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Join Date: Oct 2006
Posts: 315
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MFI Throttle Body Correlation
It appears that Lee Rice says to adjust throttle stop bolts out 3/4 turns, air screws out 2 to 2 1/2 turns. Then adjust air flow by turning throttle stop bolts. I assume he wants equal air flow via throttle stop bolts, leaving the air screws alone. Others, including Grady Clay say to keep the throttle bodies at stop and adjust air flow via air screws. Also, my car is a 2.4 S, and if I adjust it the Lee Rice way, should I only turn the air screws out 1 1/2 turns out as the Bosch Manual states.
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09-28-2009, 04:22 AM
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I just did this on my 72 and I turned out the air screws 2.5 turns. Since my car already ran good, I then adjusted the T.B. stops until I had the stacks even, flow wise. You will then have to adjust the rods, connect them back up, drive the car around, and then adjust the air screws at 3000 rpm, rods off. If your stacks are original like mine, then it's almost impossible to get the car to run perfect. Make sure you tighten all the nuts that hold the stacks to the butterflies and the butterflies to the head as I could not believe how loose mine were.
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72 911 Although it is done at the moment, it will never be finished. |
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09-28-2009, 07:17 AM
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The 2,0 and 2,2 vs. 2,4 stacks are different-- follow the instructions in CHECK MEASURE ADJUST. One is five half-turns, the other three.
If you can't set the correlation with the air screws you're unlikely to get it right with the throttle stops.
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'66 911 #304065 Irischgruen ‘96 993 Carrera 2 Polarsilber '81 R65 Ex-'71 911 PCA C-Stock Club Racer #806 (Sold 5/15/13) Ex-'88 Carrera (Sold 3/29/02) Ex-'91 Carrera 2 Cabriolet (Sold 8/20/04) Ex-'89 944 Turbo S (Sold 8/21/20) |
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09-28-2009, 07:45 AM
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John, I turned my air screws out 1 1/2 turns then adjusted throttle stop bolts to get the car to idle at 950 RPM at 180 deg. This is similar to what tobuforu did however, he set his air screws at 2 1/2 turns. Because my air screws are only 1 1/2 turns out my throttle bolts have to be turned out more than Lee Rice's 3/4 turns out in order to achieve this idle. I believe this is why when oil temp is around 210 deg. my idle is around 1100 RPM. AFR around 12.8 to 13.1 and the car runs great, however all this does not answer my origional question.
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09-28-2009, 04:41 PM
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Home of the Whopper
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Adjusting the TB stops or the air bypass screws both do the same thing, bypass air around the throttle bodies. How much you do either depends on your idle. If 1.5 turns gives you the right idle, than stop there.
Personally I use Grady's method. I start with the TBs closed and turn the adjuster until the TBs are still closed, but resting on the screws. Then I adjust the air bypass screws to give equal air flow across the cylinders and the idle I want.
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1968 912 coupe 1971 911E Targa rustbucket 1972 914 1.7 1987 924S |
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09-28-2009, 06:16 PM
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Tobluforu
Olive
The Turtle
Ruby
Brownie
