Having spent the holidays messing about with my car i'm happy to say i've finished doing any modifications for now. This is what i did:
- Removed headers and ported them to the same ID for each port as the holes in the gasket so there is a smooth flow with no obstacles in the way.
- Ported exhaust outlets (on each head) which weren't concentric as Paul at Zen said they wouldn't be, so they are now!! Again ported to the same size ID as the gasket and now a perfect match for the headers.
- Ported the headers exit (3 bolt flange end) to match the gasket ID.
- Ported bottom of the uppipe to match the 3 bolt flange.
- Ported the uppipe exit as much as i felt was safe to do without compromising the integrity of the pipe, again following the shape and ID of the uppipe to turbo gasket.
- Turbo: Hot side inlet and oulet.
- Wastegate ported (keeping within wastegate flapper OD limits)
- Turbo: Cold side inlet and outlet ported and polished for increased flow (every little bit helps)
Downpipe entry ported to match turbo exhaust oulet.
...and if that wasn't enough!!
- Purchased and fitted a new silicone turbo inlet hose from RCM. No inlet header removal required. Excellent fit and top quality product!! New silicone turbo oulet to intercooler hose and silicone intercooler to throttle body coupler, and silicone airbox hose and Aluminium coupler to turbo inlet hose.
It was an interesting experience and a task not to be undertaken by the faint hearted. To be honest without all the right tools and bits for porting it would have taken me weeks to do just using normal grinding stones so i invested in some proper carbide burring tools to remove the bulk of the metal, then different grades of stones to get the shape and smoothing of the internal surfaces, finished off by using fine grit flappers and fine wire brushes.
Baring in mind this was all done by hand the key thing here is that without jigs and machinery to set everything up the best advice is to go carefully and take your time!!
Having done some logging today just to get an idea of what needs to be done mapping wise i was chuffed to see i'd pegged the MAF good and proper!!
I have decided to start mapping from absolute scratch all over again now as the car feels completely different to drive and feels like the turbo could handle a lot more.
It doesn't spool up much earlier but when it's on song it does so more quickly and solidly. It's holding boost 1.3bar right up to the redline and that's just with the old map so we'll see how well i can exploit that further. It seems to me that i can now dial in whatever i want up without fear of making the turbo a flamethrower. Right now my only limitation is the MAF.
400bhp here we come!!

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