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Discussion Starter · #1 ·
I understand an icebox can be used to cool the air being forced into an engine, but my question deals more with relative air temperatures, including those altered by a icebox.

Let's say Im driving around the desert and the air is 100 degrees that im sucking in, and then I drive up a mountain and it lowers to 60 degrees.... does that 40 degrees difference pack enough extra air in to make a difference in the air/fuel ratio?

Second example is when Im using an icebox with water and my air temps are 70 degrees, and then for a performance run I add ice instead, and get it down to 50 degrees.... Im assuming the 20 degree drop helps add enough air to make a difference, but wouldnt I need to add more fuel to make up for that additional air (the basic point of upping fuel when using forced induction).

I guess that is my question. I dont know the formulas to figure out the % density difference at 100 vs 60 or 70 vs 50... but even if it is 5% difference, wouldnt that require a fuel adjustment? or does that happen automatically well enough?
 

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Basically if that were true it would be like people living in cold environment have really lean a/f ratios and people out in the desert such as myself have really rich a/f curve. So it probably doesnt affect the a/f enough to make a difference at all really

I seen Minesbetter dyno of a before and after dyno with the icebox. He did a base run, then added the ice box, then added ice. His a/f curve didnt really change, but he gained 20whp/wtrq by just adding the ice. Anyways this was my perspective pretty much

The reason why you would want a intercooler also is because at like 7 psi for the roots s/c its suppose to be 180 degrees hotter and getting the intercooler cools it down like 95%.
 

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Discussion Starter · #3 ·
So are you saying that it adjusts automatically to balance the a/f ratio? I thought some of that had to be manually adjusted when dealing with additional air due to compression?

I understand the logic of NA machines that use a CAI in order to up performance, but I guess I don't get how the A/F ratio would stay balanced when you are forcing more air in than in a normal intake engine.
 

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Well one thing I forgot about in my last post is that we have a IAT-measures the temparture of the air coming in. So I guess this is something the tib automatically adjust to.

One thing though is the intercooleris down by the manifold and you moved the IAT to the intake for a roots s/c, so it doesnt measure that air's temparture. So idk, maybe someone else will chime in
 

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Often when people talk air entering into the engine they don’t make a distinction between volume and density of the air. The former pertains to the amount of particles contained in a certain amount of space, where the latter is an indication of how much space those particles take.

For N/A and F/I cars the incoming density of the air is determined by various sensors especially the MAP/MAF, colder air contains more particles than the same volume of warmer air. The computer determines the A/F ratio based on air density entering the engine not volume.
Once the air is in the piping its density does not change.

F/I mainly increases air velocity. Charge coolers (e.g. intercooler) cool the air thus reducing its volume. This is why the end effect is stuffing more particles into the cylinders, however compensation for ambient air density has already been determined as the air entered the engine. When adjusting a piggyback or standalone you are adjusting for the extra o2 particles in the cylinder, not ambient air temperature. That’s why you don’t need to get your car re-tuned every day when the ambient air temperature changes.

in a setup where the map/maf sensor is placed before the charge cooler like with the icebox/alpine you have to be a little more careful as too much cooling will lean out the a/f since the computer has already determined air density. But you only have to worry if you plan on replacing the ice and water with liquid nitrogen. or decide to run the car in the north pole when you got the car tuned in Hawaii.

check out the information section of the forum the FAQ or archive sections they have a bunch of articles on F/I applications
 

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Hello,

For a good comparison as to how well our Ice Box works and how it effects the A/F's look at the first dyno in my thread that says 400whp dyno buffet. This shows a back to back comparison on the same car, same day. One is with water alone and the other was with the addition of ice. This was one of our Stealth turbo kits with our Ice Box at 16lbs of boost and 93 octane. If you notice that it made an incease in peak power, but the amazing thing is the increase in power and torque from 4500RPM and up. It picked up 40whp and 40+TQ in that area. If you notice with the dense cool incoming charge, the A/F's went real fat. This pull was with no other change accept for the addition of the ice.

Thanks T.C.
 
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