Yes it is a different DME, but you said "You would definitely have to code out the O2 sensors with the cats being that far from the engine" I was just wondering if you had data for that statement? I will probably end up with some kind of header setup on my ZHP inspired HPDE wagon, but I want to retain cats so moving them downstream is likely in the cards. I don't have a problem coding them out, but would prefer not to if I don't have to.
Current Garage... '00 R11S, '09 HP2S, '12 R12GSA, '00 Black 323iT (wife's), '02 Alpine 325iT (Eileen, Track Wagon), '02 Japan Rot 325iT
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Email to George@HillPerformance.com
Just because of the different DME, really. The primary O2 sensors that set your fuel trims will still operate just fine. The M54 stock cats are right up on the block, so the DME is looking for a signal there from the secondary O2 sensor. If you remove the cats or move them down the line, then it won't look right to the DME and throw a CEL. People that add headers or move the cats downstream have to code out the secondary O2 sensors. No big deal, really. I may even have to do it with the OE S54 manifolds.
See if you can get some secondary O2 logs from M3 guys running the Euro cats. I was also interested in running a cat in that location with aftermarket headers while retaining the stock DME coding and hardware.
-Corey
2003 Blue ZHP Sedan @ 210k
Dead due to damaged valve. Parts are being transferred to a wagon:
2003 325iT Japanrot 6MT @ 230k
I would think if anything you may not be able to get the cat hot enough. But there are plenty of S54 guys who have run Euro headers and cats with stock US tunes. I don't know how the DME would know if the cats are 10" in from the header or 40", that's why I was curious to see if that same theory would apply to the M54. Also keep in mind that aftermarket cats may not be as efficient as a BMW cat, so if they are used down stream I'm not sure that means the cat location is the issue.
Current Garage... '00 R11S, '09 HP2S, '12 R12GSA, '00 Black 323iT (wife's), '02 Alpine 325iT (Eileen, Track Wagon), '02 Japan Rot 325iT
Instagram @ HillPerformanceBimmers
Email to George@HillPerformance.com
Although I haven’t done this with my ZHP, I had this issue with a full custom exhaust in my 2001 Jeep XJ Cherokee. Had to move the cats further back which threw a code. Pulled the header out and double wrapped it. Problem solved. The header wrap kept enough heat moving down stream that it allowed the cats to work. Granted not a BMW, but a hot running straight 6 none the less. I was thinking about trying this when I get a header for the ZHP. Anyone tried this on their BMW?
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I don't think it matters how far down the cats are as long as the mixture reads the same as stock. Now there is response time that would probably play a sizable role in whether the DME likes the new setup.
I'm just going to use an Innovative LC-2 when that time comes.
-Corey
2003 Blue ZHP Sedan @ 210k
Dead due to damaged valve. Parts are being transferred to a wagon:
2003 325iT Japanrot 6MT @ 230k
Cats require heat to function properly. If they are too far down stream, the dissipation of heat can result in a fault in the post-cat O2 sensor. Not reaching their designed operating temperature results in inefficiency which results in readings that are outside parameters. Hence why they are so close to the exhaust manifolds in nearly all cars from the factory.
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Agreed. That's also why manufacturers are tending toward integrated manifolds. Gotta heat the cat up as fast as possible to reduce the most severe emissions from cold start.
Legally, I know that the position of the cat cannot be more the 3" from OEM location or the EPA will get you, but ehh.
The S54 also uses inconel for the header material, indicating that the motor runs really hot exhaust gasses through those tubes compared to the M54.
I think a more relevant question here is how far out of spec can we go before the DME flags the cat?
-Corey
2003 Blue ZHP Sedan @ 210k
Dead due to damaged valve. Parts are being transferred to a wagon:
2003 325iT Japanrot 6MT @ 230k
Well I am trying to move forward on this project and ran into an issue. Just posted on e46f so copying it here in case anyone is considering this...
So I thought I would be able to pull this off without modifying the OE midsection, but it turns out I can't shorten the rear M3 header enough to fit the OE connection. I'll have to modify the midsection too to move the flanges downstream a bit.
S54 manifolds:
M54 manifolds:
Front comparison - for this one, the S54 pipe COULD be shortened enough to make the M54 flange location work:
Rear comparison - but you can't do the same with the rear:
The S54 cat extends into where the M54 flange is, hence the need to move the flanges downstream a bit on the misdsection:
The guy on e46f saw this and moved the midsection flanges down and shared these pics of the finished product:
I just sent these to my buddy that's doing the fab work and I guess I'm taking him the whole damn exhaust on Monday