[sAmstur]

So, I know this post is probably going to be laughably dumb to most of you but I’ll take that. I’m really not super knowledgeable when it comes to engine parts and things like that.

With that being said though, I recently wanted to have my M240i fixed with an AA Catted downpipe (mainly to make it a bit louder). I wouldn’t be getting a tune on it and I’m really just curious if it would cause strain or future damage to the engine/drivetrain (or what risk I’d be taking on with it). Everything I’ve read online has been a mixed bag of results so any insight from you guys would be greatly appreciated.

[Rdurty2]

It actually makes the turbo more efficient and reduces strain. Since aftermarket downpipes are either catless or have a much freer flowing cat it reduces backpressure. Turbos love having less backpressure.

[sAmstur]

Yeah I’ve heard that but I was also told it can cause a bit of strain to the other components or it could possibly be not as healthy without a tune. Would you say that’s total crap or has some actual truth to it?

[mike@x-ph.com]

Originally Posted by Rdurty2

It actually makes the turbo more efficient and reduces strain. Since aftermarket downpipes are either catless or have a much freer flowing cat it reduces backpressure. Turbos love having less backpressure.

+1

the higher flow downpipe reduces the restriction on your turbo allowing it to reach the target boost with less work.

[Rdurty2]

Originally Posted by sAmstur

Yeah I’ve heard that but I was also told it can cause a bit of strain to the other components or it could possibly be not as healthy without a tune. Would you say that’s total crap or has some actual truth to it?

For the B58 I would say not true. While a tune will extract more power out of the engine and having a downpipe, even stock the DME is smart enough to know what to do with simple parts like intakes and downpipes. It can accommodate the increases in flow.

These engines and ecu/dme aren’t like a Subaru where it will blow up just by winking at the engine if you didn’t load the necessary “wink at the engine ecu tune”

[BG42]

I believe because german cars use a wideband o2 sensor but I could be wrong. You def arent wrong though jap ecus are pretty dumb when it comes to modding thank god for cobb tuners for subies.

[mike@x-ph.com]

Originally Posted by BG42

I believe because german cars use a wideband o2 sensor but I could be wrong. You def arent wrong though jap ecus are pretty dumb when it comes to modding thank god for cobb tuners for subies.

+1

I know back in ~2010, you had to tune your Subaru when upgrading the downpipe or it could cause engine damage.

That was never the case with BMW

[XC3LLR8]

Originally Posted by mike@x-ph.com

+1

I know back in ~2010, you had to tune your Subaru when upgrading the downpipe or it could cause engine damage.

That was never the case with BMW

This is why I was so hesitant to add a DP alone on this car. My brain was stuck in the past on a different platform.

[PNTDG42]

Most Japanese sports cars have had wideband o2 sensors for 15+ years now. But they hadn’t all been using fully electronic wastegates until more recently. With vacuum actuated wastegates, when adding downpipe, you will often see a boost spike that trips overboost protection requiring a tune to raise or eliminate overboost protection. So it wasn’t about the ecu being “dumb” it was usually just about tripping a safeguard. Subarus, those just blow up no matter what you did 😂

[mike@x-ph.com]

Originally Posted by XC3LLR8

This is why I was so hesitant to add a DP alone on this car. My brain was stuck in the past on a different platform.