Ottawa Fiero Club Forum

Working on making headers for the 3800SC in my Fiero and trying to decide whether to use one muffler with two pipes "Y" together before the muffler with the O2 sensor at this point or use two seperate mufflers with a small pipe connecting before mufflers to equilize. If using second way where to locate the O2 sensor as I would like it to read both banks still. Thanks Dan

If you use the second version with an equaliing pipe, you wont be able to use a o2 sensor to get an accurate reading of both banks, you could however connect your computers o2 sensor to one bank and add another one for the second bank for your A/F gauge.. then you could at least keep an eye on what both banks are doing...

I was considering the idea of using my gauge for the other bank just wondering how loud it would be with duals and no cats. Thinking of using two of those oval cherry bomb turbo mufflers but don't want it too loud. Either way it should flow real nice compared to stock and the big plus is removing that cross over pipe that runs under the throttle body. Should help drop intake air temps. Dan

Depending upon how you design the cross-over, you may be able to get away with a heated O2 sensor.

I don't imagine that it would work very well in a configuration similar to a h-pipe, but if you placed it in the center of a x-pipe there may be enough flow across it...

Having a hard enough time just trying to find a way to connect the two pipes with a small pipe let alone finding a way to have them both flowing together through an X pipe. Wondering if it would be ok for the PCM to only be reading one bank with an O2 sensor. Hoping if I use two mufflers to find room to put back in some of my lower trunk if not I think it will end with just one muffler that flows realy large amounts. Problem is with one good muffler it will be even louder than it is now. Decisions decisions. Dan 

There shouldn't be a problem using the O2 sensor in only one bank, but because you are using the stock ECM you also have to take into consideration the distance from the exhaust port to the O2 sensor.  The farther away you put the sensor the more your computer is going to be overcompensating for the O2 levels in the exhaust because there is a specific time that the computer waits before taking a reading (actually it more like it waits a spicific amout of time before compensating for the reading) at any given rpm.  It corisponds to the amount of time it takes for the gas to get from the cylinder to the O2 sensor.  It won't really make a big differance but expect your car to burn a bit more gas, and not run as clean, unless you can modify the tables on the ECM.


Aaron

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Thanks Aaron that is one of the reasons I am looking at using just one O2 on the one bank that way I can keep the sensor in the same area as it is now. Dan

Ended up using a single muffler with the two pipes "Y" together at the muffler and the O2 sensor located there. In all the O2 is moved 18" further, was told by a programmer that it will be ok and that he can compensate for it when my PCM is programmed. Should flow a lot better and no longer has the cross over pipe under the throttle body which should help keep the air coming in a lot cooler. Dan

I know that the 88 is lowder than my stock 85 is on the highway and it is really noticable. Will have to investigate in the spring other ways of quieting it down.