O2 bung question

[kopenytro]

Hey guys,
I have looked through the forums but stilli need some advise.
Due to space limitations I am unable to mount the O2 bung anywhere on my exhaust after the turbo.

I believe I can mount the bung on the header leading into the turbo.
Is there a preferred mounting location? I was thinking
On the bend that routes the header up to meet the turbo.

Thoughts?

Thanks again.

Kope

 

[nate007]

You always want your 02 as close to the engine as possible, and always BEFORE the turbo to ensure the most accurate readings.
Not sure where you have your turbo mounted in your sled, but most s/c guys run the wire through the front of the stock exhaust cover below the seat, and into the pipe ahead of the muffler. Try to get it as close to the header collector as possible, and dont ever install it below horizontal. If it's pointing "uphill" into the pipe, it will allow condensation to run back into the sensor, which will ruin it very quickly.
I've also welded a small (2 1/2" long) piece of pipe, cut down the center as well, onto the exhaust pipe as a guard around the sensor. Although not necessary, it may help keep anything kicked up by the track from damaging it.

 

[FLYBYU]

I've always mounted mine after turbo in down pipe. I think there is a debate about it somewhere. From AEM:
Oxygen Sensor Placement

A weld-in M18 X 1.5 boss is supplied for sensor installation. Mount the O2 in the Exhaust System at least 18 inches downstream from the exhaust port as the extreme temperatures of the exhaust can harm the sensor. The sensors internal heater will warm the sensor to the optimum operating temperature. If available, the factory O2 sensor location is usually preferable. On turbocharged engines the UEGO sensor must be installed after the Turbo Charger, if not, the pressure differential will greatly effect the accuracy of the unit. In applications with a catalytic converter, the UEGO sensor must be mounted BEFORE the converter. In applications with an auxiliary air pump, the UEGO sensor must be mounted BEFORE the pump input to the exhaust stream. Installation angle should be inclined at least 10° towards horizontal (electrical connection upwards, see diagram) which prevents the collection of liquids between sensor housing and sensor element during the cold start phase.

 

[nate007]

I have read that before as well, but keeping in mind that statement is largely geared towards automotive applications as well. They are somewhat correct about the 18" statement, but I have a hard time agreeing 100% with that since most V8 automotive and truck applications have it right on the back of the cast iron exhaust manifold, approx 8-10" from the closest exhaust port, but if that's what they want for their particular product, oh well right?
I also can only assume that "after" the turbo is also geared towards auto applications. I recently installed an AEM WB into a WRX turbo car, and it was in the downpipe after the turbo. There wasn't a snowballs chance of it going ahead of the turbo given how it's rammed in there anyway, so we put it near the factory 02 sensor. Keep in mind, cars and trucks operate for much longer periods of time, and likely would have higher exhaust temps. After running a while, my s/c'd '10 Camaro can sometimes run nearly 380+ f* temps at the inlet end of the headers at idle, and who knows how hot at full throttle... Sure, sleds will get hot, but in shorter runs and far more fluctuations in the throttle.
For the rear mount turbos on Yamaha sleds, there is quite a distance of pipe that the exhaust has to travel to get to the turbo (relatively speaking), and with the conditions they operate in, there's a larger chance of it actually cooling too much (light throttle) and not operating correctly either.
Realistically, it's probably splitting hairs here, but as long as it's not going to get moisture in it, run it where you can?
I would stay as close to the collector as possible and in front of the turbo for the best resolution, especially if you're running lower boost numbers, but that's just what I would do. Chances are, if you're running Superman boost numbers, you're not running closed loop from it while at WOT anyway.
It is different for each situation, I'll give you that, but for sleds, it's likely not going to make a large enough difference in readings to affect much.

 

[FLYBYU]

McXpress nytro and apex kits. Their setups both have after turbo before Muffler.

 

[kopenytro]

Thank you everyone for all of the responses.
I believe I have what I need to final out this part of my build.

Much appreciated.

Kope

 

[nate007]

I have to stand corrected on this one, thanks guys. I haven't seen it this way on cars, but I'm primarilly on the supercharger scene though.
I'll definitely have to read up on this topic some more in regards to turbo setups, but thanks FLYBYU for the pics.

 

[SnoBird888]

From what i have experiences with cars, turbo'd ones at that the front o2(upstream) is placed in the collector of the cast header about 10" from the closest exh port. these sensors tho are considered narrowband so they are only good at reading between 13.5-15.5. anything outside that they are inaccurate more and more. The wideband such as an AEM or Innovate lc1 requires to be put in a location on vehicles after the turbo because the pressure pre turbo is very high which can throw off the reading. these cars run 12psi stock and upwards of 30psi in some applications. Anyways i have always ran my wideband atleast 8" past the turbo in the DP so the exh turbulence has lessened and you can get a good lower pressure reading. As far as temps I see around 300-400 idleing and 1000-1150*F cruising on the highway. WOT sees 1300*F max on long pulls. richer afr's keep the temps down. What i do to keep the sensor from overheating is make a heatsick out of a piece of 4"x4" copper or aluminum sheet. drill the hole for the sensor to go through in the middle and the sheet will help dissipate the heat. being that snow is always being thrown toward it having the sensor near verticle would be the best to avoided damage. the heat sick would help deflect rocks/stuff as well so it would double task. I plan to put mine right in the collector/right after if it fits under there. otherwise going to have to go near the header-muffler connection.

just my 2 cents from what i have done with my customers/my cars in the past/present.

right from the lc-1 manual
Install the bung downstream from the turbo before the catalytic converter. The high exhaust
pressure before the turbo interferes with the lambda measurement and the high exhaust
temperatures encountered there can damage the sensor.

 

[kopenytro]

O2

Thanks for the input Snobird.

I have some new details to add.
Since my last post I have purchased an AEM Wideband UEGO AFR gauge - #30-4100.
I also have my exhaust back and am in the final stages of mock up before being sent out to be ceramic coated.

So am I to understand that I can not put the O2 bung into the header pre turbo like originally planned and need to mount it in the can for gauge accuracy?

If so, based on the pic below, can you give me a suggestion for its location.

Thanks for your help and input.

Kope

 

[TurboM700]

For the most accurate reading you will want the O2 before the turbo 12-18" away from the spark plugs. This isnt alawys easily done on the nytro so most guys like myself put it right before it goes into the turbo.

I have had mine both before and after(bungs welded in both spots) I see about .5 leaner after the turbo.

Also heat is a good thing when it comes to O2 sensors. The quicker they warm up and stay warm they will live a happy life.

Here is where I mounted mine. 1200 boosted miles and not a single problem.

 

[kopenytro]

O2

Thanks for picture and the info.
That is the same route I'm going to take.
Easier and less space restrictions.

Nice to see my header being put to good use!

Always thought you did a great job on your build.

- Mike

 

[TurboM700]

Thanks

Boost is addicting!!! She's getting turned up this yr. going with either head shim or timing reflash, intercooler, and different fuel controller.

240hp should be hard to beat around the lakes at the cabin.

Good luck with your build. Cant wait to hear how much you like boost. What are you doing for a fuel controller?

 

[SnoBird888]

In your application it will need to be mounted pre turbo. in applications with atleast 12" of pipe (no muffler) post turbo then put it there. being its on the sled the mounting location is pretty limited. afr should never change across the turbine so post turbo sensor prob was experiencing turbulent flow. it only takes 20 sec for the sensor to warm up. too much heat is very bad for the sensor and its the main reason a sensor fails early.

again your limited to pre turbo so it is what it is and many ppl have done it. miles on a vehicle are different than miles on the sled. I would expect my sensor to last 20+ plus miles were sled guys are happy with a couple seasons. 3k or so miles