Backbox delete query

[JPB]

So I've decided I want a backbox delete on my 2003 E85 Roadster 3.0i but want to keep costs as low as possible.
I know a guy near me who's happy to do the whole thing for £100-150 but said it could be cheaper if I source materials to save him time.
Obviously he'll need to either pipe bend or weld into shape to line-up with exhaust cutaway in bumper, but is this all I'll need materials-wise?
Stainless steel pipe: https://tinyurl.com/y6rvbou4
Connecting sleeve: https://tinyurl.com/y53ty84j

I should say, I want to use the sleeves instead of welding because I want to be able to swap the backbox back in if I want to.

Cheers all!

 

[Stevo7682]

Removal of the back box could lead to problems at mot time firstly with noise levels but more likely with emission levels when you remove the box you will remove the back pressure and probably affect the lambda sensor reading which could then affect the co reading also.
Stephen.

 

[Road warrior]

dont do it.. you may regret it frankly, it will be VERY loud,and you WILL lose power.

 

[Rha]

Have back box delete on a 07 Z4 coupe si, didn't have problem last April with noise or emissions on mot, no advisories sailed through. They usually don't rev it high enough for noise that would be a problem, and if they did and wasn't happy with it they then have the right to fail it, although think they would give advisery. It's a chance you'll have to take if you want a delete. Performance loss is a bit of a mistery as most don't get their cars on the rollers to see. The noise can get obtrusive but if you meter the loud pedal can become acceptable, hard to do if you like to make yourself noticeable which will eventually lead to complaints and the authority's getting involved, my neighbours have never heard my car in anger and I am carefull that they don't.


RHA, Roy.

 

[Pingu]

Half-way down the page...

https://zroadster.org/threads/pingus-m-roadster.17767/page-2

 

[Lee]

dont do it.. you may regret it frankly, it will be VERY loud,and you WILL lose power.

Rha above now owns my coupe. I had that car rolling roaded after the backbox delete. There was no loss in power. it still has the middle box and cats. Also no lamda issues. It’s had the back box removed for around 3 years now. It does drone a bit between 70-80 though. Pops n crackles make it worth it.

Lee

 

[Road warrior]

ok now look, im just offering my opinion, but please be aware unlike the si, the 3.0i does not have a middle box, which is what the fella is talking about - a 2003 3.0 i like mine

if you have a middle box it will be a resonator and is the reason you have lost no power. The back box is just a sound deadener and is why the yanks call it a muffler of course.

 

[Davz]

It's not just the si's that have a centre silencer but all n52's 2.5 and 3.0. There is a centre silencer and a smaller box which is the resonator.
Removal of the rear silencer will have zero effect on performance. Removal of the centre silencer may effect performance, it is there to not just subdue sound waves but to create a drop in pressure and create a scavenging effect to promote an increase in exhaust gas velocity. If you remove the centre box this scavenging will be affected, if you do this replace the centre box with an x-pipe which will improve scavenging, when combined with a free flowing rear silencer will give a small increase in power (3/4hp) but a much nicer sound with no drone.....better than a BB delete.

 

[spector73]

Getting my si done

 

[NCSaltLife]

I like DaveV's idea of removing the center box, add an X pipe and an improved rear silencer/muffler. I run the OEM performance version on my E90 and it sounds great.