[GianlucaM235]

Hey everyone, I recently purchased my 2014 M235i and was looking for some guidance with my plan for running a VRSF Catless Downpipe. I wanted to see if there was anyone running the downpipe with the stock exhaust setup and without an aftermarket tune. I'm not planning on pushing more power (at the moment) but I want a little more sound out of the car. Will running a catless downpipe without an aftermarket tune cause any issues with how the car runs? I've heard people say it may run rich but I've also heard that the 02 sensors will adjust for that and the car will run fine. Any advice is appreciated thanks!

[mike@x-ph.com]

It will trigger the check engine light, but the car will run fine.

The gains are minimal without a tune, but the sound improvement is noticeable.

[evo335xi]

Running this way for 9+ months no issues : )

[Felipe Cezar Toazza]

Já rodei uns 15000 km com meu 235i sem catalisador, utilizei um prolongador na segunda sonda, mesmo assim o carro as vezes liga a luz da injeção, também notei uma melhora no som do N55 fica lindo, turbina trabalha melhor tem ganhos principalmente em altas rotações, recentemente ajustei o carro com bootmod3 e precisei ficar com a melodia 1 ACN pois no Brasil a gasolina é ruim, confesso que pensando bem hoje em dia teria parado do downpipe, achei que gastei meu dinheiro a toa sintonizando, pois os mapas não foram feitos para o combustível que tenho aqui.

[XutvJet]

It will throw a constant check engine light and the car will smell like a 1970s car (i.e., raw fuel). You'll gain around 20whp/30wtq, no tune needed. IMO, the best way to go is to get a high quality catted downpipe. There's hardly any performance advantage to running catless and a high quality catted downpipe will be nearly as loud but without any rasp.

[atek]

Originally Posted by XutvJet

It will throw a constant check engine light and the car will smell like a 1970s car (i.e., raw fuel). You'll gain around 20whp/30wtq, no tune needed. IMO, the best way to go is to get a high quality catted downpipe. There's hardly any performance advantage to running catless and a high quality catted downpipe will be nearly as loud but without any rasp.

While that is mostly true, the main reason most people choose catless is the added turbo noises over the marginal performance gain.