I used a fairly cheap boost gauge today connected to the super charger bypass valve inlet hose.I was looking for a take off for my meth/water boost controller.

The reading I got at 800 rpm was 18 psi. Around 3,000 rpm 28 psi where it maxed out.

Because I am running a Eurotoys 2.6 pulley I would expect higher boost at 800 rpm compared to stock. However, if the gauge is correct, 18 psi seems high to me.

The question I have relates to how the bypass valve operates. At what psi does it close?

Does having a smaller pulley with increased boost at idle mean the valve never actually closes?

 

I think you need to subtract 14.7 from those numbers.

 

Not connected the gauge reads 0. So why do I need to subtract atmospheric pressure?

 

Well something is very wrong with that gauge then, there is no way in hell that you've got 18psig manifold pressure at idle and 28psig when your at full throttle.

 

Thats what I was thinking. I am going to wait until I hook up the Snow boost controller and see how that functions with the start psi selection.

At least I am getting the range I want at this connection.

I was not at the connection at the base of the " spreader" from the SC outlet to the charge coolers. The gauge read 18 psi to 22 psi max. Which I find puzzling.