Rear mount PTE 6765S, LS4 (5.3) 325ci, auto, E85, N2O wet shot...Have some issues with my O2 sensor after the turbo giving me scewed and scrambled readings.

It's ONLY when I grab a low gear from a low rpm into a downshift at WOT....the sensor works just fine with around town driving and idle, and moderate acceleration...and even boosting WOT from a higer rpm roll or above 35mph 2500 rpm. It doesn't always do it either? Just when it has what seems to me as a ****-ton of backpressure when I go WOT and ask for it down low...almost like it's "blowing out" from the force of the exhaust passing over the O2 sensor and it not being able to get an accurate reading....sometimes is comes back on point after the innitial WOT hit down low, other times it will send an error code and I will have to reset the wideband by key "on, offing" the car.

O2 sensor is the bosch 3737 that comes with the LC-1/XD-16 kit from innovate. The gauge will go really super lean and then super rich and ping pong a few times and give a great light show while I'm in it down low and gaining speed and rpm's with boost.

I experienced this same issue with my previous location in my pre turbo down pipe before I moved it out back post turbo. It was still in my exhaust pipe pre turbo in my downstream bung. I was only what I call, "blowing out" the O2 sensor when I was in high rpm over 5500rpm and at high speeds...only experienced it once or twice though before I moved it.

Haven't had any issues with this O2 sensor since I moved it from old set up, and even when I had it on my old turbo post turbo...

Got the new PTE unit and the turbo is positioned different now and unlike the old placement of this O2 sensor being in a slightly bent 90* pipe post turbo, it's in a straight section post turbo...same distance though...

Current sensor is mounted approx. 6" from the turbine at a 45*, or 10-11 o'clock position...so for most part I'm pretty sure mounting is correct and no signifigant changes from old set up at all really?

I have plugged an exhaust leak which has made it night and day for spooling the turbo...and I'm experiencing more backpressure now for sure I would say...I can def. feel the diff. in the car now with solid exhaust.

Wondering if anyone is having, or has had any issues with this before? or could tell me a direction to go...I know I will try to swap the sensors...that's first...but collecting what I can here now.

Thanks all,

Rossko

 

Way too close to the turbine. We experienced exactly the same problems when we had our wideband mounted too close to the turbine on our Porsche 930 road racing shop car. Move it back 18" from the turbine, and try to keep another 18" of exhaust pipe after the sensor, and you won't have anymore trouble.

 

Thanks for the heads up! Problem I have and other rear mount guys have is that there just isnt a whole lot of room after the turbo back there....

There is also a little trick with the rear mounts regarding back pressure, and how to keep it from building up and the turbo to be able to move it out of the way in the system....guys like Zombie here on Tech have got this stuff down to a science literally....and most all of the guys Ive spoke to have said that the best route to go for a rear mount and to keep it humm'n...is to wrap the hell out of the pipe, size that turbine wheel pretty well, on LSx dont be real afraid of the cold size A/R within reason, and keep that down pipe post turbo approximately 3ft. long and a gradual step up from the turbine/vband with a rule of thumb of 1.5-2.0" larger on the outlet of the down pipe compared to the turbine outlet on the turbo, and it should curve
45*-90* and turn down or to wherever you want it to lead out....

So, just have to squeeze the best I can...i can go about 7-8" after the turbo and that's about it...Like I said, I'm around 5-6" right now...

This has helped confirm my theory of the air just probably being too turbulent....

Thanks again!!

 

I have put the sensor pre turbo in a couple or rear mount cars. I know they say the heat is bad for the sensor and the pressure will skew readings, but I have had no sensor failure and the car was tuned off of that same wideband.

 

Sorry, but I'm planning out a setup and I was wondering if your experience has changed any since you wrote this? It has been a while now.

On my car it is going to be difficult to locate the WB properly in the exhaust after the turbo.

TIA!

 

Nothing has changed, I wouldnt hesitate to trust a wideband pre turbo in a rear mount deal.

 

Thank you, obviously that will help A LOT!

 

Of course, the LC-1 is more problematic than any wideband which is part of the problem.