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MFI idle bypass initial setting on a 1972 911T
I have read most if not all of the MFI information (i need an aspirin) but have a question that remains mysterious.
Lee Rice indicates that the idle mixture screws should be turned out 2.5 turns for bottom stop. the porsche CMA document states that a 2.4 should be 3/2's which i believe means 1.5 turns from bottm stop. The CMA differentiates the 2.4 from the 2.2 which has 2.5 turns from BS. is Mr. Rice correct or should I use the CMA document to set up the idle bypass?
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1975 911S Targa Silver Anniversary Edition |
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Join Date: Dec 2008
Location: San Antonio, Texas
Posts: 3,590
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It doesn't matter as long as it starts, do the flow at 3,000 rpm as per the cma. If the idle is too low open them all equally to get to idle rpm. If too high close them all equally. If you do the adjustment properly at 3000, you probably will not have to move anything at idle.
Make sure your timing and dwell are spot on. GO STEELERS!
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1973 911S (since new) RS MFI specs 1991 C2 Turbo |
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Rescuer of old cars
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I split the difference at 2 turns out when I set up the MFI on my 2.4. It doesn't really matter too much where you start, just make sure that the throttle stops and links are adjusted properly, and that all 6 bypass screws are backed out the same amount.
The initial setting is only a rough starting point. You will deviate from it when you check and adjust the vacuum on all six stacks.
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2018 718 Cayman 2.0 Priors - '72 911T coupe, '84 911 Carrera coupe, '84 944, '73 914 2.0 Last edited by Arne2; 05-28-2019 at 03:47 PM.. |
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The 2.5 turns is just a starting point . The most effective second step for me is to then take a tube and put it up to your ear , the other end just in the velocity stack and make note of how far it is into the stack. Listen to the sound , as you turn the screw in and out the sound will change . I listen for the loudest combo popping thumping . Practice and you can get all the runners sounding the same .
repete for all stacks Just an old tune at the track trick .
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Kermit, 73 RS clone, Just Part of the Team Chris Leydon ,Louis Baldwin ,Peter Brock ,Riche Clark Jerry Sherman ,Rob McGlade ,Donnie Deal Hank Clarkson ,Craig Waldner ,Don Kean ,Leroy Axel Gains |
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