compressed air injection

[s4marsh]

i've read loads of posts regarding intake temps for our turbocharged engines and the use of water/meth injection, nitrous etc, i was wondering if you injected compressed air which is very cold when discharged and very cheap into the system like other methods would it have the desired effect or cause lean burning and overheating?

[Blue_Thunder]

What do you think your turbos are doing?

You actually heat air when it's compressed (as seen with Turbos, Superchargers and bicycle pumps).

The Ideal Gas Law states that Pressure = Volume x Temperature. So any increases in pressure or reduction in volume (if the other remains static) result in a temperature increase.

[tartan_rob]

I know what S4marsh is saying. Compressed air is actually a liquid in the tank, it cannot increase in temperature as the volume remains static...anyhows, he is asking if it could be used to cool intake air.

It could but it would stuff fuel/air ratios as it is intriduced post MAF's. What maybe better is to get a CO2 spray directly onto the IC's in order to increase the heat transfer.

[s4marsh]

thanks rob at least you knew what i meant, of course i know what the turbos do blue give me some credit i build furnaces with forced induction fans bigger than your house...i'm just looking at all the different ways of cooling the intake temps and had never heard of this technique and now i know why lol

[s4marsh]

could you inject it directly after the intercoolers before the maf? would the fuel/air ratio be adjusted?

[deanobeano]

Rob

Compressed air at most available pressures (ie 300 bar cylinders) is not liquid.

That said, if fed in after the turbos, the reduction in pressure from 300 bar, to say, 1.5 bar would provide a cooling effect.

[s4marsh]

if it had a proven effect i could have a small bottle in the spare wheel well that i could charge up at home with my compressor it would be very cheap but weigh around 10kg

[s4marsh]

it also has water vapour in it as its discharged so a free aquamist function too

[deanobeano]

A small bottle say a 3 ltr pony bottle used for scuba diving,

Charged to 220 bar at a dive shop would contain 220x3=660 lts of air

Filled with your compressor at home, I'm not sure how high you could charge it to? say 10 bar?
this would only give you 10x3 = 30 lts of air

I don't think the latter would be of any use (not sure what the air flow to the six is in lts per minute, but I imagine it would be quite alot.)

[s4marsh]

about 15kg of air per minute according to my turbo calcuator at full throttle/6800rpm so a 10ltr bottle done at a proper depot just down the road would give 2200ltr and injecting small amounts to aid cooling and density it would last ages....so is 220 the max bar rating for the bottles?

[s4marsh]

or 18750 litres per min @ redline

[deanobeano]

S4MARSH
300 bar is typically the highest pressure that can be charged by a dive shop etc.
the 300 bar cylinders are different in design to the more std 220 bar variants.

According to the source below, air has a density of 1.29 grams per litre (not sure what temp this is calculated from).

if this is the case, then a 10 ltr cylinder at 300 bar = 3000 lts = 3870 grammes.

from: http://wiki.answers.com/Q/If_air_has_an ... ter_of_air

[imolas4uk]

but you would be introducing air into the engine which has not been metered by the ecu ?,water meth or co2 sprayed onto the ic`s would be better.

[s4marsh]

yeah there wouldnt be much benefit for the hassle involved rigging it up