2002#3 Posted January 24 Share Posted January 24 Assuming a source of cold air can be provided to it, will an appropriately adapted/fabricated early (small) style air filter housing and filter (see photo) provide sufficient air volume to and air filtration for Weber 32/36 or 38/38 carbs? Quote Link to comment Share on other sites More sharing options...
Conserv Posted January 24 Share Posted January 24 I don’t know the technical answer to that question, but BMW, at least, thought it was necessary to move to a larger filter and housing when they moved from a single-barrel Solex to a dual-barrel Solex. I haven’t had a single-barrel Solex ‘02 for years — and, hence, haven’t played with the single-barrel housing for years — but does a dual-barrel carb interfere with the mounting “legs” on the single-barrel housing? There are lots of two-barrel ‘02 housings out there, and more than a few have been modded for Webers. It’s a proven technology! Is there a particular reason why you prefer a single-barrel housing, or a carbed e21 or e30 housing, over the plain-as-day simplest answer: a two-barrel ‘02 housing? The challenge? Regards, Steve Quote Link to comment Share on other sites More sharing options...
visionaut Posted January 24 Share Posted January 24 (edited) They’ll be in Jacksonville this Friday night! 😜 Edited January 24 by visionaut pics or it didn’t happen? :D 2 2 Quote Link to comment Share on other sites More sharing options...
tzei Posted January 24 Share Posted January 24 (edited) Are they up and over or side by side? Edited January 24 by tzei Quote Link to comment Share on other sites More sharing options...
visionaut Posted January 24 Share Posted January 24 A stock 2 liter NA M10 needs ~200cfm of air at redline (6600) just based on volume… Quote Link to comment Share on other sites More sharing options...
2002iii Posted January 24 Share Posted January 24 (edited) I've run a modified early 1 barrel carb air filter housing on a 2 liter m10 with a Weber 32/36, no problem. Edited January 24 by 2002iii 1 Quote Link to comment Share on other sites More sharing options...
Conserv Posted January 24 Share Posted January 24 33 minutes ago, 2002iii said: I've run a modified early 1 barrel carb air filter housing on a 2 liter m10 with a Weber 32/36, no problem. OK, so why did you choose the smaller single-barrel air filter housing, rather than the larger dual-barrel housing? Regards, Steve Quote Link to comment Share on other sites More sharing options...
2002iii Posted January 24 Share Posted January 24 3 minutes ago, Conserv said: OK, so why did you choose the smaller single-barrel air filter housing, rather than the larger dual-barrel housing? Regards, Steve Wanted to keep the original look of the 1969 2002 it went on. 1 Quote Link to comment Share on other sites More sharing options...
visionaut Posted January 24 Share Posted January 24 (edited) 16 minutes ago, 2002iii said: Wanted to keep the original look Steve wouldn’t know anything about that… 😗 Edited January 24 by visionaut 2 Quote Link to comment Share on other sites More sharing options...
2002#3 Posted January 24 Author Share Posted January 24 (edited) I started this post knowing, like most of us, there are 3 types of original AFH and numerous FAQ-posted ways to modify them for 2-bbl Webers. I am good with all three; they're BMW-correct, function well, and, for a large AFH, they look good. I asked about the smaller (1-bbl) two reasons: (i) I was curious and (ii) it is smaller and not as as bulky. Certainly, adaptation will have to address (i) a smaller bottom section to fit 2 bbl's, (ii) new braces set up/attachments [somewhere!], and (iii) finding a place for it to get cold air. All are doable, I am sure. My questions remain: 1. Will it starve a 32 and/or a 38 sitting on an engine with 10 CR, 292 cam, and headers? If it will I certainly am good with the 2 later styles. 2. Is the bottom of the AFH just too darn small to adapt to 2 bbls? Thanks for all of your comments. Keep 'em coming. Edited January 24 by 2002#3 added text 1 Quote Link to comment Share on other sites More sharing options...
visionaut Posted January 25 Share Posted January 25 A reason to run a bigger ring air cleaner is to be able to run a larger air filter. A larger diameter filter will flow more air and better match the increased carb opening size… For conventional ring air filters there’s basically 2 rules of thumb for best performance: - the filters diameter-to-height ratio should about 4-5:1 - the filter diameter should be at least 3X the carb diameter ( I.e. the ring sits about one carb width away on each side of the carb There’s also a rough calculation for ideal effective filter area. For a 2 liter with a 7k redline that’s about 41 sq in. Meet or exceed that. More is better, less is restrictive… More filter surface area also means they can last longer. 1 Quote Link to comment Share on other sites More sharing options...
visionaut Posted January 25 Share Posted January 25 (edited) Coupla added thoughts… lol The highest flow rate for pleated paper material air filters is ~5 CFM per Sq In So the 200 CFM engine air requirement I mentioned up top and the 41 Sq In filtration area requirement fit… These simple calcs are minimums, so more filtration area is needed. Imagine a minimally sized filter that’s full and only maybe flowing a third to half that rate... Besides the diameter, the height of the ring filter also matters - for the 2 bbl carbs cited, you’ll want 2” free clearance min above ( in front of) the carb mouths. The domed cleaner center isn’t just pretty - it helps provides that free space, and the dome flows better than a flat top. So a too short filter height may hurt, and as carbs get bigger, you typically need more height. ( limited by the hood, of course). Tom Edited January 25 by visionaut typo 1 Quote Link to comment Share on other sites More sharing options...
'76mintgrün'02 Posted January 25 Share Posted January 25 1 hour ago, visionaut said: Besides the diameter, the height of the ring filter also matters - for the 2 bbl carbs cited, you’ll want 2” free clearance min above ( in front of) the carb mouths. The domed cleaner center isn’t just pretty - it helps provides that free space, and the dome flows better than a flat top. I agree. (before) (after) 1 Quote Link to comment Share on other sites More sharing options...
jimk Posted January 25 Share Posted January 25 11 hours ago, visionaut said: The highest flow rate for pleated paper material air filters is ~5CFM per Sq In Do you mean face area as folded or unfolded flat sheet. Various filters have different amount of paper area per sqr. in. o face area. Quote Link to comment Share on other sites More sharing options...
visionaut Posted January 25 Share Posted January 25 (edited) 20 minutes ago, jimk said: Do you mean face area as folded or unfolded flat sheet. Various filters have different amount of paper area per sqr. in. o face area. As folded, as used. Yes the fold sizes and number can vary. This is what the best of these type filters can typically flow. For comparison foam filters are more like 4.5 CFM and pleated K&N is around 6 CFM. Edited January 25 by visionaut Quote Link to comment Share on other sites More sharing options...
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