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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Tue, Dec-03-2019, 08:36:13 PM   #11
repoman89
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Default Re: How to Pass with Supersprint Headers?

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Originally Posted by terraphantm View Post
MA is one of the tougher states. You'll need to modify your tune so that the cat check passes even with the O2 sensors wrong, but you'll also need to make sure they read not-ready immediately after clearing (they sometimes check that if suspicious), and you'll also have to change things such that the CVN matches the stock tune (which basically means your checksum needs to be stock -- this can be brute forced).
I wasn't aware of this one -- any more info on how to do this? I know MSSFlasher automatically corrects the checksum. Also, are there any additional considerations for an EOBD-based tune? (e.g. CSL)
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Old Tue, Dec-03-2019, 08:51:18 PM   #12
terraphantm
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Default Re: How to Pass with Supersprint Headers?

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Originally Posted by Whitehawk8 View Post
I donít know what kind of stations youíre going to but I have never, not once, came across a smog employee who gave a single damn if I was cheating or not

I mean the place literally smelled like catless fumes when we were done and not a peep from his mouth
Like I said, MA is one of the tougher states. Your experience in IL will not be representative of everyone's experience elsewhere. My state (PA) is pretty easy. Only the very populated areas bother with OBD checks. Other counties, like the one I'm registered in only do a visual. And other counties still don't do any emissions check at all.

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Originally Posted by repoman89 View Post
I wasn't aware of this one -- any more info on how to do this? I know MSSFlasher automatically corrects the checksum. Also, are there any additional considerations for an EOBD-based tune? (e.g. CSL)
I don't, I haven't looked into it too closely.

EOBD itself isn't really an issue, but the CSL software can be an issue in that it sometime just won't communicate with emissions computers (CSL software was never subject to the emissions recall in the US a few years back). There's no current fix for that issue. I keep telling myself that I'll work on it, but I haven't yet.
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Old Tue, Dec-03-2019, 09:07:18 PM   #13
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Default Re: How to Pass with Supersprint Headers?

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I don't, I haven't looked into it too closely.

EOBD itself isn't really an issue, but the CSL software can be an issue in that it sometime just won't communicate with emissions computers (CSL software was never subject to the emissions recall in the US a few years back). There's no current fix for that issue. I keep telling myself that I'll work on it, but I haven't yet.
I'm gonna have to figure this CVN thing out either way .. spare ECU/yearly flash with a US alpha-N tune or CSL tune that happens to communicate with the emissions computers would both need it.

Maybe I should register it in NH
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Old Tue, Dec-03-2019, 09:21:44 PM   #14
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Default Re: How to Pass with Supersprint Headers?

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I'm gonna have to figure this CVN thing out either way .. spare ECU/yearly flash with a US alpha-N tune or CSL tune that happens to communicate with the emissions computers would both need it.

Maybe I should register it in NH
If the CVN is a checksum, someone like p0lar or Terra can magic that up faster than a CSL tune that passes emissions - it's called a checksum "Fixup"

Essentially, you just add a few bytes toward the end of the segment that *happen* to make the whole segment end up with your target checksum.
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Old Tue, Dec-03-2019, 09:30:24 PM   #15
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Default Re: How to Pass with Supersprint Headers?

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Originally Posted by Drewster View Post
If the CVN is a checksum, someone like p0lar or Terra can magic that up faster than a CSL tune that passes emissions - it's called a checksum "Fixup"

Essentially, you just add a few bytes toward the end of the segment that *happen* to make the whole segment end up with your target checksum.
Found a post on this in the MSS54 thread. There's nothing on how to exactly reproduce the CVN bytes, but it seems they're created somehow from a CRC16 with some mystery algorithm. Make the CRC16s match between the original and tune by manipulating the last couple bytes as you said and the CVN will match. Source: http://www.m3forum.net/m3forum/showp...postcount=4990

So the US alpha-N/disabled MAF inspection tune would work fine via this method .. CSL tune with this method would still be rolling the dice due to the comms recall issue.

edit: of course, according to this document on MA inspection procedures, they also request the cal ID along with CVN, so that may need to be forced to match some known US cal ID as well. (those 7 digit numbers beginning with a 7 I presume). Do you or @terraphantm know a method to make that happen?

Last edited by repoman89; Tue, Dec-03-2019 at 09:34:44 PM.
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Old Tue, Dec-03-2019, 09:51:38 PM   #16
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Default Re: How to Pass with Supersprint Headers?

Usually the people working there aren't paid enough to care, and as long as the OBD test passes, they won't bother even doing a visual.

At least that is my experience in NYS, YMMV.
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Old Tue, Dec-03-2019, 10:01:55 PM   #17
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Default Re: How to Pass with Supersprint Headers?

TN checking in.... Inspections? What are those? City slickers all concerned about the planet.... pffft..



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Old Tue, Dec-03-2019, 11:46:08 PM   #18
terraphantm
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Default Re: How to Pass with Supersprint Headers?

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Originally Posted by Drewster View Post
If the CVN is a checksum, someone like p0lar or Terra can magic that up faster than a CSL tune that passes emissions - it's called a checksum "Fixup"

Essentially, you just add a few bytes toward the end of the segment that *happen* to make the whole segment end up with your target checksum.
Yeah that would basically be the brute force method. I still don't know the exact algorithm, though it's clearly related to the CRC16 since if the stock CRC16 matches, the CVN also matches what it should be. Probably wouldn't be too hard to whip up some code that can do that.

Alternatively, it might not be too difficult to just force the program to send a valid code when the OBDII request is made.

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Originally Posted by repoman89 View Post
edit: of course, according to this document on MA inspection procedures, they also request the cal ID along with CVN, so that may need to be forced to match some known US cal ID as well. (those 7 digit numbers beginning with a 7 I presume). Do you or @terraphantm know a method to make that happen?
Yeah I can't remember if the calid is the 7 digit number or if it's the 211323... thing, but either way that is simple enough to force. CVN can be done by the method you mentioned, or perhaps the program code could be modified to just always return a valid number as I mentioned above.
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Old Wed, Dec-04-2019, 12:53:33 AM   #19
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Default Re: How to Pass with Supersprint Headers?

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Originally Posted by terraphantm View Post
Yeah that would basically be the brute force method. I still don't know the exact algorithm, though it's clearly related to the CRC16 since if the stock CRC16 matches, the CVN also matches what it should be. Probably wouldn't be too hard to whip up some code that can do that.

Alternatively, it might not be too difficult to just force the program to send a valid code when the OBDII request is made.



Yeah I can't remember if the calid is the 7 digit number or if it's the 211323... thing, but either way that is simple enough to force. CVN can be done by the method you mentioned, or perhaps the program code could be modified to just always return a valid number as I mentioned above.
I think OBD Fusion can output the Cal ID, and I found someone's log on e46fanatics with two 7-digit numbers starting with 7 as the data there along with two corresponding 4-byte values. Would anyone be willing to share their cal ID numbers via this or another method? My car is in the shop getting a CSL trunk and diffuser painted right now and I'm in the mood for tackling this while it's there

I found the 7-digit version string in my CSL full binary at 0x41bb4 (repeated 5 times) with the 21132500.. number before it. And of course in the partial read the version is identified in 2 bytes at 0x2 and 0x8002. tbd which of those if either forces the ID number if the 7-digit number is in fact the OBD cal id. I'll do some experimentation when I get my car back. Will have to experiment to figure out if the mss54hp method is the same as the method linked above but over some extra bytes. Lots of FFFFFs at the ends of the master and slave partial reads for the HP (that presumably do nothing) that I can use to make the cvn read correctly.

I'll document here or in the coding section once I figure it out so I can inevitably refer back to it when I need to modify my tune
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Discussing How to Pass with Supersprint Headers? in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)