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Whats the word on WB02 accuracy with a tiny down pipe.l? In my experiance as long as exh is flowing steady its reading accurate, though not so much at idle. I dont need it accurate at idle.
Id like to run a simple short 90. But if the WB02 will be wildly inaccurate at wot and cruise i suppose I can add some piping.
You'll likely have a really hard time getting an accurate reading with one that short.
The actual opening on the housing is a lot smaller than the piping, and the velocity coming out will be extremely high.
It won't allow enough time for the exhaust to disperse evenly, and you'll end up with spots that have stale air that will likely be mixed with fresh air.
You're only hope is to put the sensor on the outside of the bend radius in a spot that puts in directly in the path of the turbine wheel, and just always assume its going to read lean.
Well dang... as much as I'd like a tiny DP on there It's not worth having inaccurate info. I was thinking it was more of a heat issue and once EXH gas was flowing at WOT or cruise it didn't matter. I'll have get something longer on here. Appreciate the input! I usually run these since I have the the sensor pretty close to the exh exit on my stuff.
Aem makes a wideband controller with backpressure compensation so you can mount the widebands pre turbo. Its expensive but it would solve the short downpipe issue of a fender or hood exit. I was gonna use one on my new set up when ever I get time to start on it.
I have a 12 Buick Regal GS, and the O2 is only a few inches from the discharge of the turbo. Yet on my turbo Silverado, I put the O2 8" or more from the discharge of the turbo and it died the first time I drove it.
The typical Bosch LSU 4.X sensors don't like the heat. Recommended 12" and no closer than 9" down stream of a turbo is what I was told. Closer you are the shorter the sensor lifespan. But I've had good luck with the head insulating bungs pictured above. The new 4.9 sensors have a sensor life meter for overall sensor health to be monitored and they seemed happy right on the top of the 90* bend in My S480 combo.
Pre turbo sounds great... But the options I saw were a 4 channel kit for $658. Defiantly don't have 1300 to drop on AFR equipment. But that'd be slick on a "real race car". If it's a simple skew table I'd think you could program the offset with a Holley or MS ECU. I don't get what they do to keep the sensors alive, but it states it comes with sensors.
Well dang... as much as I'd like a tiny DP on there It's not worth having inaccurate info. I was thinking it was more of a heat issue and once EXH gas was flowing at WOT or cruise it didn't matter. I'll have get something longer on here. Appreciate the input! I usually run these since I have the the sensor pretty close to the exh exit on my stuff.
Have you checked to see how much these adapters skew the sensor output? I suspect it may be more than most would expect.
I don't know what you would call it and I don't think I could find it but I've seen people do what I would call a draft tube into it
It would probably be easy to install a small tube for a sensor within the main pipe to ensure external air cannot influence the sensor, or should have almost no impact.
The typical Bosch LSU 4.X sensors don't like the heat. Recommended 12" and no closer than 9" down stream of a turbo is what I was told. Closer you are the shorter the sensor lifespan. But I've had good luck with the head insulating bungs pictured above. The new 4.9 sensors have a sensor life meter for overall sensor health to be monitored and they seemed happy right on the top of the 90* bend in My S480 combo.
Pre turbo sounds great... But the options I saw were a 4 channel kit for $658. Defiantly don't have 1300 to drop on AFR equipment. But that'd be slick on a "real race car". If it's a simple skew table I'd think you could program the offset with a Holley or MS ECU. I don't get what they do to keep the sensors alive, but it states it comes with sensors.
After looking at this it seems to have a back pressure sensor and then uses the pressure data for the sensor to calculate the offset. I also thought it would be possible to program this effect into a megasquirt table or with hptuners maybe a custom histogram that would take into account the back pressure might work. I saw a yellow bullet thread awhile back about this. It seemed doable to me then too but then work probably made me forget about it.
as for heat the one I saw actually being used had those little heat sinks like the earlier pic on every sensor. I need to see if this is possible. Add another to do to my list. Lol.
Can you not just run back to back pulls with an extension on the downpipe and see how it skews and then you know for future pulls how far off the reading is with either a shortened DP or the sensor preturbo?
Can you not just run back to back pulls with an extension on the downpipe and see how it skews and then you know for future pulls how far off the reading is with either a shortened DP or the sensor preturbo?
pre-turbo will be affected by pressure and temperature. Unless you can replicate and account for all variances....not an option. And you'll kill the sensor faster.
Making provision in the downpipe as normal to ensure decent and exhaust gas only flow isnt too difficult. Under full load isnt always so much of an issue, lower loads where fresh air may skew readings is an issue.
Although if the sampling area around the sensor is done right, there should be no issue regardless.
I don't think it skews at all WOT. There's enough flow around the sensor to keep it happy. So you don't want to alter the tables or skew the sensor maps. They read lean at cruise an idle in my experience. I could care less about idle, but they can make drivability tuning a bit of a pain. That and the sensor life is reduced the closer and hotter it runs. Believe 900* was the suggested max temp on the standard bosch sensors. The bungs isolate the sensor quite a bit and have a tiny inlet holes. I've run them right after the turbo with no heat issues. Wondering if you could weld a SS tube to that tiny inlet and route it much close to the turbo so it couldn't "mix" fresh air in and skew the readings as much. May be more trouble than its worth...
looks like with those bungs installed you can have them up to 2" from the exh. port. So should be more than cool enough anywhere in the DP.
pre-turbo will be affected by pressure and temperature. Unless you can replicate and account for all variances....not an option. And you'll kill the sensor faster.
Making provision in the downpipe as normal to ensure decent and exhaust gas only flow isnt too difficult. Under full load isnt always so much of an issue, lower loads where fresh air may skew readings is an issue.
Although if the sampling area around the sensor is done right, there should be no issue regardless.
I've watched pre and post turbo O2's on a dyno and they didn't vary by more than a couple tenths for a given boost level. Seems like you could do the same at the track and see how far it skews. Separately, if you just wanted 1 post but concerned about accuracy due to a short DP, then bolt on an extension and dial it in and then remove the extension and see how far off it is.
I've watched pre and post turbo O2's on a dyno and they didn't vary by more than a couple tenths for a given boost level. Seems like you could do the same at the track and see how far it skews. Separately, if you just wanted 1 post but concerned about accuracy due to a short DP, then bolt on an extension and dial it in and then remove the extension and see how far off it is.
On what vehicle and what widebands were being used ? And what pressure/temperatures were you seeing pre-turbo ?.
Can't say I've seen many test two widebands before and after the turbo....simply as almost nobody does because of the known issues. Would be good to see actual data ?
Even those testing...or at least testing and making it public about individual cylinder widebands on a turbo application seem non existent. I did post to RH to do it but it fell on deaf ears. Hell...I even asked a few times for it on even a supercharged application, to no avail. And that'd be an easy test.
Although you would expect each individual runner to read differently than a single collector post turbo anyway. Would be great to see a few tests, both with long runner turbo setups and log manifold setups.
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Smallest down pipe for accurate WB02 readings? 
