free flowing exhausts

[per4manz]

hi, I was always going to treat myself to a free flowing exhaust system, such as the milltek (I have a 130PD ibiza) but recently was chatting to someone who does a fair bit of tuning and they recommended leaving the exhaust alone as some systems can make the car run erratically.
Any comments, particularly from guys with the milltek system fitted? Power gains or noisy?
regards john

 

[Mikey_H]

Hi mate,


I first of all went for a miltek cat-back non res and the car ran alot better and you could notice a slight gain more at higher speeds, the sound was great couldn't hear it when driving normally then when you got onto some open road and floored it the sound was great really sporty growl i was so pleased never had any problems car ran fine. I have recently had big turbo ect and had the downpipe and de-cat and oh my god does it make some noise lol still though when sat still you can hardly hear it just sounds like a quiet burble but when you floor it the noise is the best thing ever it gets so loud and makes a really nice noise its hard to discribe i will do some flyby vids tomorrow and post them up it sounds awesome though i would say if you just want a sporty growl when flooring it go for non res catback if you want more noise at lower rpm and huge noise when flooring it go for full system i don't regret it atall

 

[devonutopia]

Just get a 2.5" stainless pipe put in off the end of the downpipe, and upgrade the downpipe too if you can. Just a pipe, nowt more is needed, and you cannot get any more free flowing than that (no cat, no silencers, no backbox, still passes mot)

 

[UncleFester]

*cough* and sounds nasty at tickover and pull off ...... he's quite right though it will pass an MOT No need for expensive pipework unless you're going for the branded name on the pipe.

 

[mrcoyote]

*cough* and sounds nasty at tickover and pull off ......

 

[trqster]

Free-flowing exhausts will net neglectable gains on most TDI's - that's a rr proven fact. I've seen rr runs from no gains at all up to 3-4bhp at most.
Unless you have a 'big' turbo fitted no need to mess with the standard exhaust system if you're just looking after performance gains.

That said I do have a custom-made decat pipe and a direct pipe free-flow muffler/ressonator fitted, but the reasons for why I did it are basically for some reliability gains (less backpressure drops a bit the EGT's) and the very nice growl under wot you do get. You also save a few kilos in the process and for £100 or so spent I guess it's a good investment.

 

[devonutopia]

Sounds nasty on tickover? Mine doesn't in my opinion. Can hear the turbo whistling nicely though.

http://www.youtube.com/watch?v=KrRV3gZ2Ntc

 

[trqster]

Sounds nasty on tickover? Mine doesn't in my opinion. Can hear the turbo whistling nicely though.

http://www.youtube.com/watch?v=KrRV3gZ2Ntc

Nice tickover whoosh sound...
You should do a wot recording though as it sounds deffo more sweet.

 

[UncleFester]

WOT is not the problem, a Tdi with a straight pipe from the turbo sounds great like that ... pretty good through tunnels and underpasses too. Get a lovely whistle off the turbo too.

If only tickover was a little more civilised .......

 

[trqster]

WOT is not the problem, a Tdi with a straight pipe from the turbo sounds great like that ... pretty good through tunnels and underpasses too. Get a lovely whistle off the turbo too.

If only tickover was a little more civilised .......

That's because you're possibly lacking a ressonator in the piping... Mine sounds 99% like standard at tickover and regular driving even tough I have a decat pipe a free-flow ressonator as a muffler replacement.
Only noticable differences are realy at WOT just like I intended in the first place anyway.

 

[UncleFester]

I have a silencer / resonator now .... i managed a week without cat or silencer and it was just too noisy. Probably sounds similar to yours.

 

[devonutopia]

To get an idea of my exhaust on WOT, perhaps you need to see the video from my latest dyno then? Please ignore the low down smoke thing as it's just overfuelling at a point when there is zero boost - It clears up fine once the turbo starts chattering away.

http://www.youtube.com/watch?v=9BvjJjL7Z50

 

[UncleFester]

Man your car cracks me up .... it's still got that smoking habit! Does sound completely UN diesel though!

 

[devonmikeyboy]

But surely if you put a silencer / resonator on an exhaust then you have not done a mufflerectomy and therefore not made a diesel car sound like an old tractor?

 

[devonutopia]

Man your car cracks me up .... it's still got that smoking habit! Does sound completely UN diesel though!

But I never drive it to make it do that. I won't use WOT until at least 2500 rpm as thats a) the start of the sweet spot (see camshaft thread for dyno) and b) has nice clean exhaust. WOT at 1500rpm is only useful for smoking out tailgaters. A VERY effective weapon indeed.

 

[WW_VRS]

I must admit I don't quite get why they started THAT low in the revs, I never boot it at 1500 rpm as it would destroy the DMF in no time...

Suppose they have to do it on the RR to get a graph that shows the turbo spinning up etc, but I would have started at 2000 rpm with a turbo the size of the one on Jasons, I've got the TD stage 2 hybrid and it is nowhere near max boost at those rpm (yet )

 

[UncleFester]

But surely if you put a silencer / resonator on an exhaust then you have not done a mufflerectomy and therefore not made a diesel car sound like an old tractor?

Except that most 'euro' mufflerectomys still have the CAT in place which i don't - as far as i can tell the CAT acts as a kind of resonator as mine sounds a lot deeper than others i've heard that have no backbox but have retained the CAT.

 

[trqster]

Except that most 'euro' mufflerectomys still have the CAT in place which i don't - as far as i can tell the CAT acts as a kind of resonator as mine sounds a lot deeper than others i've heard that have no backbox but have retained the CAT.

Correct I would say the cat is responsible for reducing some 30-40% of the exhaust noise....

 

[devonmikeyboy]

http://www.urbandictionary.com/define.php?term=Mufflerectomy
1. Mufflerectomy

The act of totally removing the muffler and resonator from a vehicle and replacing with straight pipes, thus reducing the restrictions on exhaust flow, and giving the car a deeper, nicer exhaust sound. Usually done when new performance mufflers either do not exist or are too expensive.

 

[UncleFester]

So if you start with that, also remove the cat and then decide it's too noisy so add the smallest rear silencer you can find but leave the cat out - what does that make it? Caterectomy? Sounds like a sight problem, not an exhaust mod

By definition of the above, anyone who leaves the cat in place is leaving a resonator in place which means they've not done a mufflerectomy either.

Whether or not i believe what urbandictionary says is a moot point

Going strictly by that, the only person on here who's done it is Devonutopia!