Wideband and STS turbo

[alanderson1978]

It's been discussed that a wideband should be after the turbo to prevent inaccuracies due to backpressure. On a remote mount turbo (STS), with stock exhaust, the turbo is after the cats. I have read elsewhere that in this case, the wideband should still be after the turbo, and that being after the cats will only throw you off by about .1 or .2 AFR. Is it alright to have the wideband after the turbo, after the cats, or should this be avoided by removing or gutting cats?

Thanks

[5_Liter_Eater]

Thats an interesting question, not sure I know the definitive answer. Personally I would put the WB in the header collector, particularly if you're planning on retaining the cats.

[EC_Tune]

That particular issue is unique to rear mounts. And yes you have to put the wide band in the tailpipe and hope for the best...
As far as the cats biasing the readings, they will but as to + or - I don't know as I've seen it go both ways in the same run on the same vehicle. AFR measurements are somewhat density sensitive so if your density changes substantially over the run your tailpipe AFR will move around as well.

[cpelton]

I have heard of guys putting it before the cats without a problem. I was told it doesnt really make a difference if its upstream or downstream of the turbo. but then again I have heard that the backpressure can cause problems or premature sensor failure?
So in the end i have no clue lol i'm in the same boat, turbo goes on friday and I dont know where to put it.

[alanderson1978]

So we have:
Before the cats and deal with the backpressure, and possibly higher EGT's
or
After the turbo and deal with the cats, lower EGT's and exhaust density.

Somebody with a lot of time and a few identical widebands could figure this out, but I don't have either of those things.
Right now it looks like th best bet is gut the cats and put it after the turbo.

[EC_Tune]

Before the cat's will definitely screw up the readings of the wideband. They *are* pressure sensitive.

[alanderson1978]

Before the cat's will definitely screw up the readings of the wideband. They *are* pressure sensitive.

What about the temperature of the exhaust. Since the exhaust is so much colder, and probably more dense, will it cause a problem? It would be right before the rear axle on a truck.

Take a look at their Mustang twin turbo. It literally has exhaust tips coming out of the turbos. Widebands would be waaaaay back there.

[EC_Tune]

Yep, but it's the only way to keep pressure issues out of your wideband.

[alanderson1978]

I'm looking at gutting the cats now, just need to find a way to gut the stock cats. The local exhaust guy won't do it....

Great discussion guys...thank you

[kbracing96]

FWIW, I ran and tuned my STS with stock cats and WB 6" after the turbo for 9 months, before I got an off road Y-pipe with out issue. When I put the ORY on it my tune was still very close (.1-.2 diff maybe), I attribute the differences more to increase in air flow then not having the cats in there.

[cpelton]

i kept my cats and put the wb 6" after the turbo as well