02 bung into SSI exchangers?, Which pipe is best. Does it matter? Options

[VaccaRabite]

I'm doing some remote tuning through PMB for my injected 2056. The tune is close and I've been driving it but there are improvements that could be made now that I have had about a year and change since my last tuning session.

Eric suggested I move my O2 bung from the muffler (where I knew the location was not ideal but it got to sample all 4 cylinders) to one of the exchanger pipes (much better/hotter location, but only get to sample one cylinder.)

Tapping into the Cylinder 1/2 bank would be easiest, and I was thinking of going into Cyl 1 since the pipe is shorter and maybe a little hotter.

So now the question is what cylinder is the one I want to TIG weld the bung into. I don't track EGT so I don't really know if one pipe is hotter then another. And I want to eventually get heat back in my car so I can't go to headers which would allow me to sample all the cylinders before the muffler.

Thanks! Zach
@Eric_Shea

[BeatNavy]

Zach, can you comment on what Eric told you or why you don't think your location is ideal?

I've got a Microsquirt setup with Chris Foley's EVO II stainless steel muffler. He pre-welds a bung right into the muffler. I seemingly had no issues with it when I was running D-Jet but for some reason when I switched to Microsquirt (and a different O2 sensor) my idle AFR readings were completely useless for tuning purposes. Worse than useless. Kept pointing me to super lean when I was super rich. At throttle it seems ok, and I know tracking type 4 idle AFR can be challenging (so says Jake).

Sorry, don't have an answer to your question, but I'm curious.

[DRPHIL914]

zach, what muffler are you running? i had mine put in the Triad at the back center pipe that goes from the lower to upper section so its sensing gases from both sides where they come together.

Phil

[VaccaRabite]

zach, what muffler are you running? i had mine put in the Triad at the back center pipe that goes from the lower to upper section so its sensing gases from both sides where they come together.

I had a Triad, with a bung in the exact same spot. I wanted something a bit quieter (and as it turns out a TON lighter) that did not give up on power.

Zach, can you comment on what Eric told you or why you don't think your location is ideal?

I've got a Microsquirt setup with Chris Foley's EVO II stainless steel muffler. He pre-welds a bung right into the muffler. I seemingly had no issues with it when I was running D-Jet but for some reason when I switched to Microsquirt (and a different O2 sensor) my idle AFR readings were completely useless for tuning purposes. Worse than useless. Kept pointing me to super lean when I was super rich. At throttle it seems ok, and I know tracking type 4 idle AFR can be challenging (so says Jake).

Sorry, don't have an answer to your question, but I'm curious.

I am using one of Ben's "Quiet" mufflers. The exhaust bung is in the base of the tail pipe. As long as there is open throttle, it works but is not ideal. The exhaust gas has cooled quite a bit by then. And there is reversion when I'm shifting or at idle which leads to false lean conditions. Latency was almost a full second. It was not a huge issue for the early rounds of gross tuning but it needs to be moved to someplace earlier in the exhaust system for more accurate fine tuning.

When I had Ben build the muffler for me, he did warn me that sampling all 4 cylinders with one bung would be a challenge with this muffler. IMO its worth it over the Triad I was using before. The noise is tamed and long drives are not nearly as fatiguing and leave my head throbbing even with ear plugs. And the Triad weighs about 2X what Ben's Quiet muffler weighs.

If push comes to shove I know I can monitor two O2 bungs with Microsquirt. I'd prefer not to do that, as I REALLY don't want to have to take apart the AMP Seal plug again.

Zach
@mb911

[Mark Henry]

Don't put it in the muffler it's not hot enough for the lambda.

I'd put it in #2 as it's usually the most nominal operating P&C.

A better idea is to weld in a chunk of 1-1/4" to 1-1/2" tube between #1 and #2 pipe, about halfway between the muffler flange and the start of the "exchanger" outer shell. Weld your bung to the top of this cross pipe.

You don't have to cut the SSI pipes to match, just drill say a 1/2" hole into each of the SSI pipes.

[VaccaRabite]

Don't put it in the muffler it's not hot enough for the lambda.

Agreed. As I said I knew going in it was not an ideal location, but a compromise to get all 4. Not all of my ideas are great. Just ask my ex-wife. ;-)

I'd put it in #2 as it's usually the most nominal operating P&C.

A better idea is to weld in a chunk of 1-1/4" to 1-1/2" tube between #1 and #2 pipe, about halfway between the muffler flange and the start of the "exchanger" outer shell. Weld your bung to the top of this cross pipe.

You don't have to cut the SSI pipes to match, just drill say a 1/2" hole into each of the SSI pipes.

That's in interesting idea. Would enough gas make that hard 90 bend to give an accurate reading though? You want the sensor in the main gas flow as much as possible.

Zach

[JamesM]

I'm doing some remote tuning through PMB for my injected 2056. The tune is close and I've been driving it but there are improvements that could be made now that I have had about a year and change since my last tuning session.

Eric suggested I move my O2 bung from the muffler (where I knew the location was not ideal but it got to sample all 4 cylinders) to one of the exchanger pipes (much better/hotter location, but only get to sample one cylinder.)

Tapping into the Cylinder 1/2 bank would be easiest, and I was thinking of going into Cyl 1 since the pipe is shorter and maybe a little hotter.

So now the question is what cylinder is the one I want to TIG weld the bung into. I don't track EGT so I don't really know if one pipe is hotter then another. And I want to eventually get heat back in my car so I can't go to headers which would allow me to sample all the cylinders before the muffler.

Thanks! Zach
@Eric_Shea

As stated, reading from a single pipe is still not an ideal situation either as you want it as close as possible after all 4 pipes merge. So while you will get better response in the exchanger pipe you are only getting 1/4 of the exhaust.

As you really only need the wideband output while you are tuning provided we disable closed loop operation when done, I recommend just running a different muffler temporarily while tuning.

[914Toy]

I have recently learned from discussions with a "techy" at INNOVATE MOTORSPORTS, that the Bosch O2 sensors should be mounted in 1" long bungs (which they supply in their kits. I will be modifying the 1/2" bungs in my twin headers (911 engine). This will place the tip of the sensors just inside the header pipes - minimizing protruding into the gas flow.

[JamesM]

Zach, can you comment on what Eric told you or why you don't think your location is ideal?

I've got a Microsquirt setup with Chris Foley's EVO II stainless steel muffler. He pre-welds a bung right into the muffler. I seemingly had no issues with it when I was running D-Jet but for some reason when I switched to Microsquirt (and a different O2 sensor) my idle AFR readings were completely useless for tuning purposes. Worse than useless. Kept pointing me to super lean when I was super rich. At throttle it seems ok, and I know tracking type 4 idle AFR can be challenging (so says Jake).

Sorry, don't have an answer to your question, but I'm curious.

O2 sensor placement is a lot less of an issue when just outputting to a gauge. Only becomes a noticeable issue when you start increasing the precision of a system. I have found idle tuning is best done by aiming for best vacuum rather than a specific mixture and that ultimately the best mixture is specific to the motor. Though being able to see the mixture is still helpful as a reference.

[VaccaRabite]

@JamesM

James! How did I miss that you were the JamesM on 914World!
I'm very glad you chimed in as I clearly missed the thrust of your email to me on this.

Should I just put the Triad back on for your tuning? Is the bung in the center pipe sufficient? I don't have access to a bursch with a bung for testing. I have to think the gas in the Triad will also be too cold - but it won't have the reversion issues.

Zach

[Mark Henry]

Don't put it in the muffler it's not hot enough for the lambda.

Agreed. As I said I knew going in it was not an ideal location, but a compromise to get all 4. Not all of my ideas are great. Just ask my ex-wife. ;-)

I'd put it in #2 as it's usually the most nominal operating P&C.

A better idea is to weld in a chunk of 1-1/4" to 1-1/2" tube between #1 and #2 pipe, about halfway between the muffler flange and the start of the "exchanger" outer shell. Weld your bung to the top of this cross pipe.

You don't have to cut the SSI pipes to match, just drill say a 1/2" hole into each of the SSI pipes.

That's in interesting idea. Would enough gas make that hard 90 bend to give an accurate reading though? You want the sensor in the main gas flow as much as possible.

Zach

IMO it won't matter as there will be a flurry of crossflow. Make the drilled hole a bit bigger if you like.

I'd use square tube, easier to weld the bung to a flat surface.

[mb911]

Tuning with the muffler that will be used every day is ideal. Its funny there was another thread recently about how all of mu mufflers should come with o2 bungs in them.. I felt it unnecessary as it is not an accurate way to measure.. It really should be in the heat exchangers.. The alternative would be in the inlet of the muffler however that would impede flow without doubt.

[JamesM]

@JamesM

James! How did I miss that you were the JamesM on 914World!
I'm very glad you chimed in as I clearly missed the thrust of your email to me on this.

Should I just put the Triad back on for your tuning? Is the bung in the center pipe sufficient? I don't have access to a bursch with a bung for testing. I have to think the gas in the Triad will also be too cold - but it won't have the reversion issues.

Zach

I cant say for sure as I haven't ran that setup yet, but in theory the Triad should produce better results. The glass packs used on the Triad are pretty wide open though and the pipes are pretty large so the chance still exists that fresh air might be getting pulled far enough back into the system at idle to screw up the readings. Wont know until someone trys it.

If anything I am hoping it will at least decrease the response time for the O2 reading. right now im seeing over 1 second between a change in injector pulse width before the corresponding change in O2 reading shows up in your datalogs. I actually disabled closed loop operation in the last update to your tune that i sent this weekend for that very reason, to much lag in the sensor reading to be of any value. Dont want the engine attempting to adjust mixture real time off a reading that is already over a second old.

[JamesM]

Tuning with the muffler that will be used every day is ideal. Its funny there was another thread recently about how all of mu mufflers should come with o2 bungs in them.. I felt it unnecessary as it is not an accurate way to measure.. It really should be in the heat exchangers.. The alternative would be in the inlet of the muffler however that would impede flow without doubt.

No muffler swap on 914 heat exchangers makes enough of a difference to the motors fuel requirements to matter. If it did anyone running d-jet with aftermarket mufflers would be screwed.

In theory putting the 02 bung in an exhaust manifold would be ideal but 914s don't have single manifolds that join all the cylinders so there is no option but to compromise. Options are to put it in the heat exchanger pipe and only measure 1/4 of the gases or put it later in the system.. Wideband O2 sensors have integrated heaters so distance from the head from a heat perspective is not a problem, only becomes an issue when its to near the exhaust exit that fresh air gets back in and messes with the readings. Generally you want to be as close as you can get it after the pipes merge and before the muffler. The Bursch mufflers are probably as good as you can get with stock heat exchangers for O2 placement. the Triad looks promising, its just unknown atm how much fresh air gets back in with those.

[Frank S]

I've tried different locations for the Lambda Sensor with a muffler which is quiet simmilar to Ben's one I think (Mittelmotor).
I don't have pics, but I have mounted one sensor in the center of the Muffler and one sensor at the right sidewall of the muffler. They read exactly the same under all load conditions and might be 0.1 Lambda off at idle conditions.
Center of Muffler is also not to cold...

@Rob . i think the rootcause for your lean reading is your cam.

Will post some pics of the Sensor location tomorrow...

[Gint]

Its funny there was another thread recently about how all of mu mufflers should come with o2 bungs in them.. I felt it unnecessary as it is not an accurate way to measure.. It really should be in the heat exchangers.. The alternative would be in the inlet of the muffler however that would impede flow without doubt.

@mb911 - I never said that all your mufflers should include an O2 bung. I simply asked if your mufflers came with one. That's all.

I have a Triad also and I'm about ready to do FI. Like you I realize that the muffler is not an ideal location for an O2 sensor. And I also would like a quieter muffler than the Triad at this point in my life. Keeping an eye out for an alternative.

Subscribed to this thread.

[mb911]

Its funny there was another thread recently about how all of mu mufflers should come with o2 bungs in them.. I felt it unnecessary as it is not an accurate way to measure.. It really should be in the heat exchangers.. The alternative would be in the inlet of the muffler however that would impede flow without doubt.

@mb911 - I never said that all your mufflers should include an O2 bung. I simply asked if your mufflers came with one. That's all.

I have a Triad also and I'm about ready to do FI. Like you I realize that the muffler is not an ideal location for an O2 sensor. And I also would like a quieter muffler than the Triad at this point in my life. Keeping an eye out for an alternative.

Subscribed to this thread.

Sorry @Gint . No worries was just pointing out how it is not ideal on a type 4 muffler..

[Gint]

NP at all. (IMG:style_emoticons/default/agree.gif) I don't know of a decent solution at this time though, short of using two O2 sensors. I'm very interested in this thread at this point in time.

[Mark Henry]

NP at all. (IMG:style_emoticons/default/agree.gif) I don't know of a decent solution at this time though, short of using two O2 sensors. I'm very interested in this thread at this point in time.

I had two wide band meters on my /6 with carbs, I'm done tuning and one is off the car now. If anything I found it confusing and ended up only looking at the one meter at a time. Basically they read the same and if your engine is sound they should all be the same.
Since I have carbs and I don't really like the look I'll likely remove the other meter as well. If you're carbs, L-jet or D-jet there's no real reason to leave it on after tuning. Aftermarket EFI leaving the WB installed depends on if you run open or closed loop.

[Gint]

That's a fair point Mark. That had occurred to me that unless something was really wrong, one side should be an adequate representation of all. But still... (IMG:style_emoticons/default/idea.gif)