I'm guessing that you'd want the sensor before the turbocharger for best readings???

Since the exhaust gases are hotter would this pose a problem?

What about taking the readings from the exhaust of the turbo??

Hey Soloracer, if you read this for not telling us about the group buy !!! j/k

Mike on my friends turbo race engine, the sensor is positioned ahead of the turbo..this thing get so hot the headers glow red, and we believe this severely shortens the life of the sensor..I dont know how your going to arange the headers, but try and keep the sensor where the pipes merge, but far enough away from the turbo that the intense heat from the hot side isnt so prevalent..If you mounted the sensor on the exhaust side of the turbo, you will still hae to keep it away from the really hot areas

I read somewhere, in a bosch white paper i think, where they mentioned the lamda readings go south when the gas temps are too high. Ill see If I can find that reference...

The reason I didn't tell anyone here about the group buy is that from what I understand usually only turbo guys are really interested in them....and since we all know you can't turbo a 914 what would be the point? It would be like sending the Pope a coupon for condoms. :finger2: j/k

From what I understand you want your 02 sensor as far up the exhaust as possible. A lot of the guys that I know put it in the downpipe. Now I have read that some have had problems with their sensors burning out and and that is what has me concerned. Some of these guys are driving RX7's so their exhaust temps are higher than what we would see (try 900 degrees celcius). On my 944 Turbo the turbo is jammed way up in the the front of the motor making it hard to put the 02 sensor close. The Innovate website/forum also mentions something about problems with the sensor being too close to the turbo and they recommend putting it near the catalytic convertor. I still haven't decided where to put it but I am leaning towards just in front of the cat for ease of removal. I bought the LM-1 because I wanted to use it on multiple cars so ease of removal is important to me.

For the sensor to work, it needs to maintain an internal temperature hotter than the exhaust gasses it is trying to measure. I think it was the Bosch technical notes for the LSU4 sensors that said typically you need to mount it further downstream than you would for a normal O2 sensor. The Tech Edge BBS has a lot of reports of sensors overheating and the recommendation is consistently to mount it further downstream. WBO2 sensors are a lot more picky about the mounting than NBO2 from what I have read. You are also supposed to mount it at least 10 degrees above horizontal to avoid water collecting in the sensor.

In addition you are never supposed to run the car with the sensor unpowered. The WBO2 control circuitry must always have the heater loop operating in the sensor or it will collect carbon deposits and clog. If you aren't going to be using the sensor you must remove it.

Another note from Tech Edge:

Sensors should not be placed where the working gas pressure is much above or below atmospheric pressure, otherwise different calibration curves must be used for best accuracy.

And here are the Bosch technical notes for the LSU4:
http://www.wbo2.com/lsu/Y258K01005e03mar21eng.pdf

jkeyzer beat me to it: the WB sensors are so well heat controlled electrically that you don't need to mount them up by the exhaust ports anymore. You can mount them well back in the exhaust and still get very good readings from them.

WRONG WRONG WRONG WRONG!!!!!!! Don't mount a Bosch LSU4 WBO2 sensor upstream of a turbo!!!!! Not only will your sensor die, but while it's alive the readings will be BOGUS!!!!

The LSU4 very delicately regulates it's internal temperature. This is absolutly critical to it's accuracy. The exhaust must never exceed the internal operating temp of the sensor or it can't regulate it's self. The sensor will heat it's self sufficiently to give accurate readings on even very cold exhaust. (I can pull mine out of the exhuast and it will read the room-temperature free-air oxygen content to within a tenth of a percent. ie ~20.9%)

All the WBo2 controller makers specify that the sensor be downstream of a turbo. And many recommend that in turbo applications you mount a heat-sink to the sensor if you can't get it a sufficient distance from the turbo so it will stay cool enough.

-Ben M.

What I said.

Yeah yeah... you type faster. I started my post, got sidetracked for 20 minutes, then finished. The thread ran off without me while I was distracted. I should have refreshed before posting.

-Ben

thanks all, now we just need to figure out who will be buying, and who will be making payments

Oh, and Mike, be sure to mount your bung somewhere between the 11:00 and 2:00 possition on a horizontal piece of exhaust pipe. If it's not mounted above centerline the sensor will get condensation in it durring warmup which will flash to steam and kill the sensor. (Think popcorn)

-Ben M.

Ben, which wideband controller are you using?

I'm a little concerned that the exhaust of a 914 is so short that the sensor will overheat no matter where you put it. But so far no problems yet.

I have my bung welded after the 4-into-1 collector on my Burch muffler. The LM-1 has never reported a temp error. I doubt you'd ever have any heat problems on a 914 as long as you mount a reasonable distance from the heads. What's a reasonable distance? Not sure. You might want to contact the manufacturer. (The Innovate Motorsports guys have been real good about answering questions)

-Ben M.