FDNewbie

iTrader: (10)

Exactly what is it about cold air temps that gives more HP? Cuz to my understanding, pretty much anything that will cool the incoming air increases HP, eg. true cold air intake, intercooler, and I believe NOS even works by causing a sudden drastic reduction in temps. So how's this cold factor work?

My total guess is that you get better combustion and thus extract more energy from the process at lower temps??

MakoRacing

iTrader: (12)

Yeah cold air=condensed so theres more of it in an area...hot air is the opp....whatever you can do to chill the air helps alot.

mad_7tist

the rule of thumb is for every 10 deg F you drop the intake temp you will get a 1 percent increase in hp. assuming that you are adjusted correctly ie fuel and timing are corrected to take advantage of the deser air.

TwinTriangles

Someone had a post a long time ago with some equation stating exactly how much HP to gain from each 1degree in colder intake temp I think....

rallyboy

Err, you mean cold air is more dense, not condensed.
(If it was condensed, that would imply that it has moisture in it, which makes the air less dense)

To expand on this:
Basically, the warmer air is, the less dense it is. When you heat something up, the molecules inside it "jiggle" faster and move apart (that's why hot metals expand), fewer molecules in a give amount of volume = less density. Hot air expands and becomes less dense as you heat it.

Now, let's look at the extreme case, where you heat air up to the point where the molecules are very far apart - you get something close to a vacuum. Reviewing back to elementary school, combustion requires three things - air, fuel, and heat. You've got the fuel and the spark, but very few air molecules to combine with the fuel molecules. Hence, very weak combustion, and little power output.

With colder air, you have more air molecules in a given volume - cold molecules don't move around much. (ex. metals contract when they cool) The fuel molecules have more than enough air molecules to combine with during the detonation process, so you get more power output.

That make sense?
Felix

FDNewbie

iTrader: (10)

Guys...thanks for the fast reply

Oh and Felix...it makes PERFECT sense. It was the density part that I overlooked... so once I saw that (yea i figured that's what he meant by condensed) it was like a lightbulb when on inside lol

Am I correct tho about the same principle applying to NOS? And my guess would be with such a drastic temp drop, you vastly increase the air's density, giving great HP increases? (im thinkin, in a way, it's almost like supersaturating... except you're talking about an air medium, and you're not heating...you're super cooling)

And if that's correct, and the 10 degrees to 1 Hp calculation is correct, a 50shot would require a 500 degree reduction in temp???? (this is assuming a 50shot corresponds to 50HP). I must be wrong here...

poor_red_neck

Well, there's more to nitrous than that.

Nitrous Oxide (NOS is a brand ) is basicly just oxygen and nitrogen atoms bonded together. Now, oxygen is one of the 3 big componets of fire. Well, you can't just inject pure oxygen into an engine. Oxygen as a pure gas is VERY flamable. The nitrogen acts as a "buffer" to the oxygen. The nitrogen oxygen bond 'comes apart' at around 512 degrees C I think (that number pops in my head from reading an article on nitrous online... that number is probably off though). At that point, the nitrogen is just burned, and the oxygen is then added to the now explosion inside the chamber. This is how nitrous oxide works . Yes, the reduction in intake temperature does aid some in making power.

-Jon

EDIT--
WHOA..... this is not my terriotry. HAHA. I was searching for a topic and this popped up.. thought I was only searching for 2nd gen section. Oh well.
/edit.

Mahjik

iTrader: (1)

Check this thread out:

https://www.rx7club.com/showthread.p...5&pagenumber=2

Basically, while cold air is good, it doesn't make the same impact on a turbocharged car as it does a NA car. 10-15 degree difference before the turbo isn't going to do didley. What really matters is the temp after the IC. However, prodiving more air has shown to help the turbos spool quicker (such as additional ducting for the stock air box or just using open intakes).