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GReddy Type-S BOV Install

The GReddy Type-S BOV is one of the most popular blow-off valves available for any application and for good reason. With the Type-S flange for the Evo, it is now also one of the easiest to install on your Evolution. No welding is required and you can be up and running in no time at all. Replacing the stock plastic Evo BOV with something a little more sturdy that doesn't leak should be a priority for anyone running higher than stock boost. Additionally, adjustment is quite simple with just a few turns of the adjustment screw...there is no need to crack open the unit to replace springs and add shims trying to find the perfect setting.

1. Before doing anything on this install, we recommend doing the Single Spring Mod for the Type-S! Failure to do the single spring mod may result in poor idle/stalling and/or excessive valve flutter. Now that you've done the single spring mod, you will want to start this install with the engine cool. This will avoid any potential burns and with the engine cold, the upper radiator hose will be pliable enough to simply lift up out of the way to R&R the BOV.
2. Begin by loosening the two clamps that hold the stock BOV to the turbo inlet hose and the hose connecting it to the upper IC pipe as shown in the picture. NOTE: we have replaced our stock hose connecting the BOV to the upper IC pipe so we did not have to cut the factory one shorter when the RMR IC pipe kit was installed.
3. Remove the vacuum line from the stock BOV valve. TECH TIP: after sliding the clamp down, carefully "spin" the hose to loosen its grip on the BOV's vacuum port. Be careful while removing the hose from the BOV. Remember that it is plastic and you can snap or crack the port right off the BOV if you are too rough with it.
4. Open up your GReddy Type-S box and grab the Evo Type-S flange as well. Note to step 5
5. Using the supplied allen bolts, washers, nuts, and gasket from the GReddy Type-S box, assemble the Evo flange to the BOV as shown (bottom).
6. Now simply replace the Type-S setup where the factory BOV was, tighten the clamps for the flange and the dump and then reconnect the vacuum hose from the stock BOV to the top vacuum port (in the anodized cap). Be careful not to strip the clamps while tightening them!
7. MISC. NOTES: Depending which turbo inlet pipe and IC piping are on your Evo, location and orientation of the BOV will vary slightly. Some trimming of the hose that connects the flange to the upper IC pipe may be required for a clean connection. With the RMR intake pipe and RMR IC piping kit, there happens to be a very short distance between the flange and upper IC pipe as seen in this photo. If you do not want to cut your stock hose, it may be a good idea to head to your local auto parts store and find something comparable in size with a 90 bend in it. We cut up a molded coolant hose Gates P/N 21630 that cost us $14 at the local parts store to spare our stock hose the surgery.
8. BOV TUNING: The single spring mod is a one-time operation. Once done, the Type-S is completely and easily adjustable on the car without ever needing to remove it to replace springs/spacers like other BOVs. Simply loosen the 10mm lock nut on the adjustment screw (top of valve), turn the adjustment screw with your 3mm allen key as necessary and then retighten the lock nut....simple as that. The adjustment screw is used to change the tension of the spring inside the valve. The "harder" the setting (deeper the adjustment screw), the less prone the valve will be to being blown open and the greater the change in pressure needed to open it. Set too soft, the valve could possibly be blown open under high boost. Set too hard, the valve may flutter or not open at all. Any fluttering from too hard of a setting will be most noticeable during light throttle changes since there is only a small change in pressure on either side of the valve (re-read the bold statement above). The more you let off the gas and/or the more quickly you let off, the greater/sharper the change in pressure and the increased ability for the valve to open flutter-free. In short, for the very least potential valve flutter, adjust the spring as light as possible without it being blown open for your setup and boost level.

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