A friend of mine who also posts on Forumosa has a KTR. After trying his bike, I decided to get one too. We’re debating the value of a performance air filter. The ones we’re thinking about usually come in a cone shape and they are much smaller than the original air filter housing. Here are my questions.
1-Does it really improve performance?
2- I was told the bike would be louder. True?
3- There are two hoses plugged into the stock air filter housing at the moment. What would I do with them if I removed the air filter housing and replaced it with a performance air filter? Just block them off?
4- Would this require extensive tuning of the carb? I’m thinking about the air screw and idle screw on the carb. Will I have to mock with that after I replace the air filter?
5-Any recommendations about a specific air filter or should I just stick with the stock one?
6- I heard these performance air filters can cause problems on rainy days. True?
If you’re experienced with this topic, I’d be thankful for your thoughts.
if the center inlet is a bellmouthed “velocity stack” then maybe. and that is a huge maybe. you are more likely to get an unknown quality filter that is prone to water ingestion (if run low) and that makes a lot more induction noise. unless you are getting something where you would know the quality, such as an itg it’s a total crapshoot that what you are getting is any good.
those hoses are likely vacuum hoses for vacuum-run accessories. you need to re-route them into whatever intake tube you use if you convert to the cone-on-a-stick setup.
for what it’s worth, racecars that run filters typically run cone filters, but do so mostly out of packaging ease. a panel filter will typically flow better, and incorporating a panel filter into the plenum is a recurring theme in race and high-performance intake designs (for setups running itbs @ or near the head inlet).
Its all about reducing vacuum within the air intake. A so called ‘performance’ filter is basically a filter with a larger surface area which eases the flow of air. The less resistance to induction, the more power. This is the same reason why direct injection is better than choking the air with a choke or throttle butterfly. If you look at some modern engines such as An Audi with Fuel Stratified Injection (FSI), the air inlet is not restricted. This reduces engine lag considerably and the stoichiometric mixture can be increased up to and over 40:1, which not only improves burn and results in a cleaner exhaust, but also improves power output.
On an older engine design a ‘performance filter’ will help improve engine response and will not cause as much lag as a compact paper filter.
It really depends how much of a restriction the original air filter is. If there isn’t much of a pressure difference across the original, then you won’t gain anything by replacing it. Be aware that many aftermarket filters don’t really live up to the name. In other words, they don’t really filter much. Taiwan is very dusty so you want good filtration if you want your cylinder bore / rings to last.
Next you have the issue of smooth airflow. As mabagal mentioned, the stock air tube between carb and air box is cleverly designed to smooth the air flow and maintain velocity. Velocity at low rpm is essential to accurate fuel metering. If you fit a cone type filter straight onto the carb you can lose that velocity and make the bike a pig in traffic, even if you can properly readjust the mixture, something far beyond most local mechanics.
The hoses in the airbox will be an engine breather for recirculating oil mist into the intake. You can either reroute that into the new filter or fit a catch-can to trap the oil mist. Another may be the exhaust gas recirculation system which takes exhaust gas from the exhaust port and passes it back to the airbox. That one needs to rerouted, or the system blanked off completely. If you do that, you need to readjust the low-speed fueling.
There may also be an idle circuit air bypass that allows the carb to draw air from upstream of the filter. Not sure if you have one or not. That would need to be open to atmosphere.
Simply put, an aftermarket filter is probably only worthwhile if you are doing a lot of mods to improve breathing, like porting and a cam, plus a larger carb. Otherwise it’s most likely to cost you driveability and net you no noticeable power.
That’s more info than I was hoping for. In a good way and in a bad way… Good because it’s lots of info… Bad because dealing with the hoses looks a bit complicated… I think I will try it and see what happens. If I’m not happy with it, I’ll be 600NT in the hole and I’ll just reinstall the stock air filter housing. Thank you!
[quote=“Tinman”]Make sure to let me know how that goes. Got the fat tire installed yet?
T.[/quote]
I will. The shop has the wheel but the tire is out of stock and I don’t like the other ones they have. They ordered one for me yesterday, supposed to be in tomorrow. :discodance:
be careful on what type or brand name of filter u are getting. steer away from the local made ones and go imported.
for two wheelers we stick with K&N directly from usa (watch out for knock offs). shop owner notice a big difference on engine life. kids got tired of changing cylinders/pistons due to poor filteration. now they are willing to fork out more cash for a quality filter.
if that area is prone to water then u need to build a shroud. if u don’t want to go through all that hassle then try see if the filter company has a direct replacement for factory airbox.
If you care for my two cents, then I wouldn’t bother. Unless the engine is already a performance engine and the setup is correct, then a horse power extra or two isn’t going to really be noticed. I would also wonder what your style of driving is. If its on public roads, then again, I would tend to forget about it for all the difference it could make. You can probably squeeze out as much power by cleaning your spark plugs, replacing any old leads, and giving the car a good service. If you need to get anywhere faster than by replacing the air filter, then just leave thirty seconds earlier.
I will add that you need not convert to removing the air intake pipes to use a “performance filter”. Some filters are produced which just fit in place of the existing basic common paper filter element. K&N do these too.
I will add that you need not convert to removing the air intake pipes to use a “performance filter”. Some filters are produced which just fit in place of the existing basic common paper filter element. K&N do these too.
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That sounds like a much, much easier idea! :eh: I’m very happy to have started this topic. Very helpful replies. Thank you people.
if/when you do install the k&n note that it is a lifetime device but does need to be periodically “oil charged” using the oil they give you. not too much - just follow the directions on how much to mist. during each “oil change”, they need to be cleaned with soap and water of the old oil and then fully dried before applying the mist of the new oil.
I guess you didn’t read the post above yours…you would be better off saying
“Maybe it will increase performance and it will probably make the bike louder”… [/quote]
No, seriously, on shyte little singles, you can’t go wrong, the air box and all it’s hoses are nice cool ways to be happy and environmental and whatnot. However on bigger bikes (especially multi-carb)you don’t want to mess about as there are some fancy tolerances etc.
I guess you didn’t read the post above yours…you would be better off saying
“Maybe it will increase performance and it will probably make the bike louder”… [/quote]
No, seriously, on shyte little singles, you can’t go wrong, the air box and all it’s hoses are nice cool ways to be happy and environmental and whatnot. However on bigger bikes (especially multi-carb)you don’t want to mess about as there are some fancy tolerances etc.[/quote]
No, you can and will go wrong if you don’t deal with the EGR system or engine breathers properly. You can cause all kinds of lean running conditions and on modern bikes, already jetted very lean to start with, you can easily overheat and burn a valve. Since modern bikes are jetted so lean from the factory, if the original were at all restrictive, which I don’t believe it is, you’d be running very lean all through the load range and that would reduce power rather than increase it.
As mentioned several times, a lot of these cone ‘filters’ are next to useless, stopping only the largest particles but letting fine dust through to destroy engine components. When we are talking of small single cylinder engines the gains to be had from a filter aren’t even measurable, so I have to ask… why bother? The OP asked if there is a performance benefit from running a cone filter. I can tell you unreservedly that unless every other area of the system is maxed out for volumetric efficiency the answer is NO.
High-flow is okay and worthwhile IF the filter is effective in removing dust from the air, and IF the filter is actually a bottleneck in the system.
Look at this way. The OP was asking about a motorcycle application.
Single-cylinder. The space under the seat of a motorcycle gets a little larger with the size of the bike, but a 125cc Sanyang has an airbox about 50% of the capacity of my 955cc Triumph. The 125’s panel filter is about 50% the area of the Triumph’s, despite the Triumph having over 7 times more cylinder volume. Can you see that the 125cc bike already has a lot more filter area per cc of cylinder volume than the 955? In this case, I’d get a lot more benefit from changing the filter to a performance flat panel or independent pods than the Sanyang would.
Car application. My WRX has the same panel filter as the base 2.5i model. My WRX makes 230hp against 170hp for the 2.5i, meaning it ingests a lot more air. In my car the panel is just small enough that you can measure the pressure drop across it. In the the 2.5i the panel is generously sized for the application. A K&N in the WRX will allow more flow of both air and dust. In the 2.5i it will just pass more dust.
Your CLK will probably flow more air with the K&N panel filter. As stated before, a K&N filter is washable oiled filter. Dry, they let all sorts of crap through. Freshly washed and oiled they do a decent job of filtration. Not as effective as the stock paper filter, but not bad.
How your engine management responds to the extra air flow is another matter. In some cars, like my WRX, the ECU cannot just adapt to an increase in air flow like that for given throttle position and engine speed. It will run dangerously lean. I don’t know about the CLK, but you should check into it before replacing the filter.
I shopped for something that would fit my air filter housing this weekend and no luck. The only thing I found was a a large pad made by RPM. You have to cut it to fit yourself. It looked very light and cheap. After reading about the chances of wearing out the engine faster, running lean etc. And after thinking about the way I ride the bike… I decided that I don’t need to chance it. A bit more performance isn’t worth risking damaging the bike. It’s just a daily ride for me. I need it to last more than I need it to reach 100km/hr half a second faster. Thanks for all you advice, it helped me make what I think is the best decision.
