Over the last 30 years I have read 3 or 4 authoritive test reports on after mkt. free flow, low restriction, etc. induction air filters. These objective tests were usually conducted by automotive magazines utilizing dynomometers on American 350+ cid V8 engines. Here are the summerised test results in general and as best I can remember them:

1. Unmodified stock engines showed HP gains of 3 to 5 on the dyno. Not a number that could be felt by the average driver.

2. Engines progressively modified with free flow exhausts and custom cam shafts benifited the most with good HP gains at high rpm, usually in the 50+ range.

Now for the "IMO stick my neck out" comments; top end European performance engines utilize every "trick in the book" to produce high HP with lower displacement engines. These highly refined engines benefit little from after mkt. high flow filters. Air flow is, for the most part, already optimized. I believe this approach is the result of European policies to progressively tax cid. Insurance rate policy plays a part too. At least that's how the design mind- set started

American makers have traditionally used the "more cid is better" approach. It makes sense. Fuel was, and still is to some degree, cheep in the US. There is no tax on HP or cid. Gas guzzler tax? Come on. It's a joke to the average Caddie buyer. So what they did was put in a low cost high cid/hp engine with cheep induction/exhaust systems. Now these engines really can benifit from after mkt. air filters if "you up grade the induction, cams and exhaust systems".

Bottom line. I will believe significant Hp gains from after mkt.air filters on a Jag engine after I see dyno results. There were some guys here awhile back who were doing dyno tests on their Jags. Perhaps we can get them to do a before and after test with air filters.

 

I have done many tests (airflow/vacuum measurements), and I can concur (at least for the 4.2 engines), that you will NOT get any significant gains from other filters then stock.

A K&N filter will however be significant for the money (cheapest gains possible); about 2% increase can be expected, so there is no argument imho.

Once the original paper filters get dirty you will lose performance, whereas the K&N performance will drop much less, so the difference will be much more than 2%.

2% would fall in the dyno error margin, and to do it properly you need to do several controlled runs, which would be very expensive, not worth it.

When it comes to increased flow for modified cars, it will become obvious that you need a filter system that can accommodate the extra flow, so the stock filter becomes then a bigger restriction, but the K&N panel filter as it already flows more can offer some room there (still use one on my car, until I have made a larger filter box that gets air form outside the engine bay).

 

Has anyone who installed the K&N filters notice any improvement in MPG and how much the improvement?

Thanks

 

yes, better mpg slightly. Maybe an extra .5 to 1 extra mpg, but when you feel the difference with the filters it will make u want to mash the throttle more so it's really not a gain

 

Can probably save the effort of ebay etc, my local auto parts store has them for $41.99
http://www.knfilters.com/search/deal...x?part=33-2273

 

I have had a K&N filter on almost every car I've own since my 93 Ford T-Bird SC, and have noticed a better responce from my engine. I went to K&N web site several time when I first purchased my 2010 XF SC in 2009 and they where not ready yet for our engines. Back in july I got notice that they where ready. I purchased and installed them. I must say that it did make a difference. In August, I did the Cat back exhaust upgrade.. The car flys like a bat out of He** in perfomance mode. I think the K&N is a worth wild 1st investment. The fact that you will never have to replace the filter for the life the car is worth it by itself, Clean the filter once in a blue moon and go. That simple.. IMAO

 

You were absolutly right................ Thanks i can see and feel a diff

 

Might be a stupid question but does my 09 XF 4.2 non S/C have one air filter or two? I can only see one. I'm looking to swap out the air filter but need to know if I should procure one or two. Thanks.

 

I have used K&N on almost every car/truck I've owned..Never had an issue with the MAF getting oily..But In my older years I am getting lazier, so I've started using oiless dry filters and the best of them all is the aFe Pro Dry S brand..But right now there is none made to fit my 2012 XF..Still Waiting

 

The non-SC has one filter.

 

Perfect. Thanks.

 

Finally made the change about two months ago. Bought 2 filters and the recahrge kit with the pump bottle for about $95. I kid you not, the only dealer I could find over here in the desert that actually had the filters and kit in stock wanted $271...



They don't look so bad on the top...




Flip them over... Yeah, its time for them to go.


Airbox canister and lid were decently clean, but I cleaned it anyway.






Seat of the pants wise, I detected no difference, as I was expecting. The only numbers I have to back up the benefits of the install are the mileage range numbers as per the center display. When I bough the car in April, range with a full tank was right around 290-295 miles.

Since then, but before I changed the filters, I would see about a 1-3 mile increase in range with every fill up, but I'm sure that's due to the fact of the car was doing mostly city driving before, and now its doing mainly expressway/highway driving since I bought it. At the change out point, I was getting about 310 miles per tank. After one tank with the K&Ns in place, it jumped to 317 miles. As of this writing, its pretty much stabilized around 337.

Condition-wise, I'm working in a sea level country (less than 50 ft ASL), but with very high humidity, and this time of year, temps are always in the 100s. I'll post some numbers January, when the temps and humidity levels are significantly lower.

 

The "dirt" on the back of the filters is most probably oil vapour deposits. This comes from the clean side of the air intake so does not mean the filters aren't working. Your K&N will look the same after a few miles.

The "response" people report after fitting these "low restriction" filters is actually just additional noise. There is no objective evidence whatsoever that fitting such filters changes any performance parameter whatsoever, nor could they do so. If hp were this easy to get the OEM filter would be supplied by K&N.

Even "cold air intakes" don't really work and exhibit significant drawbacks in very cold ambient temperatures.

The stock filters flow all the air the engine can use. Period.

 

On your seat of the pants feel on performance improvement ....THERE IS improvement!!!..But I will add that it is not so much in the area of HP increase as they advertize, but the improvement you might be noticing is in the responsiveness, or quicker response to throttle..so in a sense it does feel like more power, due to the ease of air flow compared to the paper type..
CAI are a step up and only do what they mean to do as the name implies..They Work well letting in Cooler combustion air than what is collected from under the hood on typical intake engines.. and in the winter it is a mute point, as the MAF senses the air and the ECM adjusts fuel air ratios accordingly, but there is NO disadvantage in colder climates......The Jag get's it's air from in front of the radiator where it is sucking outside ambient air always..so an aftermarket CAI in the Jag would be a waste of money....

What some have done with marked improved results, is trim out some of the plastic baffling in the filter housing, this will allow for easier air flow too.

Word of advice...Every so often with K&N, especially when they are new or freshly oiled, take out your MAF sensors and douche' the elements down with MAF spray cleaner..sometimes a small bit of oil film coats them..but only in really rare cases, where someone over oiled their filters.

BTW..How many miles on those paper filters?

 

Like I wrote, I wasn't expecting any drastic change in performance. This was routine mainenance, and based on past experience with the vehicle I owned before the Jag, I went with K&N.

I'm not sure how many miles the paper filters had on them, but I bought the car with about 53K miles. I did save them, and for sure I'll take a look at what the "dirt" on the other side of the filter is for my own education.

Somewhere in my garage back in the states, I saved one of the K&N filters (Engine Inlet Barrier Filter) that I changed on a UH-60 helicopter in Afghanistan. Going to have to take some comparison pics at some point.

 

Well I just changed the filter in my jaguar 2003 s-type from a FRAM to a K&N. I have heard mixed reviews on this filter, some being it creates errors, allows dirt in, or better performance, higher gas mileage, etc. I am at that point with my car that I want the engine to last so I guess I want the best of both worlds: better performance no filtering sacrificed. I will see what happens. :-)

 

I added a K&N air filter to my car. I guess there is a bit more pep, not sure because drive in traffic. Not sure if there is savings in gas as of yet, I'll see.

My biggest concern with this type filter is the filtering. How does it compare with filtering against a regular paper type used in the Jaguars?

Anyway, I should know a change in fuel by next fill-up. As far as the HP, I will have to look for an opportunity to test it out. :-)

 

My car was purchased with K&N filters and the service tech told me that they should be removed. Apparently these cars are really sensitive to air flow changes and are calibrated for the flow characteristics of the stock filters.

 

I have been running K&N panel filters along with a custom intake (see sig) for a year or two now without any issues. I'm not sure I noticed much difference but if you have to swap out dirty filters I'd go with a set of K&Ns. Verify they aren't dripping in oil so it doesn't clog up the MAFs.

However, I have been experimenting with some air scoops I created to help route the air up into the intake snorkles behind the grill. When I placed a scoop on one side the car popped a check engine light a few miles down the road. Obviously, I'd run two air scoops, one for each intake, but I was testing one out at the time. The ECU does not like air flow differences between MAF's so I can see why a tech would rather you keep stock filters in there. I think it's a way for the car to alert the driver/dealer/tech that there is an obstruction in one intake. It's probably a bit too sensitive.

 

How often or miles do these K&N filters need to be cleaned and maybe re-oiled? How easy or hard is it to do?

Thanks