Project DBA R35 Nissan GT-R, Keeping Limp Mode Away With More Cooling

The Greddy FV blowoff valves are a new innovative design. With FV blowoff valves the valve itself can float from the diaphragm and its spring on its own separate spring. This eliminates the problem of the blowoff valve opening at idle or on overrun recovery.  If the valve opens under these conditions, it can affect idle quality and stability and cause stalling on revving or overrun recovery.  Traditionally, to stop the valve from opening like this the valve spring preload had to be adjusted stiffly.  This made the valve unresponsive to vacuum operation when the throttle was shut under boost. If the spring was preloaded lightly to make it more responsive, there was also a chance it could blow open under boost pressure and become a huge boost leak.

With the FV valve, under high vacuum conditions the diaphragm floats away from the valve and the valve is held closed by its independent low tension spring.  This gives idle and rev overrun stability. The valves spring tension is enough to ensure that boost pressure cannot blow the valve open.  When the valves diaphragm sees boost pressure, the boost pressure works through the diaphragm to help hold the valve shut.

So the Greddy FV valve is always closed when it should be closed, fully open when it should be open and still very sensitive even though it doesnt flutter, cause driveability issues or leak boost.  Its a simple yet perfect solution to make the ultimate BOV, the design makes you think, gee I wish I thought of that!

The Greddy FV blow off valve has a huge valve with a lot of flow. The large freer flowing valve is more effective in reducing surge and keeping the turbo shaft speed high.

The FV valve has the same base flange as previous Greddy blow off valves so if you have an older Greddy valve, you can upgrade it with the FV valve. The FV valve can be run to vent to atmosphere or to recirculate.  Generally speed density mass calculating ECU’s can blow off to the atmosphere but systems that use mass airflow meters like the GT-R need to have the air recirculated or the engine will run rich and possibly stall when the valves open.


  1. Mike, any need to upgrade the PS cooling loop? Our Z33 overheats the stock PS cooler and system with puny 255 Continentals on track days. The plan over winter is to install a large truck trans cooler in its place.

    1. The GT-R has the biggest power steering cooler of any Nissan I have seen so far. We haven’t heard of people having issues. I haven’t heard of a Z33 overheating the power steering on the track, autocross yes but not on a road course.

  2. I really like that BOV design. I think it’s time to retire the Greddy Type S I’ve had on my car for the past 10 years.

Leave a Reply

Your email address will not be published. Required fields are marked *