Choosing Between IWG or EWG
Airflow is critical to a turbocharger, the amount of air flowing into the turbo is as important as the amount of exhaust that releases; therefore you must carefully choose between internal wastegated (IWG) turbocharger or external wastegate (EWG) turbocharger.
An IWG turbo has an actuator that controls the boost output and diverts excess gases from the turbine wheel. IWG is much easier to install and is less costly than an EWG as an EWG requires more piping and external wastegate is purchased separately.
Compared to EWG, IWG has less failure points since EWG setup involves more parts. For example, external wastegate diaphragm wears out faster especially on those turbos without water-cool. Another advantage of IWG is that it has faster boost response. We recommend small ported engine or Subaru engine to use IWG.
Why and when to choose an EWG? An external wastegate too helps control the boost pressure, but it allows for more flexibility with the overall design, and it ultimately makes more power since the exhaust gases can be routed further away from the turbine housing.
EWG makes more power on the top end and EWG turbos are generally larger in size. Heavily ported engine are more suitable with EWG turbos as it releases exhaust flow faster, therefore reducing back pressure. Most of the larger turbos are default designed as EWG; for example, T3/T4 turbos are built without an actuator, an external wastegate is required to complete the setup. An external wastegate discharges exhaust gases faster as its outlet standard size is 38mm.