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aussieinstlouis said:
I had an idea after seeing Jim's new avatar with the bag of ice on the IC.

Cons:
more expensive ($10 vs $1.49 for ice at the 7-11)
more difficult to source (industrial gas suppliers)
could (?) produce a 'cloud' of CO2 that could get into short intakes under the hood??

Comments and/or criticisims welcome!!

Andrew
aussieinstlouis
Glad I could inspire! The CO2 short out is a stretch. I wouldn't worry about that. My main concern would be water condensing in the intake tract on humid days since that is DAMN COLD.

-Jim
 

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Superfluid SS said:
Giving that some thought, PlatinumWRX is right, but even dry ice could be overkill.

Ice would cool off the IC back to it's normal temp.

Dry ice may casue the air inside the IC to become too dence, it could lean out the motor.

--
Jeff
That's true. The air is metered before the turbo, so some form of ECU programming might be necessary to help the car run properly.

-Jim
 

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I think it's a matter of "degree" or quantity of the change. In all likelihood, you'd need a different fuel map to go from 80 degF ambient to -20degF at the manifold. Considering the turbo heats the intake charge and IC cools it almost back to ambient usually, this would be too large a chage for the stock program to handle.

I get Carlo to try it, he's just crazy enough. :D

-Jim
 

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GTRsi said:
don't you guys run coller after the i/c? I kinda thought that was the point of the IC? shouldnt the WRX have a sensor pre-throttle bodie or in the intake manifold?
It doesn't have a sensor and under "normal" circumstances, it doesn't need one. When you get into liquid N2 and solid CO2, it's a whole new ball game.

-Jim
 

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dark_rex said:
feel free to contradict, but i think that negative 150 degrees F is REALLY going to make a difference in the mass of air in the mix, never mind you'll be freezing any free water molecules in the air into an immediate solid.

dR
Mike, Law of conservation of mass. In a closed system, the mass can't change.

Once the air enters, it stays the same mass. The density of the air charge entering the cylinders is the issue. The air would become ridiculously "thick" or "heavy" for lack of a better word.

Furthermore, cold air doesn't take fuel well. Everyone remember carbuerators in winter? Bad.

-Jim
 

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dark_rex said:


:)

nice try jim, but the valves open and close at a fixed rate, so more dense air means that you can fit more into the same space at that fixed interval. this equates to more mass at the colder temp, not b/c the temp is creating mass out of nowhere, but b/c more can fit due to the colder/denser charge.

dR
You're right. At an intercooler and manifold level, I am correct, at a cylinder level, however, the closed system ends, you would be packing more mass in the cylinder. This is only true as time approaches zero however, which means we need (OH DEAR GOD) CALCULUS!!!

Damn, this is fun. :D

-Jim
 

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ProdriveMS said:
I don't believe I've contradicted myself. Look at it this way. Lets say we freeze time for a second and look at whats happening inside the motor. ...

Btw, this doesn't apply to NA engines. Colder air means you need to add more fuel.

Another potential problem might be poor fuel atomization from the colder air charge. The fuel needs tp be in vapor form since liquid wont combust and heat is used to vaporize it. This shouldn't be a problem though since in all modern FI engines, fuel is squirted on the back of a hot intake valve sometime during the compression stroke. The hot valve helps the fuel vaporize and by the time the valve opens for the next intake event, most of the fuel should be vaporized.

Alin
Alin,

Who said you contradicted yourself? We're just mulling this over.

Good call on the fuel vaporization, I hadn't thought of that.

-Jim
 

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is2scooby said:
Jim,

He did. :D

This thread has made me realize why I'm a computer geek and not an engineer. You guys are just WAY too smart. :)
Thanks, is2scooby.

"WRXed did it." (points finger like a 5 year old)

Code:
If your gonna "walk the walk," you HAVE to "talk the talk,"
but if you "talk the talk," you damn well BETTER "walk the walk."
                                                     --Mechanical Engineering Credo.
 

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KurleeDaddeeWRX said:
But I have a question. If you are in the staging lanes say. And you have your hood up and ice along the top of your intercooler for an hour or so.(This is how long we had to wait for your CLASSES.) Then you get the signal to line the cars up. So you try to get as much ice off the intercooler as you can before you run right? You start your motor and start moving forward little by little. Until you get up to the starting line. WONT YOUR INTERCOOLER GET HEAT SOAKED AGAIN AND THE ICE YOU JUST PUT ON THEIR FOR AN HOUR IS USELESS? Someone told me this so I want to run it by you guys to see what you think. Its a question not a comment.

Kurlee Daddee
(THE ORIGINAL)
Yup.
Hence, you get you ass OUT OF THE CAR and PUSH the 3000lb mofo to the starting line. I'm not kidding, ask anyone whose been to the track with me. If it's hot, I'm pushing. BTW, my IC can get as low as 40-45 degF before I run. 2barjones, care to comment?

-Jim
 

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aardvark said:
I think you guys might be confusing some issues. Namely how mass flow and volume flow are related to the workings of an internal combustion engine.

An internal combustion engine is actually a constant volume machine. Forget about cam and valve timing, etc. Every time the crankshaft in a four stroke ICE makes two revolutions, the engine pulls a certain volume of air. This volume is based on the physical geometry of the cylinders, namely the bore, stroke, and number of cylinders. This constant volume being swept by the pistons determines the volumetric flow rate when taking into account RPM. A piston engine is always constant volume at each unique engine speed. Mass flow at each unique engine speed is not constant. This is true because mass flow is affected by air density. Now, mass flow BEFORE the mass air meter and AFTER the mass air meter is always constant at any given time. Also, mass flow before the intercooler and after the intercooler is always constant at any given time. And again, mass air flow of the intake summed to the mass flow of the fuel will be the same as the mass flow of the exhaust at any given time. However, this is not the same as what was proposed above in the second paragraph. Mass flow (and therefore mass by itself) can be directly related to power production. Twice the mass flow will make roughly twice the power. So if a cylinder contains a mass (NOT mass flow) of fuel and air which is X lbs at a given engine speed, then 2X lbs of air at that same engine speed will make twice as much power.

This concept is actually the same regardless of whether it's a forced induction engine, or a naturally aspirated engine. More mass flow (read more air mass in the cylinder) always makes more power.

Piston volume (displacement) is really the only constant when dealing with an internal combustion engine. Displacement is the ONLY thing which is not effected by temperature, density, flow rates, etc. That's why it's the only constant.
Hey, Mike. :p :p :p

Thanks, aardvark!
 
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