306 hdi exhaust .. done :)

[joelww]

My cars getting some exhaust work done tomorrow as my de backbox pipe is blowing and quite frankly it could all do with welding and aligning up and also its dying for a de cat.

Im just wondering whats the best option on the hdi for both sound and power .

Either
DECAT----MIDBOX----DEBACKBOX

or

DECAT-----DEMIDBOX-----SPORTS BACKBOX (the one on the attached pic of my audi)

Please help with my decisions its driving me mad and ive only got until tomorrow to decide

Thanks

[Dum-Dum]

the sound only really changes with the number or size of boxes so for best power you want de-cat -> de-mid box -> straight through back box

This is because you want to keep the exhaust gas flow as smooth and fast as possible for as long as possible so you want to keep it in smooth pipe of all the same diameter (actually the diameter needs to shrink slightly and gradually along its length to account for the cooling of the gas to maintain the constant velocity but thats far too technical for here)

[joelww]

So instead of keeping my debackbox and getting a decat . You reckon i should get a decat .. de midbox and then a backbox (have attached a pic of the backbox still on my audi ) cheers

[mr_fish]

2.5" all the way...that'll sort you out for sound

[Piggy]

2.5" all the way...that'll sort you out for sound

2.5" is for girls...3" for the win

[Poodle]

If you ask for 3" they'll charge you £lubelessrape.99, plus it's completely pointless if you're not planning on passing the 200bhp mark. If you're after noise i'd go for straight-through to a sports backbox, hdis are a bit quiet on the exhaust side so 2.5" would probably help beef it up, backbox will do most of the work on that front though.

[Jonny81191]

2.5" straight through to that backbox will sound epic

[joelww]

Yeah ... looks like im gonna have to see if i can hacksaw off my backbox on the audi tomorrow before it goes in if its gonna sound better than the de backbox option. . Im using the standard pipework just chopping out the boxes and getting pipes welded in place if this makes a difference at all .. fingers crossed i can get the backbox off in time haha

Any ideas of what the different options will sound like ? Thanks

[Dum-Dum]

Check the audi box is straight through and not baffled though.

[Poodle]

What's the backbox on the audi like, is it baffled?

Will sound pretty rumbly if you go 2.5" straight to a rude-boy backbox. You can make it sound raspy, but you'll need lots of gas velocity, in which case you want to stick to 2.25" piping and may as well use the midbox as a backbox.

[joelww]

Im not sure to be honest its just a universak savage backbox ... it didnt do much to silence my audi when that was full straight through so i dont think its baffled and if it is not much

[Poodle]

That just means it doesn't have much packing in it, could still be baffled. Shine a light through it, that'll tell you how restrictive it is.

[joelww]

Well its getting done as i speak ... i went for a decat to midbox to de backbox as i wasnt sure how baffled my audi backbox was but also because i couldnt be bothered hacksawing it off this morn ... ill get a sound clip up later if anyones interested..


Its all done now heres a photo of how it looks .. maybe a tad lower than i would of liked but my exhaust rubbers are knackered so im hopin new onew will help lift it slightly