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[Loz]

Anyone else noticed?

On these cool mornings my 3.0 Diesel just flies along with the lightest wiff of throttle. I'm also getting 5-10% better MPG per tank! I can only attribute it to the cool weather lower running temp and more efficient combustion. It feels so much more spritely!

Anyone with a turbo intercooler should REALLY feel a difference. Not just on your "butt Dyno" but in your MPG returns...

More reason to love this season!

[Loz]

Nothing like a natural remedy to bring smiles with the miles!

[dave_boo]

Another big point to consider is that the air is more dense when it is cooler; therefore more O₂ molecules to burn...more power...etc.

[garyh]

Even trains notice the change, going under a dark cloud gives them a noticeable increase in performance.

[Loz]

Another big point to consider is that the air is more dense when it is cooler; therefore more O₂ molecules to burn...more power...etc.

Yes thats the science.

Have you felt it too? I love it, man

My morning run down the highway 15kms is usually at 2500rpm but even feathering the throttle I am seeing 2800-3000 kreep up and yes, I am getting better MPG per tank than 3 months ago when the temp needle was ALWAYS just under half way. Now it's lucky if it gets to that height in the afternoon days sun. Air cooling is increased o2 sat. Is God's gift to petrol heads!

TRannyAM,

what do you drive over here? and does it have an intercooler?

At Santa Pod in the UK we used to spray No2 on the intercooler before a run to chill it. If we could get hold of Lox (cheaper) we'd use that too. Ah, good times!

[hansnl]

Is there maybe anybody who might be thinking about the airco?

In this time and age, and the CPU-controlled diesel engines, I wonder if the 5-10 degree lower temperature really has so much influence.

[jubby]

Yeah, I've noticed it too, but only the last couple of days. The motorbikes seem better too.

We've got cool, damp air here. denser Air . Don't know why the moisture Helps, but it does seem to.

[garyh]

You can add water injection gives a cheap improvement.

[dave_boo]

Yes thats the science.

Have you felt it too? I love it, man

My morning run down the highway 15kms is usually at 2500rpm but even feathering the throttle I am seeing 2800-3000 kreep up and yes, I am getting better MPG per tank than 3 months ago when the temp needle was ALWAYS just under half way. Now it's lucky if it gets to that height in the afternoon days sun. Air cooling is increased o2 sat. Is God's gift to petrol heads!

TRannyAM,

what do you drive over here? and does it have an intercooler?

At Santa Pod in the UK we used to spray No2 on the intercooler before a run to chill it. If we could get hold of Lox (cheaper) we'd use that too. Ah, good times!

Unfortunately I'm still in Iraq; but growing up in the Rust Belt I definitely know about the benefits of cool air...

Yeah, I've noticed it too, but only the last couple of days. The motorbikes seem better too.

We've got cool, damp air here. denser Air . Don't know why the moisture Helps, but it does seem to.

Biggest thing with the moisture is the slow down of the flame edge and actually makes the A/F mixture more dense; I'm not sure how advanced the 'ECUs' are in the diesel trucks but also it could allow more boost. Supposedly there is also the benefit of the water itself absorbing some of the heat and turning to steam rather than transfering to the engine block; this steam probably has some expansion properties which helps slam the piston down providing a bit more power.

[MoonRiverOasis]

I definitely feel the difference, and I like it

Air Density is the measure that determines performance, and it's made up of Air Temperature, Altitude, Humidity and Barometric Pressure.

Air temp is the biggest over all factor in Air Density however - Lower air temparatures have a direct 1:1 relationship with Air Density - i.e. a 1% drop in temp has a 1% increase in Air Density.

Here's an Air Density calculator to play with:

http://www.dragtimes.com/da-density-altitude-calculator.php

The final Air Density number that calculates pretty much directly correlates with HP

[MoonRiverOasis]

At Santa Pod in the UK we used to spray No2 on the intercooler before a run to chill it. If we could get hold of Lox (cheaper) we'd use that too. Ah, good times!

Cheap and still effective way to reduce intercooler temps as to spray a mix of water and methylated spirit directly onto it. Back in my younger, less financially stable and total piston head days, we used to remove our windscreen washers and use them for this It's good enough to create ice on the intercooler.

We've got cool, damp air here. denser Air . Don't know why the moisture Helps, but it does seem to.

More humidity means less air density, which means less HP, so what you're feeling is just the (larger) effect of cooler air temps. The only time humidity can be of help is for removing more heat from the intercooler (i.e. like the above mentioned ghetto intercooler freezer).

Ideally what you want for max. HP is low humidity, low ambient temps, low altitude and high barometric pressure.

Edited December 13, 2010 by MoonRiverOasis

[culicine]

Speaking of cooler air increasing performance, has anyone tried to insulate their air intake boxes / intercooler pipes using some heat relective material?

I tinkered with this last year during the cool season using some thin roofing insulation wrapped arounf my standard airbox. During that weather it seemed to make some improvement though it could just be some placebo effect of making the mod (mind you the airbox was modified to remove the resonator and I use a k&N drop in). I'm thinking Anything to reduce heat under the engine bay should help - I'm thinking about air vents and removing sound insulation from under the hood (that could help heat escape more easily). Open pod air intakes seem to be a no-no here also (very high under hood temps causing heat soak sitting in bkk traffic), unless it's some kind of cold air intake, but that could be subject to hydro lock here in low rides.

[MoonRiverOasis]

Speaking of cooler air increasing performance, has anyone tried to insulate their air intake boxes / intercooler pipes using some heat relective material?

I've never tried insulating the intake parts, but have in the past gone the other way and insulated the hottest parts - i.e. wrapping the headers/extractors and fabricating insulated heat shields for turbos - i.e. these kinds of products: http://www.heatshieldproducts.com/insulation_index.php

[dave_boo]

At Santa Pod in the UK we used to spray No2 on the intercooler before a run to chill it. If we could get hold of Lox (cheaper) we'd use that too. Ah, good times!

Cheap and still effective way to reduce intercooler temps as to spray a mix of water and methylated spirit directly onto it. Back in my younger, less financially stable and total piston head days, we used to remove our windscreen washers and use them for this It's good enough to create ice on the intercooler.

We've got cool, damp air here. denser Air . Don't know why the moisture Helps, but it does seem to.

More humidity means less air density, which means less HP, so what you're feeling is just the (larger) effect of cooler air temps. The only time humidity can be of help is for removing more heat from the intercooler (i.e. like the above mentioned ghetto intercooler freezer).

Ideally what you want for max. HP is low humidity, low ambient temps, low altitude and high barometric pressure.

I disagree with you in regards to the efficiay of humidity in the cycle. The displacement of O₂ molecules is sure to happen, anything in the suspension will do that, the added cooling by the water would seem to more than make up for its determential affect. According to this chart you're only looking at some 23 g/m3 at 25 C when the air is saturated. So a grand total of 2,33 x 10^-5 g (cm³) per intake by weight or less than 2% of volume...but since the atmosphere is 21% O2 volume you're looking at ~0,4% of the total intake being affected if the water actually does displace the air (I'm not a climatologist so I don't know for sure).

[MoonRiverOasis]

I disagree with you in regards to the efficiay of humidity in the cycle.

You are free to do so

[EvilDrSomkid]

Speaking of cooler air increasing performance, has anyone tried to insulate their air intake boxes / intercooler pipes using some heat relective material?

I tinkered with this last year during the cool season using some thin roofing insulation wrapped arounf my standard airbox. During that weather it seemed to make some improvement though it could just be some placebo effect of making the mod (mind you the airbox was modified to remove the resonator and I use a k&N drop in). I'm thinking Anything to reduce heat under the engine bay should help - I'm thinking about air vents and removing sound insulation from under the hood (that could help heat escape more easily). Open pod air intakes seem to be a no-no here also (very high under hood temps causing heat soak sitting in bkk traffic), unless it's some kind of cold air intake, but that could be subject to hydro lock here in low rides.

I have put a special turbo jacket around the turbo exhaust side on the S6. Its mostly to keep under hood temperatures down.

Insulating the intake tract might have some benefit, but sitting in traffic will draw in hot air again.

Right now, all the intake hoses are high quality silicone. The stock rubber ones were all gone bad from age and heat.

I recommend against removing the insulation under the hood as this could cause discoloration in the paint. Heat spots and such.

The debate whether a K&N actually helps or not is a big discussion I will not start here, but suffice to say on Audis its wasted. The stock paper element is plenty.

Can even be detrimental to the MAF element if the filter element is incorrectly oiled.

Gratuitous under hood pic of the evil doctors ride. The turbo jacket was not installed yet.