It is definitely NOT just as simple as 'bigger is better' with an external gate.
Just think what happens on a smaller turbined turbo when all the exhaust gases go straight out a large WG.....you lose all your energy and boost drops off. WG shuts, boost spools up and then WG opens and you lose all boost etc etc etc. A viscious cycle that brings on the worst surging you have ever seen. I ran a 45mm TIAL gate on the GT4 and it surged so bad it nearly bucked the car right off the dyno. I had to do some mods to the WG valve seat to vent the exhaust gases initially in a more controllable fashion.
You are right that at top end gas flow, running unneeded exhaust gas thru the WG instead of the turbine will net you some gains but correct sizing and design is required.
A 38mm gate will be more than enough for your needs Joel and with good design of the WG return pipe it won't hurt your perf at all but will give good amd simple boost control.
Wed, 27 July 2005 07:02
