# The Urban Myth - No air filter = more power?



## fanl (Jun 24, 2004)

Use no air filter means more torque and horsepower? What do u think guys


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## AL_Sentra (Sep 5, 2003)

fanl said:


> Use no air filter means more torque and horsepower? What do u think guys



honestly more hp or not I think you should leave your filter on, you just dont want to expose your engine to the elements like that and risk tearing something up.


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## thestunts200sx (Jul 11, 2005)

yea, seriously.... Not using an air filter....DOH!, isnt rocket science.
More HP ? I can only see the gain ( this is a guess ) of no more then like 0.25 HP ....which isnt enough for me to put the engine at risk.


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## wildmanee (Nov 21, 2004)

I'd say it'd be worth a couple HP, but not worth losing your engine


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## thestunts200sx (Jul 11, 2005)

really a couple ??

Are we talking stock air box minus the filter ? or a CAI without the filter on the end, or a WAI without the filter on the end ??


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## wildmanee (Nov 21, 2004)

For a couple HP, I'd bet CAI.. I mean, the idea behind an intake system is to increase the flow of air to the engine. Having a filter is a restriction to the flow of air going into the intake. Aftermarket intakes reduce restriction and improve the flow of air to the engine.. a filter is necessary, but it is a restriction, isn't it? 


But everyone should have an air filter, I'm only theoretically speaking if there wasn't one, there'd probably be a gain..


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## myoung (Apr 15, 2002)

The Urban Myth ? More like Urban Stupid idea


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## Zen31ZR (Mar 24, 2004)

One of the reasons I will never buy a JDM engine that was previously used in a modified car, it's a well known fact that the oil is almost never changed and an air filter is often never used, sometimes for the entire 30,000 mile duration....

And yes, depending on the engine, you can pick up up to 10 Hp without an air filter. A straight through design like a K&N partially negates the airflow loss, which is mostly caused by the restrictive airbox with all it's sound baffling that is found in most all vehicles. Pulling the airbox and putting an open design filter on will often times net you around 5 Hp (crank) right off the bat, depending on how restrictive the airbox was to begin with. Turbo engines gain a little more, and the turbo spools up a touch quicker. Which is why you often see the ridiculous sight of an unfiltered turbo inlet sticking out of someones hood. Every time I see that, I hope they suck in some flys or a bird or 2 and learn their lesson.........


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## Char (Jun 16, 2005)

It also makes your engine sound alittle beefier, which is probably why most people will do it. But yeah, NEVER take that risk, you can greatly shorten the life of your engine by doing it. Best off buying a CAI.


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## fanl (Jun 24, 2004)

myoung said:


> The Urban Myth ? More like Urban Stupid idea


lol.. i agree !

I dont run without air filter.. but my fucking friends like to say that they rides become more powerfull without air filter..

I figure that a stock engine was projected to USE the air filter, all the intake is projected for it, when running without the filter can occour to loose power because many phisical phenomenon (like sound ressonance) dont happen like it was projected to do any more...


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## bahearn (Jul 15, 2002)

You will never lose power by removing the air filter. The filter is a restriction to air flow. If you retain the filter housing, all the resonances will remain. It's changes in flow direction and diameter of piping that cause harmonics, and total length that are important in intake design.

You will rarely see more than about 1% gain in power by removing just the filter. Short-term lack of filtration won't do much harm in most environments, but don't it for very long, especially in the Southwest where air-borne dust is always present.


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## Zen31ZR (Mar 24, 2004)

Car makers also use restrictive intakes and exhaust systems to lower emissions and improve low end torque for daily stop-and-go traffic use.


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## BII (May 13, 2004)

Zen31ZR said:


> Car makers also use restrictive intakes and exhaust systems to lower emissions and improve low end torque for daily stop-and-go traffic use.


And also to reduce NVH (noise, vibration, harshness). Most people don't care to hear the engine (I know, wierd, but true )

I used to run open velocity stacks on my VW on track days, otherwise the filters go on, too much risk for little reward.


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## xulhn (Aug 11, 2005)

BII said:


> And also to reduce NVH (noise, vibration, harshness). Most people don't care to hear the engine (I know, wierd, but true )
> 
> I used to run open velocity stacks on my VW on track days, otherwise the filters go on, too much risk for little reward.


sounds much meaner too, doesen't it?

it's not good advise, but power does increase without the filter. if it didn't, what would be the point in changing to a lower-restriction filter?


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## psuLemon (Apr 23, 2003)

hmmm, no filter is just going to let dirt get in your system. Does anyone know what dirt does to a motor?








Lets just say it doesn't mix.


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## xulhn (Aug 11, 2005)

psuLemon said:


> hmmm, no filter is just going to let dirt get in your system. Does anyone know what dirt does to a motor?
> 
> 
> 
> ...


dirt in the combustion chamber could lead to scratching of the cilinder walls, pistons and rings and also to oil contamination.


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## Pzych0 (Mar 1, 2005)

I read on Overboost.com that a taking your air filter out acutualy loses power on the engine. The filter actaully smoothes the airflow to the engine and the smoother the flow of air the more power you will get from the engine

They did quite a simple test to test it aswell

will post the site within the next hour gotta find it quick


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## Zen31ZR (Mar 24, 2004)

Pzych0 said:


> I read on Overboost.com that a taking your air filter out acutualy loses power on the engine. The filter actaully smoothes the airflow to the engine and the smoother the flow of air the more power you will get from the engine
> 
> They did quite a simple test to test it aswell
> 
> will post the site within the next hour gotta find it quick


Sounds like something I'd expect to read from an airfilter manufacturer as a marketing gimic. The airflow may be straightened somewhat by the filter, for about a few inches at most, but if there are any other bends in the pipe, guess what...... And if the pipe is mostly straight going towards the throttle plates, the air flow will be mostly stable anyway.


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## Pzych0 (Mar 1, 2005)

http://www.overboost.com/story.asp?id=563

ok well there is the site if anyone wants to check it out. Its a very basic test.


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## Zen31ZR (Mar 24, 2004)

Pzych0 said:


> http://www.overboost.com/story.asp?id=563
> 
> ok well there is the site if anyone wants to check it out. Its a very basic test.


Bwahahaha, they used a shop vac for those tests...... Even the smallest Honda engine pulls about 20 times that amount of air. I call BS.


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## wildmanee (Nov 21, 2004)

psuLemon said:


> hmmm, no filter is just going to let dirt get in your system. Does anyone know what dirt does to a motor?
> 
> 
> 
> ...


No kidding. We are talking about the potential power gains of an engine without an air filter though - we have discussed the negatives and I am sure that everyone that has been following this thread is aware of what damage could be done to your engine by not running with an air filter.


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## myoung (Apr 15, 2002)

wildmane said:


> No kidding. We are talking about the potential power gains of an engine without an air filter though - we have discussed the negatives and I am sure that everyone that has been following this thread is aware of what damage *could* be done to your engine by not running with an air filter.


Since everyone is in agreement that it WILL ( not could...WILL cause damage) ... then why is it even an option??? Discussing the potential gains is ridiculous..


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## Zen31ZR (Mar 24, 2004)

myoung said:


> Since everyone is in agreement that it WILL ( not could...WILL cause damage) ... then why is it even an option??? Discussing the potential gains is ridiculous..


There are people that do this, is the problem. I've read stories about it, particularly with JDM cars where the 30k engine replacement is mandatory. If your engine was by law supposed to be swapped out at 30k you'd beat on it pretty hard too.


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## bahearn (Jul 15, 2002)

Looks like someone misunderstands Japanese laws regarding automobiles. They are not forced to replace or rebuild them after 30,000 miles.


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## Zen31ZR (Mar 24, 2004)

bahearn said:


> Looks like someone misunderstands Japanese laws regarding automobiles. They are not forced to replace or rebuild them after 30,000 miles.


Looking to nail that down for certain. Read it somewhere years ago. I'll post if I find out otherwise.


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## snowcrash1984 (Sep 22, 2005)

People do stupid things all the time. I remember reading about one guys Honda project. I don’t remember how or why but he was running 20 psi of boost in to B16 with no fuel management or intercooler. He said that the car was f…g fast for the hole 24 hours of driving and then posted a picture of the block with a piston rod sticking out of the side. 
Imagine driving around without and air filter and going through, say road repair area. Cement dust 3 ft up from road crew. Yam yam.


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## Bror Jace (Apr 26, 2003)

The quick answer is 'yes' you will get more power with an open intake ... but wear will increase exponentially.

Years ago, you would see racers (sports car and F1) with completely open intakes ... or just a mesh screen over each intake port.

But remember, those guys were going to put just a couple hundred miles on each motor then rebuild it.

Running no filter on a street car is just stupidity.


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## head82 (Nov 1, 2005)

Open intake??...
Just as simply as this, when you get home after a long trip and you take a look to your radiator, you can see bugs and insects smashed on it, just figure what happens if those bugs enter in your block and what happens with your pistons...
Maybe it could be a great mix and gives us a better explosion...
Nissan powered by Bug Cells


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## cpforyou (Nov 24, 2005)

I have actually done a test on this at the reputable R&D Dyno in Gardena (www.rddyno.com). 

Without a filter it lost 1 - 2 WHP on average. The filter came with a built-in velocity stack. We found a velocity stack (with no filter), and we gained back those 1 - 2 WHP. 

This means that on this particular setup, filter really made no difference. It was the velocity stack that did.


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## 93*SE-R (Nov 19, 2005)

Years ago I owned a Cal-Look `67 VW Beetle and had a pair of Webers on it. When I removed the air filters and brought the RPM up to about 2,500-3,000 you'd see a haze of fuel/air standing above the air intakes. As you let off the throttle everything would suck back in. Just imagine everything around it being pulled in too. Dirt...bugs....spiders....leaves....and God knows what else.Granted, this was with carbs, but you get the idea.

If you need that extra couple of horses throw some good gas in the tank, like Rocket 110 and leave your K&N on. That is, you ARE using a quality filter, right? In my shop I've seen what people are sticking on their cars with CAI's....   
























And yes, I had the air cleaners OFF at shows. When I drove it I put them back on....


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## Xybus (Oct 22, 2005)

*To thread starter...*

*Sighs and shakes head*. Are you really THAT desperate for a few horsepower that you would risk the longevity of your engine? First of all, what kind of car do you have? And secondly, open your eyes to the aftermarket (even if you have a low budget, just leave it stock until you can afford the power adders you want instead of taking the cheap/free quick way). There's a little saying you should learn:

Fast and reliable is not cheap.
Fast and cheap is not reliable.
Cheap and reliable is not fast.

I'm not flaming on you, just try to think about whether or not you want your car to benefit in more than one way when modding.


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## wildmanee (Nov 21, 2004)

It's been established that running without an air filter is bad for your engine. 
The original question was simply whether or not it would provide a potential gain. Never said anything about taking his filter off.


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## b13pnoysentra (Mar 30, 2005)

fanl said:


> Use no air filter means more torque and horsepower? What do u think guys


When I first looked in the filter box when I had my car for a month, I found that there was no filter in there!! I was lyk omg, but I didn't run the car til I got a K&N drop in. Nothing got in the engine I hope, but there was dust and a dry leaf in that box if I recall correctly. Still running strong to this day with a WAI now.


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## 93*SE-R (Nov 19, 2005)

I can't believe this thread is still alive.....

With all this talk about running w/o an air filter no one mentioned the obvious: all you need is a small PORTION of a leaf or some similar fiber/hair/dustball to hit the mass air flow meter and you have a stumblin' & a stallin' set of wheels. PERIOD.


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## psuLemon (Apr 23, 2003)

93*SE-R said:


> I can't believe this thread is still alive.....
> 
> With all this talk about running w/o an air filter no one mentioned the obvious: all you need is a small PORTION of a leaf or some similar fiber/hair/dustball to hit the mass air flow meter and you have a stumblin' & a stallin' set of wheels. PERIOD.


OMG, you obviously didn't read this whole thread


I metioned among others, that if you have no filter, you will have stuff go in your motor and make your motor go boom.


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## stone (Jul 7, 2005)

b13pnoysentra said:


> When I first looked in the filter box when I had my car for a month, I found that there was no filter in there!! I was lyk omg, but I didn't run the car til I got a K&N drop in. Nothing got in the engine I hope, but there was dust and a dry leaf in that box if I recall correctly. Still running strong to this day with a WAI now.



luckily you only had leaf only. Any stone chips would cause damage to your engine.


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## surferboi_hco (Oct 29, 2005)

stone said:


> luckily you only had leaf only. Any stone chips would cause damage to your engine.



how would stones get in your engine if its atleast 2 feet from the ground..... 
i could see sand or pebbles but full fledged stones i mean r we breaking newtons law and huge stones can fly into ur enging ?!?!? 


:fluffy: :fluffy: :fluffy: lol yea this thread is officially dead :fluffy: :fluffy: :fluffy:


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## wildmanee (Nov 21, 2004)

Stone chips...


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## cpforyou (Nov 24, 2005)

Don't forget about air resonance that comes into play. Sometimes you can make or lose a few hp within certain hp ranges by making you intake tube longer or cutting it shorter.


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## 98_frontier (May 26, 2005)

what about running just the a k&n air filter without the plastic piece over it?still protects from things getting inside but will the air still be pulled in?


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## psuLemon (Apr 23, 2003)

98_frontier said:


> what about running just the a k&n air filter without the plastic piece over it?still protects from things getting inside but will the air still be pulled in?


if you are talking bout a cone filter that is fine. But you wont really gain much power, as heat soak becomes an issue.


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## wildmanee (Nov 21, 2004)

He's talking about the open airbox modification...


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## 98_frontier (May 26, 2005)

if that doesnt add any hp, what about i get a 3in piping and connect it to the throttle body and run straight down and to the left where the battery used to be and hook up a cone filter,will this pull air directly to my engine?2.4l 98 nissan.


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## psuLemon (Apr 23, 2003)

98_frontier said:



> if that doesnt add any hp, what about i get a 3in piping and connect it to the throttle body and run straight down and to the left where the battery used to be and hook up a cone filter,will this pull air directly to my engine?2.4l 98 nissan.


some filters will produc small gains, but trying to move it from the engine bay will provide better flow and gains. that is why a CAI will provide around 7-9whp while a WAI will provide 3-4


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## surferboi_hco (Oct 29, 2005)

is it hard to make ur own CAI??!?!?!?

i heard u need to drill a hole n some shyt


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## 98_frontier (May 26, 2005)

all u have to do is the canister that sit on top of the throttle body u need to dril two holes in the top so the bolts from the tb will slide through so you can screw it down, and drill a hole in the piping to fit the air sensor(youll probably have to make the wires for the sensor longer)but thats it.a good cone filter and supposedly like psulemon said, gain 7- hp,im getting mine done for 65 bux (its all about connections mane)


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## psuLemon (Apr 23, 2003)

98_frontier said:


> all u have to do is the canister that sit on top of the throttle body u need to dril two holes in the top so the bolts from the tb will slide through so you can screw it down, and drill a hole in the piping to fit the air sensor(youll probably have to make the wires for the sensor longer)but thats it.a good cone filter and supposedly like psulemon said, gain 7- hp,im getting mine done for 65 bux (its all about connections mane)


First, if you dont know how to make one, dont try. second, the only way y ou will get that 7whp is if you match the HS CAI as it is a velocity stacker and you make a legitamate CAI. Secondly, look at Nostrodomos' write up on homemade CAI, but i did that and i wish i would have gotten the hs one.


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## 98_frontier (May 26, 2005)

first of all im not making it, a shop is making me one so lets get that straight homeboy,and second how will we ever know what actually works until we try it.its all based on trial and error. id rather be proud to have tried to make one and fails and gain knowledge from that so i can possibly choose the right one next time.


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## psuLemon (Apr 23, 2003)

98_frontier said:


> first of all im not making it, a shop is making me one so lets get that straight homeboy,and second how will we ever know what actually works until we try it.its all based on trial and error. id rather be proud to have tried to make one and fails and gain knowledge from that so i can possibly choose the right one next time.


How do i know if it wont work, i guess from the one i already made and all the Research that HS did to get the best power. Is that sufficent enough info for you home boy and why would you pay a shop to make it, when its going to be bout the same price as a proven intake.


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## wildmanee (Nov 21, 2004)

98_frontier said:


> all u have to do is the canister that sit on top of the throttle body u need to dril two holes in the top so the bolts from the tb will slide through so you can screw it down, and drill a hole in the piping to fit the air sensor(youll probably have to make the wires for the sensor longer)but thats it.a good cone filter and supposedly like psulemon said, gain 7- hp,im getting mine done for 65 bux (its all about connections mane)


Have you ever heard of silicone couplers? 


And if you want to make a CAI yourself, you must:

1) Know someone that welds
2) Look at the stock intake or an aftermarket intake

p.s. this thread is getting offtopic.. I suggest you search about this stuff first before you post up in a thread that does not talk about making your own CAI


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