Why is cold air so important?

[yobbosayo]

I was just wondering, if cold air is so important (pods, airboxes etc) why are my old cars and my bike more powerful when they warm up?

Or is cold air only important for preventing detonation on EFI cars?

[Monsterbishi]

I was just wondering, if cold air is so important (pods, airboxes etc) why are my old cars and my bike more powerful when they warm up?

Or is cold air only important for preventing detonation on EFI cars?

It's all about density, cold air contains more oxygen molecules than hot air, which means on a colder day, there is more oxygen burning within the cylinders, so more power.

Cold air is good for any combustion engine - old or new.

[Scotty]

Isn’t cold air denser therefore has more oxygen and combustion works better?

[Loudtoy]

Yeah what the above to said! However when your bike/cars have warmed up the everything insie the motor is moving freely, everything has expanded to closer tolerances the exhaust has warmed up allowing gas to get further down the exhaust before it cool and gets heavy! Basicly the reason for cold air boxes and stuff is so that you stil have cold air even after everything is up to it's correct temperature and the car can make it's best power!

[riddles]

So, dumb question time. How cold is too cold? What if you were to take the air from your airconditioning, (or add a second unit) and feed that to the engine?

[Monsterbishi]

So, dumb question time. How cold is too cold? What if you were to take the air from your airconditioning, (or add a second unit) and feed that to the engine?

Basically there's no such thing as too cold, as long as the car is fuelled to cope with it.

Using a aircon unit would be most impractical, not only couldn't it flow enough air to make a difference, the parasitic loss from the aircon unit would cost more that it could gain.

[Stealer Of Souls]

Using a aircon unit would be most impractical, not only couldn't it flow enough air to make a difference, the parasitic loss from the aircon unit would cost more that it could gain.

Rumour has it some jap race teams are experimenting with this. With what limited thermodynamics knowledge I have, I reckon this would only be of benefit on a forced induction engine. A degree or two cooler before the turbo could mean five or six at the intercooler. Dunno if this would aid power production.

On the topic of Too Cold. If it's too cold doesn't the fuel have trouble staying atomised?

[Scotty]

Don’t some drag teams run air through a pipe, which has liquid nitrogen around it to get it as cold as possible?

[Disco]

Don’t some drag teams run air through a pipe, which has liquid nitrogen around it to get it as cold as possible?

I think what you're talking about is an intercooler coz when you're running all that boost and all that nitro a normal air/air or water/air won't cut it.

I remember a very similar thread from the old days... lemme find it...

aha... viewtopic.php?t=10056

thank you mr SEARCH.....

I guess the best practical set up woiuld be the old have your air intake drawing from somewhere that is the coldest and make sure that the pipe doesn't get too heated by the engine...

[Zak]

The only problem with cold air is condensation, as the water condenses and water in a motor is bad

[Disco]

The only problem with cold air is condensation, as the water condenses and water in a motor is bad

Condensation would only occur if you had like a bag of ice on the plenum or intake keeping it cool... it rains on the inside where it's nice and warm...

and If you've got condesnsation in your intake you are a nana...

[Monsterbishi]

The only problem with cold air is condensation, as the water condenses and water in a motor is bad :(

Not really, the condensate vaporises the moment it gets into the combustion chamber anyway, taking a lot of heat with it - a good thing by all means.

[yobbosayo]

I liked loudtoy's explanation. so a hot exhaust flows better?
I seem to remember some old cars used the engine coolant to heat the manifold. would this be right?

[riddles]

http://www.autospeed.com/cms/article.html?&A=0436

[Dr-X]

So, dumb question time. How cold is too cold? What if you were to take the air from your airconditioning, (or add a second unit) and feed that to the engine?

Basically there's no such thing as too cold, as long as the car is fuelled to cope with it.

BS, dude. The optimal air temperature inside the cylinder, if I remember correctly, is 42C. Once you get to very cold temperatures, and particularly icey temperatures, it makes combustion a lot more difficult.

As for using an air con system...cold air from atmosphere (on NA) is cold enough, and making the air colder is likely to make maybe a 0.1% difference, where as an air con system can drain significant amounts of power. Using forced induction, temperatures make a bit more difference, but not anywhere close enough to overcome the power loss of an AC system.

Also, as far as condensation, well a little condensation is what a lot of cars could do with, as the small amount of water in the chamber could do wonders for ping prevention.

[anthonym]

BS, dude. The optimal air temperature inside the cylinder, if I remember correctly, is 42C. Once you get to very cold temperatures, and particularly icey temperatures, it makes combustion a lot more difficult.

Dr X, Is your Phd in obfuscation? It's not in-cylinder temp that's the issue, rather fuel atomisation, which happens in the inlet port. The optimal air intake temp for atomisation for forced induction is 35-40 deg C, not sure about NA.

Using forced induction, temperatures make a bit more difference, but not anywhere close enough to overcome the power loss of an AC system.

Nope, wrong again, a water to AC heat exchanger for a w/a intercooler can be extremely effective.

[fatgtr]

slightly off topic but if u are running a pod filter with a cold air box, and u put a air compressor (an electronicly controlled one like u can get at the warehouse for $20) and u put i between the throttle and cold box will that have the same effect as a turbo?

[Dr-X]

slightly off topic but if u are running a pod filter with a cold air box, and u put a air compressor (an electronicly controlled one like u can get at the warehouse for $20) and u put i between the throttle and cold box will that have the same effect as a turbo?

AHAHAHAHAHA!!! You arent aerious, right?

[trueno]

^ It'd have to be one hell of a big pump, In a 1.6L engine at 6000rpm It'll need to flow ~70-80L of air PER SECOND to keep up, that's without producing any boost..

[matt dunn]

Howz this for a simplfied reply.

As things heat up they expand.
When the air in the cylinder is heated it expands pushing the piston down and making the power.

The colder the air is the more air you can actually fit into the cylinder,

and

the colder it is to start with the more you can heat it.