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so i'm looking at f5 fujita short ram vs. the f5 fujita cai? its like 70$ more but i'm looking for more increase at higher speeds which is the better choice?
 

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i'd go with the short ram, as i did. but i have heard though that the cai is better for high speeds. i.e. freeways
 

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While this may be the case in some vehicles when talking about intake temperatures of cold air vs. short ram intakes, I don't think it is the case with the xB. And I'll explain why I say that.

First we have to look at the three major intake designs for the xB. (I'm not taking into consideration the "odd balls" like Perrin and Volant.) You have the typical short ram design used by Fujita, Injen, YDR, etc. that are a fairly straight shot to a filter tucked behind the driver's side head light. You have the typical cold air designs like Fujita, Injen, etc. that loop through the engine bay at the stock air box location, then turn behind the headlight and then down again at the head light. And the third design like the K&N Typhoon that is a fairly straight shot from the throttle body to a 90 degree bend behind the head light, placing the filter in a similar location to other cold air intakes.

So, looking at all of these designs we should compare filter location first. There is probably a nominal 6" difference (or less) in filter location between most short ram and cold air intakes on the xB. Essentially the difference between mounted horizontally, or adding a 90 degree bend to be mounted vertically. The difference in air temperatures between these two locations is negligible. And I would bet good money you wouldn't even see a temperature difference on the intake side of the filter.

Next we need to compare the general path of the intakes. Assuming we have virtually the same intake temperature, which intake will gain the most heat through ambient engine bay temperature? Certainly not the short ram with a virtually straight shot to the throttle body. The same could be said for the K&N style "cold air" intakes. The majority of cold air intakes though have a significantly greater amount of tubing in the engine bay due to the loop at the stock air box location. This loop also sits directly above the transmission which has a tendency to run even hotter than your engine.

The last thing to consider is the number of bends. While most people only consider this as a matter related to air flow, it actually affects temperature as well. Just as the friction caused by a bend in the tubing can disrupt air flow, it also contributes to heat. Though much less a factor than filter position, or design length, the friction from these bends does contribute to the intake air temperature.

What does all this mean to you and me? Well, without actually doing any scientific tests and just following simple logic it would stand to reason that the short ram design would provide cooler air intake temperatures. Or possible designs like the K&N Typhoon. And of course, this is just my individual opinion on the issue.

For my money, I really don't think there is a better intake for the xB than the Fujita F5 short ram. The intake provides a short, clean intake run with only minor bends. It also places the MAF sensor in a better position relative to the breather hose than other short ram intakes. And finally, it is very reasonably priced.
 
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