I just made a 20 mile round trip through lunch traffic, only to discover that my freakin' Mazda dealer doesn't stock a freakin' RX-8 air filter.

"We can't order it until Monday."



Well I can order it from Mazmart today and it'll be here without the 20 mile drive.



edit: oops, not listed on their site ...

 

just go to Autozone and get a K&N drop in filter.

 

thats probably good for you.

get a k&n high flow panel filter. the end.

 

K & N is what's in there now. I didn't like finding grit on the "filtered" side of the intake and several of the race guys have switched back after similar experiences.

 

first time i've heard of that.

 

I never had that issue with my K&N, did you keep it properly oiled and maintained?

 

I do

 

i never had that issue too

 

Its been documented here by EricMyer where the racing team has blew engine because of the filter's inability to catch sand in some courses....

Need to find the thread....oh well.

I do know K&N filter is used in military vehicles/helicopters as well...and I think its ok for them

 

The filter was put in by the previous owner, a millionaire gearhead who had 15 other cars in his garage. He first registered the car with 8,565 miles on it, and I bought it 2 years later with 9,200 miles. (He had given it to his gf who managed to get stopped twice doing 50 mph over the speed limit inside of 2 months, so he took it away from her.) I assume he oiled it as he's obsessive-compulsive enough to import his own diesel fuel from Canada because he claimed the US stuff is crap, plus there is evidence of oily wetness now. At most, the filter has been used for 4k miles and shows evidence of passing bits of dirt.

The stock intake system is very good. To quote Racing Beat:

"The stock RX-8 air box is very efficient unit and finding additional horsepower through traditional approaches has proven to be a challenge!"

They have managed to improve over stock, at the cost of some noise, but their entire, extensively-modified, system using a custom-made K&N filter, shows, to me anyway, a rather small gain. Again, quoting them:

"REVi Intake Adds An Average 1.95 HP Over The Stock System - 2000-8900 RPM Range"

(I absolutely applaud them for being upfront and honest about what their system does, and the careful engineering behind it; check out the entire link given below.)

So a ~$400 system gives a 1% average h.p. gain (with a K&N filter) over stock (with a OEM paper filter). (The peak gain is ~2.5% at 9,300 rpm). How much gain can you expect from swapping a stock filter to K&N in a stock system? Something maybe, but still approximately zero.

Getting to the air filter in the stock system is a PIA. I have no interest in pulling off the accordion tube and associated vacuum lines to oil and clean a K&N every 3k miles, for essentially no gain other than the right to put another sticker somewhere. (At least the RB system should allow easier access, and it certainly opens up access to things within the engine compartment.)

YMMV

http://www.racingbeat.com/FRmazda4.htm

 

I and many hundreds of others I'm sure have never had any problems with the K&N filter.

While I'm not going to refute that Eric's story, you have to understand that is a completely different application. One case.

It takes all of 1 min to push back the air box out of the seating grommets to open it and get at the air filter. You don't have to undo anything. You don't have you have to re-oil it every 3K. On my previous 8, I re-oiled at a 15k interval just because I wanted too, not because I had too.

Why not allow your motor to breathe easier?

And to top it all off, it's still cheaper then the paper element that Mazda sells. And you'll never have to replace it.

 

Yep, but mil-spec stuff is generally not done at a price point accessible to normal humans. Even the civil aircraft version in an 180 hp plane I used to fly has a price of $205.54 (I just looked it up), and it runs in an environment far cleaner than what cars live in.

 

Speedsource uses the paper air filter. They saw a 1hp increase with the K+N filter, but blew 2 engines at Daytona a couple years back (?) because of sand getting in the engine.

I think where you live has alot to do with your risk, but realistically, 1hp gain is not worth the risk imo. I went back to paper.

 

If you dont like oiling go with Pipercross or HKS. They boh dont require oiling that I know of.

 

yup i had the same prob. but i had o wait 4 hours tops for them to ship it in so it was fast, but next time im going for k&n.

 

I ran across this as well:

"AFTERMARKET AIR INTAKE SYSTEM - ROUGH ENGINE IDLE

Applicable Models

2004 - RX8 VIN Range: 000000 - ZZZZZZ; Symptoms

030 ROUGH IDLE MTOL - 4090 Dealer Repair Information


Some customers may complain of rough or poor idling condition. The
RX8's airbox and intake system is specially designed to eliminate
restriction and create a smooth airflow over the MAF. If the customer has
installed an aftermarket air cleaner or intake system, the airflow
stream to the MAF element may be disrupted and cause an improper MAF
signal. This erratic signal results in a rough idle condition. Also,
aftermarket air cleaner elements are sometimes coated in oil to better
filter the incoming air. The oil from this type of element may damage the
MAF resulting in a poor idle or MIL related to the MAF. If a customer
complains of a rough engine idle, see the repair instructions below.

1. Check for aftermarket air intake system or aftermarket air filter
element. (Replace with factory system if necessary.)
2. If rough idle continues, check for additional bulletins / M-tips,
workshop manual troubleshotting.
3. Confirm repair. "

And a big oops! I looked more carefully and the installed filter is an AFE, not K&N. Holding it up to a light, I see numerous holes in the filter element - this thing is junk. Still, I'm goin with a good ol paper element.

 

That has ABSOLUTELY NOTHING to do with the air filter used and EVERYTHING to do with the fact that some aftermarket intakes don't inlude the screens before the MAF sensor. Also read that it applies to aftermarket intakes, NOT aftermarket filters. Aftermarket filters will do nothing to your idle.

It is these screens that smooth the airflow over the MAF and allow it to get a proper reading on the air entering the engine. Notice that the recommended air intakes like the Racing Beat or Mazdaspeed/AEM both have at least 1 screen and I haven't heard of anybody having trouble with them that wasn't caused by a bad install.

Note that I have no disagreement on just using the factory filter, but if it is hard to get for you then there is no real reason to not use an aftermarket like K&N. While true that the K&N doesn't filter as well as a stock paper element it is more than adequate to use during normal driving. Unless you are going to go off roading through some sand traps or something, I doubt you would ever have problems with it (assuming it is maintained properly that is).

 

If it does not filter as well as the stock element, why would you use it?

I've seen a lot of posts here that lead to the conclusion that the OEM oil filter is hard to beat. Is there a similar body of knowledge about air filters?

Ken

 

K&N Filters work great and you won't have to worry about buying another filter.

 

It is getting harder and harder to just push back the airbox. There is that wire that catches the sharp edge of the inlet. Seems like it would cut the wire eventually.

 

That's what I'm reading. What incentive does an aftermarket maker have to protect the engine? At least within the warranty period, the manufacturer get to pay for engines wrecked by a bad product.

(Still waiting for my filter ... grrr)

 

Here are two air filters, one new stock, and the other an AFE aftermarket with 4 k miles in service. Both held in front of the same florescent light at the same distance.

Of course the aftermarket is gonna flow a little more air - IT'S FULL OF HOLES!

 

Well your problem was that filter was crap. Not a K&N.
Don't generalize.
I'm sure many would still agree the K&N is superior to the OEM Mazda paper element.

K&N will stand with you in court and use their resources to defend any warranty claim made against you by the dealer due to the "aftermarket filter"
http://www.knfilters.com/MAF/massairpledge.htm

I also suggest reading the links at the bottom of that page regarding the claims that oil gets on the MAF...

 

Well I ran the stock filter till it needed to be changed, switched to the K&N, didn't notice much of a difference but also didn't notice and dirt and grime getting through. While I had the K&N I measured a max MAF reading around 25lbs/min. Earlier this year I switched to an AEM (dry element filter) and again no dirt or grim in the air tube and this time I measured a max MAF reading of around 30lbs/min. So there is something to be had from an intake, but gains would be gotten through tuning. As most on the forum know the AEM does include the MAF screens so idle is unaffected, in fact the biggest change I noticed was a little more fuel use when I really get into it, but that's simple thing of more air means more fuel.