The need or benefit of 2 O2 sensors?

[Chevy_Finatic79]

I'm currently putting a 90' 1500 short box 4x4 together for a buddy. he wants to run true dual exhaust and is bent on the idea he needs to have 2 O2 sensors or one for each manifold.

What I want to know is:

• if there is even a need to add an extra O2 sensor?
• how do i hook up the extra to the ECM?
• has anyone done this and benefited form it?
• how will the computer recognize the new sensor?
• if I just do a 2 into 1 with the wires will that give a bad reading?

[MORROWMUDDER]

my truck has 2 on each from the factory. the first one helps the compture regulate the fuel mix and the second one is for emmissions. its a good idea to have 2 of them but will run without them. as for wiring them up i cant help ya there sorry.

[Case 7230]

In my opinion a bad idea. Just put one in one pipe and it will be fine.

[junior3382]

If it makes you feel better, I have four of those little buggers on my pickup..... and due to this, makes it impossible to use "universal" cats due to specific temp readings..... pain in the butt if you ask me.

[Chevy_Finatic79]

well the reason I posted this, is for that year of truck it came with just one O2 sensor from the factory and I know tons of people run true dual exhaust from each manifold all the way back on that style truck with only 1 O2 sensor and have no problems.

I just want to know if it can be done and what is the procedure I need to follow.

I'm really curious about the effects of adding a sensor and the voltage readings and how the ECM will "interpret" the info. I wonder if the ECM will even "SEE" the other O2 sensors and compensate accordingly

[junior3382]

I know guys that run duals too. Run an X pipe to even out the pressure and the O2 should run normal.

[jdfenske]

use whatever the computer has harnesses for.....

odbi pre 96 weren't concerned for cat effiency, only air/fuel mix.
odbii in 1996 started using 2 sensors per bank, one before and after cat.

i believe first set measures air/fuel mix against air intake sensors , and 2nd set measures efficiency of cat...


i run x pipe and no mufflers. just after cats.


doubling up sensors into 1 harness is bad news.

in particular to o2 sensors, , the harness going to the sensors are not given voltage. oxygen passing over the sensor produces voltage, which is used to do math...which is very tiny, sometimes as little as 0.01 volts.

all other sensors are given ususally 5v, and changes to the sensor produces resistance, which in turn changes voltage.

doubling up may pull extra amps/watts. burning up drivers/readers.

easier to read changes on a square wave with a pulse width......


and don't run true duals, sounds gross.....

[Chevy_Finatic79]

well today I went into my buddy's muffler shop to have him test a suspect cataliytic converter that tunred out to be good.

While I was there I noticed a 88'-98' chevy truck on the rack so I asked him what he thought about 2 O2 sensors and two "True Duals" he said I'm cutting the cat off this one and doing just that: 2 pipes from the manifold back and two Flowmaster stainless mufflers and only 1 O2 sensor. he said he does this at least 3 to 4 times a week and has never had any complaints. no H or X pipe

so I will tell my buddy to put that in his pipe and choke it

[junior3382]

Well for the purpose of leveling out the back pressure and keeping everything uniform, it is still recomended to run a crossover pipe, but he is right, it is not nescesary. If it were me though bud, I would anyways.

[Chevy_Finatic79]

on my truck the 85' I run the true dual with no cat and 2 mufflers no crossover pipe and 1 O2 sensor and I dont know if it is just my pipes but it dont look like there is room anywhere on my truck to put an H or X pipe with out running into the tranny or driveshaft.

I run a set factory dual exhaust pipes that have never seen a crossover pipe, they did have some big round mufflers on em that I chopped off (they were some sort of BB type Muffler), why did GM send them out the factory doors like that if the backpressure was such a big deal? I'm not trying to argue or say that the back pressure isnt needed. Just wondering why GM didnt think it was such a concern