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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
A normal BOV only opens on over run when the throttle is closed.

The Synapse BOV only closes with acceleration.

In theory I do not know which is better. With a stock style BOV the intercooler might be pressurized to a small degree on cruse (probably not at idle) and there would be vacuum in the intake manifold at cruse.


With the Synapse BOV the turbo seems to spin faster and in reserve so it can increase or establish pressure faster in the gross area between the turbo and intake valve. It also should reduce drag on the exhaust at cruse.

With my reconfigured BOV that functioned like the Synapse it felt like I had better throttle response off idle, off cruse, and between shifts (stayed at full boost with sport shifts).

I do not know if my system totally depressurized the turbo to throttle body or intercooler section. It might have maintained some resident pressure in the IC and still allowed the turbo to spin at a faster rate in reserve. I believe my BOV was based on a Forge adjustable BOV which flowed more than the stock Bosch plastic C2 BOV but was still only a 1" unit.

This was on top of several tricks I played with that got my CIS to act more like an EFI than CIS as to throttle response. The other significant one was lowering Control Pressure immediately and aggressively with any throttle input. This lowered the restriction to the turbo's suction side to reduce drag from the metering plate and get it moving faster. It also reduced the 930 CIS lean surge and produced an AFR more conducive to acceleration.

I also did not have to run a fat CO and I could still maintain a fuel efficient AFR at idle and cruse. Many run a 3 to 3.5% CO or about 13/1 AFR on part load to get the fueling they need for better off idle acceleration.

Then there is the ignition side...
Old 03-26-2010, 10:40 AM
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