IF you adjust your BOV so that it does not LEAK under idle then your idle will be the same as if you recirc. all air being metered is being cunsumed.

***At idle most engines make between 17-22 inHg of vacuum. So if you adjust the BOV towards hard so that it is closed at idle that means that BOV will need to be set to open at a vacuum level greater than 22 inHg. After a shift your vacuum will go to around 25-27 inHg which is just barely over the threshold of 22 inHg you have set the BOV at. This hard setting means that the BOV will open a lot later than normal which allows more time for compressor surge to occur.

You are much better off adjusting the BOV soft to open at only 10 inHg of vacuum and reroute it. So when you shift gears and create 25-27 inHg of vacuum you are way above the threshold to open the valve. Thus the valve opens early and quickly negating the chance of experiencing compressor surge.





now...as for the running rich after shifts bit...yes it happens and yes it can cause drivability issues (i have fouled plugs from lots of low speed and part throttle driving). but this can be fixed by a S-AFC.

BTW...Greddy R can also be recirced...it has the threaded outlet as well.

Scott
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