I would have thought that a bigger turbo is the way to go, I am not sure that you will get much extra by modifying a standard one, The housing is cast and so limits any increase?I have a spare A2 1.4 TDI 75 Turbocharger here, so i was thinking about possibly modifying the internals to install at a later date alongside a custom remap.
Has anyone looked into this? Or actually upgraded theirs?
I believe the torque figures for the 1.4 TDI 75 are 144lb/ft and 195Nm respectively...There isn't a lot of info out there on modifying an A2 past a remap but if you search for tuning 1.4tdi pd on google there is quite a bit of info relating to the Lupo and Polo etc.
There is mention of one guy who tuned the AMF engine to 142hp without any internal modifications but the engine failed due to problems with the crank. This info was all read a few weeks ago so my figures might be out but there is also the issue of the gearbox being too weak to take a lot more power. I think the gearbox fitted to the 1.4 TDI can only handle a max power of 220lbft of torque. I'm sure that a remapped 1.4 TDi puts out close to 190 lbsft so there isn't much scope for more tuning.
From what I can gather the TDI engine fitted to our cars is essentially the same block as the 1.9 TDi 100 bhp model but obvioulsy without the extra cylinder. From what i've read the bigger turbo from that model car can be fitted if the inlet manifold is cut and welded to become a 3 branch manifold. The main problem with getter more power from our engines is that the turbo is just so small.
There is also a member on the german forum who has fitted a 1.9 TDI block to his A2 which is interesting.