Yes! Go for it, you have nothing to lose!!!
You instigator!

 

Gus,

Thank you for your service. We in the USA owe you a debt of gratitude for all you've given. It looks like your intuition has worked on all your cars with the extraordinary mileage you've racked up, especially since there are no signs of "ware". I'll continue to follow my advice and respect your position too.

BRGJAG,

You still have to ask? Ha, ha.

 

ha ha ha ha. Maybe I will stick with normal filters. ha ha ha

 

I think he is having fun on the sidelines!

 

When it comes to potential gains from various bolt-ons, at least the (perhaps) marginal couple of horsepower increase from the K&N filter at $70 gives you much more bang-for-the-buck than the maybe 10 to 20 horsepower increase from a new exhaust system that will be $1,000 to $2,000. I could never for the life of me see the appeal of spending so much for so little unless the extra noise gives you a charge.

Doug

 

in my case the NICE extra noise is nice but I wont spemd 1k on it.

 

Had to do something about the utter lack of an exhaust note. The noise is nice in that it no longer feels like an elderly mans car and it reminds you that you are not driving an overgrown Prius. Almost forgot I had a V8 under the hood till I got rid of the FIVE mufflers underneath!

 

I sort of feel that the stock exhaust sound, at least from within the cabin, is just about right. When I had my Corvette, the biggest complaint from most "enthusiasts" was the wimpy exhaust sound. You could not believe the number of posts on the various Vette forums where guys would spend upwards of $1,000 to have some snazzy aftermarket Borla or other system installed (with maybe a maximum hp increase of 10 to 15hp--pretty much insignificant) and after wards you would see a stream of posts complaining about resonance in the cabin and not being able to talk or hear the radio.

It seems incongruous to try and get a car of the caliber of XK8/XKR to sound like a Mustang GT.

Doug

 

The K&N filter does offer less restriction in airflow than the stock filter, and even more so the more the car has been tuned, no doubt whatsoever. Especially good is that you can still use the stock cold air filter box.

It is easy measurable if you have a pressure meter and I can confirm this myself as I have done many of these types of measurements in my quest for more horses.

How much extra in HP it will give is hard to measure (though easier if you have tuned you car), but it definitely helps and is indeed one of the cheaper mods to do. You just need to be careful when re-oiling it, that’s all.

 

Avos,

A couple of things, and hope you don't mind the discussion continuing:

Up until now, the discussion has centered primarily around the N/A and not the SC. I see by your signature you have an R.

If both N/A and SC have the same air intake design, same tubing diameter and routing, same square filtering surface area (flat-plane, not considering the filter fins as part of the filtering Sq. area), then it is safe to assume the SC is going to demand more intake volume and at a different velocity relative to the N/A. I quoted some informal test results that I read, there is almost no pressure differential on the N/A filtered compared to no filter at all, so changing the filtering material is going to have no impact on performance, but could have a lot of downside anyway. The SC is a comletely different dynamic.

With that, and back to the aftermarket filtering, assuming that the only change made is a replaceable filter cartridge, one for one, paper for oiled type, and the flat plane square surface area of the filter doesn't change, then the only way you can impact pressure diff. positively is through a more porus filtering material.

This now opens up a completely different discussion regarding the tradeoff between performance vs. a greater or faster volumetric flow along with larger particulate matter coming with it. Now, I know the "oil trapping" argument will come up, but I contend, this oil trapping has a very short life before the benefit of additional flow is reduced, and I believe that life is much shorter than the dry finned paper as it becomes comtaminated, especially since the actual filtered surface area of the paper is much greater than the oiled when the fins are included. Basically, if a brief temporary gain is felt, I believe it is short lived. The other point to make about the oiling (more or less oil), the tradeoff between more flow due to porosity vs. less flow and better filtering is probably linear. So, even better performance might be felt on an SC by not oiling at all, but the ingestion of larger particulates has to be part of that equation.

After all this, there is still the issue of the real gate. On the SC, or a modified SC, the real gate might well be the filter, or is it?. And, as modifications become greater and greater, previous gates would have been eliminated by a good tuner. At this point that tuner would be looking at changing the actual filtering surface area and not just a more porus filter to improve flow.

 

Always open to learn and discuss ;-).

The pressure difference caused by all the different parts are imo also very important for a NA engine. The less air restriction you have the more air can flow, which will benefit the NA as the SC, even though the SC has some more mechanical sucking power, it is still sensitive to air restrictions. The stock SC has already big restrictions, where the filter is one of them.

One can only say for sure if it has a difference when comparing the pressure (/vacuum), and certainly not via a dyno test without a filter (if that was what you where referring to). The altered airflow without a filter will cause an erratic airflow reading that can alter the A/F ratio and thus the dyno result, as these always have a certain error margin due to many factors it makes the readings not comparable. This is why a pressure difference check would be the best to know if a change in filter would work or not., and so far I have not tested a NA car.

So if you (or anyone else) can prove that for a NA engine there is no pressure difference between a stock filter and no airfilter, then of course it doesn’t matter, so am curious to see readings, but I do think there will be a difference.

For the SC the filter certainly plays a role, especially when you have upped the performance in another way, then it becomes even more apparent (/big restriction) no doubts there. But it is just one part (cheap one though) in the full path to the cylinders.

 

Avos,

I appreciate the dialog.

The study I read, and it pains me that I cannot find it anymore even though I've searched the web, came from some guys who set out to improve the intake system design with the intentions of creating an aftermarket intake system that improved flow and thus performance. Part of their testing included some controlled dyno runs on a stock N/A with different intake configurations (different air filters, no filter, etc.). After the dyno runs they concluded there was nothing to be gained on a N/A with any modified intake system and that, in fact, the real gate (or restriction, if any for a stock motor) was further downstream.

In other words, the "performance opportunity" was not in the intake tube or filter which is what they were after. Again, this is for a stock street N/A, which the majority of posters in this thread have. So, to these posters, the interjection of any other type of aftermarket filter isn't going to gain any performance as the air filter cannot, by itself, produce more engine performance; however, they are going to get all of the downside tradeoffs.

Now, I cannot validate these tests, and don't have them. I never saw an aftermarket intake for the N/A so I assume they abandoned the project. These guys knew what they were doing with a dyno though, because one of them owned the dyno shop.

Now regarding the SC, I believe changing to a more porus aftermarket air filter to gain flow has more impact, both positive and negative, that are exponential in measurement.

Since it is a given the flow demanded by the SC and relative to the N/A, will be more voluminous and at greater velocities, larger particulates, having greater mass at greater velocity will make it through the filter far more easily than on a N/A and might just take the oil particles with it. Not so bad necessarily to a car enthusiast or racer who might be rebuilding a lot, but not that good for a daily driver looking for that illusive "HP boost in a can", so to speak.

I know that much of this discussion has moved now to the very hypothetical so not so sure how helpful it will be to anyone wanting a definitive answer - Should I go to an aftermarket filter or stay with the stock one?

 

Anyone can prove if there is a benefit or not via the pressure meter, I would have done so if I would have a NA car in the neighborhood. Fact is that I (and still do for different tests) check the pressure (/vacuum) in the intake to check the flow for different setups, and do see a relatively big difference between a stock filter and the K&N one (and more so with a large K&N cone filter, but that is only for XKRs).

If the people you refer to have also checked the MAF reading during the dyno tests, they should have noticed the erratic behavior of the readings, and the dyno results (even if it would have been more) could not have been used as comparisson between a stock filter and no filter at all. Making a perfectly formed air intake tube/system is extremely expensive due to the different curves, and I rather think that that would have killed their project, than that they could not get any gains. Bottom line imho is there will be a performance gain also for a NA, but it will be small and not noticeable.

“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 would say yes assuming you would also appreciate the extra performance factor, as the stock box is a true cold air filter box and putting a panel filter in with more flow would help the engine a bit. But can’t tell how much, other than you will not feel the difference (except of your stock filter now is already very dirty).

In another thread I tried to show how much air is flowing thru the system/maf:

Just to give an example, driving at 50 mph or so (don’t have the exact figures with me) would consume about 60 liters of air per second, which is 216.000 liters per hour. Now translate this to 1.000 hours (so 50.000 miles), you get 216.000.000 liters of air. Depending on the air contamination (and knowing that the stock air filter will not hold every particle), I would think that there could be an effect on the MAF with the stock air filter at some point.

So even with the stock filter the MAF will inevitably become dirty.

If you go for the oiled K&N then just make sure you never over oil it after a clean. If you are afraid it would make your MAF dirtier, then you might try the FRAM filter, as that one also flows better then the stock filter, but not as good as the K&N.

If you want a filter that filkters the air as good as possible, and performance is not a problem, then stay with the stock air filter.

PS
Stay away from hot air filters (ie those that take the air from under the hood)!

 

Great discussion Avos.

This will probably remain a mystery, especially on the N/A because no one is going to invest any cost in an actual meaningful measurement that will show a delta if any or however negligible. This is what makes the marketing efforts of the aftermarket products work. It is close to impossible to validate marketing claims without spending considerable time/money; then the testing routines are always challenged. Even the stupid Tornado device making claims of 20HP to 60HP gains that is routinely sold on Ebay gets hundreds of takers, just look at the sellers feedbacks...And, they're all happy buyers too!

I find it interesting and consistent as users of aftermarket products (of many kinds) describe the performance gains. Always some variation of "It just feels faster" or "I feel it in the seat of my pants". The average person cannot "feel" or recognize a 10HP or even 15hp change at the flywheel, which is less, of course, at the rear wheels. I would be amazed if the aftermarket cartridge air filter produced even 1HP at the flywheel, unrecognizeable at the rear wheels by anyone. These products often cause a change in sound, which is misconstrued as performance. I get that misconception and usually let the person enjoy the fantasy.

So there is no misconception about me- I've chased HP all my life until recently when I've come to appreciate all that goes into a modern engine management design. I sought performance gains at the intake when the designers actually did leave something on the table. Lots of these aftermarket products have been around for a long time, back when cars didn't even have a MAFS. To give proper credit, they really worked then.

 

Thinking about this again, I am going to conduct a small experiment on my own XK8 today, if I have the time. Although it might not prove much, it could validate or disclaim one of the theories we've discussed. It will still result in different conclusions to be drawn, but...one step closer.

I'll post back if I can pull the test.

 

After our forum discussion on the K&N filter I elected to do a little checking around to get the real information on the affects of the K&N filter.

Burgxk8:

K&N flows more than a stock OEM type disposable filter, but there is no sacrifice on filter efficiency. What most people don’t realize is that K&N air filters work much differently than most disposable air filters. Disposable filters usually are made of paper or synthetic material and keep dirt from getting through by blocking particles too big to get through the surface of the filter. Paper is manufactured using a pressing process, so the fibers which make up the paper are very dense and as a result paper filters are usually very efficient. The drawback is that it is not very easy for air to pass through a paper filter so they can hold the engine back from its full performance potential. Another drawback is when the surface of the filter gets covered in dirt, air can no longer pass through, adding to the restrictiveness even more. On the other hand, K&N air filters are made from multiple layers of woven cotton fabric. The cotton is made to exact specifications, down to the exact weave and fray counts (how many strands per square inch, and how many fibers fray off the strands) and it is pleat between 4-6 layers of cotton together to create a 3-dimensional web of fibers to capture dirt particles. A small amount of oil is added to the cotton fabric to enhance its filtration efficiency. The result is an air filter that is much less restrictive than paper, but still has comparable filtration efficiency, because of this multiple layer web of microscopic cotton fibers.

Yes, some race engines get rebuilt after a very short operation time. However, the reason they are rebuilt is usually to restore combustion, check for part fatigue, etc. and the race environments they are used in usually only require a “screen” of a filter to keep out large debris that would cause a catastrophic failure. Dirt and dust ingestion would score cylinder walls over time, requiring a cylinder re-bore, increasing the displacement of the engine, which would disqualify its use in NHRA or NASCAR competition. However, there are race engines which run in much more severe conditions that go an entire season (or more) with minimal maintenance other than oil, lube, filter, etc. The top 1-2-3 Trophy Trucks to finish the 2008 Baja 1000 ran the same engine the entire season. These engines see more dirt in 1000 miles than most cars would see in 100,000 miles or more. The 1-2-3 trucks all used K&N air filters…

SeismiscGuy:

Over-oiling a K&N air filter does not cause damage to a vehicle or any sensors. Residue on sensors is the result of normal vehicle operation.

Stevetech:

As you can see the previous reasons were not supported by facts, they are just opinions and everyone’s entitled to have their own. Just be open minded when looking at the facts.

A dyno test which yielded a less than 1 HP difference between a new paper filter and no air filter at all only indicates that the paper filter tested flowed extremely well. Do this experiment: take a trip to your local auto parts store, pick 1 brand of disposable air filter, and count how many countries their filter is made in (Mexico, Canada, Hungary). Each of these filters will be made from vastly different materials and quality of paper from country to country and as a result 2 of the same filters can flow 2 different amounts of air. So just because one paper filter had very low restriction doesn’t necessarily mean that all disposable filters are the same.

Messy cleaning – Get real; you sound like a toilet paper commercial.

RJAG:

Over oiling doesn’t hurt anything and doesn’t affect the MAF, so what was the real cause of what was going on with this Mustang in the rain? My guess would be water? Oil doesn’t evaporate!

Stevetech:

Noise, “seat of the pants” performance, and actual measured wheel horsepower (WHP) are 3 very different things. Seat of the pants performance refers to the feel of being pulled back into your seat as you step on the gas pedal. This is torque, a measurement of force of how efficient of a “push” the force gives the car. Wheel horsepower is a measurement of the available power an engine has, measured where the tire meets the pavement. Both of these real-world measured values can be influenced by the air filter. The engine needs air in order to run, and the more work is wasted trying to pull that air in, the less power output you will have.

I placed calls, checked the internet and talked to many and my results were different from the ones mentioned on this topic. I found 4 to 1 in favor of the K&N filter and that is a fact!

And again we must agree to disagree!

 

Over-oiling doesn't affect the MAF?

 

I don't believe I ever said that "Over-oiling a K&N air filter does not cause damage to a vehicle or any sensors. Residue on sensors is the result of normal vehicle operation Over-oiling a K&N air filter does not cause damage to a vehicle or any sensors. Residue on sensors is the result of normal vehicle operation". If I did I was an idiot. I may have said that I was careful NOT to over oil K&N filters when I have used them. I also may have said that build-up of soot on the MAF sensor wire is normal over time. I will say that the WORST thing to do is over oil a K&N but this seems obvious.

Doug

 

Sorry... I was responding to what Gus said. At least that's what I thought I responded to...

 

There is my earlier post--NOTE THE LAST SENTENCE!

Doug