Catless Downpipe with / without tune?

[Jay-K]

So to pair up with my
(budget saving) turner motorsport "race inspired" exhaust,

i am in search for Catless DP for ultimate beast mode and HP boost up…

but also i am not planning to tune the car anytime soon, so the question is will theses carless down pipe require tunes?
and also any references?

THanks so much

[boots]

None require tunes.

[M5essex]

really? not what I heard or understood... the reason the management system cuts in and warnings appear is because they have not been reprogrammed/retuned to cope with the changes made by catless DPs.... have I got that wrong?

[Jay-K]

Originally Posted by M5essex

really? not what I heard or understood... the reason the management system cuts in and warnings appear is because they have not been reprogrammed/retuned to cope with the changes made by catless DPs.... have I got that wrong?

Originally Posted by boots

None require tunes.

Well,
after searching and doing browse,
i believe that most people here will say they have CEL, since they are mostly located in the US, where the BMW itself programmed the O2 sensors to be more sensitive (i might be wrong, correct me)

but as i am in indonesia, i get euro spec, where I believe the "sensitive-ness level" is reduced?

[greentrbo95gst]

There are no tunes available to begin with.

[JoeyLeeBMW]

RPI's downpipe hands down! 304 Tig Welded SS

[Jay-K]

Originally Posted by JoeyLeeBMW

RPI's downpipe hands down! 304 Tig Welded SS

will not light CEL?

[boots]

Yes it will. All of them will at some point except the stock modified version that spinny has.

[Soorena]

Cars with catless DPs and no tune usually run like utter crap. I'm amazed that people with catless DPs don't complain much about the change of the driveability of their cars. I wouldn't reduce that much of exhaust back pressure unless there is a supporting tune for it.

[boots]

Originally Posted by Soorena

Cars with catless DPs and no tune usually run like utter crap. I'm amazed that people with catless DPs don't complain much about the change of the driveability of their cars. I wouldn't reduce that much of exhaust back pressure unless there is a supporting tune for it.

Not true bud. Mine runs great as does some of the other guys who run the same set up. Where are you getting your info from. I don't think any of us here has complained about the way our cars run. If I had a problem it would have been fixed from day one.

[Soorena]

Originally Posted by boots

Not true bud. Mine runs great as does some of the other guys who run the same set up. Where are you getting your info from. I don't think any of us here has complained about the way our cars run. If I had a problem it would have been fixed from day one.

My friend i have experience with turbo cars.
Simply speaking, with catless downpipes you face two problems. The first problem is the airflow characteristics. There is a table written inside the DME that tells the DME when to open/close the wastegates and by how much. With OEM exhaust the DME only needs to some minor adjustment to the data it receives from the table. However, when you switch to catless downpipes the table is not as accurate as before. Therefore the DME is always calculating the big adjustment needed for the parameters it receives from the table and the whole adjustment is not as instant as before.
The second problem is the AFR. With no cats in place ECU think the O2 sensor has failed and as a result it richens the mixture to protect the engine from detonation.

Now the advanced electronics used in your car might tone down these issues but they are still there.

[boots]

I realize the engine has to recalculate for the diff in parts, but w/in that diff the car still runs fine. Until they come out with a proper tune there is nothing we can do to adjust any parameters that are out of spec. We all know that sucks.