Could this be the next "OIL"

[aviationfred]

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

[ribbert]

Just don't forget to oil your paper media filter, like the one in this old truck   It even tells you the oil level...

I think you'll find that's the "4th" kind, an oil bath filter.

[ribbert]

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

[ribbert]

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.

[Dads_FJ]

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. 

[rktmanfj]

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.

[jwh]

do the uni pod filters require any re-jetting or are they a straight replacement for airbox and filter?

[FJ_Hooligan]

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

[FJmonkey]

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.

[Arnie]

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

[yamaha fj rider]

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   

[giantkiller]

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

[andyb]

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).