RRE 323 GTX Bosch BOV Instructions

This is a photo of the stock 323 GTX Compressor  Bypass Valve or “Blow Off Valve” (BOV)

Inside the hose that runs from the pipe at the throttle body and down to the BOV, there is a restrictor that blocks the hose from 13mm down to 8mm. All your BOV air passes through this little hole. You can remove it to get some more flow through your stock BOV but with an open air filter you will hear some wicked bovine farty noises.

To remove the restrictor, find it by squeezing the hose to locate it. Pull it out with needle nose pliers.

An upgrade for a leaking BOV or to get rid of the strange noises is to replace the stock BOV with a Bosch BOV that comes stock on many European turbo cars. It is a quality part but can be had reasonably cheap. Expect to pay about $50, we keep them in stock. To connect it you will need two radiator hoses from an auto parts store. We used part numbers 71423 and 71409 from Pep Boys. I believe these are generic hose part numbers, possibly Gates numbers. If you cant get the numbers matched up, do like we did and ask for permission to climb the counter and go digging through the bins till you find what you need.

You need access to some slightly larger hose clamps, with the larger hoses and BOV, some of the stock clamps are not quite big enough.

This is a photo of the Bosch BOV installed. It uses a slightly smaller vacuum hose fitting, we used a small adapter to go from 6mm hose down to 4mm. The car this was installed on is still running stock boost. This mod eliminated the Moo Cow noises but did not make any noises that would frighten a honda or impress the ladies.

For more noise (good sounding noises… WHOOpshhhhh!) you can use a GReddy Type S BOV. It is a much more custom install best done with new I/C piping. The GReddy valve uses a two bolt flange that will need to be welded onto a pipe. The GReddy valves run about $200

The GReddy BOVs shown here are blowing to the atmosphere. With careful adjustment you can get away with this to some degree. The lower pic to the right is on a car with a TEC2 ECU that allows you to blow the air out with no problems.