2008 Subaru Impreza WRX - TMS Respons Blow-Off Valve - Modified Magazine

Proving Grounds
Blow-Off Valve
The GFB TMS Respons blow-off valve has been specifically designed to reduce turbo lag and improve throttle response. Is that actually possible with a blow-off valve, though? All it does is release pressure from the charged turbo system, doesn't it? True, but because of the adjustable spring pre-load on the TMS Respons BOV, it can actually be tuned to divert less air back into the intake and keep the turbo system charged with more air, improving response and reducing lag. GFB conducted a test [1] where it took a Nissan S13 equipped with a CA18DET and compared manifold boost pressure rise during first to second gear shifts between a stock BOV and the GFB TMS. An improvement of more than 30 percent faster return to peak boost was logged with the TMS Respons BOV and up to 40 percent more boost was immediately available after the shift.

If you want noise, then the TMS Respons BOV has a tunable venting ratio. By twisting the adjustment ring, the atmosphere port can be opened or closed, at the same time changing the position of the recirculation port. This results in possible venting ratios from 100 percent recirculation to 100 percent atmosphere and anywhere in between.

Turbo Fuse This is a nifty little device that acts as a last line of defense against an over-boost situation that could ultimately blow up your motor. It plugs in line with your BOV vacuum hose, and when the user-adjustable trip-point is reached, boost pressure to the top of the BOV is instantly cut off, which cracks the BOV open and relieves boost pressure. This prevents possible engine damage and alerts the driver that something is wrong.

Results Our '08 Subaru WRX was used as a test mule for both the TMS Respons BOV and Turbo Fuse. Despite not being able to actually simulate the response/boost test similar to the one conducted by GFB, we played around with spring pre-load settings by adjusting the screw on top of the Respons BOV. With the screw dialed almost all the way in (requires more boost to open the valve), we noticed a slight improvement in the way the turbo spooled between shifts. Ultimately, this BOV is better suited for a car equipped with a larger turbo and a front-mount intercooler, where the lag is very apparent. We have no doubt that with the right adjustment, lag can actually be decreased.

As advertised, the TMS Respons BOV can also be adjusted to vent to the atmosphere partially or fully. We played with both settings and found it worked best at a 60 recirc/40 vent split on our WRX. However, it will depend on your car and how finicky the air metering system is; you may find you can run 30/70 or have to go 80/20 to have the proper ratio for the car to run right. That's what makes this BOV so nice, though-you can adjust it to the point where it won't trigger any check-engine lights, and you'll still get that fancy noise that so many people are after.

We really like the idea of the Turbo Fuse because of how simple and effective it is. Even though boost controllers and factory solenoids have built-in over-boost protection, they still don't provide the same protection, and we've seen many cars blow their motors with those built-in safety measures intact.

Because the Turbo Fuse relieves the pressure on the BOV in an over-boost situation, it instantly drops a significant amount of boost pressure from the charge, which we noticed right away when driving. There's no mistaking when the Turbo Fuse is triggered because power drop is so rapid. It's also very smooth, rather than the all-to-common violent fuel cut functions that are found on OEM setups.

The Turbo Fuse does take a bit of time to get set up because you have to drive the car at full throttle, adjust the screw, make another pull and adjust it again until you find the sweet spot. But it's by far the simplest method of keeping your boost in check.

Test Mule
'08 subaru impreza wrx
Engine
2.5-liter EJ25
Relevant Mods
Perrin TMIC, SPT 3-inch exhaust,
K&N Typhoon
Intake

Key
Features
The TMS blow-off valve can be set to full recirculation or dump to atmosphere or a combination of both.

Full recirc mode provides silent operation just like the factory BOV and full dump gives maximum noise.

Reduces lag and improves throttle response.

Direct fit applications for many vehicles.

Turbo Fuse works with the blow-off valve to relieve excessive boost pressure when triggered.

Desired boost pressure set by user to trigger automatically when boost pressure is in excess of target amount.