The best type air intake? REVIEW of the 3 types

[wildbill84]

I am about to buy a new air intake and was wondering which style is more free flowing.
The K&N styled ones,
Or The UNI style?

I ordered a 115 main jet to experiment with a couple of weeks ago and was wondering; is it common practice to upgrade from a 108 jet, to a 115 when installing a hi-flow intake, yet keeping exhaust stock?
or should I buy a 120

Thanks, Justin

[Aerostudent]

I bought an MRP filter which is similar to the uni style (you can find it at oregonvintage.com) and I am running stock main (108) with the 38 low speed. I have a stock exhaust too, so it should be a similar setup on yours. I also think I will try the stock 35 low speed jet and see what that does, as I think the 38 is just a touch too rich. If I had it to do over again, I would order both the 115 and the 120, you're looking at 3 more dollars for what could save you a few hours of frustration and another order.
Check my thread in the 125+ section titled "tuning questions and 'blog' (updated)" there is a bit in there about jetting and my experiences with my air intake. Also look into just gutting the stock intake. Someone posted that they did that and needed a 120 main and got significant power boost from it. Just some thoughts.

Aero

[wildbill84]

Thanks for the reply Aero.

I just got back from AutoZone looking through their selection of HP air filters and the only filter they had that would even close to what I'm looking for was a valve breather and the opening was 2 5/8-2 5/16 a little big for what I need, but it's autozone, not scooterzone.

I'm going right now to check out your post. thanks

[Aerostudent]

Just a thought (one that I wish I could try), but you might look into getting a filter that fits the stock intake manifold and simply swap out the airbox itself. The box side of the manifold is about 3" so a HP car filter would probably fit, and be PLENTY free flowing for a scooter. Just a thought, One I might try when I get money...

Aero

[wildbill84]

I found this info on UNI type filters


Uni Filter air filters are unsurpassed in airflow and are the most cost effective way to increase horsepower and torque. When your engine breathes better it is more responsive and will produce more power. Installing a Uni Filter air filter will protect your engine and help to keep carbs clean by stopping more dirt. Installation is easy - and you can immediately expect increased overall performance over OEM air filters. Uni's revolutionary two-stage design not only flows more air but comes apart for easy cleaning. Simply remove your existing filter, toss it, and drop in a Uni Filter.
Uni High Performance Air Filters Facts

Open cell industrial grade filter foam represents the latest advance in air filtration technology. This section describes how and why it works so well when compared to the other three types also in common use. An optimum air filtering system is very inexpensive insurance against untimely replacement of rings, valves, bearings, and fouled spark plugs. These items represent very significant maintenance costs. Additional benefits are provided by higher performance, better gas mileage, and lower emission products.

With an engine operating at the optimum air-fuel ratio of 15 or 16 to 1 (air volume to gasoline vapor volume), it normally means that 10,000 to 15,000 'gallons' of air are sucked into the cylinders for every gallon of liquid gasoline in the tank. The exact volume of air, of course, depends on the engine displacement, RPM, and miles per gallon. For example, a 2800cc engine turning 2600 RPM at 55 MPH got 26 miles per gallon, and used 23,000 gallons of air per gallon of gasoline in the tank. You can imagine what 23,000 gallons of air and dust going into your engine every half hour would do if you had no air filtration at all.

REVIEW OF 3 TYPES OF FILTERS....... by UNI
Paper Filtration

Pleated paper elements are used by more vehicles than any other type for these reasons:

1. They are the least expensive for the manufacturer to install as original equipment from the factory.

2. For the largest percentage of operating conditions (street and highway driving) they perform well enough to satisfy the owner/driver at minimal acceptable levels.

3. The elements are dry, easy to handle, and convenient to replace.

4. Since they are 'throw away' items (cannot be cleaned for reuse), they represent a large and profitable part of the replacement market, while occupying our landfills.

Paper filters are a stacked matting of fibers creating a random weave approximately 1/2mm thick, and rely on the 'screening' effect to stop dirt particles. Airflow per square inch is so poor that the paper must be pleated using many feet of material to make a filter. All dirt or dust particles must be caught on the surface or not at all. Each time a particle is caught, it stops up a hole. From the moment you start your engine, you have a rapidly decreasing air flow rate. Paper also has two other big drawbacks for off-road use. Any moisture reaching the element causes the fibers to swell, reducing airflow even more. Another is the possibility of rupture. Paper is not a very strong material, especially where it is creased to form each pleat. Intake manifold backfires, or cleaning attempts with compressed air, usually rupture the paper leaving the filter ineffective.

Pleated Gauze or Fabric Filtration

This is another screen type that is only 1mm thick. If the dirt is not stopped on the surface, it is not stopped at all. These filters are sold on the pretense that they maintain an oil curtain for the air to pass through, thereby catching all dirt particles. It is impossible to maintain an oil curtain. The oil soaks the threads of the gauze or cloth, but does not span the openings; otherwise, the air could not get through. The dirt particles that do hit the threads have a good chance of being caught; the others simply go through. The reason the filter does not look dirty on the inside is because the dirt went into the engine. You can easily demonstrate this fact yourself by coating the inside of your housing or carb throat with a thin layer of grease to trap some of the dirt not caught by the filter or you can place a foam filter inside the gauze element to prove the same thing.

The one advantage that this type of element has over paper is greatly reduced airflow restriction; however, poor filtration efficiency is the price you pay. When dirt builds up, filtering action improves, but now the airflow is poor like paper elements.

Open Cell Filter Foam ,a.ka -UNI

The development of this special foam represented a major advancement in air filtration technology. Foam air filters now combine great airflow capability, huge dust holding capacity, and very high filtration efficiency for extremely small particles.

Fully reticulated (open pore) foam is a honeycomb of tiny, interlocking cells of uniform size, which create an impossible journey for dirt particles since there are no straight-through passageways. Each passageway (16 to 25mm long) is like hundreds of very small centrifugal/oil bath filters connected one to another. In this way, foam traps and holds the particles throughout the entire volume of foam. This is why they are referred to as 'full depth' filters in contrast to the paper or gauze elements, which are screens, or 'surface type' filters. The cell strands stop the dirt, while the oil film holds the dirt like fly paper until removed for cleaning.

[leo]

the good folks at bikers depot told me that the UNI type of filter must be oiled periodically in order for the bike to perform well.
is this true?

[Admin]

This is a pretty cool post and I may be preaching to the choir. Air/fuel intake must equal what can exhaust.

[wildbill84]

So this means I can't get ANY extra power by installing a hi-flow air filter & upjetting, Unless I spend a couple 100 on a new exhaust?

[earlwb]

I suggest using a K&N R-1070 air filter unit on a GY6 150cc engine. KNFilters.com

Not all of the K&N look alike filters are the same though.
From what some of the others have been stating on main jet sizes, when you put on a high flow air filter and you wind up with the same main jet size, that means that the air filter is not letting the air flow freely.

If you kept everything on the engine the same, and you change the air filter out, you should have to increase the main jet size some. How much depends on a number of things, but I would hazard a guess of going up to 114 or 115 main jet. In some cases if the exhaust is working pretty good, maybe a 120. But it depends on your circumstances.

[cpete1]

Wildbill
I have an 1100 Yamaha V-Star Bike. Couple of years ago I installed an air kit. (K&N air filters, new jets and a new exhaust system. What Dawg said is true. An engine is basically an air pump. There were several combinations of the above parts you could buy depending on the total upgrade you were doing. The V-Star had a very restrictive airbox to quiet noise. The stock mufflers also were restrictive. If you only changed the filters then you went to one jet but if you did exhaust also you went to an even richer jet. Without exxageration, one could expect a 20% power increase once things were tuned. It was like getting a new bike. So to get total benefit out of the filter, if you can swing getting an performance exhaust, do so. The trick is jetting and tuning everything to keep your "driveability". I'm still looking to find adaptable filter (probably K & N) and an exhaust for my new commuter 250.
One note, if you just install a low restriction filter such as a K&N, the engine could run leaner than it did with stock parts (they flow that much more air than stock). The spark plug will indicate whats going on after you drive some. Changing the jets and filter will give you some more power but upgrading your exhaust as well will give you more. Good luck with your efforts,
Later, Chris

[wildbill84]

This is the Air Filter I bought last night

Link didn't work, it's item# 290198239633 on EBAY
it's a K&N styled 48mm Chrome Power filter


I'll install it with the 115 main jet I already have and see if I see any more power, if not I'll just put it all back to stock till i can swing a new muffler.
Another member here reccomends Scooter Assassins, the seller of the K&N style intake I bought.

[earlwb]

I saw those before, but I don't know.

What we need is for someone to get several air filter units in and try them all out on a stock GY6 engine and see if they needed to change the jets or not.
Plus see if any power improvements were to be had.

In my case I gained 5mph simply pulling out the foam pre-filter in the air filter box on my 150cc engine and installing a 120 jet. The OEM air filter unit is fairly good and free flowing to start with.
I still have the stock exhaust which seems to be working Ok. I didn't really want the scooter to be loud.

[YellowScooter]

If it were me, I'd do both at the same time and only rejet the carburetor the once. The diffrence would be more noticable as well. An MRP 4stroke exhaust would put some bass in a scooters voice but it wouldn't be upsettingly loud.

[earlwb]

leo,
yes it is true, you have to use the special air filter oil on the foam air filters.
if you don't use the oil, there isn't any sense in having a foam filter on the engine at all.