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THERMAL EFFICIENCY IN CARS
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Just been out the mrs Clio and while we sat in the car with the engine off waiting for our take away :) the car got cold very quickly which is normal, but what if cars were more thermal efficient?

I know weight would be increased which is bad but it would benefit in the summer as once cold the air con wouldn't have to work so hard, right?

Am I talking rubbish here or do I have a point? We have K glass etc and light weight insulation, so could it be done? Or do car makers already take this into consideration.

Updated December 11, 2012 at 10:11 PM

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For sure

HVAC is complicated. You have to design for the people who constantly fill the car with wet stuff (would destroy insulation) and those who constantly drive with air con on (can destroy electrical connectors by cooling them down and the moisture condensing on them when the car is stopped and of course, weight.

OC I work in the building industry and you can get insulation that is moisture resistant. Yes weight is a problem but surely it could be done.

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For sure

of course it can be done, i bet a rolls royce is a lot better than a clio.

double glazing would help massively, just like it does in a house, but would also add a lot of weight, and probably at least quadruple the cost of a normal window.

again, i'm sure there are coatings that can be applied to glass, but will people be prepared to pay for it? everything on a car is costed to fractions of a penny.

as for insulation, where is it going to go? modern cars are already fairly well sealed, the door cavity is already packed with impact beams, lock mechanisms, speakers, window motors, sound deadening, and needs to leave room for the window to open, and let water drain out the bottom.

even a basic headlining and doorcard already gives a big insulating effect. i drove my completely stripped out metro in sub zero temperatures and it really wasnt much fun. even the thin board doorcards and thin fabric headlining made a huge difference to interior comfort, for very little weight or cost.

then there is the problem of ventilation. people make a lot of moisture, wet shoes and clothes bring a lot of moisture in, and a car cabin is a pretty confined space so you need good ventilation to stop stale air, which isnt just blowing fresh air in, but letting old air out without creating drafts.

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cheers,

Harry

Too many old sheds.

Ron Burgundy said...

OC I work in the building industry and you can get insulation that is moisture resistant. Yes weight is a problem but surely it could be done.

Does the same material work in -30C to 50C conditions, in direct contact with a wet item for months on end without smelling/rotting/loosing effectiveness, weigh very little and cost next to nothing? How does it perform in a fire and with chemicals such as petrol, oil, sun tan lotion, make up etc?

Orange Cola said...

Ron Burgundy said...

OC I work in the building industry and you can get insulation that is moisture resistant. Yes weight is a problem but surely it could be done.

Does the same material work in -30C to 50C conditions, in direct contact with a wet item for months on end without smelling/rotting/loosing effectiveness, weigh very little and cost next to nothing? How does it perform in a fire and with chemicals such as petrol, oil, sun tan lotion, make up etc?

I'm afraid the answer is yes to your examples. The only one I can't answer is petrol/oil, but then if you have petrol/oil in areas where they shouldnt be ie behind door cards etc then Id say the car has a problem. As mentioned in this thread you need a certain amount of air flow around insulation. If you didn't materials sweat naturally in the changing atmosphere.

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For sure

The reason they don't do it is because there isn't a need to. The engine produces several times more waste heat than that required to heat the cabin. Insulating a car so it can be sat in whilst waiting for your takeaway is probably not one of the test cases they use.

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Jobbo said...

Rev is correct, of course

NotoriousREV said...

The reason they don't do it is because there isn't a need to. The engine produces several times more waste heat than that required to heat the cabin. Insulating a car so it can be sat in whilst waiting for your takeaway is probably not one of the test cases they use.

The fact the car produces enough heat to waste is a good enough answer to me, but its ok for the air con to pump away hard and fast in the summer? I was using the takeaway situation as an example to say how quick the heat was lost.

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For sure

If it was that big an issue, cars painted black and other dark shades would not be produced.

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JL said...

Oh b*llocks you're right

Ron Burgundy said...

OC I work in the building industry and you can get insulation that is moisture resistant. Yes weight is a problem but surely it could be done.

New houses still get damp on the inside if they're left in the winter for several weeks, without the central heating on.

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ShonkySpeedHoleSpeciale

Ron Burgundy said...

NotoriousREV said...

The reason they don't do it is because there isn't a need to. The engine produces several times more waste heat than that required to heat the cabin. Insulating a car so it can be sat in whilst waiting for your takeaway is probably not one of the test cases they use.

The fact the car produces enough heat to waste is a good enough answer to me, but its ok for the air con to pump away hard and fast in the summer? I was using the takeaway situation as an example to say how quick the heat was lost.

So a couple of questions for you:

What does the typical AC unit cost the manufacturer?

How much does a modern AC unit affect fuel consumption?

How often is an AC unit actually in use (remember even when the AC is on, the compressor cycles in and out)?

How much would it cost the manufacturer to insulate cars to a higher standard?

What effect on economy would carting around all that additional weight all the time have?

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Jobbo said...

Rev is correct, of course

I don't know REV this is what I wanted to know. Is it worth it? I don't know the costs of items etc this is why I stated at the start am I talking rubbish.

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For sure

My mates E91 330 has a "REST" button. Which apparently allows the heater to work when the engine is off.

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Strong Broo Racing

scotta said...

My mates E91 330 has a "REST" button. Which apparently allows the heater to work when the engine is off.

I've had that in my BMWs...may even have it in the E38 can't remember. But it only works for a short period I think...

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BMW Car Magazine @QuentlyBentin

ShockDiamonds said...

scotta said...

My mates E91 330 has a "REST" button. Which apparently allows the heater to work when the engine is off.

I've had that in my BMWs...may even have it in the E38 can't remember. But it only works for a short period I think...

The E39 had something like this but I can't remember exactly what. Jobbo will confirm.

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Romantic BDSM

Gloucester's answer to Eddie Jordan

Ron Burgundy said...

I don't know REV this is what I wanted to know. Is it worth it? I don't know the costs of items etc this is why I stated at the start am I talking rubbish.

In that case, yes. Yes, you are. There's just no advantage to doing it. When the car is being driven it produces enough heat (or power to drive the AC) and that covers 99% of the heating/cooling requirements.

If you want heat or cooling not run off the engine, then auxiliary heating and cooling devices are available (campers, trucks, Dave90210!'s Land Rover etc.)

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Jobbo said...

Rev is correct, of course

IIRC you need an auxiliary heater to pre-warm the car, as it's illegal to leave an unattended vehicle idling.

Except ambulances, obv.

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Knackered old hairdresser's sh1tter

Jimmy Choo said...

ShockDiamonds said...

scotta said...

My mates E91 330 has a "REST" button. Which apparently allows the heater to work when the engine is off.

I've had that in my BMWs...may even have it in the E38 can't remember. But it only works for a short period I think...

The E39 had something like this but I can't remember exactly what. Jobbo will confirm.

It circulates the warm coolant through the heater matrix to allow you to use the residual heat to keep the car warm when the engine is off.

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JL said...

Oh b*llocks you're right

Si_ said...

IIRC you need an auxiliary heater to pre-warm the car, as it's illegal to leave an unattended vehicle idling.

Except ambulances, obv.

What about cars with remote start?

JustMax said...

Si_ said...

IIRC you need an auxiliary heater to pre-warm the car, as it's illegal to leave an unattended vehicle idling.

Except ambulances, obv.

What about cars with remote start?

Yes.

You MUST NOT leave a parked vehicle unattended with the engine running #HighwayCode rule 123

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Knackered old hairdresser's sh1tter

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