05-09-2012, 04:29 AM
(04-09-2012, 09:05 PM)Connor Wrote: f*ck back pressure, that's for pussy fuel lol on a derv you just want to get rid of the exhaust asap
It's actually down to the turbo, turbo engines go better the less back-pressure you have. Less restrictive exhaust will mean quicker spool, better maintaining of boost at higher revs, generally more responsive, etc.
Bear in mind that you need one box in the system for it to be legal, although you don't need the cat.
Swapping the back box for the middle box will affect the back-pressure - it'll reduce it as the midbox is about as unrestrictive as they come.
For a remap you want to talk to MrWhippy, pro_steve or TB206HDi.
You can tweak the turbo a bit, but it's not recommended before you get an intercooler. These engines have quite small turbos from the factory, so increasing boost will also be running the turbo past it's peak efficiency and cooking your intake charge, which will cost you most of the power you will have gained from upping the boost.
You could use the 406 intercooler, but for the amount of effort you've got to put in, you may as well do it properly. Have a look in the HDi, guide and project sections for ideas on how you can go about fitting a front-mount intercooler.