Originally Posted by Bosch Dealer
...if you getting surge on your engine the turbo is not suitable for your spec....
Not entirely true, perfectly possible to map your way around that and still see decent results, by artificially limiting the point at which boost is allowed to build to maximum.
As an example Doug Stirling had a GT35R on his YB, and it would *just* start to surge at about 4000rpm if it was allowed to go over 2 bar, Karl mapped it so it stayed just under 2 bar until it was at about 5000rpm IIRC, and that completely eliminated the surge and left him with what was a decent spec engine with effectively a well matched turbo IMHO, the fact it had to be limited by just a couple of psi for just a tiny section of the rev range was not something that would make you want to avoid that turbo on that engine.