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2006 srx
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Discussion Starter #1
I'm only looking at the price diferential. So is there any advantage to going kn over paper seeing how the price is $50 for the kn air filter compared to 20 for a paper filter. I've read the info about horsepower and that is not what I'm going for. Does it make money sense to keep buying paper or to go with the reusable?
 

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In the long run, the K&N will save money (don't forget to account for the cleaning kit, oil, and time - also when you clean the filter you lose your car while the filter dries). However, in the long run the K&N flows more dirt too, so you lose engine life and power as you lose compression. Here is one of the only objective tests with actual data (and not some guy's claim) I've seen online:
http://duramax-diesel.com/spicer/index.htm
I know this wasn't your question, but one other test I saw compared fuel mileage using a Geo Metro, and paper and cotton gauze were statistically the same. The paper filter already flows more air than the throttle body will let in. The only time a cotton gauze filter adds horsepower is at wide open throttle, and that is where they get their hp numbers. It doesn't make the engine more efficient, ie more power at low rpm's, but it does let more dirt in at all rpm's.
 

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'07 SRX V8 AWD 20" Sport
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I've used a K&N in my 1996 Trans Am since day 1 and now at 170k miles I am not noticing any loss in power or compression due to dirt let in by the filter. Same K&N filter too!! I usually clean and oil it every 20k miles or when it starts to look too dirty. I put a K&N in the SRX last year and so far so good. Only noticeable difference was the engine sounds a little bit louder when you rev it up. After install the SRX threw a few codes as the engine computer was adjusting to the increase in airflow, as the air/fuel mixture is now different than when using the stock filter.
 

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Base 2007 Escalade EXT, 04 Cadillac SRX V8
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I`ve tried different filters.

ACDelco $20 oem filter: worked excellent. no loss in power. Engine could breathe easily.

Fram (cheap) made the engine behave differently and transmission also got a different shift algorithm. I also noticed a loss in power.

K&N $50 filter: Noticeable positive difference from Fram. Works great. I think that I have a little more peak power than with the ACDelco filter. Haven`t seen any difference in mpg.

In retrospect, I would choose the ACdelco filter and not worry about dirt, cleaning and oiling the K&N filter.

Hope this helps.
JD
 

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2004 SRX V6 AWD
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741 Posts
I've seen side by side tests KN vs OEM in pickups in the Ariz desert.
Definitely can tell the difference with dust noticeable downstream of the filter with the KN.
In a non-dusty climate, probably no big deal.
To me, KN is a good example of great marketing of a product that offers questionable benefits.
 

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01 740iL, 99 Z28, 06 SRX V8 rwd
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88 Posts
I have seen the Duramax test linked above, and others. And I haven't used a K&N in a while on account of being scared away from them by the internets. But personally, I think I'm going back to K&N, or whatever oiled gauze filter comes with the Volant airbox.

Maybe it doesn't stop as much dirt under certain test conditions and procedures, but it clearly flows better in all of these tests. And in the real world, I know too many engines that have run K&Ns for too many miles with zero failures or diminshed performance symptoms that could be attributed to a filter not filtering well enough. Maybe its because these cars are owned by persnickety folks who change their oil more often than necessary, but I fall into that category myself, so if that's the key then I am set.

Folks are fond of saying that the throttle is the only restriction that matters, so a freer flowing filter or a less restrictive air intake won't add power or efficiency. But I don't think this is true. I've seen too many performance increases, seat of the pants, dyno, and 1/4 mile, from decreasing other restrictions while leaving the same throttle body in place. Sure, you are leaving power on the table when you reduce certain restrictions but leave other restrictions in place. For example, on an LS1 Camaro, if I put a bigger cam in but leave the stock exhaust, I won't see the same hp and torque increase that I would if I put long tube headers on at the same time. But I will see a gain. Same as if I do it in reverse - put long tube headers on but leave the stock cam - there's definitely a gain, just not as big of a gain as if you did both.

It's not wrong to do it one way or the other, just understand what you are doing and pick the route that will accomplish your goals.
 

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2013 Lexus RX350, Satin Cashmere Metallic
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Just a note to anyone who changes their OWN AIRFILTERS ON SRX>>>Be SURE the bottom pegs get in the box
or you could end up sucking dirty air in and causing damage to rings and oil burning....I found mine loose at the bottom, and I can't believe I didn't catch it, and have driven 5,000 miles that way....SO to ALL,,,if you do your own; open the hood and gently pull on the bottom from the left and make sure it does not move, oryou don't have the pegs all in....I found that putting the FILTER pegs in first,,and than putting the cover over it was the best way to get it in....sure hope I didn't damage my engine; but it does burn a little oil; but I know that is normal in some..........WORD TO THE WISE>>>>>>>>>>>.
 

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Folks are fond of saying that the throttle is the only restriction that matters, so a freer flowing filter or a less restrictive air intake won't add power or efficiency. But I don't think this is true.
You are correct. Whoever says that the throttle is the only restriction that matters is an idiot. However, at less than wide throttle, you are leaving power on the table by not having the throttle plate wide open. At nearly every other throttle position (where 99.99999% of driving is done, but not 0-60 or 1/4 mile runs or dyno testing) the throttle is the most restrictive part of the intake. That is the point of the throttle. If it didn't restrict air, your engine would continue to rev uncontollably (the throttle is the control). So, in the overwhelming majority of cases, the air filter is not the most restrictive part of the intake. If you can free up air flow past the throttle body, you can make the engine run more efficient, get more hp and better fuel mileage (and you won't use as much throttle because more air will move for the equivalent throttle position). This happens due to reduced pumping losses. If the engine can move air with less effort, less of the energy from the burned fuel is used pushing pistons and more is sent down the crank shaft.
 

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01 740iL, 99 Z28, 06 SRX V8 rwd
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Even at part throttle, doesn't reducing pumping losses in other areas result in a gain in power and efficiency? The throttle is still a restriction, but with reductions elsewhere, a smaller throttle opening might produce the same power. i.e. after you put ported heads, a bigger cam, a less restrictive air intake, and headers on a car, but keep the stock throttle body, you would get the neck snaping takeoff or smoking of the tires that previously required 3/4 throttle might happen at 1/2 throttle.

Even if it only works at WOT, that's still worth something to me. But my (admittedly, not scientifically tested) experience tells me that all kinds of airflow increases from air intakes to headers, produce gains and WOT and part throttle, even when the stock throttle body is left in place, particularly if the stock throttle body is already pretty good sized for the horsepower level of the engine.
 
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