Just picked up a 4.3l '92 Sonoma with only 70 000km!

I'm looking at running seperate pipes from each manifold, but the o2 sensor is right at the Y before the catalytic converter. What to do?

We're in Winnipeg, so we don't have the emissions control like Toronto, Vancouver, or the U.S., so that aspect shouldn't be a problem.

The ultimate goal is to achieve more power and a better sound. Just wondering if life would easier to run a bigger pipe from the Y to a dual outlet muffler?

I'm just looking for feedback/other ideas and opinions.

I'm not the greatest on this topic, but I do know some of the operating theories. Like many sensors, O2 sensors send a signal via resistance. Leaving a single sensor in one of two pipes will only measure half of the mass of O2 and lean the mixture by half. Putting two sensors in series will double the resistance, and putting them in parallel will halve the resistance. If you find out how the sensor detects oxygen (like does it increase resistance as oxygen increases, or vice versa) you may be able to find a combination of sensor(s) and wiring that will duplicate the signal. Your biggest issue will be heat. O2 sensors don't work until they reach operating temperature. Closed loop operation may never be achieved with only half of the heat energy passing over each sensor.

Another option is to use an O2 simulator. I think it bypasses closed loop operation. I know that sound is an issue. On a dual-system V8, I much prefer the sound of a system with a crossover or a 2-into-1 system. Think Camaro or Mustang sound. You certainly won't need a dedicated dual system unless you are pushing more than 400-500 hp. A 2 into 1 system with a 3" tail pipe will easily support up to 400 hp and sound better on a v6. I suggest sticking with the stock crossover and a 2.5" cat-back. That will keep your o2 sensor and add benefits of better flowing system. Any more and you may have insane resonance and lose alot of your low end torque. Keep it muffled well, too. I personally hate the sound of a free-flowing V6. Some like it, but most V6 owners I've talked to who went with a real free-flowing exhaust start out liking it, but switch mufflers really fast. Many of Walker's Dynomax series mufflers do an excellent job of flowing well and muffling sound.

Good luck and let us know how it sounds
Curtis

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