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WinRice WinRice is offline
Registered User
Join Date: Jun 2005
Location: Colorado
Posts: 700
I have to do the same thing here in Colorado.

First of all, you have to maintain right around 14.7 AFR to let the cat work, no more, no less. Your 89 has a computer under the seat that reads the O2 sensor and adjusts the AFR by a bypass valve on the fuel head. This bypass valve controls the fuel pressure in the chambers of the fuel head for fine tuning of the AFR. It does not control the WUR.

I tried to pass emissions without the lambda working and using careful tuning, and it didn't work. It's just not possible to maintain an almost perfect 14.7 with tuning alone, you need a functioning lambda system to get precise control.

You need to tune the WUR to factory specs first, then set the idle CO per the manual, and plug in the O2 sensor. Make sure your O2 sensor is good. Log your AFR for normal driving and see if it hovers around 14.7. If it does, and your cat is good, it'll pass.

I have 964 cams and no air injection, but once mine is properly tuned it passes at about 1/3 to 1/2 the limits.
1986 911 Turbo
3.3L, K27HFS, Tial 46mm, TurboKraft Intercooler, 964 Cams, Monty Muffler, MS3Pro Evo, M&W Ignition, Zietronix WBO2 Data Logger, Wevo shifter, coupler and motor mounts.
Old 05-28-2010, 05:38 PM
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