Suzuki GSX650F Forum - www.GSX650F.biz

I've heard that a K&N filter can help the performance of the bike, but I'm worried about some of the things I've heard like reducing engine durability. Are these just rumors or solid facts? Also, who has installed one of these, is it easy to do?

I've got one and see no problem with it.
Combined with a slip-on it's a great mod that helps the engine breathe better. The more air you can get through the more power you get.

A lot pf people will tell you to stay away because it lets too much crap through and will reduce the life of your engine.
This has "never been proven" and basicaly is all just campfire tales. That argument is nothing more than a theory.
The theory is that it's filtration allows more air to flow through so it will let more particles through into the engine and damage it.

I've done over 18000km with a K&N and my air box is as clean as the day I bought the bike. The truth is no one has ever been able to prove that
a K&N filter does reduce the lifespan of an engine. If they say "But my mate this and that" they are full of shit. If they refer to a web link as
proof by all means check it out. You may see some backyard tests of how clean or dirty in comparison an air filter is but "Nothing that has reduced the engines life".
You will do more damage and reduce the life of your engine by riding hard than a K&N will ever cause.

When I looked into getting one I found a comment that I thought was more truthful than anything else. It was;
For an engine to have it's full lifespan it may only need an air filter that can provide an 85% filtration rate. Your stock air filter may provide
95% filtration and a K&N may provide 93%. So the K&N air filter is still performing well above the minimal requirements for your engine.That is Fact.

Installation is easy. Take your tank off, undo the 4 screws to the filter box, remove the cover and O-ring around the groove for the lid (not required with K&N as it's all 1 piece) , swap the filter and put it all back again. Takes 10 minutes.

thanks so much, you've really helped enlighten me on this

I'm definitely gonna get one.

Forgot to mention that after installing a slip-on and putting in a K&N your bike will run lean due to the extra air intake.
You will need to have your FI adjusted to compensate for the lack of fuel. My Suzuki dealer did my FI when I was in for a service. Only takes 15 minutes to do.

Ideally the best thing is to install a power commander down the track as it gives the best possible Air/Fuel ratio mix for those particular mods.
I installed the PC-V a few months later.

well you should not have to do anything to the bike for a air filter or a slip on
The bike is fuel injected and should SELF adjust the fuel mix all by its self O2 sensor will do this for you.
Becides what is the dealer going to adjust .... The computer not

OK here we go, time for another opinion
Hold one up to the light and if that makes you happy...Party On Wayne!
You don't get something for nothing, for a K&N to breathe better than an OEM filter it has to filter less particulates than an OEM filter, it's like the law of physics...you can't get around it!
Personally I would never use one in an off-road application, but it's my honest opinion that for street use you shouldn't have any problems.

(yes this is my K&N filter, I just took the photo for this thread)

(CCPDYMMV)

OK, GSXFun requested I "chime in" on my K&N experience .

I put in new Iridium plugs last night with the K&N air filter and I can conservatively state for sure it felt like at least a 6 to 8 HP gain on today's freeway test run, but I think more than that but won't claim it. At one point it felt like it wanted to power wheelie in 3rd gear...no clutch tricks just wanted to power up. Improved air flow along with the plug efficiency gain over the stock plugs has made me very happy!

With happiness is always a little real world dashed on. The K&N filter rubber mold is a little thicker than the stock air filter. It took quite a bit of negotiating to fit it in the lower half of the air filter case without stripping down the bike. Once it was in place, it also took a bit of might to get the stock (short) air fliter case screws back in...thank goodness for long screw drivers with large handles . Before I clean the air filter next time around I will invest is 4 slightly longer replacement screws.

As for the plugs, I think it would have been easier to pull the motor to change out the plugs .

Couple of things here...first the K&N does increase airflow somewhat by reducing filtering efficiency and particle size. It is the old trade-off of particle size vs flow. The same thing occurs with oil filters, but I digress. Anyway K&Ns also use an oil coating to help with the filtering. I am not familiar with the OEM filter on the "F" yet, to know if it is oiled, but I suspect that any new bike with FI has a conventional paper filter (no oil). The "durability" issue with K&N filters has to do with particle size. Any loss if engine durability would have to quantified over the long haul, either a lot of miles or on dedicated dyno engines. Bottom line if you live in an environment that is the least bit dusty I would avoid the K&N. If not you are probably OK, but personally I would be hesitant to buy a higher mileage vehicle that had a K&N all of its life. The small HP gain is probably more like 1-2 HP and is not worth it IMO. The other problematic issue is an "oiled" filter. A small but significant amount of oil is picked up by the incoming air and can affect the O2 sensor and the feedback for the FI system as well as contaminate the catalyst (catalyst poisoning and deactivation are directly related to oil consumption passed out the exhaust - the phosphorous in the oil is what does it).

Ever heard of a yoshi box? Guess not. It adjusts the fuel map in your 'computer' more commonly and correctly called an ECU or even ECM. So yes, that's exactly what the dealer is going to adjust. As for the ECU being able to SELF adjust, yes it can, but only within the given ranges stated in its fuel map. The stock fuel map does not cater for an increased air intake. A slip-on and K&N will put the required ratio beyond the stock map ranges, so yes adjustments are needed.

GSXCherrios - did you remove the stock O-ring first? Mine dropped straight in, fit perfectly and the lid went back on like normal.

Increasing air flow does not necessarily decrease filtering performance. A combination of increasing the filter's surface area and using superior materials and better design could lead to increases in air flow, and possibly even improve filtering at the same time. The increase in surface area need not be visible to the naked eye, remember we are talking about tiny particles here. In the same way that a radiator exposes a massive surface area of metal by using many small flat coils of tubing, a filter could expose a larger surface area of filtering material while still appearing to be the same size as a stock filter.

Whether this is all true in the case of K&N filters I have no idea, I just wanted to get involved in the discusion

Another thing to note is that from what I can tell, most people are selling their bikes with less than 20,000km on the clock. Do you really care if the filter reduces engine life from 80,000km to 60,000km ?

ok this is were you are wrong about the map on the bike.
Fuel injection system have whats called fuel trim (adjust fuel ALL the time) No mater what fi system you have it adjusts fuel. So now a air filter that allows air to go threw it and then in to the intake. This is done by vaccum ok so any air that goes threw the throttle body bore (with out a mass air flow sensor in front of it) is ok. changing the volume will not matter. The fi will adjust for it no- matter what as long as the fi system is working correcty. Now if you have a vacuum leak then you will have a problem becaues the computer will add fuel to max point and still not be able to achieve the correct air fuel mix witch will put on the fi light.
Now carbs are a differnt story they will need to be jetted

[quote="BikerBoy
GSXCherrios - did you remove the stock O-ring first? Mine dropped straight in, fit perfectly and the lid went back on like normal.[/quote]

Yes sir I did remove the o-ring, but maybe the OZ quality assurance guy wasn't sleeping like the USA counterpart. I mic'd the part to make sure, but then didn't care, cramed the damn thing in there and buttoned her up. The bike runs like a champ and I'll worry about the "fit" some other day.

All I can figure, since the filter is sitting well and in the grooves is I got a poorly manufactured part or another Suzuki year fit. Whatever, all in the name of aftermarket. Maybe K&N will read this thread and send me a new one.

I do recall some earlier filters not fitting correctly but K&N aparrantly fixed that. You may have been given one of the earlier filters.?
As long as it all seals, I would not be concerned with it.
Good to hear you are happy with it. My bike ran awesome after I put the K&N in too. Just don't forget to pick up a K&N recharge kit so you can clean it when req.
Cheers. BB

There are two basic types of modern FI systems. 1) Mass Air Flow 2) Speed Density
The mass-air-flow-type system has an air meter upstream from the throttle but usually downstream from the air cleaner. This type of system will "adjust" somewhat to changes in the airbox and / or air filter. The air meter actually measures air molecules so if the restriction in the induction system is reduced the air meter will continue to count molecules. In this case it should count more molecules, as long as you don't exceed the meters upper limit.
The second type system is known as "speed density" because it has no air meter and the relationship of fuel delivery to manifold pressure and rpm is based on a pre-mapped table. This table is carefully mapped on dyno and on-vehicle to insure correlation between actual and calculated airflow. When anything skews this pre-mapped relationship the amount of fuel delivery is also skewed. Changes to induction system, exhaust, cam timing and valve sizes will all impact this pre-mapped relationship.
Now both systems have "closed-loop control" which accomodates for errors such as vacuum leaks and dirty air filters. This closed loop control is the "fuel trim" that GSXRider speaks of. There is a limit to how much compensation that the closed-loop control can compensate for. These limits typically are in the range of 15 - 20%. This is OK if you have a well-centered system, but if you induce some "errors" by reducing the inlet restriction, reducing the exhaust restriction then you bias the system toward the "lean" limit. If you really change things you can significantly change the delivered air/fuel ratio. If you throw a vacuum leak or other variation on top of this you get the dreaded "check engine" light due to a fuel trim error (the system has been pushed beyond its tolerance for adjustment and correction).
I assume the GSX650F is a speed-density system (anybody seen a Mass air meter?).
I have no idea if the Yoshi box is a "remap" or more likely a box that gets between the ECU and the sensors and/or injectors to skew the pre-programmed fuel map.

What he said

The yoshi Adjuster box connects and communicates with your ECM
it adjusts fuel metering from -10% injector duration to +10% injector duration in increments of +/-5%