Downpipes question

[p3u]

With the pre cats removed, is it true that the turbos will spool up faster due to lower back pressure? I have heard of some s4 guys having up to 500rpms earlier spool up.

Also any ideas in power gains?

Thanks!

[hahnmgh63]

That way on my Porsche so I'm sure it will be that way on the RS6. Maybe not 500 rpm's for just the pre-cats but it will be earlier. Turbo engines love no backpressure.

[vangelis]

BUMP, since engine and trans out and cats out, any advice on how to get cat-less setup done? any high-flow sport cats can fit the standard exhaust size?

[DHall1]

My opinion.....02c

We already have hi flow cats. Think about it we put down nearly 500hp stock. Our exhaust systems are already stout.

That said we have 4 cats and we could get rid of the precats.

"I" would gut the stock precats and reflash the ecu to delete the precat O2 sensor input.

Thats just me

[p3u]

My downpipes the pre cats were gutted, main cats untouched, and O2 sensors relocated to after the cats for proper readout. No codes, and sounds cool to hear the turbos spool!

[vangelis]

Please can you explain on details how can I do that now since exhaust and down pipes already out now. I need to know what parts/ tools needed to do this job and how much cost you. If you have photos for before & after that would be great. Thanks in advance.


My downpipes the pre cats were gutted, main cats untouched, and O2 sensors relocated to after the cats for proper readout. No codes, and sounds cool to hear the turbos spool!