OK, can’t help myself
. To get to the core question, does a cold air intake add horsepower…yes, cold air is denser and thus under proper conditions can add horsepower.
But how much (again, this depends and a lot of people talked about filters)?
To try to see just how much, I created a cold air setup, but used an enclosed inline type filter (rated decently above the CFM required for the 4.0L) and put it in the same location as the typical cold air setups you see for the TJ. What this allowed was for me to add and remove a snorkel intake, and then measure the difference in intake temperatures, and thus to approximate how much horsepower increase I can expect with a snorkel.
I realize this doesn’t get to the difference between the cold air intake kits without a snorkel and the stock TJ setup, but my assumption is that the difference in air temperature under the hood between factory TJ air intake and a ‘standard’ cold air setup without snorkel should be even less significant between the ‘standard’ cold air intake set up and the one with a snorkel, and that I’m not looking at differences from different filter types.
So my test was multiple passes down the same stretch of relatively flat (as flat as I could find) highway with both the snorkel attached and not attached. Again, while I haven’t done full analysis, it is clear there is about a 10 degree F temp difference…so what does that equate to?
The general equation for difference in horsepower for given intake air temp difference is that it is proportional to the sqrt(T2/T1), with T referenced to absolute zero (so start at approx. -460 degrees F and add intake temp).
For my tests, we have sqrt(600/590) = 1.0084, which at best case (max horsepower) equates to about 1.5 horsepower.
Now I haven’t fully researched it, and again I am not considering differences in filters, as to me that is a different question, so I welcome criticism if I’ve made any errors.
In the end, yes a cold air intake can add horsepower, but from a pure cold air perspective, unless you can get a large temperature difference, the gains are minimal and so doubt noticeable.
And I’m sorry if this is duplicating anything anyone else added, although I love this forum, after page 3, I was just skimming!