[M3 Eater]

So when Jb4 came out, The BMS crew said, yank out your dp fix... you don't need it anymore.

Don't sell it! In NC, it will help you pass inspection.

The question is, when i think about a DP fix, I think of tricking the ECU and sending a AFR that it will like. I am curious as to how this would not affect performance. I have read that JB4 targets an AFR, and boost to tune the car ( along with a million other secret things). If this is true, why wouldn't it have an impact on the outcome when the signal is sent through a piggy back.

Does BMS want us to take it out because the car will run better without it or because if we auto clear all codes, the light won't come on?

I think I have asked this question before in another forum but I was curious if any users have noticed a difference in performance when removing the fix.

Also, will a DP fix mask a poorly working or failing o2 sensor? I sometimes get codes that say a sensor is bad, not typical codes when running cattless. The DP fix seems to have made them go away..

[vasillalov]

Dude,

the front sensors remain. The rear sensor remain. If you are getting sensor faults then your sensors are indeed failing.

All these questions concerning the BMS product should be sent either to Terry or Mike.

[bryce]

The dpfix just modifies the secondary oxygen sensor values. The secondary o2 sensors have no effect on the engine's afr value, they just measure the variance between the primary o2 sensor afr values to make sure the cats are doing their job

[Joshboody]

^^^^ +1

I take it if you reduce a process (that's not needed), then you have more processing power available for other uses.

EDIT: I don't think the secondaries are measuring variance, but more want to see stoichiometric in certain conditions.

[vasillalov]

Originally Posted by Joshboody

^^^^ +1

I take it if you reduce a process (that's not needed), then you have more processing power available for other uses.
.

More processing power available for other uses? Bwhaahha! Like what? Play video games on your iDrive display! LOL! It is an embedded system! Go read about it before you post utter nonsense!

EDIT: I don't think the secondaries are measuring variance, but more want to see stoichiometric in certain conditions

The secondary cats are there primarily for two reasons:
a) To monitor the performance of the primary catalytic converters.
b) To tell the DME when the primary catalytic converters have reached their optimal operating heat range.

[drfrink24]

I do wish I had kept mine installed, as I was under the impression (at the time) that the JB4 suppressed just catalytic codes, which it does not, it simply brute force clears all codes that pop up. This way, when I got my misfire codes, AND of course, o2 codes, I wouldn't have had to have an awkward conversation with my SA rep about running catless.

Also, I believe that the DPFix loops back the output from the primary o2 bank, with the trim/pot adjustments to get the proper variance for your car. I don't *think* it actually simulates or alters the secondary bank (they likely are essentially unplugged with dpfix).

[Joshboody]

Originally Posted by vasillalov

More processing power available for other uses? Bwhaahha! Like what? Play video games on your iDrive display! LOL! It is an embedded system! Go read about it before you post utter nonsense!

I don't have iDrive, so no video games for me.

Originally Posted by vasillalov

The secondary cats are there primarily for two reasons:
a) To monitor the performance of the primary catalytic converters.
b) To tell the DME when the primary catalytic converters have reached their optimal operating heat range.

The narrow band o2 sensors only reports voltage (.45v being stoich) to the DME... and the DME decides how to use this info.

[M3 Eater]

Originally Posted by vasillalov

Dude,

the front sensors remain. The rear sensor remain. If you are getting sensor faults then your sensors are indeed failing.

All these questions concerning the BMS product should be sent either to Terry or Mike.

hmmm... lots of answers. Can't get more than 1 very diplomatic answer when I ask Terry or Mike. I have asked, I respect the answers they gave me and I respect the info I receive here as well. Hell, shiv has jumped in and answered questions about the n54 (msd81) that has helped me to understand why something would or would not create a particular result.

So I ask if dp fix will adjust info in such a way that the DME and any tune attached might be using bogus info in its performance enhancing calculations and your answer was......
"the front sensors remain. The rear sensor remain. If you are getting sensor faults then your sensors are indeed failing. "

I did mention that i was seeing an uncommon sensor error when the dp fix was not intact. If this is indeed a sensor that's failing, is there a benefit in fixing it if I am going to send a dummy signal to the dme anyway?

[tibra1]

The BMS uses a potentiometer to fool the ECU..thats it..its has no effect on AFRs..either u get the voltage correctly or you will throw a catless code..either b/c the ECU "thinks" you are running too rich or too lean..

The BMS doesnt influence the AFR by its operation

[M3 Eater]

I thought I read they used AFR as a target. Thats why I asked. If Jb4 has no effect on AFR directly, then it wouldn't work any better or worse with or without the dpfix installed (assuming that dp fix does more than just send the exact figures the dme is looking to see).

A) wasnt sure jb4 used AFR as a target.. (now I want to find where I read that)...


B) wansn't sure if jb dpfix used actual readings from the exhaust and fed that info back to the DME for fueling adjustments.

thanks for the feedback.

[Joshboody]

Originally Posted by M3 Eater

I thought I read they used AFR as a target. Thats why I asked. If Jb4 has no effect on AFR directly, then it wouldn't work any better or worse with or without the dpfix installed (assuming that dp fix does more than just send the exact figures the dme is looking to see).

A) wasnt sure jb4 used AFR as a target.. (now I want to find where I read that)...


B) wansn't sure if jb dpfix used actual readings from the exhaust and fed that info back to the DME for fueling adjustments.

thanks for the feedback.

AFR is adjusted by the front wideband sensors. The DP fix intercepts the signal from the rear narrow band sensors, so no effect on AFR. I believe the BMS DP fix is a separate unit, compared to procede being internal to the tune. If it's separate, I can't see any reason to disconnect it, but I don't know really.

The DME will use the narrow band signal to determine if both front and rear sensors are working properly by evaluating the switching from rich to lean... this will remain with the DP fix, since the fix is basically a resistor (or I guess potentiometer as Tibra stated) and the switching will not change.

I believe this is fairly accurate. What's the sensor error?

Hey, just noticed my post was changed above... weird... i didn't do it.

[vasillalov]

M3 Eater,

It is really simple. The AFR is determined from the front sensors, not from the rear. The location of the front sensors is the same regardless of which downpipes you are using: immediately after the turbos. The AFRs will NOT be affected regardless of your hardware choice, for as long as the actual sensors are not damaged.

The rear sensors are for making sure that the catalytic converters are actually doing their job.

[M3 Eater]

I cant recall, something like the after cat is unplugged.

[M3 Eater]

I m concerned that bad sensors may be robbing me of power somehow. I just want to get to the bottom of this. If the rear sensors are going bad, it doesn't effect performance.... If the fronts are going bad, then it will effect performance? So, If I were going to do some preventative maintenance on the ride, I should focus my attention on the front sensors and not the rears...?

[M3 Eater]

so out of nowhere, I start getting dpfix is set too strong. I read somewhere that this could mean that the one of the front o2 sensors is kaput. I guess Ill be swapping out both fronts with bosch replacement sensors.

[dlbrooks18]

Originally Posted by M3 Eater

I m concerned that bad sensors may be robbing me of power somehow. I just want to get to the bottom of this. If the rear sensors are going bad, it doesn't effect performance.... If the fronts are going bad, then it will effect performance? So, If I were going to do some preventative maintenance on the ride, I should focus my attention on the front sensors and not the rears...?

Sorry to resurrect an old thread but I have similar question; if you get a SES light because of the lack of a dp fix will that rob the car of power in anyway?

[AngelFarelli]

I have a similar post please read through and comment as I feel it may pertain to this information and I would love the help in my situation.

Post cat o2 sensor! What does it really do for dme? https://www.e90post.com/forums/showthread.php?t=1686467

I read through your thread here and my opinion is that the post cat sensor is a narrow band sensor that does read the condition of the air to fuel ratio within the post cat exhaust gases more accurately but only when within a close range of afr between 11.8:1 to 17.6:1 of afr. Narrow band sensor. With 14.7:1 being the perfect stoichiometric ratio . The afr is not just the fuel trim I think that can confuse some people



from my thread for reference..


I think I might be misunderstood but the narrow band downstream o2 sensor can determine really effectively whether or not you are lean or rich because it's measured in volts, either 0-1 volts depending on rich 11.8:1 afr giving 1 volt, or lean 17.6:1 afr giving 0 volts.
This differs from the wide band o2 sensor which is better at measuring even more lean/rich afr. This is measured by current in mA either negative reading stating there is a rich condition as rich as 5:1 afr or measuring positive stating a lean condition as lean as 20:1.

I heard that it can work when the upstream wideband o2 sensor fails as well