i'm seriously thinking about replacing factory air filters with K&N filters. was wondering if it would void any warranty and should i or should'nt i??

 

Don't do it. It's not about warranty, it's about the fuel mapping that will be thrown off. These cars have several sensors around the intake portion, one of them being the air mass / flow sensor. With the K&N these readings will be different and the computer will try to compensate either by advancing the timing (spark) and/or leaning the air/fuel mixture. This in turn will cause reduced spark plug life and an engine that will run slightly hotter. K&N is all hype in modern cars. They do work well with carburetor engines, and the power gains are questionable.

 

This is a frequent topic for motorcycles when K&N filters and after market exhaust systems are used and a fuel re-mapping device is also used (like a Power Commander) to revise the fuel mapping accordingly. I don't know if such a device is available for the Jag.

 

Go for it! I have one in my 99 xk8 and looking to get one in my 2000 S-Type. I also had one in my 96 Toyota Rav4 from the day it came off the showroom floor. I recently gave it to the VA as a donation @ 266,000mi and oil consumption was less than a half a qt. It is a good produce and the myth that it causes damage is only supported by those who over oil the filter when cleaning or the ones that never used it. I should also note that the problems of over oiling is a matter of just re cleaning and that includes the MAFS.

 

Excellent!! You are spot on Maybe_XJ, spot on! ANYTHING that alters the original design air flow will impact fuel mapping. I know many, many folks will argue with me, but I just can't tell you how many cars I have "repaired" simply by removing a K&N. Sometimes the effect is subtle, sometimes massive. The best example I can cite is our Rover guys. One of their air boxes has a baffle that can get out of place and make a small obstruction in the incoming air. Kind of like laying a pencil across an open vacuum cleaner hose. That minor obstruction/restriction causes a full size Range Rover to fall on its face during acceleration, even sets rich fueling faults. It took a very qualified tech three days to pin that down.

Sorry K&N lovers, leave 'em to the carburetors!

Cheers,

 

I am so sorry but I strongly disagree with your comments that k&N is not good for the car. I have responded to 3 maybe 4 posts on this and you can do the searches. I still have it in my 99xk8 with 119,000mi and it runs great! K&N causes no harm! I totally disagree.

 

Some ECUs can compensate for the different readings given by the air mass sensor, and no car owner will ever know. But keep in mind that this compensation is done through spark advance - this can cause premature spark plug wear. It also **might** slightly increase the engine operating temperature, and if the gasoline used is low grade (87) this can cause detonation.

My point is that there is potential for problems that cannot be detected by the car owner. These cars use a combination of open and closed loop engine management systems (open while engine is cold, closed after it's warmed up) and these management systems rely heavily on what all engine sensors are telling. K&N filters WILL alter these readings. By how much and if this amount will mess up the fuel mixture depends on each manufacturer. Maybe the cars you have are more forgiving.

I tend to trust a little more in the engineers that created the engine ECU than the ones that created the K&N filters.

 

Honestly, at 470hp,what incremental benefit do you see in using a K&N filter? Our cars have platinum maintenance, so I wouldn't think it would be the maintenance aspect. Just curious more than anything...

 

I see a lot of “Some ECUs can compensate”, “this can cause premature spark plug wear”, “**might** slightly increase the engine operating temperature”, “My point is that there is potential for problems” and the last is “I tend to trust a little more in the engineers that created the engine ECU than the ones that created the K&N filters” I see no factual information to support your information and I can tell you that I can find information to support my side.

The point I am trying to make is that we have an opinion on how we feel about this filter and yet we are back to the beginning.

I am not doing this to upset anyone in fact I will make a survey to see how many are in use in Jags and how many have been removed for problems. I deal with what is!

 

K&N filters are good filters, and I can definitely recommend them. Airflow over the MAF sensor is important, altering this only slightly could cause readings that are off, that is a fact. The air will also have its favorite path where it wants to flow, and this will become obviously also dirtier than other spots, and also this could have an effect. The ECU will learn during closed loop via the O2 sensors, what the "true" airflow should have been (although that is also influenced by fuel flow which could have been off) and alters the mixture during closed loop. It will use then what it has learned for the open loop runs (pedal to the metal)

I have done many measurements, and have not come across any issues/strong deviations from the MAF sensor by using a K&N filter (I have also tested others).

I have also done vacuum measurements (in intake) without any filter, and then you will clearly see an erratic behavior of the MAF sensor, not good of course. I just wanted to know what the difference in airflow was in different setups, and obviously the vacuum was lower again without filter (indication of more airflow).

The K&N was certainly the best filter in terms of airflow, and the difference between a dirty paper filter and the K&N (also dirty) becomes even bigger.

So I can highly recommend these based on measurements (not an opinion), and would guess about 2% performance gain, cheapest increase in terms of dollar per hp out there.

 

I have used K&N air filters before in a muscle car with fuel injection (just like all modern cars) I used to have. In a stock setting, the K&N was a complete waste of money, proved by mustang dyno and later fuel map log readings. Only after I made other changes to the car (more aggressive camshaft, gmmg exhaust, higher flow heads) is when I was forced to reprogram (re-flash) the ECU and I was able to see how lean the mixture became prior to those mods, just because of the K&N. Now, after the changes and re-flash, I was using volant intake (pretty much same as K&N filters) and I had no issues, and I was putting 447hp on the rear wheels on a naturally aspirated car (probably 500hp at the flywheel).

So if the original poster wants to use a K&N, go for it. I'm just saying I have had experience with these, and the retired GM engineer that probably forgot more about engine ECUs than all of us can claim to know - who worked on my muscle car - told me that all these after-market filters on stock, unaltered cars are not only a waste of cash but can cause the problems I mentioned on my prior posts. It did happen to my car and I wasn't aware of it until I inspected the spark plugs and saw the logs, but hey it's your car so do whatever you want

EDIT: I just realized that K&N is a sponsor of this site, saw a "K&N for your Jaguar" banner here so I'm not surprised the moderator favors it. That's ok and fair enough.

 

I have a k&n on my 03 STR. No problems as of yet.

 

Quote:

Originally Posted by Maybe_XJ

Some ECUs can compensate for the different readings given by the air mass sensor, and no car owner will ever know. But keep in mind that this compensation is done through spark advance - this can cause premature spark plug wear

Not sure what sort of ECU you have used on your muscle car, but going from your explanation I can only conclude it was an ECU that wasn’t able to keep the mixture right under all conditions.

This has totally changed on our cars, they nowadays use wideband O2 sensors to keep the mixture right under closed loop (contrary to what you say), and from what it has learned under these conditions will apply this when under open loop.

However as said, I have not measured any odd behavior (except when running without a filter) with the K&N panel filter, and am using this one already for the last 120Kmiles.

Your last comment give a strong hint that you might be prejudice, as I assume you don't know the moderator personaly to understand why he wrote what he did.


I am more than happy to dig into the technicals and try to bring facts on the table, but will step out if prejudice plays.

 

I think we have a winner!

 

You won a K&N air filter! LOL.

 

Removed because of the decrease in low end torque.

 

I ran them on my Lexus IS350, 370Z and now my S Type R. Never a problem with any of them, and it keeps a lot of filters out of a landfill.

 

I have a K&N in both my '01 Stype and my '05 S Type R. Both with no problems. Could only enter 1 on the survey though.

 

Disclaimer: THIS IS MY OPINION!

The argument that the K&N filter changes the airflow over the MAF is spurious, at best. The airflow is constantly changing. As your paper filter gets dirty the airflow changes. When the temperature changes the airflow changes. When it's humid the airflow changes. The K&N simply allows a tiny amount more air to flow through. The MAF detects that and allows an amount of fuel proportionate to the amount of extra air to flow into the cylinders.

THE ONLY TIME A K&N FILTER IS GOING TO MAKE A DIFFERENCE IS AT FULL THROTTLE. When the throttle is partially closed, the throttle is the most restrictive point of the airflow in the intake system. A restrictive filter simply reduces the amount of air that can flow through, and the ECU compensates because the MAF senses the amount of air flowing past it. Here's an example: if you normally use 50% throttle to drive 60mph on a level road, and you switch to a K&N filter, the K&N reduces the "friction" in the intake system. Because there is less friction, MAYBE you then only have to use 49% throttle to drive the same speed. HOWEVER, the MAF is detecting the total airflow, and the total airflow hasn't changed. It takes the exact same amount of fuel and air to drive at X speed, therefore the ECU is dispensing the same amount of fuel to mix with the same amount of air as before you switched filters. The ECU's job is to compute the amount of fuel required based on the amount of air flowing into the cylinders.

At full throttle, however, the story is different. If you have a restriction in the air supply, the cylinders can't suck in as much air, therefore they can't burn as much fuel. Once the throttle is fully open, there is no way to get more air into the cylinders without forced induction (supercharging/turbocharging, etc.). The exception is that if you reduce the restriction of the airflow, it allows a small amount of extra air into the cylinders. The MAF detects this extra air and injects a tiny bit of extra fuel. This will give you more power at full throttle, but that's the only time the K&N will be noticed by the ECU.

And before someone points out that the engine needs to use less power to suck in air with the K&N, that's correct (if you believe what they say), but that difference is minuscule. A box fan on high speed only uses 100 watts, which is about an eighth of a horsepower. The box fan is pumping more air than the engine is drawing in. The tiny difference the K&N makes might free up a tiny fraction of a horsepower, but that's going to be barely noticeable when it comes to fuel economy.

 

I want to offer up the attached document as proof, if you will, that an air filter that is “different” than the one ENGINEERED to be used, CAN affect the way a Mass Air Flow sensor reports incoming air. The XF supercharged engine has a twin air intake system that has two MAF sensors. The two are needed only because one inlet tube can’t supply enough air under all conditions. The two snorkels feed ONE inlet to the engine. Since the two MAF’s feed the same inlet, it shouldn’t matter how much air comes thru which sensor; as long as the ECM has the total amount it can fuel accordingly. As you will see in the bulletin, Jaguar Engineering has found that a filter can make a difference. It apparently has to do with turbulence in the induction system. It’s the concept that makes a tuned exhaust, headers, and variable intake manifolds work. I can’t think of the term for it right now, if we were talking about liquids it would be fluid dynamics. Anyway, Jaguar found some intake air filters altered this turbulence and caused a mis-reporting of incoming air that resulted in misfires. For that reason they came out with a matched set of air filters to be sure the sensors reported air correctly.

I’m not adding this to condemn K&N filters specifically, just to back up the notion that ANY filter that is not as designed can cause issues. That’s just science and physics. There is way more going on under the hood of a modern engine than most of us will ever comprehend fully. It’s basically a case of “we don’t know what we don’t know”.

From practical stand point, I just don’t think they are a worthy addition, or risk, however one wants to look at it.

Cheers,