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I was thinking about gutting the pre cats & removing the x pipe to add some power & noise. But I am thinking just keep standard x pipe & fully de-cat the exhaust. Anyone done this & have a vidoe of this ???

I think just gutting the precats will suffice. Removing the mains will give you a headache every mot time and there is no real benefit to removing them. The pres are the main and biggest restriction. I will be doing min at some point. Does seem a bit of a lottery without a remap as to whether you need to space the O2 sensors though.

I've just had the centre silencer removed and it's perfect. Just enough noise with the valves open, quiet when not. I am going to get the pre cats done too at some point but heard this is mainly for extra power rather than noise

I would be getting a remap with getting the cats done but just wondered if I would get the same noise with gutting the cats save doing the x pipe. It's noise & a bit more power I am after. In total I was thinking about gutting cats, remap & cold air feed

You will naturally get more noise from gutting the pre cats because you are removing a restriction in the system which means faster air flow and more noise out the back. The cold air feed won't add any major power gains but should give you more induction noise depending on which one you go for.

Batfinnk wrote:You will naturally get more noise from gutting the pre cats because you are removing a restriction in the system which means faster air flow and more noise out the back. The cold air feed won't add any major power gains but should give you more induction noise depending on which one you go for.

I will probably just go for the pre cats then see how loud they make it & if I want more do the x pipes. I am just going for standard air box but remove the aux rad & do it that way. Hopefully won't heat soak as much & it seemed to do on the dyno last time

Does eml light come on if you gut pre cats? I would of thought it wouldn't as it's still got the second cats in place

m14rrv wrote:Does eml light come on if you gut pre cats? I would of thought it wouldn't as it's still got the second cats in place

Yeh I believe it does as there will be a O2 sensor in the precats also I presume, but with a map it clears any lights or warnings. I was also told that when pre cats are gutted tho loose the 5.5k kick so need to map it back in

the lambda spacer goes in after the cats not before,

Plus I may be wrong but don't think the 5.5 kick has anything to do with the exhaust. I'm sure it on the intake side?

Rick_RS4 wrote:the lambda spacer goes in after the cats not before,

There is already a sensor in there though

Batfinnk wrote:Plus I may be wrong but don't think the 5.5 kick has anything to do with the exhaust. I'm sure it on the intake side?

I was told it was something to do with the back pressure in the exhaust but I am not 100% sure haha

Dec369 wrote:

Rick_RS4 wrote:the lambda spacer goes in after the cats not before,

There is already a sensor in there though

yes the first one reads the gasses the engine is making, the second one reads them after they have been through the cats, if the second one senses more flow ( due to cat gutting) it throws a cel, so you space it so its not in the exhaust flow, so no cell

Is any one running spacers on the 2nd sensors? If so what spacers you running

I run a full non res valved, cat bypass Milltek system. Valves closed quieter than with cats, S button valves open = gods thunder, screams its bolx off at 8k revs in 3rd.
Absolutely 100% love it and recommend it. More HP and Torque see the following thread:

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