Hi All,
I've recently (750 miles ago) had an engine rebuild on my 2003 newage WRX so have been limited to 4000rpm. As part of the process I had a decat up-pipe and some port matching done.
Everything is going fine. The engine pulls really well if treated gently up to the imposed 4000rpm limit with no hiccups or undue noises.
If however the pedal is hit a bit hard and the turbo allowed to boost, there is a an alarming sound from the engine bay at around 3000 - 3500rpm. When you lift of it dies a bit, but re-occurs when the turbo is brought back online.
I've been told that it's probably a ratting heat shield, but it only occurs when the turbo is on boost, not when driving gently up through the revs, and I can't make the same 'rattle' when the var is stationary (ie no load / no boost).
I've checked and cleaned the boost solenoid, and blown through all the piping from the wastegate actuator and the manifolds, and all seems clear. There also seems to be no drop in power so there's no boost cut-off coming into play. I don't have a boost guage so have no idea if there is a degree of overboost as a result of the decat up-pipe. What are the sumptoms of overboost? (Other than bits of engine coming through the bonnet...)
Basically stumped and would be grateful to hear you views...