Another decat thread

See my garage for specs if need be but I currently run a Nur spec R and a First decat (I still have the second cat in place) and currently see about 1bar boost. I have now recently purchased an EBC (Blitz Dual SBC Spec R) and intend to run 1.2bar max (have 3 settings - 1) 1bar 2) 1.1bar 3)1.2bar ) anyway, I don’t have an AFR gauge and although I have had my car on the rollers recently and the AFR's are spot on, would the ecu be able to add fuel sufficiently to compensate for increased boost? and the main question I was wondering is would it be beneficial to remove the second cat and run 1.2bar controlled by the EBC (with a 1bar rr) compared to running 1.2bar controlled by the EBC with the second cat still installed? In other words would I see any more power from removing the second cat under the same situations, if you know what I mean. Thanks guy's.

When stock ecu see's more than standard boost it overfuels so afr's will be richer.

Think the second cat may act like a RR but im not sure but take it out anyway and get a nicer sound!

It way over boosts with the second cat on it's own. I seen 18-20psi when the first cat was taken out before it hit fuel cut (before I fitted a FCD) and I'm sure it would have continued to creep higher. I then added a rr as wel and it allowed me to keep a steady 1bar boost.

I would remove the second cat if there are any benefits of doing so but if I wont see any gain's I might as wel save my money or put it else where.

Sorry i cant help anymore as mine had both removed when i got it.

Apparently its EGT's you need to worry about with the second Cat still in. I an running the same setup you currently have with a profec II. Stock with the Profec off I see about 0.9 bar.

If I was doing it again I may research taking the second cat out and putting the correct restrictor ring in. The problem I have is the boost fluctuates too much due to outside temp and sometime its easy to forget and see an excessive boost figure.

EGT's were one concern as I would be putting extra stess on the turbo's to force gases through the cat when I enable the EBC compared to letting it create boost naturally.

I have read as well that keeping a cat (not only helps getting an MOT) but can also help with the life of the turbo's. Something to do with helping keep back pressure on the turbo seal's and preventing turbo seal failure. Is this correct?

Yes, but surely that only counts if you're limiting the boost by using the CAT. I'd have thought that if you're pushing the turbo with an EBC to counter the effect of the back pressure produced by the 2nd CAT, then you'll be doing more harm to the turbo's as they push harder to spin at the same rate against a greater back pressure.

I suppose your right. So in keeping the 2nd cat while using an EBC will more than likely cause more stress on the turbo's and may cause higher EGT's. Although it works fine at the moment with my current setup allowing natural boost against the resistance of the cat, the cat will offer no benifit's what so ever (performance wise or turbo life wise) when I introduce an EBC into the equation. Infact it could do more harm than good.

Best to get rid of then.

Thanks for the input guy's, it's been helpful

I take it you wanted to keep the 2nd cat on, to stop the frolics at MOT time or the random roadside tests? Ever considered a race CAT?