[Excorcist]

Hi, I have been reading up for the past 2 hours on all the threads concerning this,

I live in NV where they just do a obd scan

I just ordered a set of catless DPS and am wondering if JB4's built in Code clearing will pass smog, from what i understand it will not because the system will not read "ready"

So I believe i need the BMS 02 SIM and then it will pass smog?

Can i make one of these myself for 2.00$ like vishnu has shown here http://www.e90post.com/forums/showthread.php?t=151315

Also There IS a difference between BMW 02 sim and BMW DP fix correct? I could only seem to find DP fix on there website and it says that it is not needed if you have a JB4...


I know my roomate welded a Cheap universal 02 sim into his Subaru and he passed smog, can I do something similar?

Anyone with knowledge on the Subject I REALLY REALLY appreciate your input, dont feel like replacing DPS everytime i smog. thanks!

[ashmostro]

O2 SIM = dp fix.
You will need the Sims to pass obd. Don't use the code clear function.

[napeHbNYC]

Yep, do fix is what you need. There were a few used ones in classifieds. New is $99. Install, put on map 0. Drive around, pass. Take out.

[mike@x-ph.com]

You need the DP fix, we can help

[ashmostro]

Originally Posted by napeHbNYC

Yep, do fix is what you need. There were a few used ones in classifieds. New is $99. Install, put on map 0. Drive around, pass. Take out.

No real need to take them out. Car runs fine with them in.

[napeHbNYC]

There is a need. Confirmed by BMS, even on the 11pm setting it is not fully of and they highly recommend to take it out FYI.

[ashmostro]

What is the actual impact

[Tzu]

Originally Posted by ashmostro

What is the actual impact

Long term fuel adaptations and sensor wear calculations.

[ashmostro]

Front or back sensor? My understanding was the back sensor is not used in fueling at all. Appreciate the elaboration.

[ashmostro]

So why doesn't the fact that the rear sensors are now seeing un-catalyzed emissions screw up trims even more?

[Dyyd]

Excellent question, I would like to hear the answer to this as well.

[Dyyd]

No comment to this anyone?
Also this is the only thread where I have seen claims that the post-cat sensors affect fuel trims.

[ashmostro]

There's a thread that I started elsewhere that had a lot of great participation and explains exactly why the DP fix affects the fuel trims if left in long term.

Clicky

[Dyyd]

Read through the thread.

Main reason for sims to supposedly cause problem is that post cat narrowband o2 sensors are used to calibrate the wideband sensors.

It seems that there are 2 opinions on how the sims create problems:

1. Post cat signals are summed/mixed with sims and hence do not allow for fuel trims/o2 sensors to be adapted ber bank.

2. It is stated in the thread that sims cut down the lo/hi transitions of the post cat sensors to create cat-like output values. This can cause wideband o2 sensor calibration to go off.


My take on this:

For the 1. This is plausible if sims actually do this. This could be avoided if the sims handled banks individually (I do not know if there are such that do or if this is the default way they work).

For the 2. This is plausible if this is how the sims work. I thought they were quite simplistic adjustable resistor that just trims the o2 signal strength which should not cause any calibration issues.


So does anyone have hard fact on how the o2 sensors work : simple resistor or more advanced logic?


Post thoughts: The o2 sims would obviously not work the way cats do in wot/full throttle closure situations and those might be the times that some calibration is indeed made so even in the case of simplistic resistor they might indeed cause a problem.

Conclusion (note to self) use sims only for passing inspection for best results.

[bmwhp]

when i went through the emissions testing; i forgot to turn the jb4 map to 0. After several attempts the emission's person could not get the computer to communicate and then used the sniffers. At this point I thought I wasn't going to pass because I have catless downpipes. The results came in and I passed the sniffers because our cars have two sets of cats. next time I will remember to turn the JB4 to map 0

[ashmostro]

Your points are good, but exclude the important fact that the input criteria shifts depending on the test being performed, and that is why sims - which are just pots- are unable to satisfy both conditions.

a) when the engine is accelerating, the secondary sensors are looking for a certain amount of reduction in O2 compared the the primaries, which correlates to cat efficiency. If there's too much O2 left then the cats are below target efficiency and a cat code is tripped. DP fix addresses this.

b) when decelerating, the engine is pumping O2 and can be trimmed with just enough fuel for the secondaries to be pinged for stoich (since they are narrowband sensors stoich is easy to find, and doesn't drift). That's what the pre-cat widebands are re-calibrated to and also what the O2 sims cannot...simulate

[Myrder]

Originally Posted by napeHbNYC

There is a need. Confirmed by BMS, even on the 11pm setting it is not fully of and they highly recommend to take it out FYI.

Do you have a citation for this? The PDF for the DPFix states "with 11pm disabling the DPFIX all together."

[ashmostro]

See above link

[Myrder]

Originally Posted by ashmostro

See above link

Thanks I'm familiar with that thread but did not see where Terry or anyone states turning to 11 doesn't disable the dpfix. Did you interpret otherwise? Just wondering.

[ashmostro]

Understood.

It's just a potentiometer... nothing fancy.

[2Times]

If the guy who's name is on the fix says to take it out... I don't question it.