The Honda PCX / Forza / ADV150 / SH Forums

I'd like to chime in here with my opinion on air filters.

Every time I see filters being discussed on forums people throw around the word airflow and talk about increased air volume. What I rarely, if ever, see mentioned are velocity and pressure.

The reason that people are experiencing a loss in performance on the low end with a high flow drop-in or pod is due to a decrease in intake air pressure.

When you increase the volume of air coming in through the filter without increasing the engine's demand for air, your net result is increased air velocity and decreased intake air pressure.

Velocity is determined by the ratio of intake air volume to the cross-sectional area of your throttle body opening. If you allow more air than necessary past the filter you speed up the velocity through the throttle body at the cost of pressure. The pressure of the intake air is what helps it flow into the combustion chamber. Decreasing pressure is the opposite of what you want when looking to gain performance.

If you were to do nothing but change the filter to a high-flow and dyno the bike, you'd notice a decrease in torque from In the first 60-70% of the RPM range and a very minor increase in HP in the upper RPM range. Whether or not this trade off is worth it is up to you, but your torque loss will be greater than your HP gain.

I'm just some guy on the internet so, like any information you find there, take this analysis with a grain of salt. In my opinion the high flow filters are best left to the big bore kits with larger throttle bodies.

When I installed my pod, it did nothing but increase noise (no performance losses though).
Adding an open exhaust gave me a boost however..., but I had the pod on before the exhaust so not sure if it was the exhaust alone?

For what it's worth I installed a SIMOTA high-flow airfilter and junked the snorkel. (from Taiwan - cheaper but otherwise exactly the same as BMC / K&N etc).

As with every motor vehicle I have ever fitted a high-flow airfilter to (from inline 4's, twins, triples even cars and utes)... I notice absolutely zero difference whatsoever. Maybe an ant's whisker louder due to de-snorkeling but in the underground car park even an ant's fart will echo off the walls to some degree. Probably my imagination.

Seat of the pants-o-meter results are inconclusive to say the least but I reckon the snorkel removal is worth at least 0.05kg and that alone should recover some 0.0001kph with a tailwind.

Hey guys and girls,

I just went for a ride and can confirm the snorkel removal results in the most wonderful, deep note from the engine. Really nice, I highly recommend taking it out and trying for yourself (takes all of 1 minute to remove airbox cover, take out removable snorkel and refit cover).

I enjoy the deep bass resonating from the airbox cover now. It's not loud, just noticeable.

Ah, the old airbox tinkering trick. Never ceases to amaze me the difference it makes in engine note.

Agreed, sounds like motor instead of a sewing machine. i am aware that my K&N install may not increase performance at all, but it sounds great and I now have a cleanable cone filter that will last as long as my scoot.

This sounds and works sweet too.

http://www.knfilters.com/mobile/mProduc ... od=HA-1213
Here is an update on the K&N filter. They have one for 2013 pcx 150 now.

kramnala58 wrote:This sounds and works sweet too.

PCX Canister Breather 02.jpg

PCX Canister Breather 01.jpg

I love the sound of this one. How the PCX a is supposed to sound IMHO ..... Covers up the Ricky ticky noise. What gram rollers are you on. I love the 12gram with this air filters. Also is your adjustable.

I use a Simota air filter. It has larger filtering surface than the K&N.

MKE PCX wrote:I'd like to chime in here with my opinion on air filters.

Every time I see filters being discussed on forums people throw around the word airflow and talk about increased air volume. What I rarely, if ever, see mentioned are velocity and pressure.

The reason that people are experiencing a loss in performance on the low end with a high flow drop-in or pod is due to a decrease in intake air pressure.

When you increase the volume of air coming in through the filter without increasing the engine's demand for air, your net result is increased air velocity and decreased intake air pressure.

Velocity is determined by the ratio of intake air volume to the cross-sectional area of your throttle body opening. If you allow more air than necessary past the filter you speed up the velocity through the throttle body at the cost of pressure. The pressure of the intake air is what helps it flow into the combustion chamber. Decreasing pressure is the opposite of what you want when looking to gain performance.

If you were to do nothing but change the filter to a high-flow and dyno the bike, you'd notice a decrease in torque from In the first 60-70% of the RPM range and a very minor increase in HP in the upper RPM range. Whether or not this trade off is worth it is up to you, but your torque loss will be greater than your HP gain.

I'm just some guy on the internet so, like any information you find there, take this analysis with a grain of salt. In my opinion the high flow filters are best left to the big bore kits with larger throttle bodies.

Partially correct.
Flow speed and velocity, and pressure are equally important characteristics. Even more especially in a thumper single cylinder engine like the pcx or forza the flow is never smooth but a fluctuating so it works very differently than a continously flowing system.
An ideal filtering element should provide unlimited flow and flow regulation should be done elsewhere. In case e only changes the filter, but other elements of the intake are untouched then the only thing happens that you have reduced a possible bootle neck at the filtering element - as the flow is limited by the connecting pipe, diameter of the throttle and the throughput of the head intake channels and intake valve.

I helped out on a big air cleaner study some years back. It was for a small diesel, but still had some interesting findings. One was that the OE filter flowed better and cleaned better than K&N. They sacrifice fine filtering for flow as it turns out.

Just adding a higher flow air filter isn't likely to make a significant increase in power,
since the stock muffler canister still limits air flow through the engine. You might
gain another hp or two by installing a higher flow aftermarket canister as well.

In any event, the stock engine is already producing 13.6 hp from 9 cubic inches, so any
big power increases would require much more radical changes to the engine than
just increasing the air flow......and those kind of upgrades could put you near the
Forza price range at some point.....and possibly cause reliability problems and
frequent drive belt changes.

Every motorcycle that I have ever owned had Stage 1 engine performance mods
(in one case, a factory race kit); however, I decided to just leave the PCX motor
stock. For around town riding, that seems to be good enough for me.....but some
people really enjoy making more power from the little PCX motor just for the joy
of it, and that is OK, too. Whatever......

J.

maddiedog wrote:At least you'll never have to buy a paper filter.

Nice review and test Maddie. I just sold my old Vario125 and bought a new Vario150 because the PCX is ridiculously overpriced here. Vario150 share the same engine as PCX150 but much lighter and with only half the price.
I just want to share how you can reuse your OEM paper filter over and over again:
My Vario125 odometer was 40k+ km when I sold it. And I've never bought any air filter other than what came with the bike. I clean it in every oil change (between 4000-5000km, whenever I remember to change it)
The cleaning procedure is simple:
1. flush the dirty filter with CLEAN fresh gasoline from inside out. Never reuse the the gasoline. You'll need 1 liter of gasoline for a dirty filter. I just use squirt bottle to clean the pleated paper filter.
2. Immediately when the filter is still wet soaked with gasoline, shower it with hot water ( inside out). I use hot shower set to max. (85C). Keep showering until there's no oil left in the filter.
3. Dry it. Under the sun or just use the hair dryer.
4. Oil the paper with 10-15cc clean engine oil. I tried more than 15cc using 10W30, not good, the engine bog down. The best method to oil it evenly is to use vacuum cleaner behind the filter while you spray the oil using detail touch up airbrush gun.
5. reinstall the filter

I just installed the K&N in my 2017. Seems to be quicker. The engine noise is a bit more excessive. Any thoughts on what would cause that?

RuckinEMT wrote:I just installed the K&N in my 2017. Seems to be quicker. The engine noise is a bit more excessive. Any thoughts on what would cause that?

I noticed absolutely no difference in performance with my K&N filter.
And my aftermarket exhaust was already too loud to hear any change in induction noise over it.

BUT, take that resonator (everyone calls it the "outer snorkel"...) out of the airbox and hear that tractor turn!
The PCX has very noisy induction, and the stock setup does a marvellous job of quelling all that unwanted noise.

I'm not really surprised you can hear a difference with a stock muffler. But I doubt you'll hear a difference over the Yoshi.

chicaboo wrote:

RuckinEMT wrote:I just installed the K&N in my 2017. Seems to be quicker. The engine noise is a bit more excessive. Any thoughts on what would cause that?

I noticed absolutely no difference in performance with my K&N filter.
And my aftermarket exhaust was already too loud to hear any change in induction noise over it.

BUT, take that resonator (everyone calls it the "outer snorkel"...) out of the airbox and hear that tractor turn!
The PCX has very noisy induction, and the stock setup does a marvellous job of quelling all that unwanted noise.

I'm not really surprised you can hear a difference with a stock muffler. But I doubt you'll hear a difference over the Yoshi.

Perhaps its in my head? ha! Low speeds are definitely faster, not by much. I haven't had a chance to get it up full speed. I'm going to double check the filter to make sure it's installed properly.

Also, No Yosh yet. Hoping to figure out why the header pipe doesn't fit. The only thing I can think of is the redesign of the center stand. Ugh.

RuckinEMT wrote:

chicaboo wrote:

RuckinEMT wrote:I just installed the K&N in my 2017. Seems to be quicker. The engine noise is a bit more excessive. Any thoughts on what would cause that?

I noticed absolutely no difference in performance with my K&N filter.
And my aftermarket exhaust was already too loud to hear any change in induction noise over it.

BUT, take that resonator (everyone calls it the "outer snorkel"...) out of the airbox and hear that tractor turn!
The PCX has very noisy induction, and the stock setup does a marvellous job of quelling all that unwanted noise.

I'm not really surprised you can hear a difference with a stock muffler. But I doubt you'll hear a difference over the Yoshi.

Perhaps its in my head? ha! Low speeds are definitely faster, not by much. I haven't had a chance to get it up full speed. I'm going to double check the filter to make sure it's installed properly.

Also, No Yosh yet. Hoping to figure out why the header pipe doesn't fit. The only thing I can think of is the redesign of the center stand. Ugh.

If you look on the bottom left side of the crankcase near the oil screen bolt, does it say 149cc or 153cc?
Also, 125 and 150 PCX's don't have interchangeable exhausts. But I'm wondering about the 149cc EU spec...

It's the 153CC ESP version. Also, I know the exhausts are not interchangeable. When I spoke to the sales rep at Yosh, I made it very clear It was for a 2017 PCX 150

Figured it out... they sent me the non eSP header pipe. Hoping they can expedite one from Japan...

I didn't see any difference in my Corvette when I added it. GM specifically states that a KN filter voids warranty and that it can cause damage and poor performance. It was well known that the oil residue used in those filters can be drawn in and plate the mass air flow sensor wire on a car and give erroneous resistance measurements to the CPU hence resulting in poor performance and those style air filters can attract dirt and plug sooner hence more cleaning. I dunno how it will function on a bike and even if they have a MAF.. but Maddiedog did a very good real world test .