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<insert witty title here>
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Difference between 175 and 185 air correction screws?
600 ft. elevation, for a Weber carb setup on a 3.0L.
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Current: 1987 911 cabrio Past: 1972 911t 3.0, 1986 911, 1983 944, 1999 Boxster |
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08-19-2011, 04:26 PM
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Registered
Join Date: Feb 2008
Posts: 1,438
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The 175 will provide a richer upper RPM fuel delivery (above 4500 RPM) than the 185. If engine stutters or resists reaching high RPM you can install the smaller air correction jet and give it a try. Keep notes. Be methodical. Use a tail pipe exhaust analyzer to be sure.
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Paul Abbott Weber service specialist www.PerformanceOriented.com |
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08-19-2011, 06:00 PM
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<insert witty title here>
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Sorry, should've been more clear. I know it'll mean a leaner mixture at high rpms, the question is how much. WOuld it be noticeable in a regular street car that sees a couple track days per year? Can it be compensated for with a slightly overall richer mixture?
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Current: 1987 911 cabrio Past: 1972 911t 3.0, 1986 911, 1983 944, 1999 Boxster |
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08-20-2011, 03:52 AM
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It's a 914 ...
Join Date: Jan 2008
Location: Ossining, NY
Posts: 4,734
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In case this is any help ... I've heard a rule of thumb is that a change of roughly three air corrector jet sizes = one main jet size, in terms of the magnitude of the enrichment you can expect.
Scott |
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08-20-2011, 06:17 AM
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<insert witty title here>
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I'm pretty new to carb setup (tried it once for an entire day and half a tank of gas, end up taking it into the shop), so I'm not even familiar with what changing the main jet size would do.
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Current: 1987 911 cabrio Past: 1972 911t 3.0, 1986 911, 1983 944, 1999 Boxster |
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08-20-2011, 10:55 AM
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Wer bremst verliert
Join Date: Jan 2005
Location: Toronto, Ontario
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The difference is exactly 10.
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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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08-20-2011, 02:47 PM
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<insert witty title here>
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Hey, we have a comedian in the house! Damn Canadians...
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Current: 1987 911 cabrio Past: 1972 911t 3.0, 1986 911, 1983 944, 1999 Boxster |
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08-20-2011, 04:28 PM
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It's a 914 ...
Join Date: Jan 2008
Location: Ossining, NY
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Christien,
Is there a particular issue you're trying to address by changing the air corrector jets? Normally you'd change air correctors to adjust the enrichment at high RPM under load. Scott |
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08-20-2011, 06:01 PM
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<insert witty title here>
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Good question - don't know why I didn't explain earlier. I've currently got Webers on a 2.0L, and I've got a 3.0L coming next week. I need to rejet the Webers, and I've got someone who's got most of the stuff, but 185 air corrrections, whereas the recommended is 175. I'm trying to determine if they'll work, and why or why not. It's partly practical (would be easier to have one less shipping cost into Canada) and partly academic (still trying to learn the details of how carbs work).
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Current: 1987 911 cabrio Past: 1972 911t 3.0, 1986 911, 1983 944, 1999 Boxster |
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08-21-2011, 04:15 AM
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It's a 914 ...
Join Date: Jan 2008
Location: Ossining, NY
Posts: 4,734
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185 air correctors will cause slightly leaner running in the upper RPM range than 175 (air correctors work the "opposite" of main and idle jets). If you're pretty sure about the 175, sounds like it would be better to have them. Plus, jets are cheap. Another way to look at it is than 185 to 175 is not a very big jump for air corrector jets, so you could try making the other jetting changes and see how it runs.
Scott |
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08-21-2011, 08:35 AM
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1972 Porsche 911T 2.4
