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kucharskimb kucharskimb is offline
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Join Date: Aug 2004
Location: Houston, TX
Posts: 895
okay... here's one more opinion. i'm also battling my webers at this time, and am going back tomorrow for another group dyno armed with some more main jets.

my setup is a 2.2E stroked to a 2.4. in essence, your motor with about 9.6:1 compression (yours is probably 10:1).

for the carbs, i have:

idle: 60
main: trying 135 as i was lean at 130, have 140s on hand
F3
180
34 venturies

from your graph, i'm guessing that your A/F looks like it does because you were at cruise and then jumped on the gas. it momentarily went lean until you got the fuel shot from your accelerator pump, which then sent you super rich. not what you were talking about with the narrow band sensor, but a good lesson to remember to be smooth on the gas.

when setting up the mixture at idle, it's all on the mixture screws. you can do all sorts of compensating for the wrong size idle jets with the mixture screws. after closing them, turn them out 1/2 turn at a time until you get max rpm, then another 1/4-1/2 turn out.

the mixture screws will continue to influence your A/F until about 1500rpm, then you are all into your idle jets.

if you want to see if the idle jets are too big, you can test them by opening all of your air correctors at 1/2 turn increments. this is the same as leaning out the idle jets. PMO suggests this. Bieker Engineering does not.

around 3500, you are transitioning to the mains at partial throttle.

at WOT, you are ONLY using your MAIN jets. so, yes, you have the ability to leave WOT alone, and only correct your cruise (part throttle) A/F ratio.

couple troubleshooting things that i have had to deal with:
1. are your idle AIRWAYS clean and unblocked?
2. do the gaskets that go between the carb body and the float bowl covers have the holes pre-punched to allow air into your idle circuits?
3. are any of your float needle valves stuck open.
4. are any of your accelerator squirters stuck open (there are several small check balls in that system)

IMO, your setup is too lean, but the dyno shows otherwise. also, not sure why you are not making more power. DIN v. SAE is less than 1% difference.

i'll post my results from the dyno tomorrow with the final jetting setup. maybe it will give you something to go on.
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72 911T Targa - Sold

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Old 02-03-2006, 10:21 AM
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