O2 Sensor Placement?

[isiahstites]

Today I built my exhaust for my bike (v-twin) and was curious as to what is the best location for the O2 sensor?  I running an O2 this year so I can log A/F. I know I do not want it near the end of the pipe as you can end up sampling "fresher" air, but I am not sure how close or how far away fron the head it should be.

Scott

[SPARKY]

NA or turbo?

[Sumner]

Today I built my exhaust for my bike (v-twin) and was curious as to what is the best location for the O2 sensor?  I running an O2 this year so I can log A/F. I know I do not want it near the end of the pipe as you can end up sampling "fresher" air, but I am not sure how close or how far away fron the head it should be.

Scott

Considering how short your pipes will probably be I would get it close to the head and maybe put a copper heat sink on it.  That is what we've done on Hooley's car and Phil's car.  I can't remember what the recommended do not exceed heat is, but think it is around 1500.  We've run over that according to the EGT, but it is further up the pipe.  If you have problems with reversion up the pipe you will see big spikes in the data log graph as that is unburned O2, likewise ignition misses will show up the same way for the same reason.  

c ya,

Sum

p.s. tell me about the fairing now  .

[isiahstites]

I can get it with in 3 - 4 inches of the head, is that to close? Is there a industry standard for 02 sensors?

I believe Bennet's Preformance is running the same or a similar fairing and they have been 189 or 190+ I do not remember the number they ran, but they are running a bigger motor than I am. Other than them I am not sure if there are others with a v-twin running the same fairing.

Scott

Considering how short your pipes will probably be I would get it close to the head and maybe put a copper heat sink on it.  That is what we've done on Hooley's car and Phil's car.  I can't remember what the recommended do not exceed heat is, but think it is around 1500.  We've run over that according to the EGT, but it is further up the pipe.  If you have problems with reversion up the pipe you will see big spikes in the data log graph as that is unburned O2, likewise ignition misses will show up the same way for the same reason.  

c ya,

Sum

p.s. tell me about the fairing now  .

[Sumner]

I can get it with in 3 - 4 inches of the head, is that to close? Is there a industry standard for 02 sensors?

What is the total length of the pipe??  I tried to find a picture of the heat sink I made, but couldn't.  Have you seen them?  I think there is an example with the LM stuff.  I think our sensor in the stude is about 12 inches from the open end, but I would try not to get it any closer as I can see some reversion up the pipe at lower rpm's in the data log,

Sum

[Jonny Hotnuts]

I may not be correct in saying this but for some reason I have the idea in my head that it is not how close to the head it is, it is how far it is from the end of the pipe. It would be conceivable that on a very short, free flowing exhaust that an O2 sensor will not read correctly no matter how close it is to the head. And getting it hot (along with leaded fuels) will eat up widebands.

The motor will send exhaust pluses down the pipe and in between these pluses will be a low pressure area. The low pressure area will have a vacuum affect sucks in fresh air. We had our O2 dead in the middle of our collector last year (about 15" of primary tubes into a collector [4 into 1] and about 20" of 3" pipe (without muffler) to the back and it did not work.

This year because we are using the ultra cool Bazzaz Performance FI controller with automatic mapping it is imperative that our O2 works. I wouldn’t mind getting it closer past the collector (just hope that one cylinder reads good enough for 4!) and replacing the O2 every 3-4 years but I am set on making the pipe as long as it needs to be to read correctly.....our motors health depends on it.

To make a long story short....I recommend putting it within 5-8" and maybe a few more inches added in length to the pipes.

[Sumner]

I may not be correct in saying this but for some reason I have the idea in my head that it is not how close to the head it is, it is how far it is from the end of the pipe. It would be conceivable that on a very short, free flowing exhaust that an O2 sensor will not read correctly no matter how close it is to the head. And getting it hot (along with leaded fuels) will eat up widebands.

The motor will send exhaust pluses down the pipe and in between these pluses will be a low pressure area. The low pressure area will have a vacuum affect sucks in fresh air. We had our O2 dead in the middle of our collector last year (about 15" of primary tubes into a collector [4 into 1] and about 20" of 3" pipe (without muffler) to the back and it did not work.

This year because we are using the ultra cool Bazzaz Performance FI controller with automatic mapping it is imperative that our O2 works. I wouldn’t mind getting it closer past the collector (just hope that one cylinder reads good enough for 4!) and replacing the O2 every 3-4 years but I am set on making the pipe as long as it needs to be to read correctly.....our motors health depends on it.

To make a long story short....I recommend putting it within 5-8" and maybe a few more inches added in length to the pipes.

When you say it didn't work, what didn't work?? Erratic readings?? 

I'm guessing that the 3 inch pipe after the collector might have been so large that O2 could come back up it messing with the readings.  Other than that it looks like you had enough pipe length after the O2 to work. 

Who's wideband controller are you using??  You are right the leaded gas can cut down on the life of the O2, but for the limited time we run our motors it isn't a big concern I feel, yet we take a spare.

The only problem I see with getting close to the head is exceeding the save temps for the sensor.  If you have to get so close that a heat sink won't work you always have the option of making a scavenging pipe setup like in the attached picture.  I input for it (scavenge pipe) can run up the pipe to an area close to the head.  This system has the benefit of not getting the O2 sensor hot, yet getting the input to it a long ways from the outlet of the exhaust.  I made one for us, but we haven't needed to use it.

c ya,

Sum

[Harold Bettes]

Howdy All,

The placement of O2 sensors is somewhat critical in my experience with a couple of caveats:

A) The sensor should be placed into service at a junction (collector) point.

B) The sensor should be placed into service only in the top 180 degrees of the pipe / collector to decrease H2O contamination.

C) If the sensor is to be placed in service on a single pipe, it should follow the suggestions in B above AND be far enough from the end as to not spoil the readings by short circuiting atmospheric oxygen to the sensor. That is normally at least 8" to 10" from the end or at least in front of a muffler if used.

Regards to All,
HB2

[Sumner]

......................
B) The sensor should be placed into service only in the top 180 degrees of the pipe / collector to decrease H2O contamination. ..........

Hi Harold good points, but I think the one above is not so critical for a race motor.  On the street where you can get condensation in the pipes overnight and then blow that on the sensor I agree you want the sensor on the top and that is where I have it on my truck.  On a race motor especially with the open pipes and the heat at our events I wouldn't worry about it as much, especially if mounting it there becomes a hassle space wise.

When you say in point A at a junction could you elaborated on that some so I have a better idea what you are talking about and if the H2O thing is different that what I mentioned above maybe clarify that for me also.

Thanks,

Sum

[narider]

I went in at 1 o'clock, 10" from the back of the exhaust valve on mine.

Good? Bad? Right? Wrong? I don't know and don't really care to tell the truth. I had to pick somewhere, it was an easy install, I get clean logs from it and as long as I don't move it... all my traces are relative to themselves(which is all that matters to me). Not to mention it not being in my way or hard to R&R. 





Todd

[Jonny Hotnuts]

When you say it didn't work, what didn't work?? Erratic readings?? 

I'm guessing that the 3 inch pipe after the collector might have been so large that O2 could come back up it messing with the readings.  Other than that it looks like you had enough pipe length after the O2 to work. 

Who's wideband controller are you using??  You are right the leaded gas can cut down on the life of the O2, but for the limited time we run our motors it isn't a big concern I feel, yet we take a spare.

Yeah the readings were all over the place.
I just measured the distance and it was really only about 12" from the end of a 3" pipe. I would not have been surprised if my wifes hand could reach the O2 tip. I am SURE it was because the large pipe (not to mention that it is a dead straight shot) with the sensor within 12" that caused the prob.

I am using the FAST wideband logging A/F meter.
http://www.compperformancegroupstores.com/store/merchant.mvc?Screen=PROD&Store_Code=CC&Product_Code=AFMeter&Category_Code=


It is for sale and I will make someone a SWEET deal on it.
Will post this and Power Commander 3 USB in the for sale section soon.

BTW:

SUM....Love the "remote" mount O2 diagram....will likely end up with something on those lines
.

[Sumner]

I went in at 1 o'clock, 10" from the back of the exhaust valve on mine.

Good? Bad? Right? Wrong? I don't know and don't really care to tell the truth. I had to pick somewhere, it was an easy install, I get clean logs from it and as long as I don't move it... all my traces are relative to themselves(which is all that matters to me). Not to mention it not being in my way or hard to R&R. 





Todd

Todd that looks really good to me and as long as the logs look good that is all we care about.  Looks to me that you are plenty far from the end of the pipe.

That motor looks really nice, now if I could only hear it.  Have Dep put it on YouTube running  .  Thanks for posting the pictures,

Sum

[Sumner]

.................Yeah the readings were all over the place.
I just measured the distance and it was really only about 12" from the end of a 3" pipe. I would not have been surprised if my wifes hand could reach the O2 tip. I am SURE it was because the large pipe (not to mention that it is a dead straight shot) with the sensor within 12" that caused the problem.........

We had that problem on Phil's car with it just up in the open collector.  With the car running I jammed another piece of pipe a couple feet long on the end of the collector and the problem immediately went away, so I then knew the sensor was too close to the end.  We then had to move the sensor up past the collector and up into just one pipe closer to the head, but still probably 14-18 inches from the head.  That worked,

Sum

[Harold Bettes]

Sum and All,

The contamination that is possible from water is part of the problem of combustion. During cold fire ups it is worse than when at full chat.

The chemical balance of something like iso-octane at a chemically correct (stoichiometric) burn looks like this:
C8H18 + 12.5(O2 + 3.76N2)     =   8CO2 + 9H2O + 47N2  Note that on the right side there is a gob of water that is produced. Sure it slobbers more on cold fire up. The heat from this stuff burning is what we try to turn into push on the piston(s) and eventually it becomes usable power at the output shaft.

Hope that helps provide some clarity to what I was trying to point out. The experience of others such as placing more pipe in service keeps from atmospheric oxygen polluting the readings is good stuff. The time pulse issue is probably much worse at idle or sub 2000 than at other RPM references.

Regards to All,
HB2

[isiahstites]

I went in at 1 o'clock, 10" from the back of the exhaust valve on mine.

Thanks for the pictures and your input. Curious as to what logging system you are using? Also, any reason you went with the back pipe instead of the front? I know the back tends to run a bit leaner, is that the reason?

Scott