Custom Exhaust - Need help.

[Pigfarmer]

Firstly I've never had an exhaust fabricated before. Looking to get a non-res cat-back system.

Went to Topgear (Longlife) in Bridport yesterday and we discussed a 3" decatted cat-back system.

Few questions:

Is there any point having a 3" system starting at the 2dry cats as the down pipes obviously aren't.

Is a 3" system going to be as loud as a Scooby? (don't want that at all).

Is it a hell of a lot more difficult to bend 3" piping? They said it is, and therefore costly.

X-pipe vs H-pipe? (Neither of which were mentioned yesterday).

Seeing as I already have pre-cats is it necessary to have fake 2dry (straight-through) cats produced to keep the MOT man happy, or can you just forget them all together?

Any advice on back boxes regards keeping the sound non-offensive yet purposeful and very much a V10?

They initially quoted me 1k and then 'remembered' the fake cat fabrication and the price rose to 1300.

This is new potatoes to me, have a few appointments elsewhere in the coming week or so but wanted to gain real knowledge for the car before being taken up the garden track, tipped upside down and shaken until all my hard earned pennies fall into their pockets...

[bam_bam]

Buy this http://forum.rs246.com/viewtopic.php?f=64&t=108731
Job done.

[C6NVS]

+1

[Pigfarmer]

ohhh.

[R33]

This is a very personal view and one based on only one personal experience but here it is anyway.

I bought an expensive custom exhaust for my B7 S4 that included downpipes and CAT's. It looked great and was promised power gains but it was overall a big mistake for several reasons:

-It droned and my wife hated it
-The noise wasn't that great really and my neighbors hated it on a winter morning
-Worst of all though it restricted power rather than added power. After the exhaust it went to MRC for a stage 2 remap and it basically added no power at all and based on their experience MRC thought the exhaust was what was restricting the power.

So after £2500 spent on the exhaust and remap it made 333ps Vs the standard 344, great!

I'd never change my exhaust again unless it was for an expensive very tried and tested off the shelf aftermarket exhaust from a reputable company. Custom exhausts should only every come with a written guarantee of an improved performance figure.

Whilst I'm ranting can we all stop calling them "zorsts" too, is it just me or does this sound really chavvy and Max Power?

[Pigfarmer]

Plus. it's a nightmare when searching....

[classba]

This is a very personal view and one based on only one personal experience but here it is anyway.

I bought an expensive custom exhaust for my B7 S4 that included downpipes and CAT's. It looked great and was promised power gains but it was overall a big mistake for several reasons:

-It droned and my wife hated it
-The noise wasn't that great really and my neighbors hated it on a winter morning
-Worst of all though it restricted power rather than added power. After the exhaust it went to MRC for a stage 2 remap and it basically added no power at all and based on their experience MRC thought the exhaust was what was restricting the power.

So after £2500 spent on the exhaust and remap it made 333ps Vs the standard 344, great!

I'd never change my exhaust again unless it was for an expensive very tried and tested off the shelf aftermarket exhaust from a reputable company. Custom exhausts should only every come with a written guarantee of an improved performance figure.

Whilst I'm ranting can we all stop calling them "zorsts" too, is it just me or does this sound really chavvy and Max Power?

+1

[RS6chris!]

My car standard without map made 600ps on filters and custom exhaust.

My exhaust isstraight back to rear silencers, no x pipe, very small back boxes....no resonation, sounds mental....IMO better than milltek and super sprint...but that's IMO.
It's actually probs toooo loud and can drone a little on motorway, but doesn't really annoy.


Have no idea if it made any difference power wise?...but figures tend to say it did?

[Pigfarmer]

Yeah, that suggests you got the 20/30 (depending on what was already lost through age) BHP increase a more expensive aftermarket exhaust would give.

I think the main issue is this. The likely-hood of having had an exhaust as well built as your seems to be in terms of power increase is somewhat of a gamble when it comes to custom jobs due to the fact that each fabricator will do their own thing, whereas a definitively designed aftermarket exhaust will have the guaranteed.

Seems to be the crux to me at least. But then I have no idea about exhausts...

[classba]

My car standard without map made 600ps on filters and custom exhaust.

My exhaust isstraight back to rear silencers, no x pipe, very small back boxes....no resonation, sounds mental....IMO better than milltek and super sprint...but that's IMO.
It's actually probs toooo loud and can drone a little on motorway, but doesn't really annoy.


Have no idea if it made any difference power wise?...but figures tend to say it did?

Hmmmm, not 100% correct there. A stock car with just performance air filters will give you just over 600 PS. I know this because a friend's car with that set up has produced 602 on MRC's rollers recently.

[RS6chris!]

Well there you have it...an exhaust makes no difference.

[Pigfarmer]

Hmmmm, not 100% correct there. A stock car with just performance air filters will give you just over 600 PS. I know this because a friend's car with that set up has produced 602 on MRC's rollers recently.

I've had the ITG's sat in my cupboard for over a week now and your telling me I could get 20+bhp just by bolting them in?

I know what I'm doing tomorrow...

[classba]

Yes pigfarmer.... Get busy tomorrow and make sure you clean the inside bottom of the air boxes whilst you at it. A bit of an advice for you... try soak up the excess filter oil by squeezing it with a kitchen towel because over time, they will drip onto your air box and will turn hard.

[andy]

Just for some more numbers, mine made 585 with Milltek cat back and 600.1 with ITG filters added. I bought the cat with the Milltek fitted so I don't have a completely standard start point so can't say if the Milltek made the difference from 572 or if the cars generally make a little more than stock anyway?

I would not of thought a cat back system would free up any power as the Cat's are the restrictive part in the system.