Damp weather - better running??

[philKS2]

Before I discovered the S2, I owned a 16v Audi Coupe.

A guy who was going to tune it told me they ran better in damp weather cos of the way they are set up...

I have so little technical knowledge I have no idea if this could be true... BUT I always felt the car was smoother and more responsive on damp misty days.. perhaps the power of suggestion, lol ??

Anyone know the science behind this... is it true of the S2 as well??

P (ps am in the UK so damp weather in plentiful supply)

[S2central.net]

Oh I love this stuff... This is how they should get kids (well boys anyway) interested in science at school - forget all that pure theory nonsense - demonstrate with practical applications of the science to make it meaningful.

Yes - cold/damp air is better for engines as the colder it is, the more dense it is - essentially there are more air molecules sucked into the engine when the air is cold. Modern cars have a good accurate measurement of air mass coming into the engine... The more air you have, the more power you make.

This is why we have an intercooler - to reduce the temperature (and therefore increase the density) of air after it leaves the turbo and before it reaches the engine. Without an intercooler, our cars would be much less potent.

Paul

[EspenW]

Cold air: always better
Moist air: (almost) always worse

SAE and DIN correction factors correct for humidity. The higher the humidity, the lower the O2 content.
However, on an intercooled turbo car, humidity, and especially rain, can have a positive effect due to increased efficiency of the intercooler.
Damp air does not have the positive effect of cooling the intake charge as water injection has as it is already in a gaseous state. It is the transformation of the water form liquid to gas state that absorbs heat from the charge with water injection.