needs to compress again (to keep the coils cold), it re-engages the compressor pulley clutch. If you have the ac "on" and listen with the hood open, you will be able to clearly tell when this process occurs.

Lafiro · 09-11-2009, 11:37 PM

Exactly.

Ok fact is, even though the light is on that says the A/C is on, does NOT mean it is engaged 100% of the time.

It only turns the compressor on for a certain amount of time, then turns it off for a certain amount of time. Either that or it does so by temperature somehow, depending on where the knob is turned too.

So for everyone to understand this:
You are is losing 20%(on our stock engine) or so of power when the A/C ( the compressor ) is engaged! And just to clarify one more time for everyone, the compressor is NOT engaged 100% of the time, but it cycles on and off.

This should be the end of people giving out wrong information.

ozmdd is right as well (post above mine).

09-08-2009, 03:19 AM	#19
cali yaris ULTIMATE View User's Garage Drives: 07 Yaris Turbo Join Date: May 2007 Location: Canoga Park, CA Posts: 14,859	Lafiro, what "engine load" are you scanning exactly? is this from the OBDII? __________________ Micro Image forums, online store and shop are now closed. It was a great eight year run, but it was time to focus on other things. I'm still selling parts on eBay under micro*image seller ID and customers can still make requests for anything specific.

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09-08-2009, 01:48 PM	#20
IllusionX It's the illusion you see View User's Garage Drives: 07 Yaris Sedan Aero Join Date: Oct 2006 Location: Brossard, QC Posts: 3,888	Does the AC on the yaris really cycle? I believe it stays on all the time, untill you turn it off. What you hear kicking on and off is the radiator fan...

09-08-2009, 02:00 PM	#21
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	No, the compressor definitely cycles. As for whether or not you can feel the difference, well, some people wouldn't know the difference if two cylinders weren't firing. If you pay close attention, and particularly if you measure fuel mileage, you can tell the difference even in huge V8 powered vehicles. But it's proportionately a greater effect as you go to smaller engines with less total power.

09-09-2009, 01:48 PM	#26
47_MasoN_47 What I thought I'd do was View User's Garage Drives: 09 Yaris Sedan Join Date: Aug 2009 Location: Northwest Alabama Posts: 1,140	I could tell the difference in power in both my Yaris and my old Ranger if I had the AC on. The difference in my Ranger wasn't as significant as in the Yaris, but that's probably because it had a lot more power than it needed anyway (I had the 4.0 litre V6 in a 2wd). If I'm going uphill I've gotten to where I just turn off the AC no matter the temperature because it seems like I'll never make it if the AC is on.

09-10-2009, 02:52 AM	#29
ddongbap Banned Drives: yw calls me douche and racist. Join Date: Aug 2007 Location: hay Posts: 2,183	This thread is going to be another one of those threads where people just spout out information that they've heard. I've dyno'd the car, with and without the AC on. 3 whp difference.

09-10-2009, 11:13 AM	#30
Lafiro Drives: 06 Yaris Sedan Join Date: Jun 2006 Location: NYC Posts: 694	Alright, the clutch is engaged when its ON, hence why cold car comes out the vents, and then its disengaged, meaning its OFF, meaning also NO load on engine, which is why the air gets warmer. You know when its engaged or not, the car either feels faster for a minute, and then it doesn't. My guess is that ddongbap dyno'd his car just when the compressor disengaged. Now lets see you argue me wrong on my hypothesis.

09-10-2009, 02:24 PM	#33
mikenacarato SIPNDEW View User's Garage Drives: 15 STI Join Date: Oct 2008 Location: Brentwood, TN Posts: 2,281	The ac compressor clutch does NOT stay engaged all the time when the ac is on. the thermistor (toyota term), cold control switch, or its also knows as an ac thermostat. it is in the climate unit and should be stuck somewhere in the fins of the evaporator. and as yarishilton said, it measures the temp of the evaporator.

09-11-2009, 10:10 PM	#35
ozmdd Reluctantly Crouched... Drives: 2008 Yaris HB M/T Join Date: Oct 2008 Location: DFW, TX Posts: 867	A/c compressor clutch turns on and off as the unit cycles. You still get cold air if the fan is blowing air across the cold coils. When the system needs to compress again (to keep the coils cold), it re-engages the compressor pulley clutch. If you have the ac "on" and listen with the hood open, you will be able to clearly tell when this process occurs.

09-11-2009, 11:37 PM	#36
Lafiro Drives: 06 Yaris Sedan Join Date: Jun 2006 Location: NYC Posts: 694	Exactly. Ok fact is, even though the light is on that says the A/C is on, does NOT mean it is engaged 100% of the time. It only turns the compressor on for a certain amount of time, then turns it off for a certain amount of time. Either that or it does so by temperature somehow, depending on where the knob is turned too. So for everyone to understand this: You are is losing 20%(on our stock engine) or so of power when the A/C ( the compressor ) is engaged! And just to clarify one more time for everyone, the compressor is NOT engaged 100% of the time, but it cycles on and off. This should be the end of people giving out wrong information. ozmdd is right as well (post above mine).