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Dog-faced pony soldier
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Carb sizing calculator?
Is there a good calculator or matrix somewhere available as an online resource that matches up carburetor sizes (bore, jet size, etc.) with engine displacement size (e.g. 2.2, 2.7, 3.0, 3.2, etc. . .)?
I am considering a carb conversion for my 2.7, but it'd be nice if someone has put together a table showing appropriate matchups. If not, maybe I'll start one.
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A car, a 911, a motorbike and a few surfboards Black Cars Matter |
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02-02-2008, 07:21 AM
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Crusty Conservative
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I don't have it handy, but the Weber formula is in Bruce Anderson's original High Performance Handbook...
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Bill 69 911 T Targa, 2.4E w/carbs (1985-2001) 70 911 S Coupe, 2nd owner (1989- 2015) 73 911 T Targa, 3.2 Motronic (2001- ) |
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02-02-2008, 07:33 AM
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Registered
Join Date: May 2003
Posts: 3,346
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There are formulas but since the only choices are 40 and 46 for the carbs there is not much need for one. The venturi sizes are also known for each type engine. If you have a race engine up to 3.2, you should use 46mm carbs. If you have a street engine 3.0 or smaller you should use 40mm carbs. Bigger than a 3.2 race engine should probably use PMO 50mm carbs.
-Andy
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72 Carrera RS replica, Spec 911 racer |
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02-02-2008, 02:25 PM
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Dog-faced pony soldier
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Thanks for the info, but that's kind of a non-answer. The venturi sizes might be "known" to some, but not to all, certainly not to me. As such, I'd appreciate actual numbers rather than generalized statements about how ignorant I apparently am. Yes, I looked and yes, I searched. Excuse me for asking an honest question. I certainly didn't think it warranted a condescending put-down.
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A car, a 911, a motorbike and a few surfboards Black Cars Matter Last edited by Porsche-O-Phile; 02-04-2008 at 12:51 AM.. |
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02-04-2008, 12:49 AM
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Join Date: Aug 2007
Location: Austin, TX
Posts: 328
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Maybe this will help. This comes from Pat Braden's book on Weber Carburetors.... I'm working on the same issue. I'm carbing a 2.7 in mild configuration, so the chart says about 34mm venturi. Hope this helps!
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02-04-2008, 05:27 AM
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Dog-faced pony soldier
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That's exactly the sort of thing I was looking for. Thanks so much!
Like you, I'm considering a carb conversion to a 2.7, but I need to study up.
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A car, a 911, a motorbike and a few surfboards Black Cars Matter |
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02-04-2008, 05:42 AM
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Registered
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Rule-of-thumb Venturi size =20*SQRT(Cylinder Volume in cc's/1000*RPM of peak HP/1000)
(From the Bradon's Weber book)
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John '69 911E "It's a poor craftsman who blames their tools" -- Unknown "Any suspension -- no matter how poorly designed -- can be made to work reasonably well if you just stop it from moving." -- Colin Chapman |
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02-04-2008, 06:56 AM
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Sorry you took it as a put down. I just didn't feel like opening up my books right then. I thought you were asking for a formula and I was just saying the numbers are available in books like Bruce Anderson's so you don't need to use a formula.
-Andy
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72 Carrera RS replica, Spec 911 racer |
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02-04-2008, 07:35 PM
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Wer bremst verliert
Join Date: Jan 2005
Location: Toronto, Ontario
Posts: 4,767
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My 2.7 with factory Heat Exchangers and sport muffler was happy with the following:
40IDA3C 34 vents 60 idles 140 mains F26 emulsion 180 air correction All the screws were a little different but all around 1.5 turns out.
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2007 911 Turbo - Not a toy 1985 911 Cab - Wife's toy 1982 911 3.2 Indiash Rot Track Supercharged track toy 1978 911 3.0 Lichtbau toy "Gretchen" 1971 911 Targa S backroad toy |
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02-04-2008, 08:27 PM
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1970 Porsche 911S 2.2l MFI
1969 Porsche 911E 2.0 E
