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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N55 Turbo Engine Tuning and Exhaust Modifications - 335i Tuning > VRSF catless downpipe fix - Is it Okay if I leave it?



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      08-18-2018, 01:57 PM   #23
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Quote:
Originally Posted by MIL.SPEC View Post
Well that is new information. I thought you leave DP fix in all the time?

My engine light just came on and my car started idling rough. Is that normal or do I have bigger problems?

I left my DME reader at home today.
How long ago was your DP Fix installed?

I'm not sure either, seems like there's a bit of conflicting information. I installed the N55 DP Fix two weeks ago and want to avoid this problem if possible.
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      08-24-2018, 04:20 PM   #24
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Quote:
Originally Posted by cRo5 View Post
How long ago was your DP Fix installed?

I'm not sure either, seems like there's a bit of conflicting information. I installed the N55 DP Fix two weeks ago and want to avoid this problem if possible.
The other week.

It seems this is more hassle than it's worth. May as well find a place that can deal with this and take off the DP fix. I don't think it's worth the hassle after installing it and having it still not fix all the issues.
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      08-25-2018, 04:27 PM   #25
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Quote:
Originally Posted by cRo5 View Post
How long ago was your DP Fix installed?

I'm not sure either, seems like there's a bit of conflicting information. I installed the N55 DP Fix two weeks ago and want to avoid this problem if possible.
N55 you can leave it installed but the DP fix only works on pneumatic waste gate cars
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      08-26-2018, 10:07 PM   #26
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I installed mine last night and it's throwing codes. Tiago is being non-responsive. Can anyone help?
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      08-27-2018, 08:40 AM   #27
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Kind of a stupid question... will an aftermarket catted downpipe for n55 resolve all the issues with throwing codes and showing ready status in order to pass emissions?
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      08-27-2018, 09:52 AM   #28
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Quote:
Originally Posted by bill109 View Post
Kind of a stupid question... will an aftermarket catted downpipe for n55 resolve all the issues with throwing codes and showing ready status in order to pass emissions?
The DP fix does NOT suppress codes, rather it fixes the signal coming from the pipes so that the electronics believe your O2 sensor is receiving the signal it would see with a Cat present.

Beyond that you still have to deal with any other issues.
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      08-27-2018, 09:57 AM   #29
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Let end this with we all agree that IT IS NOT OK TO LEAVE IT ON.
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      08-27-2018, 07:42 PM   #30
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Quote:
Originally Posted by J3 View Post
I installed mine last night and it's throwing codes. Tiago is being non-responsive. Can anyone help?
what codes are you getting?
is it this one, O2 sensor after cat shorted to B+
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      10-11-2018, 11:25 AM   #31
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Originally Posted by Pladi View Post
Let end this with we all agree that IT IS NOT OK TO LEAVE IT ON.
So whatís being done to get rid of the CEL? Iím about to install FMIC, Catless Dp, and CP upgrades in 2 days. I purchased the VRSF DP Fix for emissions. If I donít install it, can I clear the CEL with the JB4? Iíve read you can and you canít. Just like leaving the DP fix on. You can and canít is what I read.

So if I do all this work and get a CEL, whatís my solution? Just trying to be prepared.

2016 M235i xD (dp, cp, fmic, jb4, muffler bypass)
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      10-11-2018, 01:43 PM   #32
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Originally Posted by saadams95 View Post
So whatís being done to get rid of the CEL? Iím about to install FMIC, Catless Dp, and CP upgrades in 2 days. I purchased the VRSF DP Fix for emissions. If I donít install it, can I clear the CEL with the JB4? Iíve read you can and you canít. Just like leaving the DP fix on. You can and canít is what I read.

So if I do all this work and get a CEL, whatís my solution? Just trying to be prepared.

2016 M235i xD (dp, cp, fmic, jb4, muffler bypass)
Get a tune that disables it. Idk if the new jb4 firmware does. The DP fix should only be used to pass emissions
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      10-11-2018, 04:08 PM   #33
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Quote:
Originally Posted by saadams95 View Post
So whatís being done to get rid of the CEL? Iím about to install FMIC, Catless Dp, and CP upgrades in 2 days. I purchased the VRSF DP Fix for emissions. If I donít install it, can I clear the CEL with the JB4? Iíve read you can and you canít. Just like leaving the DP fix on. You can and canít is what I read.

So if I do all this work and get a CEL, whatís my solution? Just trying to be prepared.

2016 M235i xD (dp, cp, fmic, jb4, muffler bypass)
Quote:
Originally Posted by lwgrenier View Post
Get a tune that disables it. Idk if the new jb4 firmware does. The DP fix should only be used to pass emissions
The DP fix will keep the CEL off if you are driving normally. If you are heavy on the pedal the CEL will come on even with the fix. When emissions time comes, make sure to revert back to a stock or stage 1 file where the O2 sensor is turned on so you can have readiness for emissions. During this time, make sure you are light on the pedal. Also, I have had my DP fix in for over a year without any issues.
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      10-11-2018, 04:12 PM   #34
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Quote:
Originally Posted by NRigs View Post
The DP fix will keep the CEL off if you are driving normally. If you are heavy on the pedal the CEL will come on even with the fix. When emissions time comes, make sure to revert back to a stock or stage 1 file where the O2 sensor is turned on so you can have readiness for emissions. During this time, make sure you are light on the pedal. Also, I have had my DP fix in for over a year without any issues.
Do you have an N55 with the VRSF DP Fix?

Also, have your AFR values been changing? I've read about how it throws those values off? Have you noticed an increase or decrease with this? Also what mods are you on?
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      10-11-2018, 04:42 PM   #35
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Quote:
Originally Posted by saadams95 View Post
Do you have an N55 with the VRSF DP Fix?

Also, have your AFR values been changing? I've read about how it throws those values off? Have you noticed an increase or decrease with this? Also what mods are you on?
I am a 2011 N55. My AFR values are where they should be. I believe it throws the AFRs off for the N54 engines, not N55. My mods are dp, air intake, intercooler, chargepipe and MHD stage 2+.
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      10-11-2018, 04:45 PM   #36
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Quote:
Originally Posted by NRigs View Post
Quote:
Originally Posted by saadams95 View Post
Do you have an N55 with the VRSF DP Fix?

Also, have your AFR values been changing? I've read about how it throws those values off? Have you noticed an increase or decrease with this? Also what mods are you on?
I am a 2011 N55. My AFR values are where they should be. I believe it throws the AFRs off for the N54 engines, not N55. My mods are dp, air intake, intercooler, chargepipe and MHD stage 2+.
I think I might just be doing the MHD BEF cause then I can just use the speed limiter delete also. Just have to figure out which BEF I will need.
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      05-01-2019, 05:14 PM   #37
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Quote:
Originally Posted by IllSic_Design View Post
You are NOT supposed to leave it on forever, it can and will alter your fuel trims.
it does... CEL prevents ur car from goin into Closed-loop. Your DP fixed cars are staying in constant Open loop where fuel trims operate from default protocol via maf/o2 sensors data. Over time the lack of open loop feedback/data has a cumulative effect on Ltft.. which then causes ur Afr to grow increasingly rich.. causing rough operation, fouled plugs, wear on fuel injectors .. hpfp and so fourth

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      05-02-2019, 04:23 AM   #38
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My VRSF DP Fix is on setting #8 im on E50 tune. CELs will keep coming back and I have a heavy foot.

So our options are?
1. Switched circuit for DPfix to turn off while car off no wiring diagram? to avoid CELS
2. Must go back to stock map and use 91-93 octane and baby it for closed loop and do emissions. So DPfix will be receiving signals unlike when tuned.
3. Remove DPfix and get instant CELs and never get emission ready but drives good? So how is this fine again? Have CEL tuned out?

Last edited by N54rsenal; 05-02-2019 at 04:37 AM..
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      05-02-2019, 02:10 PM   #39
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Use a tune that will remove the CEL if it's a big deal. The codes/CEL are doing no actual harm to the engine, it is just saying there is an issue with post cat o2's which just measure how well your cat converters are functioning.

Now if you leave the DPfix in you could do harm to the engine as it will alter your fuel trims and your car will not be running optimally.

If you need to pass an emissions test then use the DPfix for those times only, remove asap after passing.
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      05-03-2019, 04:29 AM   #40
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I went into my MHD options and checked boxed stock downpipes while having a Custom E50 tune and my tuner said Post Cat O2s CELs are removed. Im driving it easy under 4k rpms and my VRSF DP Fix is working now, all the readiness tests are complete except for evap which takes the longest.

https://www.vr-speed.com/vrsf-catles...435i-535i.html
I got mine as a option with my Catless Downpipes from VRSF #DPFIX, notice how its not saying N54 models!

Could I just turn the dial to the 11oclock/pm off position on the DP Fix or do I have to remove it completely?

"With the wires facing away from you, counter-clockwise is stronger, with 1pm being the strongest setting, while clockwise is weaker, with 11pm disabling the DPFIX all together." BMS DP Fix PDF page 9
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Last edited by N54rsenal; 05-03-2019 at 05:08 AM..
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      05-03-2019, 10:17 PM   #41
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Quote:
Originally Posted by N54rsenal View Post
My VRSF DP Fix is on setting #8 im on E50 tune. CELs will keep coming back and I have a heavy foot.

So our options are?
1. Switched circuit for DPfix to turn off while car off no wiring diagram? to avoid CELS
2. Must go back to stock map and use 91-93 octane and baby it for closed loop and do emissions. So DPfix will be receiving signals unlike when tuned.
3. Remove DPfix and get instant CELs and never get emission ready but drives good? So how is this fine again? Have CEL tuned out?
I like #2 every once in awhile to recalibrate ur trims. Watch it if switching from e85 to 93 octane if this applies. Perfect time is dead heat of summer couple weeks. Better to have efficient back pressure in the hot heat. Plus dp sound phenom in winter.

Re: the dp fix has gotta be massaged a bit when 1st installed. U have to adapt it. Install > setting 11pm (dp goes in standby) > then turn knob 1/8th and go drive 20+ mi > Bring up ur BC dashboard-mpg while driving and cross reference to ensure dp fix is keeping ur mpg relative to spec. If ur mpg significantly changed then u gotta keep adjusting the dp fix knob by 1/8 each time until u find the best/closest setting. U def wanna baby this cause could screw things up if provide too much too soon. Ull get a couple stubborn codes. Ur carís other sensors will also adapt better to the changing dp fix setting if u do it slowly patiently... thereby lessening chances for triggering a fault > Keep driving and adjusting by 1/8 until ur good. You may get initial faults when adjusting but ALWAYS erase any triggered faults then drive to check if that fault comes back. A lot of times just BS fc wont come back a 2nd time.. meaning the given parameter was stretched just briefly

Unless u have something wrong with ur whip, or u caused a fault by impatiently adapting dp fix to ur car, CELs should NOT trigger just by removing dp fix. What happens.. Ur down pipes will simply trigger an SES fault per the post-cat 02 sensor ..prob bank #1. Like the dude above me said, this doesnít impact ur car whatsoever other than wont pass emissions tests. Only Downstream. The SES will come and go every 20ish starts... kinda weird some pplís cars the SES stays on permanently but still no big deal. If u have CELs even after ur dp fix is removed ... and resetting the faults with obd didnít help, u might have to bring that bitch for simple bmw software reset. Or u can try a couple resets ur self then take it in if no luck. This rare tho.

When I have dp fix on, I leave my obd plugged in too .while constantly monitoring the trims 🔥👀 then youíll know when to remove it for recalibration
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      05-07-2019, 12:43 PM   #42
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Is there any proof that leaving a DP fix in will affect fuel trims over time? I hear this a lot, but have never seen proof.

Is it different for N54 vs. N55?

It is my understanding that the pre-cat O2/lambda sensors should be the only ones that have the ability to affect fuel trims (and AFR). The purpose of the cat is to process and "clean" the exhaust, so the post-cat O2 sensor isn't really seeing the true AFR, or is seeing a processed version of it, and thus should not have any say in the fuel trims. The

Please correct me if I'm taking out of my ass.
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      05-07-2019, 08:57 PM   #43
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I passed emissions with evap being incomplete will be scheduled back in 3/2020 because plate sticker. I had checked the stock dp setting in MHD and just quick reflash/rewrite and reset O2/lamba adaptations while still running a E50 tune and dp fix at setting #8.

Now all I need to know is what I can do to make tuning my car easy as im working with my tuner on a pro E50 tune? Remove dpfix or setting 11 disabling/standy?

Should I watch STFT1 and STFT2 in my logs only as 3 gear pulls or when driving on app?

My codes E50 dpfix#8 vs 93 dpfix#7
And sensors are installed, read that they are needed.
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Last edited by N54rsenal; 05-08-2019 at 02:47 PM..
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      08-12-2019, 10:19 PM   #44
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Quote:
Originally Posted by ferocity02 View Post
Is there any proof that leaving a DP fix in will affect fuel trims over time? I hear this a lot, but have never seen proof.

Is it different for N54 vs. N55?

It is my understanding that the pre-cat O2/lambda sensors should be the only ones that have the ability to affect fuel trims (and AFR). The purpose of the cat is to process and "clean" the exhaust, so the post-cat O2 sensor isn't really seeing the true AFR, or is seeing a processed version of it, and thus should not have any say in the fuel trims. The

Please correct me if I'm taking out of my ass.
I have heard that someone I know well has had their Standalone DP Fix on at 5 OClock from 45k miles on the clock to about 186k miles and counting. Still has the original O2's and car still runs. So I'm still waiting on proof for needing to remove the stand alone DP Fix

Would resetting adapts count as resetting the Long term fuel trims? I think this might have been done a couple times during service visits over the lifetime.

Last edited by fazman; 08-12-2019 at 10:25 PM..
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