Heating and fuel consumption.

Sp0_0k · Sep 14, 2022

I just noticed that fuel consumption can go pretty high if you use heating a lot, as it cools down the engine and extra fuel is required to heat a diesel engine.
Could it be more efficient to use eberspacher parking heater while driving?

andyinluton · Sep 14, 2022

Sp0_0k said:
I just noticed that fuel consumption can go pretty high if you use heating a lot, as it cools down the engine and extra fuel is required to heat a diesel engine.
Could it be more efficient to use eberspacher parking heater while driving?

You cant on a T6.1 it switches off as soon as you get to about 4mph and doesn't come back on.
I cant see how a Diesel engine will use more fuel just because you have the heating effectively cooling it down. You just get a heater that puts out cooler air.

Does your temperature gauge drop?

Best just turn your heated seats on, which in turn will put a load on the engine & make it work harder & therefore hotter.

Sp0_0k · Sep 14, 2022

Driving at low temperatures like -10 and below definitely cools the engine down and when using heating heavy gauge even somtimes drops from 90 to 70

andyinluton · Sep 14, 2022

At those temperatures, running a bit of air through a heater matrix to heat the cabin is insignificant compared to the cooling effect of the air going through the radiator.

Any increase in fuel consumption is more likely to be because the auxiliary engine heater is being used.

If its that cold you might consider going retro & putting a bit of cardboard in front of the radiator.

WelshGas · Sep 14, 2022

andyinluton said:
At those temperatures, running a bit of air through a heater matrix to heat the cabin is insignificant compared to the cooling effect of the air going through the radiator.

Any increase in fuel consumption is more likely to be because the auxiliary engine heater is being used.

If its that cold you might consider going retro & putting a bit of cardboard in front of the radiator.

Good old Radiator Muff, a must for the Landrover Defender.

sidepod · Sep 15, 2022

If I started monitoring fuel consumption against heating use, my better half would start packing!

She’d probably have a point.

yossarian · Sep 16, 2022

Piston aerospace liquid cooled engines often include a thermostatic radiator bypass valve, operating on the same principle as a TRV. Google 'vernatherm'.

yossarian · Sep 16, 2022

andyinluton said:
You cant [use the parking heater] on a T6.1 it switches off as soon as you get to about 4mph and doesn't come back on.

Mine certainly worked while driving last winter. It shuts off when switching off after driving. Not sure if there is any other runtime limiting logic.

andyinluton · Sep 16, 2022

yossarian said:
Mine certainly worked while driving last winter. It shuts off when switching off after driving. Not sure if there is any other runtime limiting logic.

My T5.1 did - turn on heater via remote 20 mins before going out in the morning, set dashboard ventilation to recirculate to redistribute the heated air coming out the B pillar until the engine has warmed up.

T6.1 wouldn't do it, as soon as I drove off the heater turned off.

Also used to turn on T5.1 heater before stopping to let it get up to temperature, again T6.1 wouldn't let me. I cant remember now if you could even get to the heating menu on the overhead console whilst driving.

yossarian · Sep 16, 2022

Possible we had different software...

andyinluton · Sep 16, 2022

yossarian said:
Piston aerospace liquid cooled engines often include a thermostatic radiator bypass valve, operating on the same principle as a TRV. Google 'vernatherm'.

Your Cali engine has one - its just a thermostat.

Sp0_0k · Sep 16, 2022

Running more tests and I am surprised so far how big is the influence.
The effect is highest when trying to put heating on before the engine came up to working temperature.
Had like 10l per 100km consumed when running heating at high, trying to dry the interrior after wet weather. Normally it is below 8
Even alternator is taking less at high loads.
Taking over 80 amps from alternator for onboard batteries I had below 8l consumption.

Could have been wise for VW to go with electric heating as some manufacturers do
1) Instant heating even on cold engine
2) Nice heater on a hookup
3) Better fuel economy as it turns out as well.

P.S. yes started to analyze consumption with 2,5eur per liter

Sp0_0k · Sep 16, 2022

andyinluton said:
You cant on a T6.1 it switches off as soon as you get to about 4mph and doesn't come back on.

Works fine on T6 Beach. Turned on while driving, warm and toasty.
Couldn't have ever imagined it might be more cost effective, compared to as I expected "free" heat from engine.

yossarian · Sep 16, 2022

Sp0_0k said:
Couldn't have ever imagined it might be more cost effective, compared to as I expected "free" heat from engine.

The physics don't work very well either. A 2.4kW resistive electric heater would need 200A to drive it.

In an ideal world the aircon would be driven by an electric motor, the vehicle battery would be in excess of 48v and the aircon would be able to run in heating and cooling modes (just a few valves to achieve).

Sp0_0k · Sep 16, 2022

We run 400watt heater in winter -20'c outside.
It is like 3 cubic meters you are heating. At 2,5kwatts it will be an oven.

yossarian · Sep 16, 2022

Sp0_0k said:
We run 400watt heater in winter -20'c outside.
It is like 3 cubic meters you are heating. At 2,5kwatts it will be an oven.

A human being's heat output is about 100W. The smallest marine / vehicle heater I've seen is around 2kW, I forget the VW fitted heater specs but around 3.5kW from memory. The temperature delta you're likely to achieve in an uninsulated steel container with a tent on top with only 3 of your friends to help you heat it is negligible. The relevant factors are primarily surface area and R value. And don't forget there is a 0.05 square meter hole at the top of this arrangement creating a large thermosyphon.