Decat vs sports pipes

[washy]

Just driven home having had decat and JP sports pipes fitted. Actually intended just to get a decat and keep standard rear box but had a slight misunderstanding with the dealer and they fitted both in one go!!

Anyway, it sounds horrible and has lost power without a doubt. Around idle and at lower engine speeds/throttle openings it sounds a good bit bassier and that I like. However, when I give it some the noise is WAY over the top for me. Very harsh and utterly intolerable.

From here I can go to whichever configuration I like without a cost implication so what's going to be the nicest balance and best for performance? Do I put the cats back in and keep the sports pipes and if I do will it kill the full throttle noise but retain a bassier thrum (my 4.2 had just sports pipes with the cats in and sounded nice). Or do I leave the cats out and put the standard back box back on. Will this muffle the loss of whatever silencing the cats give.

Perhaps more importantly what's caused the drop in power (definite loss in surge as the torque climbs just below 4000rpm) is it the absence of back pressure at the cat just prior to the lambdas or is it the back box. Or perhaps a combination of both?

I imagine Joolz will know what's going on here but if anyone else has any experience of the various setups please let me know.

Firstly, I think I'm going to pop the cats back in and see how that sounds and performs as it's easiest to undertake myself this weekend.

Apologies for the shocking grammar.

[satman]

Suprised to hear you have lost power...mine didnt feel any different to be honest, and at 381bhp with emerald remap, Im sure its not down on power! In fact I would say that my car feels more throttle reponsive than before decatting, (even before the remap)....and I love the sound of mine!
Still, good job we all have different tastes, otherwise the world would be a boring place!

[davidd]

I always thought that std backbox and decat was the way to go.

Worked for me at any rate.

D

[washy]

Davidd - did it get much louder with the decat and standard box?

[cirvy]

Up until now, i had a spell of sports pipes & de-cat, it was too much & not particularly tuneful to my ears!
Also, i easily got blackflagged at Donny with that set up, even managed to be too loud with bolt-on silencers attached!

We have now revised it to de-cat & standard factory back box which should be better (fingers crossed)!

Having said that, a couple of weeks ago at Donny, a Cerb with that set up was blackflagged on the same trackday as me

[ajcerb]

if i remember correctly Joolz reckons de-cat and std box is his preferred option but no doubt the man himself will be along at some point

[washy]

ajcerb - you're right. I have spoken with 'the man'. Standard box going back on on Monday. I'll see how that is.

[dannylt]

Yep decat & std back box. Only noisy at full throttle then, but you'll need to watch the mikes at Donington, under the gantry stay right & short shift, and same after the old hairpin before the bridge.

[cirvy]

Thats interesting, i wondered where they were

[washy]

I imagine I'll end up putting the cats back in. I like it quiet. Would've liked more bass and to avoid expensive cat replacement but can't see it happening.

Good tip on Dono Danny, thanks for that.

[arcbeer]

Std back box and no cats is the way to go. Always sounded good and you save the cats, they just end up getting blocked and over heating anyway.