Aircon : no more extra consumption ?

[haelewyn]

Did a test today... Aygo X envy.

Mainly big roads. Sticked to the same speed. Fifty km to go there... And later to get back

Consumption exactly the same.

4,2 liters per 100 km to go there with Aircon on at 25 degrees C.

Back, same distance, same speed but no Aircon at 18 degrees. Still 4,2 litres per 100 km. Realistic consumption as I saw this number before with Aircon off.

Is Aircon no longer making the car consume more petrol ?

Aircon was working perfectly and was set to automatic / 20 degrees.

[FROSTYBALLS]

I've never been bothered whether or not the air con does have a fuel consumption penalty, as we'd rather be comfortable.

We usually just leave it on the whole time.

[Roy124]

With aircon there are two options, taking in ambient air and recirculation.  Logically, recirculating previously cooled or heated air will use less energy than using fresh air. 

 

[haelewyn]

I was using fresh air.

[PCM]

I guess you don't get something for nothing... but, I would always use my A/C regardless of what it consumed.

On a hot day it makes such a huge difference. Couldn't be without it!

🌶️

[haelewyn]

Of course I am using it when it's hot.
And didn't have to use it in the evening when the air was cooler outside.

But the main point is :  what is the difference on this modern airconditioner system that it seems to run without causing extra fuel consumption..

I don't suspect the fuel meter to deviate and show the consumtion of 'aircon off' when it is really on. 😁
 

[Stivino]

15 minutes ago, haelewyn said:

it seems to run without causing extra fuel consumption..

It might "seem" to but, it isn't.  The first law of thermodynamics says; you can't get something from nothing.

 

[Mooly]

It uses more petrol whenever the compressor is running in just the same way it uses more petrol if you turn headlights or wipers on. All the energy ultimately comes from the primary fuel source, the petrol in the tank.

As far as aircon goes I've found it makes little noticeable difference in most conditions but of course under lab conditions that difference would be immediately apparent.

Keeping the cabin at 18C when in full sun and with the ambient air temperature at 30C and I'm pretty sure you would notice a difference over many miles.  

[Donrald]

I keep the air conditioning on all the time. Local journeys I get about 46 mpg but on a longer run I have had 57.51 overall.

[flash22]

The mk1 and mk2 used a traditional pump with an electro mechanical clutch, the x as far as I'm aware has now caught up with the rest of the Toyota cars and has a constantly driven pump with a variable electronic valve

A Traditional pump is either on or off and will pull 10-15% engine load

A modern pump is variable and it is constantly driven, it has a much lower load making it more efficient

[haelewyn]

I think that's the answer I was looking for ...
You can feel it while driving too.
With the old system, you suddenly lose a lot of power when you switch it on.
In the new Aygo X that is less the case.

It must be more efficient than the previous one as it also works better.
IMHO :  less consumption, less loss of hp, better result inside the car = the system has to make less effort to cool the car.

[haelewyn]

4 hours ago, Donrald said:

I keep the air conditioning on all the time. Local journeys I get about 46 mpg but on a longer run I have had 57.51 overall.

I see your overall consumption is 57.51 miles to the gallon (uk). I get about the same.

On ideal drives it goes to 78 mpg UK for me...

But since I drive short rides often (and most of my calculation was in winter conditions-bought the car in January 2023- ), the general number for me is 56 mpg UK.
This general average will still drop a bit in summer.

Until now, I have almost never used the aircon. Just on small distances and on the weekend as a trial case 🙂

[mrfixer]

A small car airconditioner compressor requires a power input of around 2kW (depends on heat load). The Aygo engine has maximum power output of 53kW, but obviously in steady speed driving is probably producing less than a third of that.  So you're probably looking at around 10% of engine power - but clearly depends on many factors. Variable displacement compressors are a little more efficient that older 'bang-bang' clutched systems - but its very marginal.

[Mojo1010]

My previous diesel would dent the fuel in the summer in slow traffic conditions with the Aircon on. Current MK3 Yaris hybrid hardly notice much. 

[Cyker]

That's a bit surprising! One of the things I noticed with my Mk1 D4D is the AC barely dented the mpg; Maybe 2-3, whereas everyone else with petrol cars hardly used their AC because they could almost see the fuel gauge dropping while crawling through traffic with it on  

That's one nice thing with the Mk4 hybrid - I can't even tell what the effect is on mpg! I know if I use it, it's much harder to get into the 80's of mpg, but if I'm driving normally with the mpg in the mid-70's it doesn't seem to make much difference!

That said, it does make the engine run more on a hot day if I'm stuck in traffic - That piddly 0.7kWh traction Battery can't run the AC on its own for long on a hot day it seems! The Mk3 might have the advantage there since it has twice the capacity!

 

[haelewyn]

I also noticed it has a different influence on start-stop.

When I stop somewhere, the engine goes off and then the blower goes (a lot) more slowly in automatic position of the ventilation system.

Of course, with the sun burning on the black car roof, the engine will restart in 15-20 seconds. I assume cause it measures the temperature going up and wants to produce cold air.

I THINK the shutting off and on of the Aircon system, which was clearly noticeable in the Aygo II, is not present in the Aygo X.

Which confirms flash' idea that the X has the newer system of Aircon built in.

[zuh]

Hi,

I noticed the same thing.

I usually reach 4,4L/100 km or 64,2 UK mpg.

Last weekend, I used the AC for the first time and for the first time, my fuel efficiency improved!!!

My only explanation was that it might took some time before having a measurable impact.

Thanks for your information.

[haelewyn]

I always consume more when I go from A to B

Compared with returning from B to A.

Starting off with a cold engine makes a huge difference.

Will be less noticeable in summer though.

Driving off in summer becomes less bad and general consumption drops a bit anyway.

[haelewyn]

As suggested before by other participants :    There IS a noticable extra consumption when doing shorter trips and town driving with aircon on.

About 20-25 percent extra.