Matt H

his is a 90 (according to the sig) and if it is a direct replacement then he much have meant crossover pipe.
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Bri Bro

The LSU4 is sensitive to the temperature of the exhaust gas. The heater in the sensor attempts to keep the tip at 750C. Here are the ranges of temperatures for the LSU;

Operation temps <930C (570 at the hexagon housing)
Max temp <1030C (630C at the hexagon housing)

In the application notes it states that the exhaust gas should be keep below 850C (500C at the hexagon housing). So, if we assume most people have modified their engine or exhaust system over the years, you need to measure the exhaust pipe temperature to find a spot were the MAX exhaust temp is slightly under 500C on the exhaust pipe.

The O2 sensor tip also needs to be pointed downward at least 10 degrees from horizontal in a part of the pipe were water doesn't collect. Water kills O2 sensor fast, lots of experience using the rattle test after they stop working.

Chas

Thats some good info Brian....do you know if the stock location of the stock o2 sensor satisfies the 10degrees down from perpendicular and "high and dry" requirements of the wbo2 sensor?

adrial

I would say it satisfies high and dry just by looking at it, but temperature wise I dont know...

If someone wants to stop by with a working car, I could use a laser temp gun to measure temps so long as your cat pipe/test pipe isn't polished and isn't very shiny.

Chas

Damn...let me know if you'll be in the Northern VA area with that laser temp gun...other wise I might just give it a whirl and see how she does....

I'm thinking I should be fine on the crossover... I did receive this reply from plxdevices regarding pressure...

"...Yes, readings will be a bit off with high pressure, but is more affected
on the lean side. Find a location with the lowest pressure possible...."

Does anyone have any info on whether the 25+psi between the headers and the turbo hotside can throw off the sensor?

cpt_koolbeenz

adrial - That would be very helpful!
Anyone in NY that could drop by and check. I really don't want to have to replace the new o2 sensor in 10k.

adrial

You have the O2 sensor in the crossover pipe? depending on location on the x-over, there's a very good chance that spot doesn't fulfill the requirements...

The stock location (right off the cat pipe)....should be fine, though.

Is there more than one stock location on the turbos?

Chas

koolbeenz, if you can work that out...could you post what you two find out as far as temperatures across the pipes?

Chas

hahah sounds like I really need to get under my car and look around...anyone know for sure where (how many?) locations are?

Bri Bro

The location of the stock O2 sensor is on the Turbo exhaust inlet, the pipe is close to vertical so it would be hard for water to collect near the sensor. At the stock O2 location, the pressure and exhaust temperatures are very high and you would get an over temp warning from the LSU4 O2 controller (if equipped to sense this). For the LS4U, a better location would be after the Turbo were the temp on the pipe is below 500C. I started out using a L1H1 in the stock O2 location with exceptable results but the unit failed way before its expected lifetime. So I moved the bung to the other side of the Turbo exhaust. My pipes are starting to have lots of O2 sensor holes in them...not a good thing.

In my application, I found the best location for the LSU4 was near the front of the CAT, but every application will be different. Lots of folks who were using the L1H1 and switched to the LSU4 have had to move their sensor away from the engine to avoid overheating issues. There is no one answer to the location issue.

On another note, I am starting to think that EGT sensors are the most dependable and inexpensive solution to A/F measurement. It would require the use of a WB sensor to determine what the exhaust temp is at the desired A/F ratio. After that, the EGT are almost bulletproof and a lot less expensive.

adrial

My bad, it is before the turbo.

So, why dont we place it after the turbo? That should be fine in terms of pressure and temperature.

FYI On a k26/6 with MAF and 17psi boost...EGT temps in the x-over exceed 1600 degrees Farenheit. (1600 is where the gauge maxes out).

Magown

Turbo Tim, put my 02 bung in my 3" test pipe. I had to grind away half of the bung material to keep the sensor wire from rubbing against the body. This is an awful location in my opinion, because there is no way to route the wire as it is pretty much encased in hot exhaust pipes. The only place I could route it was through bottom of the heat shield. The problem is, I can't get to the sensor connector, it's floating between the heat shield and the steering rod. If I ever have to disconnect it, it's going to be a real pain in the neck.





It works but I would like to mount it with more of an angle as the Bosch technical paper for the LSU 4 requires.

Tim sent me another bung, I'm debating on where I will mount it.





You can see the stock location at the top of this pic.





I'll probably mount the bung here in this bend and run the wire up over the starter to the back of the engine.



Oil leaking $hit box

Bengt Sweden

I would love to see Adrial finding out max temp with a laser gun (at 260 km/h) ;-)

adrial

You can do anything with duct tape and a mirror .

Yeah I guess I didnt really think that through eh?

cpt_koolbeenz

Wouldn't placing the 02 sensor further away from the engine change the reaction time of the sensor and the ECU? Maybe it wouldn't be that great of a change with the exhaust speeds? It would make a difference in temperatures with a change in hotsides as well, correct? It would be interesting to see the difference between the "S" 951s and the non "S" turbos. Anyone in NY that could bring adrial your car?