Exhaust system

[mattie007]

At the moment, I have just a 3.5" Piper backbox.
I want a full sports exhaust system as my cat has started to rattle quite badly.
What parts do I need and can I expect any gains in bhp and sound?

Matt

[afcbadam]

yours is a 120 isnt it? are you changing the piper back box? i paid £400 fitted for a janspeed cat back and decat. stainless steel of course. gave a decent gain in bhp, combined with a inner wing, the car revs better and isnt as sluggish as it was after 5k rpm. the sound is superb. sounds the nuts imho. jake (phate) is running around 195bhp iirc with similar mods to mine so gains are offered. he will confirm this im sure. im sure gains will be similar on a 120 as they use the same cat back system.

expect yours to be less than £400 as the decat for the 180 is £100 and i have seen the decat for the 120 go for £30 on ebay, but they are mild steel.

there are other options out there to consider but from experience and other comments the janspeed is up with the best of them. this is if your changing the back box as well. the janspeed centre section is £140 from ptp. i expect it will be cheaper from janspeed direct

hope this helps

[stamford]

From what I gather the 120 is best left alone with regards the decat route as it needs the back pressure. Best bet is go for a decent cat back pipe to compliment the back box you already have.

[afcbadam]

i decated my previous k series and it worked well. the cat back didnt offer a lot but as soon as i decated it i noticed a good difference.

[mattie007]

Thanks for the replies, but not sure what to do!
Im keeping the backbox as I like it.

So, its a decat or sportscat? What would people go for?

[afcbadam]

a decat is worth a couple of bhp more is is a lot cheaper. i would go for the un restrictive janspeed centre section and a de cat. should give you a noticable gain.
either way you will get a better noise. the 120 still passes the mot with a decat fitted as it has a pre cat fitted in the manifold.

[wilko66]

From what I gather the 120 is best left alone with regards the decat route as it needs the back pressure. Best bet is go for a decent cat back pipe to compliment the back box you already have.

:lttd: I've heard this too, I have standard cat then janspeed mid, and x power thruflow backbox. I think if you go the janspeed it has to be with the 421 manifold, which isn't cheap, also you loose the pre cat.

[StragglaSteve]

Thanks for the replies, but not sure what to do!
Im keeping the backbox as I like it.

So, its a decat or sportscat? What would people go for?

Dude, got myself a stainless steel powerflow system a couple weeks back for £300 fitted. The guy said he can add on a sports cat for an extra £150, didnt have the money at the time but think thats what im gonna go for next month.

Still sounds a bit raspy, put that down to being new and needing to settle but it hasnt settled yet! so maybe im stuck with the rasp :( love the popping noise it makes though!

Got a video but i need to work out how to convert the file type as i cant seem to view it on PC :|

[mattie007]

Have you noticed any gains in performance?

[afcbadam]

Have you noticed any gains in performance?

i noticed a good differenct on my 1.6 k series with an exhaust. mainly the decat.

the 4-2-1 manifold isnt that expensive. these have gone from £135 on ebay. they are easy to fit so labour would be reasonable aswell. the manifold is ment to give the best gains on the k series exhaust system. the pre cat would be lost so a sports cat should be fitted to keep on the right side of the law. a decat could be fitted if you are happy to bolt the origional cat in for mot's, thats if it fits to the aftermarket manifold

[starfire039]

I've got a peco stainless steel cat back, the noise is amazing, but will need a decat and induction kit to complement. I didn't really notice any performance increase if i'm honest, but i think with an induction kit and 52mm TB all three components will work well together for a nice 5-10bhp.

I'm in the same situation as you, my flexi pipe is fooked and squeaks, I cable tied the mount a little bit which stopped the squeaking but makes the exhaust knock against the heat shield occasionally :( so I'm going to need to replace the down pipe. I'd rather get a decat, purely as it's cheaper than getting a downpipe with a cat in, I guess.

basically the more exhaust components you change, the more noise and burbling you're going to get. I wouldn't buy a sports cat as you'll pass MOT anyway with the pre cat in the manis, and if you don't pass, just keep your old downpipe and swap it, might add 20-30 quid to your MOT, but it's cheaper than the extra for a sports cat.

i'd agree with stamford in saying the 120 probably won't get any gains with a decat, maybe a loss but i don't know, due to it needing the pressure. a decat is best on a turbo car, but it will sound much better, which might be worth it.

we're in the same boat with the 120, you will need to go all out and buy 52mm tb, induction kit and then a nice exhaust system for a gain in power, which wn't be as high as a 180, but you'll notice the difference for sure.

i noticed a difference by removing the rear seats and extra crap from my car i don't need more so than a new exhaust :D

[afcbadam]

I've got a peco stainless steel cat back, the noise is amazing, but will need a decat and induction kit to complement. I didn't really notice any performance increase if i'm honest, but i think with an induction kit and 52mm TB all three components will work well together for a nice 5-10bhp.



you should get around this is you do everything. sometimes the tb needs setting up. when i fitted mine i was able to ulter it my self by turning the adjusting screw a quater of a turn. if it needs any more than this its a main dealer job. costs about £35 iirc