The MK6 Fuel Consumption (Most / Least per Tank) Thread

[LiFers]

The hotter the air, the thinner it is, the less O2 is in it.

In a N/A engine this is not a big deal, until you reach quite high elevations and then power loss, fuel consumption increases.

In a turbo car, this makes more difference because normally the car has more air and hence O2 in the cylinder to work with.

In an engine with such small capacity (1.4L) that relies heavily on a Supercharger and Turbocharger for it's normal power band, it would make a big difference. Then add Airconditioning load to that as well...

You will find the same problems with high altitude.

[cme2c]

I'll see if I can check it out on mine, as we have a hot week coming up. Perhaps a bigger intercooler would help?

[cktsi]

In a N/A engine this is not a big deal, until you reach quite high elevations and then power loss, fuel consumption increases.

In a turbo car, this makes more difference because normally the car has more air and hence O2 in the cylinder to work with.

I thought it was the opposite that N/A cars are more sensitive to less dense air (either due to higher temps or less air pressure at altitude) simply because the induction isn’t forced as it is in turbo & supercharged cars. By definition, forced induction means you have more control over air going into the combustion chamber.

However, irrespective of the mode of aspiration, all cars would be affected by higher temps.

I think it’s just the A/C. Case in point it was still around 34C out west in Sydney last week on the afternoon trip home and I switched off the climate control system & opened all my windows and sunroof. I actually managed 8.4l/100km on the trip home instead of the usual 9.3l/100km (note it’s only a short 7km trip). I normally run the climate control unit… so it was probably a combination of lighter traffic & the fact I wasn’t running A/C

On Saturday I ran the A/C for a short 4km trip and used 16l/100km as I was stuck in traffic & the climate control was running near full blast (chewing fuel at 1.3-1.4 l/hr at standstill instead of the usual 0.7-0.8 l/hr)

[MurphyTheElf]

I tested the change in consumption in my GTI, using the airconditioner as the only point of difference. I watched the consumption figures on the MFD during a mixed freeway, suburban street drive. It was approximately 2l/100km, also. The temperature was in the mid 20's.

[logger]

Should be reasonably easy to quantify. Someone with VagCom take a look at 002,2 (Engine load in %) with AC on and off. Also 050 & 057 look at RPM stabilisation in relation to AC status.

[Maverick]

I don't know if it is happening to you guys also, but I noticed the fuel consumption of my 118TSI increase by about 2 litre/100km in the 30 plus degree hot days we have been having these last couple of weeks. During my daily commute to work I get around 7.3litre/100km and it jumped to 9.2 with the hot weather and A/C running. I don't think A/C should bump the fuel consumption up that much.

How long is your commute? Do more people drive when it's hot (ie more traffic)? Are you sure that your driving conditions are the same?

The AC system used in the Golf is very economical but depending on the difference between the outside temp and inside desired temp can use a lot more fuel for a short period when the AC has to work flat out but will drop off after this when it only has to maintain a temperature.

Don't forget that in high temperatures that the cooling fans will be running flat out as well.

Winding down the windows also uses more fuel and generally the AC will be more economical to run then have the windows down.

[Corey_R]

I'll see if I can check it out on mine, as we have a hot week coming up. Perhaps a bigger intercooler would help?

I've heard that a bigger intercooler does make for a more efficient engine. You'll also experience some more HP due to the cooler air temps. On the APR site here they discuss some results of testing they did on the APR FMIC vs the stock MKV GTI intercooler, but they don't mention anything about fuel economy (I guess it's a bit harder to test).

So maybe Guy or someone can elaborate whether the better effiiciency from cooler temps having the larger intercooler would relate into better fuel consumption if it were driven normally.

[Guy_H]

Colder Air is better air for any combustion engine

[cme2c]

Colder Air is better air for any combustion engine

Guy, do you have any intercooler replacements for the 118TSI ?

[cme2c]

I'm wondering if the air control in the climate control makes a difference, particularly the automatic recirculation. Seems to me to be easier to keep 21 degree air at 21, than bring 39 degree air down. This is a different case to the car full of 40+ degree air in the carpark. And why Mrs cme2c only liked black. Just a thought or 2.

[Maverick]

I'm wondering if the air control in the climate control makes a difference, particularly the automatic recirculation. Seems to me to be easier to keep 21 degree air at 21, than bring 39 degree air down. This is a different case to the car full of 40+ degree air in the carpark. And why Mrs cme2c only liked black. Just a thought or 2.

Putting the AC on recirculate makes a huge difference, some fresh air is still introduced but not much and the air going into the AC will be higher than the 21 it's coming out at.

Also don't run the AC at 21 if you want to save fuel, run it at like 25. It's the differential temperature that dictates how the AC will operate.

This site has some info that is relevant especially his tests on his golf.

http://www.airconditioningforcars.co.uk/ACpage05.htm

[GolfAtom]

How long is your commute? Do more people drive when it's hot (ie more traffic)? Are you sure that your driving conditions are the same?
.

It's around 23km and the comparision was noted over weekly intervals and the traffic conditions were the same. This week is going to be a scorcher so I will be monitoring my fuel consumption closely.

My other car is diesel powered and it's fuel consumption doesn't seem to change with ambient temperature. I'm told diesels are more efficient than petrol engines under load.

[sillygogo]

I would say the A/C did most of the damages.

usually idle at 0.3l/Hr ...with A/C is around 1.7l/Hr...

It pretty cool that the units change when the vehile idles..from L/100km to L/hr.

[cktsi]

I think it’s just the A/C. Case in point it was still around 34C out west in Sydney last week on the afternoon trip home and I switched off the climate control system & opened all my windows and sunroof. I actually managed 8.4l/100km on the trip home instead of the usual 9.3l/100km (note it’s only a short 7km trip). I normally run the climate control unit… so it was probably a combination of lighter traffic & the fact I wasn’t running A/C

This afternoon I had the A/C on and my afternoon trip home used up 10.4l/100km. I know it's not totally scientific & like for like with my trip last week without A/C, but both occasions it was > 30C whereas my average of 9.3l/100km is from winter/spring.

usually idle at 0.3l/Hr ...with A/C is around 1.7l/Hr...

Wow! My idle uses 0.7l/Hr at best (or 0.6 without A/C). 0.3 is tiny. Does anyone else's TSI do around 0.3?

The AC system used in the Golf is very economical but depending on the difference between the outside temp and inside desired temp can use a lot more fuel for a short period when the AC has to work flat out but will drop off after this when it only has to maintain a temperature.

Absolutely agree the A/C will work harder during cool down versus maintaining. I have noticed the idle l/hr consumption with A/C is significantly less during "maintain" than during "cool down" (0.8 versus 1.3)

[Stealthy]

The same happens in my 103TDI. Probably not as much though.
My average without air conditioner is 5.3l per 100km versus with air conditioner is 6.0l per 100km.
It really decreases the further I go (obviously).

Someone mentioned recycling the air rather than having fresh (hot) air coming in. Does the "auto" not do that itself? I have never had climate control before, so I've just assumed that on "auto" it would do all that for me. I am bloody lazy!