Why I don’t worry about the air filter

[670cc]

The Honda maintenance schedule for the NC recommends air filter replacement at 12,000 miles. I do mine at 24,000 miles, no sooner. The NC air filter area looks very large, to me, compared to other vehicles. I compared an NC filter to a Dodge V6 3604cc engine’s air filter. The NC filter measures approximately 32 square inches, while the Dodge filter is about 48 square inches. The Dodge filter is about 1.5 times the size of the NC’s, while it’s engine displacement is over 5 times the size.

The white filter in the photo, next to the NC filter, is the Dodge filter with 24,000 miles on it.

One could argue I did not measure air flow characteristics, etc, in this comparison. This is just a visual comparison. I don’t change NC filters at 12,000 miles as I believe they are way oversize for the engine displacement.

 

[MZ5]

I, too, do not change Wiley's air filter at 12,000 miles. That assumes I'm using the Honda paper air filter, and that I'm using the bike for commuting and other on-road stuff (which is essentially all I use it for). I've observed the same as you re: visual loading, and I don't see it as necessary in any way.

 

[hulkss]

Air flow would be better compared by comparing the amount of fuel consumed as the air/fuel ratio in gas engines will be about the same. So if your NC gets double the gas mileage (uses half the fuel) of another vehicle it will consume half as much air.

 

[670cc]

Air flow would be better compared by comparing the amount of fuel consumed as the air/fuel ratio in gas engines will be about the same. So if your NC gets double the gas mileage (uses half the fuel) of another vehicle it will consume half as much air.

That’s a good point, but the air filter should ideally be sized for maximum demand airflow, not average or typical. So if the Dodge 3,604 cc engine can make up to 265 horsepower, and the NC could make about 50 hp, that might suggest roughly 5 times maximum air flow could be needed for the big engine, much like the displacement is also 5 times. Yet again, the visible physical difference in filter size is only 1.5.

 

[Lomunchi]

The real test of a filter is rarely used and isn't that complex. Pressure drop indicates when a filter has become loaded beyond what the manufacturer requires. A "good" furnace, for instance, will indicate when to replace the filter by the pressure drop across it, not time dependent. The pressure delta increases with increased loading.
Also note that size is a pretty simplistic comparison, though I think you stated that. A few steps better is surface area of the filter material. To do that you'd either need some detailed measurements and some fancy math, or to disassemble each, lay them flat and measure the surface area. Then you need to know the penetration resistance of the media involved at the particle sizes it will run into in it's environment. Simply put; smaller holes block out the larger particles. The manufacturer understands best the size of the particles that your engine can survive inhaling.

Bottom line, you can't judge visually or my measurement when a filter needs to be changed without the proper equipment. Go with the OEM recommendation and, yeah, over the life of the bike you may have replaced 4 more filters at $20 apiece but you'll make sure your bike isn't accumulating crap somewhere inside.

Disclosure: I work for a company that builds filter test equipment, particle counters and sizers and mask integrity testers. Some interesting (?) videos here: https://www.youtube.com/c/TSIIncShoreview/videos

 

[hulkss]

That’s a good point, but the air filter should ideally be sized for maximum demand airflow, not average or typical. So if the Dodge 3,604 cc engine can make up to 265 horsepower, and the NC could make about 50 hp, that might suggest roughly 5 times maximum air flow could be needed for the big engine, much like the displacement is also 5 times. Yet again, the visible physical difference in filter size is only 1.5.

Yes, they should be sized for peak flow, but you were writing about cleaning intervals. Dirt will accumulate based on the volume passed through the filter over time.

 

[Deleted member 1183]

A Friend of mine had the filter replaced on his Strom at around 14,000Kms. It was very dirty. I generally don't replace filters (like 670CC) until I have 30/35,000kms on the odo. In general they are not nearly as dirty as my Friends'. Why is this ? I have a theory. My friend rides most of the time with much larger throttle openings than me. He freely revs his bikes through the gearbox. By comparison I short shift most of the time. Surely he is inducting a lot more dirty air over a given mileage than I am ?

 

[670cc]

The real test of a filter is rarely used and isn't that complex. Pressure drop indicates when a filter has become loaded beyond what the manufacturer requires. A "good" furnace, for instance, will indicate when to replace the filter by the pressure drop across it, not time dependent. The pressure delta increases with increased loading.
Also note that size is a pretty simplistic comparison, though I think you stated that. A few steps better is surface area of the filter material. To do that you'd either need some detailed measurements and some fancy math, or to disassemble each, lay them flat and measure the surface area. Then you need to know the penetration resistance of the media involved at the particle sizes it will run into in it's environment. Simply put; smaller holes block out the larger particles. The manufacturer understands best the size of the particles that your engine can survive inhaling.

Bottom line, you can't judge visually or my measurement when a filter needs to be changed without the proper equipment. Go with the OEM recommendation and, yeah, over the life of the bike you may have replaced 4 more filters at $20 apiece but you'll make sure your bike isn't accumulating crap somewhere inside.

Disclosure: I work for a company that builds filter test equipment, particle counters and sizers and mask integrity testers. Some interesting (?) videos here: https://www.youtube.com/c/TSIIncShoreview/videos

Thanks for the detailed explanations. That all makes perfect sense, except the part about changing frequently to “make sure your bike isn't accumulating crap somewhere inside”. How does a filter that has trapped dirt over time allow crap to accumulate “somewhere inside”. Seems the more dirt a filter has trapped, the less anything goes through it, whether dirt or air. I’d think a dirty filter can’t allow more dirt to pass through to the engine, only cause performance to degrade. Or did you mean something else?

About the best price I find on 2012 OEM filters is near $40. Where do you buy them for $20?
17210-MGS-D30 ELEMENT, AIR CLEANER MSRP $47.56 OUR PRICE $39.00

 

[halfSpinDoctor]

I like changing all filters immediately when a vehicle is new to me: engine air cleaner (i.e. air filter), cabin air filter (on cars), oil, etc., then keep an eye on it from there.

 

[Lomunchi]

Thanks for the detailed explanations. That all makes perfect sense, except the part about changing frequently to “make sure your bike isn't accumulating crap somewhere inside”. How does a filter that has trapped dirt over time allow crap to accumulate “somewhere inside”. Seems the more dirt a filter has trapped, the less anything goes through it, whether dirt or air. I’d think a dirty filter can’t allow more dirt to pass through to the engine, only cause performance to degrade. Or did you mean something else?

About the best price I find on 2012 OEM filters is near $40. Where do you buy them for $20?
17210-MGS-D30 ELEMENT, AIR CLEANER MSRP $47.56 OUR PRICE $39.00

Point taken on the 'dirty filters work better than clean filters' point. I guess my point was more that the manufacturers know better what level and size of contaminant as well as what back pressure it's designed to overcome for their engine and the cost to do what they recommend is low. Honda doesn't make their primary money on filters so it's not like razors and razor blades.

 

[kpinvt]

I never changed the air filter on my departed 2014 with 27K miles on the clock. The bike consistently got 64+ MPG the whole time I owned it. The new owner was aware of this and not concerned.

Edit: I stopped using Fuelly years ago when my son Max started riding with me.

 

[wheel_of_steel]

I find that the NC has very uneven airflow through the filter. When I remove a dirty one, it looks like maybe 1/3rd of the filter media has been clogged, whilst the outer edges of the filter are clean.

The NC has compromised flow through the airbox. Whereas my car evenly uses its entire air filter.

I think the NC would be wearing out it's air filter a little more often due to that inefficient flow in exchange for the utility of the frunk.