I have an Ecodiesel Summit and have been contemplating getting a CAI and am looking at the AFE one...landed here while doing some general research about how the CAI's perform on the Jeeps as this is my first jeep.
One thing that I have found while researching for my previous vehicles is that the design of the intake system and cooresponding results can be somewhat deceiving. Here is what I mean - and I know there are differences in dyno's, temps, etc, etc. that affect the results -
When you look at the dyno results that KN posts on their website for their 5.7l intake (http://www.knfilters.com/dynocharts/63-1563_dyno.pdf
), they cut the graph off below 3000rpm or so but you can you can see on the curves that the stock (blue) HP and Torque are actually better with the stock system than the KN system (red) up to about 3000 rpm's where the KN then takes over, you can see just enough of the curves to see them flip over each other before they cut off the rpm range on the x/horizontal axis. Think about where your engine is in the rpm range for the majority of the time you use it. On almost every other car that I have tried the KN system on, their dyno curves all mimic the same thing, the stock systems outperform the KN at lower/useable rpm ranges. And what I have read online and experienced on my own vehicles is that the loss of low end torque and HP is noticeable...lots of posts on the various make/model forums about a loss of low end umph after adding a CAI...I think the curve explains why. Not bashing KN or anything just pointing out my own interpretations. There are two 5.7l intakes, the other ones curve looks better...at least they don't flip at the lower range but again the graph is cut off so may still flip over at a lower rpm than shown on the graph. Maybe those that are not as satisfied or are experiencing some lag are using the one I linked to above and not the other one? When you look at the curves for KN 3.6l option, you can also see the flip on the lower rpm range where the stock system is better than the KN system as well (http://www.knfilters.com/dynocharts/77-1560_dyno.pdf
I am considering the AFE intake for my ecodiesel so not quite an but for apples-apples comparisons, but here is the AFE dyno chart for the 5.7l (http://afepower.com/catalog/54-76205...76205E1600.jpg
) - compare the curves to the KN curves...you will see that outside of a short bump in the lower rpm range, the torque and HP curves of the AFE are above the stock system...from what I have researched online and experienced on my own cars, the AFE doesn't have the loss of low end torque feeling....
Not affiliated at all with AFE or KN, just trying to provide some helpful things to look for when picking an intake system...
Not alot of options for the ecodiesel yet (ever?) but looks like the AFE would be a solid choice for that engine as at least there is a consistent (outside that one small rpm range which is kind of weird) improvement shown for the non-stock system especially in the low/useable rpm range...
Long winded answer but to sum it up - I wonder if those that feel a lag or no increase in performance after CAI installation is due to actually loosing low end hp/torque?