| Author | Message | ||
     Spatten1 |
I just got a K&N, and I'm a bit confused. The XB9 air filter surface area looks to be two to three times that of the X1 and as big as most 3.0 liter car engines', which flow much more air. I don't understand how the stock filter is restricting air flow, unless it is made of friggin construction paper. It seems like it has to flow more than a K&N for the X1. I'm just baffled that the stock filter is restrictive when it is so large. Has anyone changed the filter without making any other mods at all and done a dyno run? Anyone try one on a flow bench? | ||
| Gowindward  |
Why a filter for an X1 when you have an XB9? | ||
| Charlieboy6649  |
http://www.knfilters.com/facts.htm#FACTS Filtration 101 explains this pretty well. I know everyone here in the desert uses K&N as the standard: Trucks, Dune buggies, bikes, etc. That's got to speak for something... | ||
| Fullpower  |
spatten you are on to something there. it is quite obvious that the stock xb9 air filter has more than adequate surface area for an engine that size. and would quite easily supply the needs of a full size half ton pickup with a v8 engine under normal street use. | ||
| Spatten1 |
Goinward, I just got a filter for my XB9, I was comparing it to the size of the X1 filter I bought for that bike last year. I used to work for a propane carb factory and my experience was that, like Fullpower said, this filter is big enough for a small block. It makes me think that I might have wasted $ by moving to the K&N. That is, unless, the stock filter has especially horrible flow characteristics for its size. Thats why I am curious if anyone has done dyno runs with only a filter swap on an XB9. | ||
| Lpowel02  |
i don't know the ins and outs of this but... if you hold the 2 up to a light, you'll see the K&N lets a lot more light through...so it must let a lot more air flow through...right? | ||
| Briz31  |
The difference is in the material used, one is constructed in a material that is restrictive in air flow, tighter weave lesser quality fibre v's compact high flow micro fibre. Both are made to high standards and within the specified regulations. The whole issue of surface area shouldn't really be a problem, it's the construction and material used that really makes the difference. | ||
| Spatten1 |
I understand that the material is more restrictive on the stock filter, but with sufficient surface area it should not make any measurable difference. There will be a surface area threshold under which the same volume of air will flow at a specific pressure differential. It would not matter whether it was paper or fiber, both will flow the same volume of air if they are both way over-sized for the application. In other words, there are enough of the smaller holes in the stock filter to flow the air required with little resistance if the filter is HUGE. | ||
| Metalstorm  |
The K&N for the XB is the same size as the stock XB filter right? Then perhaps it's all about air velocity? That's my guess. | ||
| Spatten1 |
One more thought, the Japanese liter bikes flow a lot of air, probably twice that of the Buell 1000. From what I've seen, their paper filters are this size or smaller. They spend big $ for titanium and magnesium all over the bike. If they needed to spend another twenty bucks to get any performance advantage out of an air filter, resulting in bragging rights and 1000s more bikes sold, they'd do it. Performance is all that sells those bikes and they are engineered to the hilt. From what I understand, the K&N won't do anything on those bikes to improve power unless flow is increased by exhaust, head work, etc. In stock form the paper filters are sufficient and, usually, just changing the filter will not increase performance. I may be off base, and would love to hear someone else's experience. | ||
| Gowindward |
Okay, I'm less confused now! I would agree that a clean stock filter is good enough and would guess you could get little improvement over it. The K & N seems like a PIA, cleaning and reusing vs tossing a dirty stock filter and replacing with a new stock filter. | ||
| Briz31 |
You know... I love this place... This is like the R&D factory workshop, all these ideas thrown together, nutted out and questioned over and over to create the ULTIMATE performance result from these beautiful V-Twin engines. | ||
| Spatten1 |
Briz31: AMEN! | ||
| Spike  |
Check these out: http://www.bobistheoilguy.com/airfilter/airtest1.htm http://home.usadatanet.net/~jbplock/ISO5011/SPICER.htm Personally, I don't use my K&N any more. My personal experience isn't exactly scientific, but it convinced me. Once while servicing my XB I wiped my finger around the inside of the rubber velocity stack. I wasn't too surprised to see that I had picked up a noticable amount of black stuff on my finger. What did surprise me was how thick and gritty the dirt felt when I rubbed my fingers together. I don't need a slide rule to figure out that any particles big enough to be perceived by me rubbing them between my fingers shouldn't be sucked into the crankcase. I cleaned up the rest of the velocity stack and switched back to the stock Buell filter. I checked the velocity stack a few thousand miles later using my now patented "finger test" and was happy to find out that it was much cleaner and less gritty. Also, I agree that the sheer size of the stock XB filter has to prevent it from providing much restriction. For what it's worth, Harley has moved away from K&N filters in their Screamin' Eagle air cleaners. The new SE air cleaners have a white paper/cotton/fiber looking filter with a rubbery blue seal that looks curiously similar to the OEM Buell filter. I still haven't found any documentation indicating why harley made the switch, but I can only assume they had good reason to do so. | ||
| Charlieboy6649 |
Ultimately, I like the K&N cuz I can clean it. That was appealing to me. Very dusty climate I live in... | ||
| M1combat  |
Every vehicle I've ever put a K&N filter on has made more power and noticeably so. I don't know if they filter better, but they do make more power. | ||
| Spatten1 |
Spike, those links have excellent information, thanks! Everyone should give those a read. Hey, when I was in college I worked at a shop near you. It was MC Supply in Chapel Hill (1989 or so). It's gone now, but the guy who owned it is Gary at 751 Motorsports. | ||
| Glitch  |
I like the K&N cuz I can clean it. And you only need to buy one. | ||
| Norrie |
One more thought, the Japanese liter bikes flow a lot of air, probably twice that of the Buell 1000. From what I've seen, their paper filters are this size or smaller. They spend big $ for titanium and magnesium all over the bike. If they needed to spend another twenty bucks to get any performance advantage out of an air filter, resulting in bragging rights and 1000s more bikes sold, they'd do it. Performance is all that sells those bikes and they are engineered to the hilt. The manufacturers dint fit K&N as standard so they can charge you a fortune to supply and change the stock one. Apparantaly the stock filter flows better than a K&N when you but quickly blocks up. The K&N keeps a better flow over time. I believe you get a better flow because when I had my in line 4 Jap bike I fitted a K&N with an aftermarket exhaust and the bike run to lean. I put the stock filter back in and it run fine. That tells me you get more flow through a K&N. Norrie. | ||
| Kowpow225 |
About the dirt on the velocity stack. Any filter which claims to flow more air will flow more dirt as well. (There is always a trade-off isn't there.) The oil applied to a K&N is sort of the mediator in this situation. A stock filter relies only on obstruction for filtering. K&N uses oil to "absorb" the dirt to cling on the filter. I'd like to put a HEPA filter on my bike for longevity purposes, but it wouldn't run as strong as it should. | ||
| Kowpow225 |
Read Charlieboys link again.....The 3rd one down. | ||
| Bigj |
You guys are missing the point, somewhat. Only one cylinder draws through the filter at a time. That is why a 1000cc twin need a bigger airbox/filter than a 1000cc four. | ||
| Outrider  |
Question: Doesn't the stock air filter have something to do with sound deadening to help pass the EPA Noise Tests? That may help you rationalize the larger yet denser configuration of the stock filter. Am I close??? | ||
| U4euh  |
Those sites above that Spike listed are a very interesting read. I may be convinced to keep the stock filter on after allespecially with all the air lid mods that I have done  (Message edited by u4euh on January 18, 2005) | ||
| Geoffg  |
Hey Spike, thanks for those links. Funny, I did a fair bit of internet research on air filters a few years ago, to decide if it was worth it to get a K&N for my diesel pickup! (I decided at that time that any extra airflow was not worth sacrificing cleanliness--I use Baldwin filters in my truck) As far as filter area is concerned, if it was truly an issue with the XBs you would not expect the FAST system to flow as well as stock, since it uses a smaller filter. | ||
| Opto |
When I went back to the stock filter from the K&N on the XB12 (dealer was worried about my bike running lean with stock ecm and Drummer and K&N early last year, before we realized it really was OK to run the stock ecm on a 12 with pipe and filter)it felt noticeably weaker, the bike was definitely sad in comparison. Big difference. I put the K&N back on after one weekend and started smiling again, never going back to a stock filter. If you can't feel the difference then there's no point running it. One thing that worries me about the XB filter setup is that it's really easy for the filter to not seat properly when fitting the upper airbox section. When I first checked the filter on my new bike I discovered the upper seal on the stock filter had been creased over during factory fitment and could have been leaking air/dirt. These days I lubricate the upper seal to ensure it seats nicely. | ||
| Spatten1 |
Opto, that is the first XB back to back filter comparison I've heard (with no other variables). Interesting and surprising. I fit the filter to the top half of the air box first, because I could still see the bottom as I seated it. If you want to see a poor air box setup, check out the X1. Whoever designed that thing needs to go back to flipping burgers. I ended up modifying the intake so it would take a large universal K&N because I could not make the stock airbox seal out dirty air to save my life. Anyone else running the stock airbox on an X1 should cover the intake hole with their hand sometime and see if it chokes off the motor. Mine would run on unfiltered air leaking around that huge perimeter gasket no matter what I did. | ||
| Craigster |
I agree with BigJ, your XB9 is trying to suck 500cc through with each intake pulse.. My Firebird is only feeding 700cc per cyl with a filter 3 times the size of the XB's Twins need a big @ssed airbox for ram air to work correctly as well as plenty of intake plenum volume on turbo bikes for the same reason. | ||
| Kowpow225 |
The key is not only volume, it's velocity as well. That's where the K&N wins out. I believe the K&N can flow more volume and velocity as a bonus. (Granted, with filtering efficiency diminished.) | ||
| Aesquire  |
I'v put K&N's on all my bikes. They do flow enough better that rejetting was a good idea. Avoid over oiling. It takes very little to work as designed, and over oiling will oil up the whole intake tract. ( and your legs & motor on a exposed filter rig, like an inline engine with conical filters. They come pre oiled now, but a thin line of oil down the middle, when re oiling is plenty. Let sit for a bit, installed is fine, and you will see the oil spreads pretty far. |
