In testing of stock bypass valves, we saw repeated internal leakage at boost levels as low as 8psi in the FA20 and 19psi in the EJ variant. As always the case with GrimmSpeed Products, we focus on form AND function, and these units are no exception. We aimed to create an extremely durable bypass valve that could hold double the pressure of the stock unit, while still being a stylish part that compliments the other GrimmSpeed Parts under your hood.
Material and Design
We started the ground-up design with the valve body and base for each popular fitment. Both are CNC-machined out of billet 6061 aluminum alloy for its strength and light-weight. They are then anodized in either a black or red finish to give them a brilliant appearance, provide corrosion resistance and match other GrimmSpeed offerings. Compared to the stock cast unit on the EJ STI and plastic construction on both the 08-14 and 15-21 WRX platforms, GrimmSpeed Bypass Valves not only stand out, but are guaranteed to stand the test of time.
For the internal components of the valve, we chose to utilize a machined brass piston for its anti-corrosion and low thermal expansion characteristics. Our piston seats onto an internal O-ring to create a perfect seal, eliminating boost leaks common in OEM and cheap aftermarket BPVs. In order to make sure this could keep up with high power levels, we chose to use a massive 38mm diameter piston/sealing ring for the ability to dump pressure quickly. This is especially important on high boost applications to keep the turbo from sustaining damage and the BPV maintaining leak-free operation. A precisely-tuned steel spring alleviates the need for any tuning or adjusting of the valve, with no engine tuning required to run the unit.
Buna-N O-rings were the next logical choice due to their resistance to degradation from fuel and oil exposure. In addition, all of our O-ring grooves utilize a single dovetail design for superior retention. This guarantees the O-ring will not fall out and has the perfect crush for sealing the body together. To top things off, we employ a swivel fitting on the valve to make for easy installation and accommodate best-routing on custom setups. A GrimmSpeed signature branding badge graces the top of each unit so that everyone will know you chose the best valve in the biz.
Both the 08-14 WRX/05-09 LGT and 04-21 STI (EJ) fitments utilize the same valve but with different footprints for use across a broad range of vehicles including Legacies, Foresters and Bajas with the proper intercooler setup. The STI unit reuses the recirculating elbow from the factory BPV, ensuring precise alignment and a perfect fit. All this makes for a total plug-and-play package.
- CNC-Machined 6061 Aluminum
- Corrosion resistant anodized finish, available in both red and black
- Oversized 38mm brass piston for superior flow
- Precision-tuned steel spring for long life
- No tuning or adjustment required
- Single dovetail O-ring grooves with Buna-N O-rings for great oil resistance, retention, and leak free operation
- Swivel air fitting to aid in install and for accommodating custom setups