So [dons flameproof suit] if global warming leads to a new ice age in Britain, we'll all get more mpg from our cars.
Cool.
8-)
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No, weather up in the wastes of the north west, temps have taken a while to cool down. Certainly the improvement in the economy has be conincident with a slight cooling, but the economy did not deteriorate as we went into summer. So, must be a running in thing.
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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I beg to differ. The economy is cooling. Its going to be a long hard winter.
Indeed much cooler and damper in Surrey now, the engine os now sounding very sweet and quiet, in fact I have to turn the radio up to cover up the noise of the now whining gearbox.
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"So [dons flameproof suit] if global warming leads to a new ice age in Britain, we'll all get more mpg from our cars."
No!
A lower air temperature does not give denser air (which may give better consumption). At colder temperatures the mpg will go down significantly as the engine takes that much longer to reach its ideal operating temperature.
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Megane dCi jumped from 49MPG to 56MPG at about 10K.
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My 406 has jumped from 39mpg to 44mpg over the last 2 or 3 weeks with no real change in driving style, fuel used or any other factor. I can only put it down to the cooler weather meaning the air con isn't working so hard to keep the interior cool. Also the weather not being so miserable I need my lights, heated window etc on all the time. I'm expecting the economy to dip again when the weather gets nasty.
Average economy now 44.4mpg, measured brim to brim, covering around 300 miles a day in all conditions.
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Lordy - forgot about climate control! I wonder if thats the difference?
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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"So [dons flameproof suit] if global warming leads to a new ice age in Britain, we'll all get more mpg from our cars." No! A lower air temperature does not give denser air (which may give better consumption). At colder temperatures the mpg will go down significantly as the engine takes that much longer to reach its ideal operating temperature.
Oh, so intercoolers are there to make economy and power output worse. And air intakes as low down and forward as possible are there solely to ensure you can't drive through floods.
Silly old motor industry for using them.
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"A lower air temperature does not give denser air"
Oh! thats what we get fog at mid day on a summers day when the weather is hot then?
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Okay, my appologies, maybe a gross over simplification.
The density of air at road level and at three foot off the ground is almost the same. The car engine will not notice the difference. There will be a much greater difference between sea level and a mountain pass at 2000 metres and this will affect the car engine.
The increase in density due to a supercharger or turbo is far more significant and will have an effect.
Does an intercooler not serve (in part) to cool exhaust gases that may be reused by the engine.
Fog on a mid-summer day has nothing to do with the density of the air. The main driver for fog and mist is that the air has become saturated with moisture at that temperature and can hold no more with out forming droplets. Droplet formation can be promoted by the presence of particulates in the air.
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The intercooler is on the induction side of the turbo, providing cool, dense air for maximum combustion.
I drive a chipped 156JTD sportwagon and have done for 3 years. I've got to understand turbo diesels and Alfas quite well in that time.
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"providing cool, dense air"
Relatively speaking. Intercoolers use the same cooling water as the engine, so they are far from cold, but they still do a useful job, as the air passing through the turbo (induction side) gets very warm thanks to the compression (think bicycle pump).
I'm beginning to wonder if the benefits of acetone in the fuel (see other thread) are at least partly due to its volatility, which would also have a cooling effect...
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Anyone got a car where the intercooler is connected to the car's cooling system? I haven't. It's an independent unit, using airflow and large surface area to cool the air and isn't connected to the radiator or coolant system.
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In my Passat diesel there seems to be two little radiators low down in the front corners. Hues they are the intercoolers. Probably full of oil from the leakage visible from the pipework.
Now my OIL cooler is water cooled.
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I wasna fu but just had plenty.
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Intercooler inlet pipes and the intercooler itself can foul with oil spray from the turbo. Most turbos these days seem to use a liquid bearing, floating the impeller on a pressurised oil bath. If this leaks it gets sent in a fine mist down towards the intercooler and collects in there.
If you remove the intercooler and the turbo-to-intercooler pipe and give their insides a good clean (hot soapy water), ensure they are nice and dry and reinstall you will see a marked improvement in performance and economy of your car as the oil prevents the intercooler from, er, cooling.
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Sorry, use HSW for the pipe but best to use a volatile degreaser of some kind for the intercooler. Don't use it on the pipe as it will rot it.
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Went to fill up today - 233 miles and a gnats whisker under 10 gallons. So 23.3mpg. Third tank at that level! A 15% improvement.
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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"Anyone got a car where the intercooler is connected to the car's cooling system?"
Probably not - sorry. It was an unthinking assumption I made when peering at a friend's new diesel (shudder!) - I'm pleased to report that he got rid of it a short time later, as it made such a horrible racket.
Nice illustration of turbo loop here:
auto.howstuffworks.com/turbo7.htm
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at 22mpg, the heading should read "overusage of fuel improved from unacceptable to bad".
I think some of you are paid to write copy for oil companies:-)
EDIT:
having carefully considered the above, I don't withdraw it but suggest some might also write copy for manufacturers of gas guzzlers (eg all Subarus). Wait till oil is $100 per barrel..(and still cheap).
madf
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$till $kint,
Sorry to hijack this thread. Removal and cleaning of the intercoolers by me is highly unlikely.
Removal of the frontal bodywork , grille etc. looks necessarry to get at things.
Probably explains why my mpg is not as good as when I first got the car.
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I wasna fu but just had plenty.
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Yes its bad and now only slightly less bad, but at least I am driving a car with charisma and speed, and its nice being different without being flash. Besides at 9,000 miles pa, if I bought a Golf TDI, I would probably save no more than £700pa. I can live with that expense.
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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A lower air temperature does not give denser air
Yes it does,that's why hot air balloonists fly in the early morning when the air is cooler and denser.
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A lower air temperature does not give denser air
Yes it does according to Charles Law.
that's why hot air balloonists fly in the early morning when the air is cooler and denser
No they don't, they fly in the early morning or evening because the air is more stable (the sun causes strong vertical currents which in turn can create clouds during the daytime). Vertical air flow of just a few knots is great for gliders but not much fun in a balloon.
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"A lower air temperature does not give denser air."
I gave this response with respect to situation.
Whilst technically it is incorrect, the difference in the density of air at -5°C and +30°C (typical environment temperatures for a car) will have very little effect on the fuel economy of a car.
Altitude will have a far, far greater effect on air density!
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No they don't, they fly in the early morning or evening because the air is more stable
Yes yes yes, but is the balloon's fuel economy stable?!
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L\'escargot.
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OK
Filled up tonight and 23mpg again! I'm really happy!! I bet I'll get at least 30mpg on a run now rather than 27.
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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Espada III
have you had the MAF sensor checked on your motor. Getting 30+ mpg is pretty good going on a 2ltr turbocharged Subaru engine. I get about 20 - 25 from the Impreza but it is mostly used for fun on the weekend. A knackered MAF will cause lean running leading to det leading to big repair bills.
Subaru's MAF sensor is a weak spot in the Impreza engines but cant comment for sure about the forester. Maybe worth a check just in case.
Leon
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Thanks - it's due a service soon so will ask them to check. The 30mpg will only be seen on the motorway cruising at below 85mph.
As you will see from my profile, most of my driving is urban and suburban, so poor economy is taken as read for any car I drive. It's just that 20mpg is taking the mick a little, for a car a lot smaller than my old Volvo S80 2.9. So 23mpg is what I would expect.
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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There are a few misleading comments in this thread, cooler air IS denser hence an internal combustion engine will run more efficiently in cooler air because denser air contains more Oxygen for any given volume, yes an engine may take slightly longer to warm up in cooler ambient temperatures though the difference is minimal and is usually dictated by the drivers demand for heat in cold weather as opposed to the actual thermo dynamic properties of the engine in differing ambient temperatures.
The fact that cooler and therefore denser air is desirable is the reason for the existence of intercoolers, an intercooler cools the ambient air therefore ensuring that more oxygen is crammed by the turbo / super charger into the combustion chamber.
Another factor here is moisture in the air, moisture aids the combustion process, by slowing the burn it helps to ensure complete and efficient combustion, by the same token it has anti knock properties thus electronically managed engines can run closer to the optimum ignition/injection timing therefore being more efficient and perceptably more responsive to the driver.
Hence it is no surprise that fuel economy improves with onset of cool damp autumnal mornings.
Lastly, yes altitude is a a factor in air density though the altitude range across the most of Europe, yet alone the UK, is to small to make any noticable difference.
Regards.
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Excellent. A simple well reasoned argument which we can all understand and learn from - Thanks
I wonder how noticable the improvement in fuel economy is, just by changing atmospheric conditions? i.e. is my improvement in economy solely down to the onset of Autumn or has the car finally 'run in'?
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Espada III - well if you have a family and need a Lamborghini, what else do you drive?
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I wonder how noticable the improvement in fuel economy is, just by changing atmospheric conditions? i.e. is my improvement in economy solely down to the onset of Autumn or has the car finally 'run in'? --
I would suggest that the effect of changing atmospheric conditions is likely to be more of a sudden change, and therefore more noticable from day to day, than that of the engine being fully run-in, after all the weather can change over night though the run-in process can take many thousands of miles with only minute changes to the engines charateristics from month to month yet alone day to day.
One other thing also weather/season related, which may already have been mentioned, the improvement was not simply due to the effects of aircon/climate was it? Either air con being switched off completely or if you have climate control set at a constant temp it will be less of a drain on engine power as the ambient temp nears or passes the set temp.
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