General TwinAir Thread (including MPG)

[jrkitching]

Just remember that if you've got the heater on then that's more energy being converted into heat and therefore not pushing you forward.

Actually, it depends on whether the engine is hot or cold.

Before it's fully warmed up, I'd agree you want the heater off so that the engine will get to operating temperature as rapidly as possible. But once it's got there, that heat is an unwanted byproduct and the engine has to use some of its power to get rid of it, by driving the water pump & circulating the coolant. Once you reach the point when the radiator fan cuts in, you're using a tiny bit more power for cooling (that electricity has to be generated), so it might save you a miniscule amount of fuel to turn up the heater & reduce the electrical load from the fan.

In practice, once the engine is warm I doubt even I'd be able to detect the mpg difference, so perhaps the best advice is just to use the heater to maintain a comfortable temperature in the passenger compartment.

Getting the engine up to temperature, particularly in the UK winter, is another matter altogether, and I've long been of the belief that some form of thermostatically controlled grille shutters (cowl flaps, if you like) could be of significant benefit.

 

[306maxi]

well the water pump is driven by the timing belt so there is no extra power loss there.

 

[bgunn]

TA doesn't have a timing belt But yeah, the same issues apply.

 

[ahmett]

TA doesn't have a timing belt But yeah, the same issues apply.

No timing belt? Lucky you!

 

[RobinPJ]

Maxi - when you don't have the heater on do you have to open the window a bit to stop the car from steaming up? I recall the manual for my mum's Renault 5 claiming that a partially open window increased fuel consuption by something like 4%.

 

[ahmett]

Heater doesnt add fuel consumption, but using the AC does. I drive without a jacket in my car as i like being comfortable when i drive! I wait until the temp bar goes above minimum before opening the heating unless i am absoutely freezing!

 

[306maxi]

Maxi - when you don't have the heater on do you have to open the window a bit to stop the car from steaming up? I recall the manual for my mum's Renault 5 claiming that a partially open window increased fuel consuption by something like 4%.

Not generally. If I did need to demist I just turned the heater and air con on till it was demisted, turn the air con off, open the window ever so slightly to let all the warm moist air out and closed the windows and turned the heater off.

I quite like the cold tbh and it's a bit pointless to heat the car up like the tropics only to then have to get out into -5 degree "heat" and feel colder than you would have if the car was a bit closer to the outside temp.

 

[306maxi]

Heater doesnt add fuel consumption, but using the AC does. I drive without a jacket in my car as i like being comfortable when i drive! I wait until the temp bar goes above minimum before opening the heating unless i am absoutely freezing!

The energy has to come from somewhere Peak efficiency occurs when the engine is hot. Putting your heater on in the winter (I'm talking about the UK here) will negatively affect your fuel consumption. It might not be a huge amount but it's still going to affect consumption.

 

[ahmett]

Not generally. If I did need to demist I just turned the heater and air con on till it was demisted, turn the air con off, open the window ever so slightly to let all the warm moist air out and closed the windows and turned the heater off.

I quite like the cold tbh and it's a bit pointless to heat the car up like the tropics only to then have to get out into -5 degree "heat" and feel colder than you would have if the car was a bit closer to the outside temp.

Thats how many people get sick by the way. Their house or car is 30 degrees, then outside is -5. Not so good for the health!

 

[RobinPJ]

The energy has to come from somewhere Peak efficiency occurs when the engine is hot. Putting your heater on in the winter (I'm talking about the UK here) will negatively affect your fuel consumption. It might not be a huge amount but it's still going to affect consumption.

Maxi - using your logic, I shall remove the radiator and cooling system from my car to stop all that energy being dissipated and wasted. I look forward to the vastly improved fuel consumption.

 

[ahmett]

Maxi - using your logic, I shall remove the radiator and cooling system from my car to stop all that energy being dissipated and wasted. I look forward to the vastly improved fuel consumption.

Not to mention your car being 10 kgs ligther, improving consumption and handling!

 

[306maxi]

Maxi - using your logic, I shall remove the radiator and cooling system from my car to stop all that energy being dissipated and wasted. I look forward to the vastly improved fuel consumption.

My point was that the heat isn't always a waste product and a warm engine is key to efficient combustion

 

[pearce_jj]

75*C for power, 95*C for economy I seem to recall from Tuning the A-Series Engine: The Definitive Manual on Tuning for Performance or Economy: Amazon.co.uk: David Vizard: Books.

I was quite surprised after reading a VAG paper on their TSi engine that even the latest-and-greatest are running at only about 23% efficiency in real terms..., in other words 3/4's of the energy in the petrol is simply wasted. I doubt future generations will thank us for that.

I wonder what efficiency 1950's American V8's were running at?

 

[ahmett]

75*C for power, 95*C for economy I seem to recall from Tuning the A-Series Engine: The Definitive Manual on Tuning for Performance or Economy: Amazon.co.uk: David Vizard: Books.

I was quite surprised after reading a VAG paper on their TSi engine that even the latest-and-greatest are running at only about 23% efficiency in real terms..., in other words 3/4's of the energy in the petrol is simply wasted. I doubt future generations will thank us for that.

I wonder what efficiency 1950's American V8's were running at?

I would say the same pearce. Their high fuel consumption was because of their size, not because of their lack of efficiency. If you think about it, fuel consumption hasnt improved much in the past 40 years, its just that engines have become smaller and thus more fuel efficient. I mean 0.9l?? haha those american v8's were like 6 liters!

 

[306maxi]

75*C for power, 95*C for economy I seem to recall from Tuning the A-Series Engine: The Definitive Manual on Tuning for Performance or Economy: Amazon.co.uk: David Vizard: Books.

I was quite surprised after reading a VAG paper on their TSi engine that even the latest-and-greatest are running at only about 23% efficiency in real terms..., in other words 3/4's of the energy in the petrol is simply wasted. I doubt future generations will thank us for that.

I wonder what efficiency 1950's American V8's were running at?

The thing we should really think about is preserving petrol and gas for use in cars. Because unless some sort of synthetic fuel is found then all the glorious american V8's and V12 Ferrari's and so on will never turn a wheel again whilst powered by internal combustion.

I could easily commute to work in an electric car tbh and not use fuel which could be used for far more interesting things like motorsport and running classic or interesting cars. Problem is that there's no real alternative for most people to petrol/diesel at the moment.

 

[jrkitching]

The thing we should really think about is preserving petrol and gas for use in cars.

Well we're doing our bit.

Taking a look at the figures on Fuelly, I reckon most folks could save 20% of the fuel they use, starting today, without changing or modifying their cars, simply by changing the way they drive.

We need a fundamentally different attitude as a society to the way we use energy. It's no use expecting someone else to make the changes, whether that be government, car manufacturers or fuel producers. As long as the majority of folks value performance over sustainability, we'll continue to rush headlong like lemmings over the precipice.

 

[306maxi]

Well we're doing our bit.

Taking a look at the figures on Fuelly, I reckon most folks could save 20% of the fuel they use, starting today, without changing or modifying their cars, simply by changing the way they drive.

We need a fundamentally different attitude as a society to the way we use energy. It's no use expecting someone else to make the changes, whether that be government, car manufacturers or fuel producers. As long as the majority of folks value performance over sustainability, we'll continue to rush headlong like lemmings over the precipice.

Compleeeeetely agree.

One thing I quite fancy doing if we move to somewhere where it's practical, would be to put a groundsource heatpump in to heat the house. It sounds completely bonkers to most, but you can heat your house in the winter from the heat from the ground which a metre or two below ground will be 8 degrees or so year round.

It is also well over 100% efficient as well, because for every unit of energy you put in to pump the refrigerant around, you get more heat back into the house. You can also cool the house in the summer too......

Leaves gas free to do things more efficiently in places where it's far more convenient.

 

[pearce_jj]

Ground-source is VERY expensive purley from a civil engineering perspective, unless obviously it were a new-build where the ground is being dug-up anyway. But air-source can be just as good and a fraction of the price (retro-fit) - have a look at Daikin's Atherma solution. But yet again, we digress!

 

[306maxi]

Ground-source is VERY expensive purley from a civil engineering perspective, unless obviously it were a new-build where the ground is being dug-up anyway. But air-source can be just as good and a fraction of the price (retro-fit) - have a look at Daikin's Atherma solution. But yet again, we digress!

Interesting. I had just assumed that they weren't anywhere near as efficient as ground source heat pumps!

I don't see the problem with us digressing Using less fossil fuels is always a good thing and is half the reason why people buy the Twinair

 

[Geddes]

But air-source can be just as good and a fraction of the price (retro-fit) - have a look at Daikin's Atherma solution. But yet again, we digress!

I'm sure it's marvellous if it's installed correctly but we have Daikin air source heating in the building here and it's generally the same temperature as it is outside