Looking for better aircleaners for flatslide carbs
- Thread starter jseng1
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For my '73 750, I'd like to be able to run the stock air cleaner assembly, or at least stockish. We'd need bellows to connect JS carbs to the stock air cleaner plate, and we'd have to cut down the thickness of the perforated metal to match the dimension of that thinner K&N filter, that some one on here found, and that is of the same circumference as the stock one (so it fits under the stock air cleaner front plate).
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Not a new idea Jim or raw monkey rump image. After I saw dust inside manifold with well sealed air box k/n filter I hung in on wall and orders a few real Norton paper elements and switch after a couple of tire or chain replacements. The factory air box position and size will be hard to beat flow vs filter wise except for non factory fittings. I've seen the air split around engine then slap back together in explosive splash right behind carb throats where air box grill is. I shorten air boots now for easier and better fit but check em more after a hidden crack cause premature ring job.
http://www.ebay.com/sch/sis.html?_nkw=H ... 0213585591
http://www.ebay.com/sch/sis.html?_nkw=H ... 0213585591
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So JS sent air filters for testing. Here is the test setup. 34mm
Here are the air filters I tested at JS request. All were tested dry except the K&N"s which were pre oiled.
From left to right.
First -Open carb- no air filter --------------------------------------- 206.5 CFM
#1 dry unifilter -half taped up to simulate a short filter --------181.6 CFM
#2 dry unifilter - full length--------------------------------------------181.9 CFM
#3 Taiwan K&N copy -dry #150154-----------------------------------181.2 CFM
#4 Emgo K&N copy - dry #150035-------------------------------------178.3 CFM
#5 XS K&N copy -dry----------------------------------------------------195.2 CFM
#6 K&N dual filter -one side taped up-oiled------------------------163.7 CFM
#7 same as above with no tape---------------------------------------195.2 CFM
#8 stock paper filter -non baffled backplate------------------------204.5 CFM
Here are the air filters I tested at JS request. All were tested dry except the K&N"s which were pre oiled.
From left to right.
First -Open carb- no air filter --------------------------------------- 206.5 CFM
#1 dry unifilter -half taped up to simulate a short filter --------181.6 CFM
#2 dry unifilter - full length--------------------------------------------181.9 CFM
#3 Taiwan K&N copy -dry #150154-----------------------------------181.2 CFM
#4 Emgo K&N copy - dry #150035-------------------------------------178.3 CFM
#5 XS K&N copy -dry----------------------------------------------------195.2 CFM
#6 K&N dual filter -one side taped up-oiled------------------------163.7 CFM
#7 same as above with no tape---------------------------------------195.2 CFM
#8 stock paper filter -non baffled backplate------------------------204.5 CFM
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Here are some flow rates I tested previously for comparison.
FCR 35 with velocity stack-------------------------------228.3 CFM
FCR 35 with small CNW K&N -oiled----------------------206.6 CFM
Mikuni vm34 -open or velocity stack, no change----194.5 CFM
Mikuni vm32 -open or velocity stack, no change----190.8 CFM
Amal 30mm concentric w/offset velocity stack------175.9 CFM
Amal 32mm concentric w/offset velocity stack------188.8 CFM
The Amals loose 15% of flow without the velocity stack. Jim
FCR 35 with velocity stack-------------------------------228.3 CFM
FCR 35 with small CNW K&N -oiled----------------------206.6 CFM
Mikuni vm34 -open or velocity stack, no change----194.5 CFM
Mikuni vm32 -open or velocity stack, no change----190.8 CFM
Amal 30mm concentric w/offset velocity stack------175.9 CFM
Amal 32mm concentric w/offset velocity stack------188.8 CFM
The Amals loose 15% of flow without the velocity stack. Jim
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Norton's is big and looks like a paper wrapped ham in a can but a beautiful functional form to me and my rings. Interesting an Amal flows enough to feed 100+ hp though of course few of our engine can suck on em that hard. As much if not more so, filter flow into carbs has a whole lot to do with its straightening out turbulence eddies. Now repeat the test but throw some vacuum cleaner or drive way dirt on em... then wipe inside of tester with a tissue before next test.
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So,as the stock filter have to feed two carbs, I wonder what that does to an overall flow rate?
comnoz said:
So the 32mm Amals flow about 160 CFM, which is a pretty significant drop from either Mikuni, which explains the seat-of-the-pants difference I feel between my 32 Amals and my 34 Miks at the higher rev band..
Since the foam filters are supposed to be oiled, I wonder what kind of drop in flow you could expect that way?
http://www.unifilter.com/cleaning-oiling/
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Jim,
This is great information. Too bad there isn't a way to test how much dirt they pass.
Why did you tape half the K&N? It looks like the open K&N has the best air flow compared to the other aftermarket filters.
Not sure why the K&N filter I have is not in the group. It's a nice looking chrome 4 1/2" diameter that looks similar to the old BSA and Triumph filters.
http://www.knfilters.com/search/product ... od=RC-1950
Dennis
This is great information. Too bad there isn't a way to test how much dirt they pass.
Why did you tape half the K&N? It looks like the open K&N has the best air flow compared to the other aftermarket filters.
Not sure why the K&N filter I have is not in the group. It's a nice looking chrome 4 1/2" diameter that looks similar to the old BSA and Triumph filters.
http://www.knfilters.com/search/product ... od=RC-1950
Dennis
I think the flange is too big and you would also never get to fit them side by side on a Norton.dennisgb said:
I used these, RU-0982 a set of 2, and if you have a single, this will work great for it also. I now run this filter on My TM40-6 and have a spare, left overs from the JS setup. Same size flange.
http://www.knfilters.com/search/product ... od=RU-0982
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Here here here, bite your tonques that a bigger single can flow more than two slightly smaller carb with sexy racy filters, shame on you, you have been warned. And don't trip on your lips either, no Sir Ree Bob. Universal references all state it takes ~140-50 cfm mixutre flow to burn 100 ish hp amount.
As these extrapolations are made between flow and HP bear in mind that Jim's data is at 28" WC and you are equating actual engine airflow to HP, and these are 2 totally different things. Often, the relationship between actual airflow and HP is much closer to 1.6-1.7 cfm/HP. Only in the highest compression ratio engine with optimized cam and pipe could one produce 1 HP/1.4 cfm actual airflow. Airflow measured at 28" WC provides ~ 0.26 HP/cfm, so 2 cylinders flowing 150 cfm ea (with all inlet tract components in place) at 28" WC (Jim's best heads) would produce ~ 78 HP, which dovetails nicely with reality.hobot said:
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Everybody seems to be concerned with how much air passes through the filter, but no one as yet has addressed the subject from the actual filtering point of view, i.e how effective are the filters for preventing dirt from entering the engine.
Some few years ago, David Vizard did many tests to evaluate a large number of filters from different manufacturers, and he always placed the K&N on the top of his list for best filter. But he also made the comment that the K&N was an incredibly effective filter, and furthermore, when apparently really dirty would still allow much more clean air to pass through than any of the others.
I'm sure Jim's results are valid for the elements he tested, but they all look like new filters to me, so the tests are really only half meaningful, a set of dirty elements might tell a different story.
Some few years ago, David Vizard did many tests to evaluate a large number of filters from different manufacturers, and he always placed the K&N on the top of his list for best filter. But he also made the comment that the K&N was an incredibly effective filter, and furthermore, when apparently really dirty would still allow much more clean air to pass through than any of the others.
I'm sure Jim's results are valid for the elements he tested, but they all look like new filters to me, so the tests are really only half meaningful, a set of dirty elements might tell a different story.
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