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911nut 911nut is offline
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Join Date: May 2001
Location: Michigan
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Originally Posted by RarlyL8 View Post
The O2 sensor only affects the A/F ratio at idle. No danger in throwing it away.
Once you use a Gunsen or LM-1 and know where 2.5% is you will be able to tune it by ear. My guess is you're close now.

The O2 sensor feeds a signal to the lambda computer which, in turn, varies the fuel pressure in the lower chamber of the fuel distributor via the frequency valve, affecting enrichment. The lambda computer will keep the AFR at 14.7-1 so the cat will do it's job.
Unplugging the O2 sensor will run the system in open loop mode, allowing 12.5-1 AFR (by setting CO at idle to 3-3.5%) on CIS. A CO set at this value improves torque.
Paul B.
'91 964 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, - 210 lb
Old 07-25-2007, 12:35 PM
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