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Old 02-07-2010, 03:33 AM   #26
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Stock sensor moved to bellmouth, vs PLX SM-AFR (Bosch LSU 4.2?) in bellmouth:



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Old 02-07-2010, 12:02 PM   #27
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Quote:
Originally Posted by gabedude View Post
I tuned a v8 twinscroll that had the stock 02 post turbo. It was a few years ago, so it would be interesting to compare my logs of my WB vs the stock one.
I was thinking the same thing. The JDM twinscroll setup puts the o2 sensor there I would assuem due to the isolation of exhaust gasses from the twinscroll headers.

Tony
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Old 02-07-2010, 03:16 PM   #28
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Originally Posted by Turn in Concepts View Post
I was thinking the same thing. The JDM twinscroll setup puts the o2 sensor there I would assuem due to the isolation of exhaust gasses from the twinscroll headers.

Tony
I didn't notice anything different in the mapping as far as O/L C/L fueling goes. You might think that Subaru might have tried CL fueling into boost.
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Old 02-07-2010, 09:46 PM   #29
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Originally Posted by gabedude View Post
You might think that Subaru might have tried CL fueling into boost.
They do that in 07 STIs don't they?

There's a CL enrichment table that seems like it ought to allow staying in closed loop at AFRs well below 14.7, has anyone messed with it yet? For my car it showed up in Merchgod's last set of definitions. (Others may have gotten it sooner, others might not have it.)
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Old 02-07-2010, 10:00 PM   #30
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The stock sensor, moved to the downpipe is accurate. I tuned both of my 02 WRXs that way. I had an aftermarket wideband, it read comparably to the stock sensor moved post turbo. The aftermarket one broke, I never got another one, no need. On the 02 wrx at least, you can rescale it to read down to 10.5 to 1 if you want to.
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Old 02-07-2010, 11:07 PM   #31
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Originally Posted by NSFW View Post
They do that in 07 STIs don't they?
Just 3/4 of a second into high loads is all at 14.7:1.

Quote:
Originally Posted by NSFW View Post
There's a CL enrichment table that seems like it ought to allow staying in closed loop at AFRs well below 14.7, has anyone messed with it yet? For my car it showed up in Merchgod's last set of definitions. (Others may have gotten it sooner, others might not have it.)
I have that table. I would limit the AFL and AFC corrections first though. You don't want a big AFR swing at high loads.
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Old 02-07-2010, 11:19 PM   #32
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Quote:
Originally Posted by NSFW View Post
Stock sensor moved to bellmouth, vs PLX SM-AFR (Bosch LSU 4.2?) in bellmouth:

I cut out your images
Couple questions. First, what is the equation for the regression you did on the data? What is the R value? How did you handle the x intercept? Ideally this would be zero. I don't know how the sensors will react in that area of the graph, but it will have an affect on the regression.

Last edited by van_dutch; 02-07-2010 at 11:19 PM. Reason: colors
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Old 02-08-2010, 12:57 AM   #33
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Beats me. I just logged both, made a scatter plot, and used Excel's polynomial fit thing. I played with the poly order until it looked about right. That's 4th-order.

Why do you ask?
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Old 02-08-2010, 03:23 AM   #34
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Beats me. I just logged both, made a scatter plot, and used Excel's polynomial fit thing. I played with the poly order until it looked about right. That's 4th-order.

Why do you ask?
I'm an engineer and when I see data plotted without that kind of stuff, it rings bells. Playing around until it looks right doesn't really cut it. I'm just curious about the comparison. Without stuff like the equation and the R (really R^2) value, a comparison like that is pretty useless. You can draw numerous shapes that look right. Without an R^2 value, you have no way of judging how well a given curve fits. The equation is telling for a comparison of how they line up.
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Old 04-07-2010, 06:14 AM   #35
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Quote:
Originally Posted by van_dutch View Post
I'm an engineer and when I see data plotted without that kind of stuff, it rings bells. Playing around until it looks right doesn't really cut it. I'm just curious about the comparison. Without stuff like the equation and the R (really R^2) value, a comparison like that is pretty useless. You can draw numerous shapes that look right. Without an R^2 value, you have no way of judging how well a given curve fits. The equation is telling for a comparison of how they line up.
The comparison isn't useless, it's just statistically not sound. From eyeballing the graph (as an engineer, you still remember how to eyeball something? ), I would say the stock sensor tends to underreport the AFR by 0.2 to 0.6 units. This is pretty important of course in tuning, but I would think that after having seen that graph, you could just absorb a 0.4 unit offset in your tuning and get about the same level of precision in the tune as with using other sensors.
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Old 04-07-2010, 12:54 PM   #36
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The problem here is that you assume the aftermarket wideband must be the "true" value simply because it's aftermarket and because it's advertised as being more accurate. You really need to use a completely different instrument (5 gas analyzer) that isn't subjected to the same limitations of the normal wideband design.

FYI I've since been tuning with the factory wideband relocated post turbo. Seems to work well enough, and I will acquiesce on the location issue. I do trust it more when it is post turbo.
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Old 02-28-2013, 11:26 AM   #37
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Originally Posted by arghx7 View Post
The problem here is that you assume the aftermarket wideband must be the "true" value simply because it's aftermarket and because it's advertised as being more accurate. You really need to use a completely different instrument (5 gas analyzer) that isn't subjected to the same limitations of the normal wideband design.

FYI I've since been tuning with the factory wideband relocated post turbo. Seems to work well enough, and I will acquiesce on the location issue. I do trust it more when it is post turbo.
Hi there,

I have a JDM blob eye twinscroll. by default the a/f sensor is post turbo at the bellmouth of the downpipe. do i need to recalibrate the sensor voltage table before i use it to tune?

thanks buddy!
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Old 03-27-2014, 01:44 PM   #38
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I know I'm resurecting an old thread here, I've got a 99RS that I've done a turbo kit on. I bought a Wideband O2 for tuning and a narrowband gauge for long term monitoring. I've been looking for the information on how to hook up the narrowband but cant find which wire off the sensor to splice. There are two white wires and one black one off the front O2 sensor. The rear has an extra grey wire. I just want to know which one sends the voltage signal to the ECU or how I would find that out. Pretty sure its not the black one. Anyone know this??
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Old 03-27-2014, 04:14 PM   #39
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Why not just leave the wideband in all the time? Mines been going strong for almost 2 years and 45000 miles. A new sensor for it being only 80 bucks if it does fail. It monitors flawlessly and most importantly under boost which your narrowband will not perform as well due to its limited range. My sensor is 3 inches from the turbo outlet on top off the dp with a slight offset from center to avoid the ac lines.
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Old 03-27-2014, 07:09 PM   #40
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Originally Posted by flyboynextdoor View Post
I know I'm resurecting an old thread here, I've got a 99RS that I've done a turbo kit on. I bought a Wideband O2 for tuning and a narrowband gauge for long term monitoring. I've been looking for the information on how to hook up the narrowband but cant find which wire off the sensor to splice. There are two white wires and one black one off the front O2 sensor. The rear has an extra grey wire. I just want to know which one sends the voltage signal to the ECU or how I would find that out. Pretty sure its not the black one. Anyone know this??
Black wire on the front sensor is the one you want. The whites are the heater. The rear is post cat, you don't want to monitor that.
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Old 10-14-2020, 09:26 PM   #41
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Old thread.. but here is the result of testing I performed to compare the OEM front sensor in my 04 FXT to my MTX-L...


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Old 10-14-2020, 10:50 PM   #42
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The oem front sensor is like a magnet that is attracted to 11.03. Although I wonder if some of the stickiness to 11.03 is due to smoothing. For example my wideband will show spikes above 11 occasionally, in areas that the oem front sensor can register, but those spikes do not ever show on the front sensor. I am guessing it is the difference between the raw signal from the wideband and the smoothed from the front sensor.
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Old 11-01-2020, 11:15 PM   #43
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Originally Posted by TurboQueef View Post
Old thread.. but here is the result of testing I performed to compare the OEM front sensor in my 04 FXT to my MTX-L...
The pic didn't show up for me, so I pulled the image URL from the quote:
http://www.n8rws.com/Final%20result.jpg

I had basically the same result with my 05 LGT and PLX wideband. Not exactly identical, but close enough that the difference doesn't matter.

Quote:
Originally Posted by tabrad View Post
The oem front sensor is like a magnet that is attracted to 11.03. Although I wonder if some of the stickiness to 11.03 is due to smoothing. For example my wideband will show spikes above 11 occasionally, in areas that the oem front sensor can register, but those spikes do not ever show on the front sensor. I am guessing it is the difference between the raw signal from the wideband and the smoothed from the front sensor.
The floor at 11.03 is just something in the ECU software. Mine bottomed out at 11.1 if I remember right. Your true AFR is richer, but it's impossible to say how much richer because the logger won't show anything richer than 11.03. But that's no big deal if you just target 11.25 or something like that.

I spent a lot of time digging around in the ECU software for the reason that the readings bottom out like that, but couldn't find it. I'm guessing it stems from a limit somewhere in the hardware that sits in between the sensor and the software.
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Old 11-11-2020, 05:41 PM   #44
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NSFW, if I were to permanently relocate my front o2 sensor behind the turbo without touching the current tune, would my closed loops long term fuel trims change? How about drivability?


car is an OBXT with a JMP VF52 and catted DP.
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Old 11-15-2020, 09:02 AM   #45
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NSFW, if I were to permanently relocate my front o2 sensor behind the turbo without touching the current tune, would my closed loops long term fuel trims change? How about drivability?


car is an OBXT with a JMP VF52 and catted DP.

No change in driveability for me. I adjusted the calibration to get the AFR readings to match my Innovate gauge but it was close enough with OEM values in my opinion. One thing to consider however, is you will not see readings lower than 11.15 (and I could not overcome this with any settings in the tune).



I use my OEM sensor in the down pipe for tuning my FXT. My target (on pump with meth/water) is 11.8 at hit to just over 12 at redline.
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Old 11-19-2020, 02:08 AM   #46
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No issues for me either. The ECU didn't seem to notice the difference at all.
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Old 11-26-2020, 02:08 PM   #47
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Thanks for the replies. I will need to give it a go then.
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Old 11-27-2020, 01:55 PM   #48
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Pretty much evey wide band I have used is less accurate then the OE in stock position in closed loop the closets one I have used was my AEM Uego even that was about .2 to .4 richer then the OEM one.
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