Comparison
Garrett T04Z = .70 A/R T04S compressor cover.
Billet Z-P = .70 A/R T04S compressor cover.
Garrett T04Z = T04Z/T04R compressor wheel.
Billet Z-P = T04Z/T04R compressor wheel.
Garrett T04Z = Cast aluminum back plate.
Billet Z-P = Anodized billet aluminum back plate.
Garrett T04Z = Cast iron core.
Billet Z-P = Anodized billet aluminum core.
Garrett T04Z = Steel ball bearings, phenolic (plastic) bearing cages.
Billet Z-P = Full complement Aeronautic grade silicon nitride (ceramic) ball bearings. No bearing cages.
Garrett T04Z = GMR P trim turbine.
Billet Z-P = Inconel P Trim turbine.
Garrett T04Z = Garrett T04 exhaust housings.
Billet Z-P = Depending on availability. Billet T04 exhaust housings, Garrett T04 exhaust housings, Precision Turbo USA T04 exhaust housings.
As you can see both of these turbo's are very similar.
Other than the obvious Billet core the main differences are the materials the turbines are made from and the ball bearing system.
Inconel is a superior more robust material for turbines.
The silicon nitride ball bearings used in the Billet Turbo's are perfectly matched Aeronautic grade ball bearings and races.
The silicon nitride balls are over 200% lighter, have a truer shape and can handle quite a lot more heat and punishment than steel balls.
Full complement ball bearings mean they do not use a bearing cage.
No bearing cage means no extra weight or drag on the ball bearings.
Because the ball bearings are lighter, they have a truer shape, are made of stronger materials and have no extra drag or weight from a bearing cage they spin up faster and can handle more punishment by design.
There is nothing wrong with Garrett's turbo's and they do a great job of mass producing turbochargers.
The Billet Turbochargers are a high end performance turbocharger.
Regards,
Ricky Numeyer