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Do you have a de-cat on your willie

Anyone thats done this to their willie - did you get more va va voom?:eek:

Or was it all a bit limp?:oops:

Ive been planning a de-cat but seen mixed responses to them.

Carlos - I can tell you early next week when Ive got my Willy back. It had a de-cat pipe on when it went in, but its having a new cat fitted. If it feels sh*te, Im putting the de-cat pipe back on.

It felt pretty good with the de-cat on, but it made an annoying buzzing noise at about 3000 - 4000 rpm which was very audible from outside the car and Im not keen to have it back.

Seen a couple of posts this week saying that it doesnt make much difference, so we shall see....Ill let you know how it goes.


Cheers Rhys - Ill look forward to that - I need new tyres which are more important than a de-cat anyway but the thought of more power (arg arg arg) is always too much!

Ive got some new 195/50 P6000s that are going on the car as soon as I get it back. Ive been driving round on bald tyres with slow punctures up until now. Cant wait as the handling is pretty spectacular on the slightly skinnier and totally shagged 185 tyres.....whats it going to be like when its running right?! :D


Ive got a Hill Power De-Cat on mine and it made a very noticable difference. The car seemed to pull away alot easier and it did free up the top end quite alot too. I would say it is probably one of the best value mods i have done so far.

  silver valver/hybrid

at the midland rolling road day, benh and ben j both made around 10 bhp more in their 16v than mine, we all have similar mods but they two have both got decat pipes.
  williams and trophy

hehe well ithink my r/r results speak for themselves lol

de-cats do work

ive got a devil decat on mine but must admit that the power suffers a little low down, and seems to pull thru the lower revs a lot faster with the cat on.

but with the decat on and normal driving(for me lol) above 4k rpm it feels a hell of a lot better than it does with cat on. tested within the the last couple days, altho it is quite a bit louder too but theres always some penalty to pay for power hehe

Id just like to point out that Ive also got head work and cams - as well as a de-cat! So Id be expecting to make more power anyway (although I think my engines running rough at the moment - another story).

I fitted the de-cat a day before the RR day and its difficult for me to comment on any performance difference as I hadnt driven the car in a couple of months before I put the de-cat on. What I can tell you is that its noisy!!

Id take it straight off if I was commuting to work every day in the car or if I did lots of slow speed/round town/motorway work. In those sorts of situations it makes the car sound a bit Nova-esque. But if, like me, you drive the car purely for recreation on quiet country roads, its fine and adds a little poke at lower revs (on a Valver anyway). It also spits flames; I never saw the reason why the Mongoose exhaust systems tailpipe extended so far from the bumper - now I do, it saves my bumper from melting!
  Audi S3

if u had a silanced de-cat then u get rid of the buzzing noise as i had that problem with the straight thro i had on b4.

derv i got 125.5 ATW at the midds rr day and i have the same modds as Ben j (ben H has head and cam work tho)


Hmm....might go for a silenced de-cat pipe as suggested. Also, do a chip for £230 that includes a basic launch control feature, programmable change light and full throttle gear changes. Says it is only for "Phase 1" at the moment, so Ill have to ask them if itll fit to a Willy 3, but def. sounds promising.

  BMW Z4 2.5si Sport

I bought my car with the decat / filter already fitted, so cant comment on any performance difference. I can however say my car got 163bhp / 141lb ft torque on a rr, so would imagine the decat made most of this difference. SOunds sweeeeet as too.

Give Hillpower a call. Their de-cat pipe is about £75 but there is a very generous Cliosport discount (takes it to about £50)....dont know if it is silenced though.

Also the one above doesnt include VAT or shipping...

  Clio 197

I wouldnt dare decat a car here. I think the punishment involves cattle prods in private places...

I have got the Hill Power de-cat - and my exhaust also makes that annoying buzzing sound at 3-4k revs. The rest of the system is std.

Would fitting a Magnex cat back exhaust cure the buzzing noise? It really is becoming irritating, but i want to keep the de cat cos the car seems more repsonsive (that could also be due to the Stage 1 HP chip and Induction kit though!).

I had a de-cat on my old valver, but that was with a Scorpion stainless system and I never had the buzzing noise that I have now. Any thoughts?


my car is a 19 16v but im running a williams engine, mines been rolling roaded with and with out the de-cat and it made 9bhp difference. This is with an air filter and chip both times.
  Audi S3

its all down to personal preferance really but i didnt like the buzzing noise so got the silanced pipe so now its as it was with the cat on just a little louder!!