Do You Need The Air Filter Box?

[RickL]

I'd look this up myself if I had access to my service manual - it's in a crate somewhere between here and Hawaii right now. My question is, can the stock air filter box be removed and an aftermarket filter (like a K&N or Uni) be fitted to the intake? Seems to me that would let the FJR breathe a little better. Has anyone done this mod? Is it doable?

 

[ionbeam]

My question is, can the stock air filter box be removed and an aftermarket filter (like a K&N or Uni) be fitted to the intake? Seems to me that would let the FJR breathe a little better. Has anyone done this mod?

Since the FJR has been available State side for 3 model years I doubt that there are many things that *haven't* been tried. For better or worse, accidental and intentional.
There certainly is a K&N that drops right in. It costs HP but, it drops right in. Several people have drilled, snorkled, deleted pieces and shaved bits around the air box but the gains if any were too small to make a meaningful difference. Yamaha actually designed the air box for a specific volumn and flow rate <_< and did a pretty good job :lol: To get any real benefits from an intake mod you will probably have to do complimentary and equal rework on the exhaust side.

Alan

 

[Warchild]

There certainly is a K&N that drops right in. It costs HP but, it drops right in.

Cost power? Not from my long-term experience. I've been running a K&N in two different FJRs for the past 50,000 combined miles now..... no, I haven't dyno'ed it, and don't need to: the bike runs no different whatsoever with the K&N filter installed; no more power, no less power.

The reason I run one is strictly for maintenance longevity. As a LDRider, I don't feel like buying paper filters 3 or more times a year. The K&N filter more than does the job for me.... as indicated by my avatar, the bike isn't all that slow...

 

[radman]

If you are thinking pod filters, no, there is a intake air temp sensor in the airbox that would have to be relocated or eliminated somehow. And I agree with WC on the power gain or loss equation. I installed a Uni filter, no gain, no loss, only the convenience of a washable element. Joos, I think, on the Brit site, went through the intake system hardcore, with dyno testing at each step, and found no improvement of any consequence was to be found in altering the intake system.

 

[ionbeam]

Anecdotal information from other sites, people claim Dyno data that the K&N lost power. The numbers they were claiming were so small that it could be accounted for by run to run variations. The only reason I posted second hand information was because there were three or more people reporting very similar results.

Bad, bad posting information that I didn't have first hand experience with. :headbonk:

Alan

 

[Randy]

Anecdotal information from other sites, people claim Dyno data that the K&N lost power. The numbers they were claiming were so small that it could be accounted for by run to run variations.

One of the reasons for the inconsistant results is probably due to the fact that the filters, after being cleaned or on initial use, were incorrectly oiled. Not enough oil and, while achieving good air flow, you're losing filtering capability. Too much oil and you're causing too much restriction.

I have yet to see any true evidence of a K&N actually causing a power increase over a brand new stock filter. If that data exists somewhere, I would be interested in reading about it. Many people claim they notice a bump in power when they went from a stock to a K&N, but, in most cases, the stock filter was used up and it's only natural that a new filter, be it a stock or K&N, is going to result in an improvement.

 

[ionbeam]

Many people claim they notice a bump in power when they went from a stock to a K&N...I have yet to see any true evidence of a K&N actually causing a power increase over a brand new stock filter

While I don't have motorcycle evidence I do have cage evidence. I have time slips from New England Dragway where we ran a series of tests that included air filter swaps. Converting from a flat box type paper filter to a K&N cone did make a small positive difference. We added a high flow exhaust and it made a huge difference. After adding the high flow exhaust with H pipe, putting a paper filter back in produced notably and repeatable less power. But, a big lazy V-8 responds to the little things much better than a highly evolved factory motorcycle engine, say something like an FJR1300. B)
Alan

 

[radman]

Yeah, cage intakes are pretty restricted. The actual exposed area of the FJR paper filter roughly equals that of the flat filter on my wifes Bonneville 3.8. Motorcycle intakes are pretty well optimized for horsepressures compared to most vehicles. If the wifes 3.8 had the power output per cc that Frank does, it would have 422 horsepower. If oil capacity is compared, the 3.8 would have 12.4 quarts. As you can see, performance spec wise, the Feej is pretty far out there.

 

[C&C]

I concur, a K&N will give more of a maintenance benefit than a performance gain. There may be a small gain but this would be at WOT. Gas mileage would be a wash, unless the paper element was grossly restricted.

 

[RickL]

If you are thinking pod filters, no, there is a intake air temp sensor in the airbox that would have to be relocated or eliminated somehow. And I agree with WC on the power gain or loss equation. I installed a Uni filter, no gain, no loss, only the convenience of a washable element. Joos, I think, on the Brit site, went through the intake system hardcore, with dyno testing at each step, and found no improvement of any consequence was to be found in altering the intake system.

@radman,

Yup, that's what I was thinking of - something to eliminate the box entirely.

But from all the postings, sounds as if it wouldn't matter much. Back to the drawing board....

RickL