o2 sensor with duals

[thatclappedsilverado]

was planning on doing true duals but its looking like im either gonna get rid of my o2 sensor or have to get an xpipe to get the corect readings
any one have an idea on what to do? id like to have true duals but id be fine with an xpipe if need be. its a 95 k1500 305 tbi only has the o2 sensoring the manifold and infront of the cat

 

[b454rat]

I've only ever had 1 305 vortec, so not super familiar with it. But they have 1 on each manifold, then 1 after the cat, as you stated. So in order to put duals on it, it will have to be after the cat, (obviously) then use a Y-pipe to split into duals.

 

[PlayingWithTBI]

TBI systems only used 1 O2 sensor on the driver's side exhaust. The PCM doesn't care about post-cat trims. The further down the exhaust the slower the PCM will react to AFR. There is a parameter in the .bin that you can change to delay the response so you are actually responding to the exhaust instead of it being too late and your PMC will be searching causing a stumbling idle.

Edit - just put your O2 sensor in the collector of your header on the same side.

 

[Knuckle Dragger]

Too far back and a single wire will not heat up enough. It should be fine in the collector but if it were mine I'd switch to a heater O2 to be sure. Like ^^^ said one will work in either side.

 

[PlayingWithTBI]

Too far back and a single wire will not heat up enough.

Good point, I forgot to mention that. A 3 wire HO2 sensor is good a 4 wire HO2 is better, it won't rely on the body of the sensor grounding to the exhaust.

 

[Supercharged111]

I converted to a heated O2 when I put longtubes on my 88. Worked like a champ, had it right behind the collector.

 

[b454rat]

Dunno how missed the 95 part lol

 

[PlayingWithTBI]

I converted to a heated O2 when I put longtubes on my 88. Worked like a champ, had it right behind the collector.

My NBO2 (3 wire) is in the collector of my shorty header and my WBO2 is in the collector of my "Y" pipe going to 3" single exhaust. I did delay the response for my EBL trims and am running on it (still monitoring the NBO2 feedback). Eventually I may revert back to the NBO2 after I'm done playing with it but, there's always something else to play with, LOL.

 

[Supercharged111]

When I was dealing with transients, I observed about a .25 second lag from TPS movement to WBO2 change. You could watch the truck chug in the data before the AFR told what was happening.

 

[PlayingWithTBI]

Here's a snap shot of the table where it delays response (in milliseconds) vs GmSec (Grams/Second air flow through the exhaust "calculated"*) meaning the faster the engine runs, the shorter the delay for the computer to respond to the O2's feedback. IOW, there's a window in which your tune and placement of the O2 sensor will be affected.

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* Note - Grams per Second usually is 1 gram/Liter of displacement so, a 5.7L will show around 5.7 Gm/Sec. Here's an excerpt from another site's thread "Tuning With the EBL"

"Grams per second is also a relatively close approximation of HP. The relationship seems to be about 1.2 grams / HP. So take peak grams per second, times 1.2 and you get about crank HP. Or just simply grams per second is approximately your wheel HP after drivetrain losses."

So, with my engine, at idle it shows 23 Gm/Sec.

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Which means I have to adjust my scalar for AirFlow - Displacement lower to see 5.7 Gm.Sec so the computer will use the lower end of the tables. Confusing huh? I'm confused too, but trying to get my head around this, lol.
This is fun stuff!

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