TXGS

Does it really make a difference if the O2 sensor is installed before or after the cat? PLX M300 instructions indicate the installation should be before the cat but at least 24 inches downstream from the engine block. Stock manifolds on a 430 won't give 24 inches.

Dx3

iTrader: (13)

I am pretty sure it needs to be before the cat, but I think it could be less than 24". In your case I would go before the cat and <24" as opposed to after and >24".

Jonny

TXGS

Just talked to the tech at PLX. It can go after the cat. It won't affect the reading. The only issue is the timing of the reading, but the difference is very small. Phew, that made my day. Thanks for the input DX3

sbgs400

hey txgs i've installed a couple of zeitronix widebands on two of my cars and the instructions for those said to install the sensor before the cat for better accuracy. so i'm surprised that they said it was ok to install after the cat.

TXGS

According to the tech at PLX the accuracy issue has to deal with the timing of the signal. Mounting before the cat will give you a reading sooner than after the cat. But as he said this timing issue is minisucle. You will still receive the same reading just a little later (milliseconds).

JPI Racing

Who was tech? The reason why we have 02 sensor before and after the cat is to measure the efficiency of the cat. By hook up a scanner and taking the reading off it the two voltages are clearly differenty. We always put wideband before cat!
JPI

GILLEXUS

iTrader: (14)

I've always heard that before the cat gave a little more acurate A/F readings. With that in mind, how acurate are the air/fuel readings with Dyno machines since those reading are all taken from the tail pipe.

sbgs400

A/F readings don't have to be taken at the tailpipe, some dynos may do that because the car they are dynoing doesn't have a bung for the wb sensor. every dynojet and mustang dyno that i've been on has used my pre-cat wb sensor.

TXGS

How are you able to install a wideband sensor before the cat? There isn't any room to install an additional bung before the cat. Or do you switch the stock narrow band sensor with a wide band sensor?

RMMGS4

iTrader: (5)

I welded a bung roughly 80 degrees off from the factory sensor on my driver side header.

I'd take a pic but don't think I can do it without putting the car on a lift.

JeffTsai

iTrader: (1)

I pulled off my stock O2 and put the wideband there. Usually if your car is NA...the heat will not be as extreme as in a turbo car. I think mine is about 7-8" away from the engine right now.

Also, I thought you get a much more accurate reading if the O2 is before the cats because the air mixture is not yet altered/catalyzed.

JPI Racing

We welded a bung and it worked great. Make sure you disconnected the battery terminals before hooking up any welding equiments. It will fry the ECU.
JPI

JPI Racing

Jeff,
His is a GS430 not 300 so it will be a little different from yours.
JPI