Relationship between idle jets and idle mix screws |
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Relationship between idle jets and idle mix screws |
era vulgaris |
May 9 2016, 04:06 PM
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#1
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J is for Genius Group: Members Posts: 982 Joined: 10-November 13 From: Raleigh, NC Member No.: 16,629 Region Association: South East States |
How much can one compensate for the other?
For example, with larger jets and idle screws further in, could you tune a set of carbs identically to another set of the same carbs that had smaller jets with the mix screw further out? I want to experiment with going a little leaner at idle and seeing how my engine likes it. I'm trying to decide if I should order a smaller set of idle jets or if I can achieve the same result by just turning the screws in further. Basically, what is the difference? Don't they achieve the same ends? Obviously there's a limit on the rich side because there's only so much fuel a jet will allow to flow. But if you're trying to lean it out, what's the difference between going to a smaller jet or just turning in the screw? |
Justinp71 |
May 9 2016, 04:27 PM
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#2
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Senior Member Group: Members Posts: 1,584 Joined: 11-October 04 From: Sacramento, CA Member No.: 2,922 Region Association: None |
On all the carbs I've worked on the idle screw just sets the mixture at idle, once you open up the throttle there are additional fuel holes that draw in more fuel on the idle circuit. The larger the idle jets the more fuel you draw overall. The idle circuit typically runs the motor up to 3k rpms.
However the farther out the idle fuel screw is you do get a little more fuel past idle. I have my car tuned with a leaner idle, but larger idle jets. Then when you idling at a light your not burning extra fuel and its a little less smelly. Then when you get on it, its all smiles. I did notice its a little harder on cold start this way though. |
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