Quote from: VaughanCustoms on June 26, 2013, 04:24:17 PM
I have been doing some research about pod filters or uni-pods on CV carbs and many people say its just a bad idea.
Foam vs Paper
Nothing to do with CV carbs specifically.
The most expensive engines working in the harshest environments, earth moving and mining equipment, protect their engines with paper filters.
Long haul trucks, where every mile they can get out of a motor means money, use paper.
The most high performance cars in the world, Ferrari, Lamborghini, Porsche etc all use paper.
The fastest production bikes use paper.
Aeroplanes use paper.
Even you lawnmower uses paper.
The entire automotive industry with the exception of one model Ford (carbon impregnated dry foam lifetime filter) and the Fiat 500 (gauze) use paper.
YET.....
The net is overflowing with laboratory tests, scientific experiments, graphs, charts, YouTube evidence and testimonials providing irrefutable evidence that foam is better.
So it is no surprise that you will find people telling you it's a bad idea.
The answer ? ? ? ? ? ? ? ? ? ?
Noel
Yeah I mean my Cougar has a K&N my Cobra has a K&N full intake so did my Ranger and my girlfriends Explorer and we love them. I really like the idea of not always having to replace my filter just clean and walk away. I guess pehaps I am just frustrated with my bike that I have a cotton media type filter on the bike and got a jet kit and got thrown for a loop. I have had this bike for a month now and she hasn't left the garage. My Cobra is able to get full use of the K&N because the computer has been tuned for extra air and full so I would assume it needs to be the same with the bike. Your tolerance levels on a motorcycle are definatly less than on a car running rich or lean in a car you will not really feel much performance difference but on a bike you can go from running to not running. I will have Randy tune up my carbs for me and I am sure it will fix the issues. Time to put it into a experts hands and as I learn more I will hopefully be able to return the favor in the future. I am working on getting a new job that I would work less hours and make more money so thats always good to not be on a huge money crunch all the time.
I think the "bad idea" is because removing the air box and modifying the system needs a fair amount of experience to make it work correctly; which we have here. The cv carb works great if it is set up right but a small change in velocity upsets the system.
Pat ( I think he mentions it is his favorite subject) and others have explained this pretty well in the files section. Added to the mix is that the is really very little increase in performance until you are in the very high RPM range....although the added intake noise sounds sweet to some!
As an example, we had an XS 400 with BS 34 carbs. It would not start or run with the airbox cover off. Put it on and it started and ran great.
Many people new to bikes get into trouble (including myself) just doing what we did back in the day with cars. No worky that way. :wacko3:
As everyone knows a carburetored car will run fine with the air cleaner off and it is (was) common to replace the stock air cleaner with a more simple system. But those cars did not have CV carbs.
Some bike shops will not work on bikes that have the system altered.
Jeff
Just don't forget to oil your paper media filter, like the one in this old truck ;) It even tells you the oil level...
(http://i208.photobucket.com/albums/bb37/campsimonette/FJ%20rally%20Buffalo%20City%20Wisconsin/100_3879_zps37ad6ccc.jpg) (http://s208.photobucket.com/user/campsimonette/media/FJ%20rally%20Buffalo%20City%20Wisconsin/100_3879_zps37ad6ccc.jpg.html)
A few guesses:
Paper filters are probably cheaper to produce and thus cost the manufacturer less money.
There is more money to be made by selling you a new filter every time vs. a one-time sell for a filter that you can clean and reuse.
Paper filters are very good filters, and they should be cheap unless you have to buy them from a m/c dealer.
I use foam filters because they are cheaper than the stock filter and I can maintain it myself.
Hooligan
(popcorn)
Quote from: FJ_Hooligan on June 27, 2013, 11:43:21 AM
...a one-time sell for a filter that you can clean and reuse.
Hooligan
Well, I know this supposed to be non-CV/FJ specific but why else would this discussion be had on the FJ forum, so here is the facts as I have witnessed over the years of working on FJ's, FJ powered race cars and building hundreds of carburetors.
There are three different media types commonly used for air filters:
Paper
Cotton Media
Foam
Paper is the O.E. filter of any form of manufacture; a single layer filtration media.
Cotton media is the highly touted "performance" K&N filter; a single layer cotton/oil filtration media. K&N used to advertise the gain of "(put a number here) by installing the filter. They have since been sued too may times for false advertising and they now claim,
"Designed to Increase Horsepower and Acceleration".
Foam is usually "Open Cell" Polyurethane Foam; dual layer foam/oil filtration media in the FJ application.
Paper filters use a tight weave media that air must force its way through as it is cleaned of dirt. The paper filter is well documented to be the most restrictive.
Cotton media is a single layer media that requires the oil to be present for absorption of dirt particles and proper filtration.
Foam uses a dual density foam. The outer layer is a course open cell foam that is oiled on the outside to absorb the dirt particles and the inner layer is a finer density that is able to provide secondary filtering.
The issue of the FJ specifically is the camshaft timing resulting the valve overlap and the initial opening of the intake valve while still in the exhaust stroke. The millisecond of opening the intake valve prior to completion of the exhaust stroke of the piston results in backwash. When this happens the fuel in the carbs is exhausted out through the carb throat in a fine mist.
When the stock air box is installed the exhausted fuel mist is never in contact with anything but the boots inside the air box. So, paper, cotton or foam media types are not effected but the mist and all filter well.
When the air box is removed the filtration media is now placed at the throat of the carb opening. This then creates an issue with the fuel spray/mist coming into contact with the filtration media.
When this happens the fuel breaks down the paper type medias causing them to fall apart.
Cotton media filtration filter is usually a very course media which requires oil to filter. The fuel mist contacts the cotton media and washes away the oil. This then makes the filter about as effective a window screen over your carbs.
The dual density open cell polyurethane foam filter is able to absorb the fuel mist via the inner smaller density foam before it can reach the outer layer. The outer courser density foam stays oiled because the fuel mist cannot reach the oil and complete filtration is achieved.
The cotton media and foam filter are both a washable/serviceable filter that can be used for many years. The issue the becomes, do you want to be able to wash your filters in the sink or do you want the fuel mist to wash your filters and render them useless? If you have a K&N carb mount filter, take it off after you have some miles on it and see if the red oil is still at the bottom of the filter near the clamp. I find it usually is just light brown colored cotton media paper only.
I personally only use and recommend the UNI/RPM dual pod filter. They are usually half the cost of K&N filters and they do twice the filtering. I speak on this topic from an person with coming up on 20 years of FJ experience building engines, carbs and racing & riding them for years.
If you want the best air filter for you FJ buy the dual foam filter. Is addresses the specific issue of camshaft overlap & fuel misting while still maintain the oil for effective filtering.
If you don't believe me, take off your filters or air box. Warm up the engine and crank on the throttle a few times while looking down at the carb throats, you will see the fuel spray out of each carb. Heck hold you hand pretty close the carb and crank the throttle, you will see just how wet your hand gets. Now imagine that spray coming out of every other stroke of the 4cycle engine. So at 5000 rpms the fuel mist comes out of each carb 2500 time per minute.
That is a lot of fuel spray and you need a filter that can handle the absorption issue and the K&N "one-time sell" filter is not the best thing for your engine as you don't get a chance to wash it yourself, the engine does it for you.
RPM Dual Pod Foam Air Filter (http://www.rpmracingca.com/proddetail.asp?prod=Carb%3ARPMPod)
Randy - RPM
I wuv you Randy!
Why does the fuel not break down the oil when it is suspended in foam, but does when it is suspended in cotton? Is the theory that it doesn't get past the finer inner layer, but the oil is on the outer layer?
Thanks for that post, Randy, that was great. Adding it to the wiki. :mail1:
Still messy, but lots of data there to be organized later:
http://fjowners.wikidot.com/pods (http://fjowners.wikidot.com/pods)
Quote from: fintip on June 27, 2013, 05:41:43 PM
Why does the fuel not break down the oil when it is suspended in foam, but does when it is suspended in cotton? Is the theory that it doesn't get past the finer inner layer, but the oil is on the outer layer?
Not theory...experience.
It is not so much as it "breaks it down", but dilutes it and allows it to be ingested into the engine as it is too thin to stay in the filter.
Yes, the cotton media filters are a single layer and require the oil to filter.
The foam is a dual layer approximately .620-.750" or 5/8-3/4" of an inch thick.
It has been a long time since I cut apart a K&N filter, but I believe the cotton media was about .020-.025" or 1/50 of an inch thick.
Another test is to hold a cotton media filter up to the direct sunlight and see how big the sun is through the media. When you hold up a dual density foam filter is almost looks like a kaleidoscope because the sun is being diverted from direct through the media and must change directions of the dual density media.
Randy - RPM
I had a severe fuel leak over the weekend and removed the stock airbox and carbs to investigate. Found a stuck float. Got everything cleaned and put back together. Getting the airbox and (for the loss of a better term) stock velocity stacks back on was an endeavor that I NEVER want to experience again. :dash2: :ireful: Thank You Randy for your input on this subject. I just ordered a set of the Uni duel pods.
Anyone need a used Uni stock foam air filter?
Fred
Fred, I could use it. I'll convert eventually, but not yet, and I do need an air filter.
Quote from: racerrad8 on June 27, 2013, 05:01:27 PM
RPM Dual Pod Foam Air Filter (http://www.rpmracingca.com/proddetail.asp?prod=Carb%3ARPMPod)
Randy - RPM
Will be ordering a set very soon. We all wuv you Randy, :lol: :lol:
Quote from: ribbert on June 27, 2013, 05:10:58 AM
Quote from: VaughanCustoms on June 26, 2013, 04:24:17 PM
I have been doing some research about pod filters or uni-pods on CV carbs and many people say its just a bad idea.
Foam vs Paper
Nothing to do with CV carbs specifically.
The most expensive engines working in the harshest environments, earth moving and mining equipment, protect their engines with paper filters.
Long haul trucks, where every mile they can get out of a motor means money, use paper.
The most high performance cars in the world, Ferrari, Lamborghini, Porsche etc all use paper.
The fastest production bikes use paper.
Aeroplanes use paper.
Even you lawnmower uses paper.
The entire automotive industry with the exception of one model Ford (carbon impregnated dry foam lifetime filter) and the Fiat 500 (gauze) use paper.
YET.....
The net is overflowing with laboratory tests, scientific experiments, graphs, charts, YouTube evidence and testimonials providing irrefutable evidence that foam is better.
So it is no surprise that you will find people telling you it's a bad idea.
The answer ? ? ? ? ? ? ? ? ? ?
Noel
Every lawn mower I've ever used hasn oiled-foam filter.... Otherwise, dead on.
Quote from: Dads_FJ on June 27, 2013, 09:39:17 AM
Just don't forget to oil your paper media filter, like the one in this old truck ;) It even tells you the oil level...
(http://i208.photobucket.com/albums/bb37/campsimonette/FJ%20rally%20Buffalo%20City%20Wisconsin/100_3879_zps37ad6ccc.jpg) (http://s208.photobucket.com/user/campsimonette/media/FJ%20rally%20Buffalo%20City%20Wisconsin/100_3879_zps37ad6ccc.jpg.html)
I had a '51 F-1 in highschool, had that very filter on it.... Loved that old truck!
Quote from: fintip on June 27, 2013, 07:31:42 PM
Fred, I could use it. I'll convert eventually, but not yet, and I do need an air filter.
fintip,
Send me your information in a PM and I will send the filter. I just ordered the pods from RPM this evening. So it may be next week before I send the filter your way.
Fred
Quote from: Dads_FJ on June 27, 2013, 09:39:17 AM
Just don't forget to oil your paper media filter, like the one in this old truck ;) It even tells you the oil level...
(http://i208.photobucket.com/albums/bb37/campsimonette/FJ%20rally%20Buffalo%20City%20Wisconsin/100_3879_zps37ad6ccc.jpg) (http://s208.photobucket.com/user/campsimonette/media/FJ%20rally%20Buffalo%20City%20Wisconsin/100_3879_zps37ad6ccc.jpg.html)
I think you'll find that's the "4th" kind, an oil bath filter.
Randy has much to say about the K&N vs the Uni and I agree.
I also agree that paper cone filters mounted close to the motor are no good, for the reasons mentioned and because they are generally not big enough anyway.
But, this still doesn't address the question of why manufacturers universally use paper.
Three of the examples I gave cover protection of very expensive engines in harsh environments, outright performance in super cars and bikes and longevity and economy in trucks. In all of these examples cost is not the issue but best possible performance in their relative goals.
I can't see why a paper filter should be restrictive if it's big enough and they can be serviced many times before replacement.
The one thing I can't agree on is the fuel misting and valve overlap theory. The principle can be FJ specific or general because all engines have valve overlap and the fuel misting/spitting is a phenomenon of all engines with a carby per cylinder. It happens on other motors but is simply drawn into another cylinder via the manifold.
The basic principal of valve overlap is that by the time the inlet valve opens at the end of the exhaust stroke the piston is very near to TDC. At this point there is virtually no exhaust gas left in the combustion chamber but the expelled gas in the exhaust system has velocity. With both valves open this velocity starts to draw in the fuel/air mix through the inlet valve. This also flushes the combustion chamber but closes before the fresh charge follows the old one out the exhaust.
If you think about the amount of vertical movement the piston has left before TDC (it's getting the least amount of vertical travel per degree of crankshaft rotation at this point) when the inlet valve opens it's not really enough to cause a significant pulse back through the carby and there is already an established direction of air flow out the exhaust anyway.
Some people also believe it comes from the inlet valve remaining open past BDC when the piston starts to rise.
What I was taught and makes the most sense is that (very simply) when the inlet valve closes, the high speed incoming mixture suddenly hits a 'brick wall' and compresses and bounces back, which is the mist you see. Because the fuel travelling up the jet also has velocity, that is carried with the air which is the spitting you also see sometimes.
Having said all that, I run Unipods on my bike. I love the induction noise! I hate servicing them.
Noel
Quote from: RichBaker on June 27, 2013, 11:52:11 PM
Every lawn mower I've ever used hasn oiled-foam filter.... Otherwise, dead on.
Well, all the mowers I've owned or worked on have paper but I'm sure there are plenty that have foam.
All the blowers, brush cutters and chainsaws here have foam though.
Quote from: ribbert on June 28, 2013, 10:07:17 AM
Quote from: RichBaker on June 27, 2013, 11:52:11 PM
Every lawn mower I've ever used hasn oiled-foam filter.... Otherwise, dead on.
Well, all the mowers I've owned or worked on have paper but I'm sure there are plenty that have foam.
All the blowers, brush cutters and chainsaws here have foam though.
Maybe it's a USA vs. Aussi thing, but most lawnmowers I've encountered have foam.
Quote from: Dads_FJ on June 28, 2013, 10:10:48 AM
Quote from: ribbert on June 28, 2013, 10:07:17 AM
Quote from: RichBaker on June 27, 2013, 11:52:11 PM
Every lawn mower I've ever used hasn oiled-foam filter.... Otherwise, dead on.
Well, all the mowers I've owned or worked on have paper but I'm sure there are plenty that have foam.
All the blowers, brush cutters and chainsaws here have foam though.
Maybe it's a USA vs. Aussi thing, but most lawnmowers I've encountered have foam.
All the B&S engines I've had used foam, but my new Honda mower engine has paper.
do the uni pod filters require any re-jetting or are they a straight replacement for airbox and filter?
Quote from: jwh on June 28, 2013, 12:35:38 PM
do the uni pod filters require any re-jetting or are they a straight replacement for airbox and filter?
You will need to shim the needles.
Hooligan
Quote from: jwh on June 28, 2013, 12:35:38 PM
do the uni pod filters require any re-jetting or are they a straight replacement for airbox and filter?
If you are only changing the air box for UNI pods you may not need to rejet. Your exhaust is still restrictive so standard jetting should work. You will enjoy changing your pilot jets to #40, idle will be easier, less lean.
Quote from: jwh on June 28, 2013, 12:35:38 PM
do the uni pod filters require any re-jetting or are they a straight replacement for airbox and filter?
You can probably get away without re-jetting, but you'll have better performance if you shim the needles (or move the clip down), replace the idle jets with #40, and replace the mainjets with 115s (probably).
Each engine responds slightly differently to changes and you really should do plug chops or use an EGA to determine jettting.
Arnie
Dirt bikes I have encountered almost all used oil covered foam filters. You would not believe what these look like after a weekend out in the desert. If these filters were letting dirt in to the engine they would have failed a long time ago. Use a good foam filter oil not engine oil.
Kurt
I personally am totally anti k&n. They do flow massive amounts of air but they also flow massive amounts of really fine dust. I roached my built atv motor. I had three filters so I could change them out easily. So no it wasn't due to lack of filter maintenance. Anyway after it roached the motor I ran my finger inside the intake. And you couldfeel all the really fine grit. I have 2 sets of k&n filter pods and a k&n replacement for the stock air box $10 +shipping for each if anyone wants them. The 2 fj's I have now came with them
Only minor things to add to the discussion:
Some oiled contton filters are more than one layer. Couldn't tell you who makes them, but was researching this very subject a few days ago for a different project and that came up. Not sure that it actually matters, though.
You can also get dry foam filters, at least for some automotive applications.
The other standard "race" filter is no filter at all. I wouldn't consider going that route for anything, ever, myself. It in theory is the least restrictive, but it also allows more grit to be ingested by the motor and eventually you'll lose the valve seal at the seat, as well as adding wear on the rings. It's not that you won't get that efect anyhow if you've filled up the tank in something other than laboratory cleanliness, but there's no reason to encourage wear to those areas.
If the argument is between paper, cotton, and foam, I think OEM's are going to tend to use paper because it becomes a replaceable service part that costs less than the other alternatives. This means that not only will the OEM have less trouble with their dealers making mistakes like over/under oiling a filter, but it'll cost less and take less time to do a swap to a known good condition (new), and that's going to cut down on warranty claim problems.
In my own experience, I've run K&N and open bellmouths at the racetrack with no appreciable difference in performance. I personally put oiled foam (UNI) on my cars/bikes now because they give good filtration results and flow as much as anything else, while costing less in the long run than the other options. I've seen both K&N and UNI filters fall apart over time though, so I don't consider any of them to last forever despite advertising claims or guarantees to the contrary. Sure, I could in theory send my old broken K&N's in for replacement, but then what do you use in the meantime, nevermind the time/bother involved with sending them back. UNI's seem to hit the performance/cost sweet spot the best for me.
Like oil, the condition of what you're using matters more than what type it actually is, and it has to be used properly (the right amount and type of oil in a filter for example).