38mm valve for good boost control on up to 58mm turbos depending on design of mechanical control system (wastegate priority).

Included with every TiAL F38:
* F38 Assembly
* F38 Valve Seat
* 2 TiAL Air Fittings
* 2 Mounting Bolts
* 1 Spring of your choice of pressures

NOTE: Wastegate spring pressure will be the lowest boost you would be able to achieve with a properly designed boost control system. A good quality boost controller added on to the wastegate system should be able to allow roughly a couple psi more than double the boost from the wastegate spring pressure alone.

Example: Several vehicles tuned here at KO Racing with 10psi springs in the F38 have been able to achieve 22-23psi maximum with the additional of a boost controller and engine management systems.