STAINLESS EXHAUST HEADER, ENGINE rpm PROBLEMS?!?!

[dok47]

I bougt SPORT STAINLESS EXHAUST HEADERS (see attachment) without first taking look under hood
Now i see OEM headers have catalyst or pre-catalyst built in or i am wrong, but it looks like catalyst to me!?!?
My question is: does any one have experience with repolacing those OEM with aftermarket ones and does it efect way engine runs? Unstabe, variable RPM or any thing? Because i know people say that is not smart to remove catalyst from newer typ of engines they dont run smooth any more? But maybe it has real catalyst below car and these are just some pre catalyst...
I had them on my ex E39 and they were fine, better sound and i think it run better too, but on E39 there was no catalyst built in OEM.
What you say guys?
Thanks
here is link of STAINLESS EXHAUST HEADER to see what I am talking about:
http://cgi.ebay.com/ebaymotors/01-03-04-05-06-BMW-X5-3-0L-M54-STAINLESS-EXHAUST-HEADER_W0QQcmdZViewItemQQcategoryZ33629QQihZ006QQi temZ160274422614QQrdZ1QQsspagenameZWDVW

[Weasel]

Yeppers, the OEM manifolds do have the cats built in... and from the looks of it, the shinny new headers have straight pipe between the upstream and downstream o2 sensor bungs... and the only thing past that is the huge 26" long 2 in 2 out resonator, then the mufflers at the rear.

I'm not sure, but guessing you don't have to worry about emissions tests in Austria. But the check engine light will be on with faults stored for "catalytic converter efficiency" It would possibly cause lean mixture faults also, I've worked on a couple of E46 330i's that had lean mixture faults from aftermarket exhaust.

But some nice performance engine software would help with that, is there a dinan dealer around you? I know with other vehicles, like mustangs and the like... you can "turn off" the downstream o2 sensors to avoid SES lights after cat removal... dig deep enough you'd might find a quality programmer with that feature. Maybe the "shark injector obd II software" from this link? It looks like it might be custom programmable?

http://www.turnermotorsport.com/html...ne%20Chips#TOP

[dok47]

so there is no any other catalyst after those on headers...hmm i am not worried about emissions but i am worried abot geting some error messages and lights going up all the time...probably i could not sleep tight any more ...si is better if i just quit of this project...no there is no dinan here...
Thanks

[Weasel]

Looks like the headers have a decent return policy... bring up the whole no cat = fault codes problem to them, se if they offer a solution. Otherwise, shouldn't be too hard to return.

[dok47]

If sensors read more emision since catalyst is removed what that means? is it going to efect performance or is it going to result more or les usage of fuel? Or none of above except error message?

[motordavid]

Just wondering what one thinks headers are gonna do for the normal/standard driving experience
on a ~5,000+ lb car?
GL,mD

[Weasel]

Originally Posted by dok47

If sensors read more emision since catalyst is removed what that means? is it going to efect performance or is it going to result more or les usage of fuel? Or none of above except error message?

The upstream O2 sensors read the fuel mixture, and that's what the DME uses to adjust the fuel trim. The post-cat O2 sensors simply monitor the cat converters to ensure they're working properly, for emissions purposes. The removal of the cats will give codes for that. What I can tell you I've seen with the M54 3.0i is that you might get lean mixture faults due to the lesser back pressure. The DME fuel calibration is very precise on these vehicles, and with oem software, it will likely go "out of range" for what it can compensate for. But finding a quality performance software program should compensate and allow for the less restrictive exhaust and allow you to get the power gains desired. And depending on the software, could possible "turn off" the post-cat o2 sensors as can be done with domestic American "muscle cars".