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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Tweak for passing sniffer test with cattless DPs



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      12-03-2012, 02:17 PM   #1
Lux3m35i
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Tweak for passing sniffer test with cattless DPs

Hey guys,

I will receive some AR downpipes from Mike in the next weeks. Since in Luxembourg we have to pass the test every year, I start thinking about how to pass the test with cattless DPs.

First thought was about AirFuelRatio. Most of us are using piggybacks which allows to upload costume maps. Would it be possible to set up a map with richer A/F ratio? Based on the fact that a rich mixture produce less emissions. Would it be applicable?
In valet mode few people reported that they pass ODB2 emission test but seems to fail with sniffer.

The second idea was to do a E85/gasoline mixture. Ethanol mixtures results in lower emission. Our cars have no problems with ethanol mixtures, few guys are using 50/50 blends with a corresponding mapping or running their cars with 10-20%. But will it change emission in a significant way?

Hopefully some of you did researches in such kind of things. What I am missing are some test and results! In most emission threads there exist a lot of contradictions of people claiming they passed and failed the test.

Or is it all about having some luck and a friendly inspector on that day?
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      12-03-2012, 05:50 PM   #2
Dave W.
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Which emmission gases do they test for over there?
From my research the lowest emmissions are found at 14.7 AFR. If you go richer you will lower NOx (oxides of nitrogen) but raise hydrocarbons (HC) and CO. If you go leaner NOx goes up while HC and CO go down. You can lower NOx by retarding ignition timing, so the best bet is to tune it lean and retarded.

If you use E85 it will lower HC and CO but raise NOx.
I like to do a pre-test to see which emmissions are out of range on my car first, then make adjustments and re-test later.
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      12-03-2012, 06:45 PM   #3
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Good luck, sniffer test with catless DPs is gonna be a bitch
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      12-03-2012, 08:32 PM   #4
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here is a fix = take an envelope, fill it with $$$ and you can figure out the rest from there
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      01-09-2013, 04:15 PM   #5
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I did a emission test before and after installing kittyless DP's. For those who are interested in which way the emission will change with DP's.

First shows catted DP's.


cattless


I also tested N/A mode which did result in slightly better values, but is probably because of measuring tolerance.

So do I pass emission sniffer test? Yep I do
But only because in my country, you have to undercut a certain maximum value which is all the same for every car in the country.
I always thought that each car has to keep its limits given by the manufacturer. I don't know how they check emissions in other countries and states.

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      01-09-2013, 05:23 PM   #6
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It says oil temp, but I guess that is ambient temp in Celsius? Sniffer doesn't know the oil temp, it could be read from OBD though.
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      01-09-2013, 06:22 PM   #7
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That's quite impressive as what I searched on the internet most states have a limit from around 65-120 PPM of HC on the results I found with people failing. That being said I've also thought that some emissions test facilities favor certain cars. When I had my 87 Supra I had a hard time passing with all my original parts. My buddy in his 91 Camaro V8 (was in the late 90's) with a hollowed cat had way better scores than I did.
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      01-09-2013, 07:18 PM   #8
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Quote:
Originally Posted by jippii ensio View Post
It says oil temp, but I guess that is ambient temp in Celsius? Sniffer doesn't know the oil temp, it could be read from OBD though.
Actually it is ambient temp in celsius, yep.

Btw I Used 98 ron gasoline.
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      01-09-2013, 09:40 PM   #9
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Wow.. those numbers help eliminate some of the "guilt" of catless DPs huh?
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