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· V4 CyclePath...
6,827 Posts
Discussion Starter · #1 ·
Dirty air is so damaging to an engine that Honda calculated the RC45
Joey Dunlop rode at the IOM TT could lose 10 bhp between the start and
finish of a race, just because it runs without air filters. On race
bikes, the overall power advantage given by removing the air filters
outweighs the power loss during the course of a race. But over the
longer distances covered by the new 6 engine rule in MotoGP the damage
done by unfiltered air may prove disastrous... Will we see air filters in

Quote Tuner Tony Scott

"Valves and their seats suffer badly from dust. The dirt particles
cause little pit-marks on the valve surfaces. to cure this I have to
machine the valve seat, polish the valve and then lightly lap them

Quote MCN
Modern ram-air intake systems can make things worse. They direct dirty
air towards the throttles from the scoops in the nose of the bike,
rather than from under the seat where there's less flying dust. This
is why bike manufacturers fit air filters, to reduce damage.

Filters generally consist of a large surface area of material folded
to fit the smallest space. The bigger the surface area, the less the
resistance to airflow.

Space restrictions on motor cycles mean there's a limit as to how big it can
be. It's possible that a speeding 8OOcc machine will pass more than 200 cubic feet
of air through the filter every minute.

Filters should be changed regularly. Few can be effectively cleaned as
it is not possible to remove all the dirt particles lodged deep in the
mesh. If a paper element is badly clogged it can sap 8bhp from a 600
for cause it to run rich by reducing the amount of air getting into
the engine. This will increase fuel consumption, so delaying
replacement is not cost-effective. According to Tony Scott, different
fllters can improve a bike's power. "Changing to less restrictive
fllter, and mapping, will gain about 2bhp on a 600."

The more efficient the filter at blocking airborne particles, the more
it will slow down the airflow and reduce engine power. High
performance fabric type filters are less restrictive than paper
filters and offer more power, but will allow more dirt into the
engine. K&N's tests with extremely fine dust show they are best at
filtering this material, but some say it is an unrealistic test, as
that dust does little harm. K&Ns should be lightly oiled before use,
to help trap harmful dust.

Quote John Rowland
"A K&N filter is not as efficient as a paper filter, but it will trap
particles sized 25 microns or more, which are the real nasties. The
dust sinks into the oil and will not be drawn loose again. A paper
filter may stop dust of down to 15 microns. Anything of five microns
or less will not be harmful to the engine;"

I don't know about you but all this talk about dirty air getting into our prized
engines makes me want to go out clean my homemade K&N...


· Registered
2,606 Posts
Good one Larry.
All I know is that Ten Kate has always run OE filters (minus the mesh wrap) on their WSBK machines despite being sponsored by BMC. Just like HRC was still running Elf race fuel in their NSR500 despite being sponsored by Repsol.
A couple of years ago they experimented with BMC filters at Monza ostensibly to see if the "freer flowing" filter gave them an edge over OE on that very fast track but really to keep the Italian sponsor from mumbling because news of their "lack of commitment" had leaked out. The result: no improvement over OE.
If OE is good enough for Ten Kate it's good enough for me.

· Is that Duke Red Enough?
308 Posts
This thread appears to be less about MotoGP air-filters and more about excuses to post yet more pictures of Mr...

I can't even bring myself to type it without my fingers gagging.:D

· Premium Member
3,881 Posts
it's bad news(2 made for tv movies from the guys who made the young ones)

believe this quote is from them

I could play Stairway to Heaven note for note when I was 12 years old.
Jimmy Page didn't actually write it until he was 22.
I think that says quite a lot.

the album had some great guitar work by brian may(yes-thats him playing!)

YouTube - Bad News - Bohemian Rhapsody

· Is that Duke Red Enough?
308 Posts

After all this time!

Someone GETS IT!

Thank you Simon.

· Currently: Moderating
12,714 Posts
Yes, explain that to Mrgrn!!! :banghead
And while you're at it, please explain how to make good carbon.:banghead

Happy to see everyone hijacking the Uncle Fester's thread for a change.:rockon Only one post about the topic was made. Well done guys!
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