Unofficial Royal Enfield Community Forum
Royal Enfield Motorcycles => Bullet with the UCE engine => Topic started by: ryanof on July 07, 2011, 09:53:05 pm
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Hope this is not a dumb question.
What is the purpose of the black plastic that goes over the air filter
inside the air box?
Is it really needed? Has anyone run without it?
Thanks for your time.
Ryan
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Running change here in Ca. 2011.
The hinge on the metal air filter box can pass thru fine dust and water thru the gaps in the hinge halves.
Our first bikes had no plastic cover for the first 6 months. Only issue would be a small amount of water laying in the bottom of the airbox after riding in the rain.
After install, it MIGHT have a slightly quieter intake honk but no one has reported any negative effects.
Black C5's still seem to be the fastest.
;)
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Hope this is not a dumb question.
What is the purpose of the black plastic that goes over the air filter
inside the air box?
Is it really needed? Has anyone run without it?
Thanks for your time.
Ryan
When the lock on your airbox 'splodes, it keeps the metal bits from getting sucked into your engine....
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I don't know which bike you have but on my G5 under the outer sheet metal cover is a plastic cover or lid for the airbox. It is held on with several screws and it uses a rubber seal to prevent air from getting inside the plastic air box.
With the plastic cover removed I see in the air box the metal disk that seals and restrains the actual air filter. This disk not only retains the actual air filter but it forces the dirty air to pass thru the filter element before it can get into the engine.
Removing this metal disk allows the air filter to be removed.
Once done, I can see a hole in the back wall of the airbox and this hole is what allows the air to flow into the box.
This results in air entering the box on the back side and flowing into the inside of the air filter. After passing thru the filter the air then flows towards the front of the air box and into the rubber tube that connects the air box with the fuel injector body.
If the engine is run with this plastic air box cover removed, unfiltered air will flow directly into the rubber tube and then into the engine.
Allowing unfiltered air directly into the engine will allow the dust in the air to rapidly destroy the piston rings and the cylinder bore.
Running their engines without air filters back in the old days is the primary reason they seldom got over 2000 miles on their engines before they had to rebuild them by re-boring the cylinder and replacing the piston and rings.
If your air filter system is anything like mine I would never suggest that you run your engine without that cover in place.
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When the lock on your airbox 'splodes, it keeps the metal bits from getting sucked into your engine....
Well sure, that too.
I should clarify. I was talking about the plastic shroud update to the C5's.
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It is there as a low $ retrofit for leaky airboxes that allowed unfiltered air to enter the engine through gaps and such on the airbox. The otherway people were repairing this flaw was with a wrap of tape around the seam and hinge area of the box.
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Thanks for all your responses. My air box seems to be tight enough but I will keep the plastic shroud just in case.
I have a B5 and I hope there won't be any 'sploding of the lock any time soon.
Has anyone tried the Corvair air filter on the UCE engine? I remember someone saying if fits right in. There is a K&N for that year Corvair.
http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_x_17400403-P_x_x?cm_mmc=CSE-_-Google-_-VALUE3-_-VALUE4&ci_src=14110944&ci_sku=17400403
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In these posts I've noticed that there are those who don't recommend K&R filters. Someone please assist this gentleman. Me too, I wanna know.
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Hmm, I'm pretty happy with the K&N filter in my C5. It seems to let more air into the system. The OEM felt starved at times.
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There is a BMW filter that fits the C5 and G5, ( the number slips my mind, I've got to find it), but I don't know about the B5.
The K&N filters are great. I've used them in a lot of cars and bikes. They've always performed as advertised.
Bare
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It is there as a low $ retrofit for leaky airboxes that allowed unfiltered air to enter the engine through gaps and such on the airbox. The otherway people were repairing this flaw was with a wrap of tape around the seam and hinge area of the box.
For the C5 in the states, this retrofit is available free from your dealer. It is now standard equipment on the C5. If you run without it 1) if the hinge, hinge springs, or lock break those metal bits can get sucked into the engine and 2) dust can and will easily be sucked into the intake unfiltered through the gaps in the hinge. Talk to your dealer, get the free retrofit. Tape works too but it's ugly.
K&N filters: There are several that will fill. They flow better but simply do not filter as well as a standard, good quality paper filter. K&N always claims more flow, never better filtration. I've seen a few oil analysis reports from people running them on different bikes. Silica levels in the oil were high, indicating that dust is getting through the filter, down the cylinder, past the rings and into the oil. All that said, there are lots of people who've been running them for many years/miles on various things that are still running so anecdotal evidence seems to suggest they can't be too terrible. The reason they are popular off road is not because they filter better but because the oiled cotton gauze won't collapse like paper if it gets wet.
Corvair filter: I used a paper one and it worked just fine. I'm sure the K&N would fit too but I don't think you'd be able to use the Corvair filter and the C5 air box tetrofit, the filter's just too big.
http://www.enfieldmotorcycles.com/forum/index.php?action=gallery;sa=view;id=3328
http://www.enfieldmotorcycles.com/forum/index.php/topic,10706.0/all.html
Scott
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In these posts I've noticed that there are those who don't recommend K&R filters. Someone please assist this gentleman. Me too, I wanna know.
K&N filters have larger pores in the filtering media than paper filters. Larger pores pass larger volumes of air and larger particles of dirt or dust.
Only the end user can determine if the operating environment is compatible with paper, oiled cloth or oiled foam filters.
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You guys ever see bikes with just open snorkels? Some do have screens across them.. what are they called?
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Venturi with rock catcher attached?
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These are called velosity stacks. The idea is for the shape of the funnel to get a smooth, lminar flow of air going into the carburetor.
The irony is that A) putting the screen right on top disrupts the flow so much it negates any advantage of the stack and B) it doesn't filter out anything bigger than a medium sized bug so the engine is going to wear out fast. Even bolting a cone type air filter right to the stack isn't so great. The stacks really need to be run open to the air to work properly.
The proper way to do it is build a large air chamber around the stack and place a filter on the chamber. If you really want to go whole hog you can provide a positive pressure to the chamber. Lots of sport bikes have this exact setup. Throttle bodies connect to a large ari box, there are stacks inside the box, there's a filter on top of the box, and the lid to the filter is connected to ducts that face forward on the bike and channel air in to create positive pressure.
Scott
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Ya thats 'em. Makes sense. I always wondered why people trusted those things, I guess they are ok with a bit of wear!
[ok since I've officially put this off topic..]
I thought about creating a positive pressure situation on my air box by wrapping a 1/2 circle around the back of the filter and then I was thinking that the air would sort of be forced into the back of the filter. I'm probably not describing this well...
(http://farm6.static.flickr.com/5028/5888405186_c704fa4734.jpg)
So like in this pic, on the back side, put some sort of cover that would direct more air into the filter. It could attach to the two metal sides and have a snorkel/venturi-type doohicky on the top and bottom to catch and force air into the element as I rode.
I just whipped this up in photoshop..
(http://farm7.static.flickr.com/6015/5932041854_db9beb7532.jpg)
Would it work?
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Your idea might work and it might not.
An old engineering slogan says, "Common sense does not make for good engineering."
Air doesn't always behave like common sense would think it would.
Increasing velocity for instance reduces pressure so directing some fast moving air past the outside of the filter could actually reduce its ability to suck fresh air into it.
Without knowing exactly how much air was being sucked thru the filter you really don't know how large the accumulator would have to be to keep it from restricting the airflow at the rear.
It basically boils down to things that look like they would improve things (like airflow) often have the opposite effect. That's why big companies spend millions on testing ideas before they are used or rejected.
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+1. Just leave it ;)
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As Arizoni sez, You can't for more air though the filter. The best place for a filter to be is in a big box that supplies the volume of air that the filter and engine require without forcing the issue. If you try to force more in,as Arizoni sez, it just dams the flow. I'm not sure if the Enfield is the best setup as it comes, but without a flow meter and other measuring devices, dynos, etc, you'll never know.
I've seen one setup that used a K&N that is longer than the one you're showing on a much straighter tube running into the injector. It looks like a better setup, but I haven't seen dyno run data on it yet.
Bare