One thing I didn’t like about the turbo set up was that I wasn’t being rewarded for revving the engine. There was plenty of mid range torque which is always useful for exiting a corner at a lazy rpm, but from a pure driving perspective I’d rather the performance lived a bit further up the rev range. So I bought a bigger turbo…
VF28 with 32mm restrictor vs TD04L-13T
Hopefully not too big!! It’s a VF28 turbo so still from the Impreza range. This should mean it bolts up to the existing manifold and downpipe. It’s a bit bigger than the TD04 but not too much bigger, I don’t think. It’s a ball bearing turbo which should help spool but the exhaust turbine is much bigger so overall it should come along a few rpm later than the TD04. It’s got a 32mm restrictor for rallying fitted which needs removing, which was job one. Apparently once it’s removed it’s just the normal housing underneath.
The first problem I had was I couldn’t get a hacksaw into the welds, so out came the dremel. This didn’t take long to cut through the two welds and from there the restrictor came straight off.
Curses! Won’t be getting any silicone hose on that! I ordered a remanufactured housing from Turbo Dynamics for £12 plus the vat so no great expense. By remanufactured, I think they meant painted! The inlet had a bit of pitting in it but I presume that’s not a problem else they wouldn’t have reused it.
Lastly, a photo comparing the two exhaust housings. Notice how much bigger the turbine is on the VF28.
TD04 (left) vs VF28 (right) exhaust housings
Westfield build, Mazda SDV 