97 Xk8 can I put in a KnN air filter in the stock box? The regular filter is not real cheap so why not a KnN???????????? I read through some other threads about Cold Air Intake stuff that is too much for these cars. I would think I could drop a KnN in the stock box?

 

I did, and surprisingly, stays pretty clean after all this time...checked it twice now after 60k miles and hasn't needed 'refreshing' with the K&N cleaner/oil treatment.

 

no computer codes saying the car don't like it in there?

 

Ditto here. Installed a K&N some time ago and no problems. What I would really love is some way to convert the current intake into a twin intake setup. I believe the new series XKR have this but it looks like there are too many obstructions to have a second intake tube snake along the drivers side of the engine to the front.

Doug

 

I had it in the car, removed it and reinstalled it. This car runs better/great with the K&N filter just do not over oil the filter the residue will attach to the MAFS.

 

K&N can be a double edged sword. It is free-flowing, but that has drawbacks too. You will get more silica (sand) into your engine.

Yes, the performance improves slightly, and racers use them everywhere. But remember that race cars typically have their engines rebuilt every couple of races, so silica getting into the engine is no big deal in the big picture. Over time, however, this might cause problems. I just had an oil analysis test done on my XK8 (the first oil change since buying the car a couple of months ago) and the old oil already had a higher than normal level of silica in the engine. This could be from mechanical work being done (filthy mechanic hands) or from an overly dirty filter. I do not have a K&N, but installing one will only increase this problem. Not sure I want to go that route for dubious HP gains.

 

K&N has been around a long time and if you follow the posts on the various car enthusiast car forums these are pretty much the de riguer first thing that anyone did with their car. There must be hundreds of thousands of accumulated miles from people using K&N filters and I would imagine that if there truly were any serious problems from using them they would certainly be out of business by now. The typical problems come from over-oiling and getting residue on sensors.

Doug

 

True enough, they have been around, and they do sell a lot of filters, mostly to people who never notice a difference in performance if that's all they do to the engine. A race engine will benefit at WOT, and as mentioned, race teams do not care about long term wear and tear when they constantly rebuild engines. If you can afford this, go for it. But test your oil sample before and after using a K&N. You will have more silica in your oil. It may not seriously damage the engine before you sell or total the car, but it'll be in there. Your call.

 

bought it and put it in my car as well, until service rep advised otherwise. would have thougth twice, coming from the source, but new filter was free with the regular maintenace. so, keeping it out for now.

 

I do not use oiled filters or recommend them for all the reasons previously stated. Additionally, there are no performance gains on an AJV8 either in an XJ or XK over the factory engineered intake system. The engineers simply left nothing on the table to be gained by aftermarket filter replacements. I read a report online some time ago, but do not have access to it, that the difference between a dyno run with a new paper filter compared to a dyno run with no filter at all was less than 1 HP gain on a NA XK8 (not an R). So, performance is not a feature on these Jaguars, leaving only the feature of clean and reuse, but as stated, you have to know what you're doing when oiling. I've seen these terribly over oiled. If they're underoiled, they become a sieve instead of a filter with the drawbacks already stated.

Finally, cost. I buy paper elements for $10/$15 depending on the source and brand. I can buy 5 to 7 paper elements for the cost of one oiled. If I changed the paper filter every 12K miles which would be very frequent I can make it 60K to 75K miles with new filters before the cost crossover point and, no messy cleaning, oiling, just open the top, throw away the old, replace with a new one....but I do respect one's option to spend his money in ways that makes him feel good.

 

I like that Steve. Well put. I had one on my Mustang GT and went through the grief with the MAF of over oiling then the anguish of wondering if I didn't oil it enough. In a heavy rain, it would always light up the trouble code and I'd have to dry it out, pull the battery connection to reset the codes. I also had to carry a sensor cleaner can plus the special hex tool to undue the MAF on the road. I wouldn't do it again for a touring car. My R goes plenty fast and I've already received my first ticket with it.

 

I am not an automotive engineer but, I have to say, the circuitous route that the air has to take from the filter box back through a somewhat crooked tube and then finally down and around the final 90-degree bend to the throttle body does not seem very performance oriented to me. Wouldn't it have been much simpler and more efficient to have the throttle body mounted at the front with a more direct intake path?

Doug

 

Doug,

Possibly, on the question about circuitous routing, but there are several factors that I imagine would have been considered in the design.

The first is - What are the dynamic volumetric and flow requirements of the pistons on intake stroke at WOT (I assume this condition would represent the most volume/flow demanded)?

Second- Where is the gate? Is it intake tube? Filter? TB? Intake manifold ports? Intake valves size? The TB is the ultimate restriction to flow unless it is WOT.

When you think about the intake filter and tubing, this would represent the simplest in mechaincal design adjustments as the tubing can be sized to accommodate the highest desireable demand, even considering a dirty filter which represents a significant proportion of the operating condition over time.

And, actually on the X350 and S-Type apps for the 4.2L, that is exactly what Jaguar did. The TB is moved to the front and a very short "air shovel" makes its way right over the top of the engine compartment front rail taking fresh cold air right from the front grille. Still, the gate downstream to the cylinders would be the real restriction.

 

My 1995 Corvette also had the front-mounted throttle body and the intake was pretty direct. The only "weakness" seemed to be that the filter drew hot air from inside the engine compartment. What many folks did was to "flip" the intake so that it poked through the radiator shroud, thus sucking cooler air and getting a bit of a "ram" effect at highway speeds. In the XK8/XKR, while the air is sucked from outside it certainly gets heated up during the long path to the throttle body. Again, while I am just a structural engineer and not an automotive engineer, I have always heard that cooler/denser air is a plus for performance.

Doug

 

Steve I disagree with you again! The performance gains you say do not exist do take place and the only problem I have is that I have no way of proving it other than sending you the seat of my pants and I plan not to do that. I do agree and mentioned previously that over oiling the filter can and will be a problem with the MAFS. As for the cost comparison I am unable to speak for others but for me it was never a question. As for the quality of air being presented to the TB and cylinders I would venture that it is insignificant by comparison. However, I have no supporting information other than a clean TB.

 

Gus,

I hear the "seat of the pants" performance gains alot, in fact, always. Noise is a wonderful thing!

Debating perception cannot be done, But, if a dyno run with and without an air filter didn't even produce one full HP difference, how could the installation of an aftermarket filter magically produce more HP than no filter at all?

Now, there could be significant performance gains realized from the weight reduction in your wallet, and that has a way of feeding the seat of the pants too. Good that you percieve you got your money's worth. I personally hate it when I throw $70 out the window and work hard to justify it in my mind too.

 

Steve, sorry but you are not entirely correct! Take a moment and read a few of the FAQ http://www.knfilters.com/faq.htm while I do a little checking around and I will get back with you.

 

Gus, old buddy, I think I am beginning to understand how your perception is being influenced now. Some people believe everything they read on a site trying to influence their buying decision. A company selling a product will position it in the best light with whatever they can scrape together.

There is something to know about performance claims based on dyno runs. Anyone who has been around a dyno for even a short time knows that you can pretty much get anything you want from a dyno. Just changing something as simple as the testing weather conditions can influence a dyno output; Influence it enough to make a great marketing statement about performance gains that sounds research based.

Given that you feel a performance gain from an aftemarket air filter, would you be interested in another performance device, with claims to improve gas mileage and performance too? Try this device. Read what they say about it:

http://cgi.ebay.com/ebaymotors/ws/eB...76140540257442

Totally coincidental, but I found it right below an auction for an oiled aftermarket air filter. I've seen these devices advertise as much as a 20 to 60HP gain just by installing it. Maybe the performance gains of these two devices are additive? Combining them might get an XK8 close to the performance of an XKR. It's only a 100 hp gap.

Gus, As always, I enjoy your engagement and these discussions, but please remember, there is no need on my part to change your perception and I am ready at any time to agree to disagree.

 

No Steve I do my homework and move with caution. My theory in lift since my tour of duty is that I trust no one or anything. If I go into battle I test the gun and check it for accuracy. Your e-bay device is still there for you to purchase. I do not have the information to support my opinion other than my cars right now. I have a 1996 Toyota Rav4 with 262,000mi (working on 300,000) and it presently uses aprox ½ qt of oil ( oil change every 5000mi synthetic oil) and it has a K&N filter from mile 000,005. No evidence excessive ware at this time! It may fail tomorrow but I would not put the blame on the K&N filter. I also have a K&N in my 99xk8 114,000mi and will install one in my next car. My opinion on this is based on many things and not only on what the manufacturer wants me to read.

 

soooooooooooooo yes or no to a KnN in the xk8?? ha ha ha