Winter power

[Greg Roles]

AC is continuously variable, and draws about 5nm at idle and drops to about 1nm on acceleration, even down to zero when accelerating "off boost". I'm convinced there's very little drag from the AC when power is demanded, in my Golf anyway! I confirmed this with Vag Com via the AC unit itself, but sure there is always the belt turning the pulleys and more siginificantly, generator.

I agree an S3 IC or even the mighty APR would be the berries, but IMHO some ducting to seal the stock IC to the front of the car, and a on demand water mist is all most traffic drivers could EVER need, at least that's what I've found with many weeks of trial and error testing. Just the alloy ducting alone in my TDI dropped the IC output down to ambient under normal conditions in summer, whereas prior both Polar and myself were seeing about +5 degrees.

Heatsoak at the lights is any turbo cars greatest enemy in normal everyday driving.

Diesels always suffer in cold weather on startup, given there's no spark plug to heat things up, and glow plugs only happen for a short time. Nature of compression ignition I'm afraid. Any turbo car will feel more spritely in cold weather, but Sharkie is right, only to the ability of the ECU to inject extra fuel - a stock map will be limited. I'd have to say my TDI feels peppy these colder days.

Sorry to butt in on a Tig thread, but this is stuff I love to get into!

[clip]

Sorry to butt in on a Tig thread, but this is stuff I love to get into!

Don't apologise, great read!

[krracing]

Yeah, thanks for the input Greg - always nice to hear another view.

Air-Con aside - fuel consumption increases slightly in colder weather; colder, denser air = more fuel.
+ as a result, engines will produce more power in colder weather.

[jimbomort]

Cause you drive normally and standard Tig has plenty of usable power for normal driving. How ever you should notice the small improvement in the fuel economy.

Its an interesting one - fuel economy in colder conditions. Heavier fuel consumption from cold with the colder conditions, better air intake but also higher density air to push through. On a recent drive to Sydney and back in 'relatively' cold weather I noticed two things.
1. Our fuel economy was worse than expected (MFD 7.8 way down, 7.3 way back, being 8.0 and 7.5 real as measured). I would have expected an MFD reading more in the high 6's very low 7's.
2. That I noticed wind noise from our roof bars and roof box far more than normal (and it wasn't excesively windy)

1. could be because we had the roof box on, though I have achieved better fuel economy on similar trips with the roof box on in warmer conditions. It is also possible that the roof box was not aligned with the car as well as it should - I checked, possibly off a bit but not obvious.

I have noticed in other cars that Aerials will whistle when conditions are colder and I have noticed our roof bars are noiser now in colder conditions - I presume from the air being more dense?

I did a search on the net, and contrary to what you might think air density is actually lower when humidity is higher. So hot humid air, is significantly less dense than cold dry air. This is due a law of physics observed by Avogadro, see USATODAY.com for a fuller explanation. Conditions in summer up here are generally hot and humid.

Higher air densities are probably most relevant at high speeds, but its interesting to note that even at around 110klm/hr, a Tig is pushing through 1 tonne of air every 7 seconds, or almost 5 tonnes every klm travelled (av air density is 1.2 kg/m3, and assumign frontal area of 2.2*1.8m). So air density may well affect fuel economy, just as wind direction (head or tail) will. Colder conditions may not equate to better fuel economy, though I dont know the balance b/w upside of higher density air going into engine versus car pushing through higher density air to get anywhere, especially at highway speeds.

[clip]

I thought it was just about the added moisture in the air on cool misty nights or mornings and how that effects combustion temps and burning - similar to what water injection tries to emulate. But all I really know is the Tig loves it

[MountainBikeMike]

Its an interesting one - fuel economy in colder conditions. Heavier fuel consumption from cold with the colder conditions, better air intake but also higher density air to push through. On a recent drive to Sydney and back in 'relatively' cold weather I noticed two things.
1. Our fuel economy was worse than expected (MFD 7.8 way down, 7.3 way back, being 8.0 and 7.5 real as measured). I would have expected an MFD reading more in the high 6's very low 7's.
2. That I noticed wind noise from our roof bars and roof box far more than normal (and it wasn't excesively windy)

1. could be because we had the roof box on, though I have achieved better fuel economy on similar trips with the roof box on in warmer conditions. It is also possible that the roof box was not aligned with the car as well as it should - I checked, possibly off a bit but not obvious.

I have noticed in other cars that Aerials will whistle when conditions are colder and I have noticed our roof bars are noiser now in colder conditions - I presume from the air being more dense?

I did a search on the net, and contrary to what you might think air density is actually lower when humidity is higher. So hot humid air, is significantly less dense than cold dry air. This is due a law of physics observed by Avogadro, see USATODAY.com for a fuller explanation. Conditions in summer up here are generally hot and humid.

Higher air densities are probably most relevant at high speeds, but its interesting to note that even at around 110klm/hr, a Tig is pushing through 1 tonne of air every 7 seconds, or almost 5 tonnes every klm travelled (av air density is 1.2 kg/m3, and assumign frontal area of 2.2*1.8m). So air density may well affect fuel economy, just as wind direction (head or tail) will. Colder conditions may not equate to better fuel economy, though I dont know the balance b/w upside of higher density air going into engine versus car pushing through higher density air to get anywhere, especially at highway speeds.

Bit of a dig, but this was very interesting