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Dual Exhaust & the O2 sensor - could it be a reality?

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big-blue

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Hi ya!

I am looking at doing a true dual-exhaust on my '91, however I have a pesky O2 sensor in my way ;-) . Seriously though, how do folks handle true dual exhaust and an O2? I am thinking that you can't just do one side because the PPM will be way low - so do folks just wire up two, one for each side? And if that is the case, how does the computer see the voltage difference of the two, since there is only one "stock" wire?

Maybe dual exhaust is a pipe dream (no pun intended) and I should just do new cat back.
 
I believe there is one O2 sensor in the manifold or just below it in the pipe. Have the pipes made just like any other dual system, just with the bung in the pipe. I had a 93 Blazer, had true full duals, didnt' affect anything, other than the sound. (which was awesome)
 
Just weld an O2 bung in one side. That's the way it is from the factory. Going to duals doesn't change anything. I've had headers and duals in mine for 10 years, no problems. While you're at it, I'd recommend going to a 4-wire (self-heated) sensor. If using headers, the sensor is usually farther back by the collector and the headers cool the exhaust much more than manifolds. Heated sensor solves a lot of potential problems.
 
Yeah, you just put it on one side and live with it. I've heard of mounting the sensor in a crossover pipe to solve this "problem", but the response is too slow there. Better to have a quick reading than try to do some kind of averaging. The ECU can't adjust for two different mixtures anyway and there is only 1 set of injectors. The only reason 1 bank would be leaner/richer than the other should be from misfires. Cylinder to cylinder will vary slightly due to the wet manifold design of TBI, but that should be about the same from 1 side of the engine to the other. To "fix" that would require MPFI anyway.
 
Blue85 said:
Yeah, you just put it on one side and live with it. I've heard of mounting the sensor in a crossover pipe to solve this "problem", but the response is too slow there. Better to have a quick reading than try to do some kind of averaging. The ECU can't adjust for two different mixtures anyway and there is only 1 set of injectors. The only reason 1 bank would be leaner/richer than the other should be from misfires. Cylinder to cylinder will vary slightly due to the wet manifold design of TBI, but that should be about the same from 1 side of the engine to the other. To "fix" that would require MPFI anyway.
Click to expand...

Good points. Thanks for the reply!
 
Not to open up a can of worms, but duals are pointless unless you just want them. Single 3" is the soup du jour anymore. Cost/complexity/quality issues/ability to work under the truck is normally hindered with a dual setup vs. good single.

There is no performance to be gained in a stock application with duals, and if you want look, go with a single in/two out muffler. I'll concede that the early "pancake" converters are performance robbing, but that's a simple fix with a modern replacement. Ignoring emissions testing/legality of removing one, these trucks benefit from a converter...there is something to be said about not being blinded/choked by exhaust when you are traveling at low speed or sitting idling.

Replacing the stock flat converter wouldn't hurt, but best bang for the buck would come from headers.
 
dyeager535 said:
Not to open up a can of worms, but duals are pointless unless you just want them. Single 3" is the soup du jour anymore. Cost/complexity/quality issues/ability to work under the truck is normally hindered with a dual setup vs. good single.

There is no performance to be gained in a stock application with duals, and if you want look, go with a single in/two out muffler. I'll concede that the early "pancake" converters are performance robbing, but that's a simple fix with a modern replacement. Ignoring emissions testing/legality of removing one, these trucks benefit from a converter...there is something to be said about not being blinded/choked by exhaust when you are traveling at low speed or sitting idling.

Replacing the stock flat converter wouldn't hurt, but best bang for the buck would come from headers.
Click to expand...

Thanks for the reply. Yeah, wasn't considering ever removing the cat. It already has an updated one. So I was thinking about getting a second one for the other side. The main reason why I was going to true duals is that I don't like how the Y pipe crosses under the trans pan.
Regardless, I just got new cat back single put on this past Friday. Local muffler shop made me one heck of a deal. And I needed something since I the old muffler rusted out and the fumes wasn't exiting out beneath the truck.

image.jpg
 
If your concern is the y-pipe, you'll find some pics (sorry, going to take some searching) of "y-pipes" others have made that get the crossover much further forward...with the proper headers, you'd get some performance gain to boot.

I believe the cool y-pipe pic I last saw was on the Hedman Header thread.
 
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