We Test Synapse Engineering’s Synchronic Blow Off Valve and DV Diverter Valve

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The Synchronic BOV is hidden under the charge pipe but the routing is nice.

The guys at JWT told us that this sometimes happens with their kits on the dyno when an aftermarket BOV is used.  However we started to tune the Synchronic BOV to get rid of the resonance, first we went from applying vacuum to both piston substrates to just the larger area outer substrate to reduce the valve’s sensitivity to vacuum signal. This greatly cut down the resonance.  Next we switched to the small substrate for the least piston area; this got rid of nearly the entire problem.  Finally we increased the spring preload slightly and the problem went away totally.  When tuned like this, the valve still functioned incredibly well, blowing off crisply when the throttle was lifted even in the slightest with no compressor surge at all.  We were very impressed. The Synchronic valve also has a large third chamber on the bottom side of the piston with an external port in case you would want to port it to pressure in front of the throttle body to give more closing force to the valve.  This option is hardly used but it is there if you need it.

Often when turboing cars that have not been turboed from the factory, especially ones with Mass Airflow Meters, we have seen stalling when the throttle is lifted, especially on cars with big aftermarket BOV’s.  We usually solve the problem by cutting the spring on the BOV so it opens easier, usually at 250 mm of hg, but this is a hit or miss proposition. The Synchronic valve could be easily tuned in this sort of situation.

This sweet set up pumps out more than 620 whp!

Typically you cannot install a BOV to dump to atmosphere on cars with a MAF either because at idle and other times of high manifold vacuum a BOV is usually open and air would bypass the MAF causing all sorts of issues.  The Synchronic valve can be tuned with the spring preload set up high with the manifold vacuum on the small substrate so the valve is closed at idle but can still blow off under boost when the throttle is closed. By making the valve open a lot with lots of control area, compressor surge can sometimes be tuned out, especially on cars with quick spooling turbos like the EVO. 

Another thing that the Synchronic valve can be tuned around is low intake manifold vacuum caused by big overlap performance cams.  These can reduce vacuum signal by about half.  Adding piston area and reducing spring preload will make up for a loss of vacuum signal restoring driveabily and reducing surge through proper BOV operation.

The large range of adjustability possessed by the Synchronic BOV has allowed us to tune out some resonance problems we were experiencing on the dyno.