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We've all seen the dyno pulls showing a drop in hp from swapping oem filters for aftermarket, but what is this really from obviously most will think its from flowing too much air and creating turbulence in the air box but has anyone ever checked? actually flowed the filters to see if this is the problem? One thing to consider is maybe they are flowing less air from being able to filter out smaller particles. If this was found to be true i would much rather be down a couple of hp and keep my motor as clean as i can on the street. and keep a set of oems for the track if i found it that necessary.:D
 

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Discussion Starter #3
Yeah im not saying you gota go out and buy some k&n's so your bike dont blow up in 1000 miles but do you think it could make a difference between going 50k or 100k miles without a rebuild?
 

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Nope, not at all. Anything that small getting through the OEM filter isn't going to make a difference. Honda built the RC as a street bike. I trust them enough to have an air filter that fits the bill. Stick with OEM, you can't go wrong.
 

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Yeah im not saying you gota go out and buy some k&n's so your bike dont blow up in 1000 miles but do you think it could make a difference between going 50k or 100k miles without a rebuild?
I think frequent oil changes with quality oil and filters are going to do much more than air filters. But what do I know, I only have something like 13k on mine.
 

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Discussion Starter #6
I think frequent oil changes with quality oil and filters are going to do much more than air filters. But what do I know, I only have something like 13k on mine.
Thanks for the imput guys, on a side note what kind of oil filters are you guys running? I've always used oem Honda but I cut one open the other day and wasn't very impressed, looks like a fram on the inside, paper filter material, and I have seen sevral fram failures and will no longer put then on anything I own, this doesn't mean that the oem's will fail but I'm just scared of them, has anyone run the royal purple filters?
 

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I use k&n oil filters because that's all the cycle gear by me has

For the record I've used fram filters religiously on every automobile I've ever had (hundreds of thousands of miles) and never had an issue with one. I've been a member of several different car, truck and motorcycle forums over the years and have only ever heard of one failure of a fram filter.
 

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Discussion Starter #8
I use k&n oil filters because that's all the cycle gear by me has

For the record I've used fram filters religiously on every automobile I've ever had (hundreds of thousands of miles) and never had an issue with one. I've been a member of several different car, truck and motorcycle forums over the years and have only ever heard of one failure of a fram filter.
I also used fram a while back but after 2 failures caused by the paper filter falling apart and starving the motors of oil I will never use them again, a rep for Jasper engines also informed me that they broke contract with fram because of multiple failures and no drain back diaphragms. I'm not saying people don't run alot of fram filters all around the world and get away with it but all it takes is just one faulty filter to destroy a 15k dollar motor. Compared to the royal purple filters the frams are at an obvious disadvantage cut one open and you'll see what I'm talking about.
 

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I would suggest a visit to RougeRC51, and see the dyno run charts for yourself.
And to really run the numbers on the volume of the OEM airbox, to the CFMs that each cylinder inhales 1000-8500rpms a minute. I would think there would be a great suction- rather than there would be a problem with turbulances inside the airbox..
And have to agree with a few of the member here - 1) oil changes remove more contaminates. 2) the paper oil filter, and air filter(with proper changes have been on combustion engines, with documented multi-millions of miles. Without the rebuilding.
And one last point. Consumer Report has done the study and report of the "Air,Oil filter pro's and con's.. and seem to be unfavorable to any one company.. And your K&N filters were of the worst on the market.. Purolators, were some of the best air flow, with very little filtering.. I will stay with the OEM..
I could probably save enough $$$ to rebuild the engine after a 100,000 miles. or so.
 

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Can you buy them without the mesh or do you mod them and what is the point of not having the mesh?
You have to mod them yourself. Increased airflow is the reason for removing the mesh.

I would suggest a visit to RougeRC51, and see the dyno run charts for yourself.
And to really run the numbers on the volume of the OEM airbox, to the CFMs that each cylinder inhales 1000-8500rpms a minute. I would think there would be a great suction- rather than there would be a problem with turbulances inside the airbox..
And have to agree with a few of the member here - 1) oil changes remove more contaminates. 2) the paper oil filter, and air filter(with proper changes have been on combustion engines, with documented multi-millions of miles. Without the rebuilding.
And one last point. Consumer Report has done the study and report of the "Air,Oil filter pro's and con's.. and seem to be unfavorable to any one company.. And your K&N filters were of the worst on the market.. Purolators, were some of the best air flow, with very little filtering.. I will stay with the OEM..
I could probably save enough $$$ to rebuild the engine after a 100,000 miles. or so.
While I like so many others went to Rogue for their knowledge on 51's I can only take so much of what that site says with a grain of salt. Especially when it comes to some dyno tunes from 2002. A lot has changed in dyno and airfilter technology in the last decade. On a dyno you cant accurately reproduce the forced air that the bike would draw in out on the highway or race track. There are to many unknown factors IMO to simply suggest aftermarket airfilters are no good when all you have to go on is a dyno run.
 

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As this thread has devolved into talk about oil filters in addition to the air filters it started out as... I've seen more than one FRAM oil filter come apart. One of them personally starved the top end of my motor for oil effectively toasting it.

OEM Honda oil filter- Notice the pleats, metal end caps and silicone seal


Fram oil filter (cardboard end caps, epdm seal, reduced pleats & media height)
 

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While I like so many others went to Rogue for their knowledge on 51's I can only take so much of what that site says with a grain of salt. Especially when it comes to some dyno tunes from 2002. A lot has changed in dyno and airfilter technology in the last decade. On a dyno you cant accurately reproduce the forced air that the bike would draw in out on the highway or race track. There are to many unknown factors IMO to simply suggest aftermarket airfilters are no good when all you have to go on is a dyno run.

Really? What has changed so much in the last decade in regards to tuning or air filters? Please be specific as the only thing I have seen change in the industry is the effort dyno tuners are willing to go to that insures they are properly optimizing their maps. Fewer & fewer tuners go that extra mile to get apples to apples comparisons. Hell most dyno tuners don't even know what A/F ratio to tune an RC51 to let alone take the time to do a map properly to begin with.

For the record the exact same K&N filters that we tested that negatively affected performance on the RC51 10 years ago are the exact same filters being sold today for the RC51. There has been no design change...

You are correct that you cannot effectively simulate ram-air effect on a dyno and the testing I have done proves you don't need to. Maps created on the dyno when done properly come out almost exact to the cell number as they do on an Auto-Tune targeting the same A/F ratio when tuned in real time on the race track.

Forcing air down the throat of a bike is a good way to totally screw up a map. In fact at one point I got 136rwhp out of an RC51 by shoving an ungodly amount of air into the snorkel and adding fuel to match, but when we took the bike off the dyno and tried to ride it on the road with that map it was so rich it fouled the plugs almost instantly above 9000rpm.
 

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Really? What has changed so much in the last decade in regards to tuning or air filters? Please be specific as the only thing I have seen change in the industry is the effort dyno tuners are willing to go to that insures they are properly optimizing their maps. Fewer & fewer tuners go that extra mile to get apples to apples comparisons. Hell most dyno tuners don't even know what A/F ratio to tune an RC51 to let alone take the time to do a map properly to begin with.

For the record the exact same K&N filters that we tested that negatively affected performance on the RC51 10 years ago are the exact same filters being sold today for the RC51. There has been no design change...

You are correct that you cannot effectively simulate ram-air effect on a dyno and the testing I have done proves you don't need to. Maps created on the dyno when done properly come out almost exact to the cell number as they do on an Auto-Tune targeting the same A/F ratio when tuned in real time on the race track.

Forcing air down the throat of a bike is a good way to totally screw up a map. In fact at one point I got 136rwhp out of an RC51 by shoving an ungodly amount of air into the snorkel and adding fuel to match, but when we took the bike off the dyno and tried to ride it on the road with that map it was so rich it fouled the plugs almost instantly above 9000rpm.
So you agree there has been change. :)

I know better than to argue with the boss so we'll leave it at that.
 

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Discussion Starter #18
As this thread has devolved into talk about oil filters in addition to the air filters it started out as... I've seen more than one FRAM oil filter come apart. One of them personally starved the top end of my motor for oil effectively toasting it.
Thanks for posting up the pics LDH any thoughts on royal purple oil filters and the filtering abilities of the oem air filter vs a k&n?
 

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Thanks for posting up the pics LDH any thoughts on royal purple oil filters and the filtering abilities of the oem air filter vs a k&n?

I don't know jack shit about Royal Purple Oil filters. Ever since the FRAM filter destroyed one of my engines I have used nothing, but OEM oil filters period. Honda on Honda's, Suzuki on Suzuki's etc. It is cheap insurance to know the filter is made to the OEM spec up to an including bypass valve rates if required.

When it comes to air filters the more air they flow, the less ability to filter debris they will have. That's pretty much a given.
 
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