So gutted RS4 downpipes, the 200CPI RS4 cats and the stock RS4 cat back.
My car was a bit of a pig to get the downpipes off of requiring hours of patience, brut force and technique which I was more than happy was not down to me!
The outcome is pretty much what I wanted, satisfaction of knowing I have improved the whole system including the bottleneck (cats), OEM noise levels, no fears of knocking, boom or drone, all for roughly the equivalent price of just a Miltek dual catback which I am not sure would have met my requirements.
The tone at idle is slightly deeper and has a nice note. On the move there could be something marginal in the noise but to be honest it's as quiet and refined as it was before, so far as I can tell so far. Considering the gutted cats and we also added an additional RS4 style opening to the airbox, I am pleasantly surprised. Either that or I am am still all confused by a quick run around the block with only downpipes on the car! Now that was loud!
My car was already running good timing and could not run any more according to MRC. I was hoping for more but on a back to back peak maf comparison run 24 hours ago, it's only slightly up and nothing to write about.
The car does feel pleasant to drive however, always seems to have an urgency to it and is much happier to pull round to the higher revs without giving you it's own signs to change up. Pick up is certainly more perky than before.
On the basis of how it drives compared to the actual peak maf increase I was hoping for something by the way of FATS time improvement and here there is something a little more noticeable.
Previously my absolute best time has been 5.062, but not something I could reproduce easily, most times coming in around 5.2.
Again, I did some fats times 24 hours ago. Absolute best was 4.934 but again could not reproduce and other runs for the evening were between that and 5.2. Considering outside temp was only 4C and I kept the car moving, heatsoak not a massive issue here.
Runs with the RS4 exhaust tonight, heavier fuel load and outside temp 11C instead of 4C, I consistently got low 4.9s accorss three runs and on a last run on the way home on an incline (I don't normally measure here) I got a 5.02.
So the FATAS times just about collaborate the car feeling a little more keen to rev, epsecially at the higher revs, but other than that, I don't belive I have anything more than a minor BHP gain, perhaps up to 10BHP.
I mentioned fabrication earlier, this is how we got an RS4 backbox to sit in a prefacelift S4 bumper cut out:
Twin offset 3" rolled tailpipes, cutom fitted
I can't deny a greater peak maf increase would have been nicer to see, but all in all I am quite happy and am glad I went the RS4 route.
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