Some added info from Tial:
The QRJ also has a unique v-band set of it's own (different than Q/QR), and threaded v-flange that allows for it to mount directly where a Q or QR was originally. There's also a 'diffuser' outlet for atmospheric discharge, and, of course, you can also simply run the unit without any discharge adapter of any kind, and this is very common. It's also very loud in that configuration.
As for which is best for you, that's more about flow than boost pressure (which is irrelevant), but consider this:
Q has flow to support 1800HP worth of bypass flow
QR has flow to support 1200HP worth of bypass flow
QRJ has flow to support 900HP worth of bypass flow
All three are capable of a significant amount of bypass flow, so unless you are exceeding the peak flow rate of whichever BOV you currently have, there's no reason to change unless you simply prefer the feature or fitment of one over the other.
All of that aside, we typically will suggest that a customer consider the QRJ for many applications, as the design favors a more linear power transfer for on-off throttle, which is advantageous for road and road/track cars, particularly those with FWD or AWD configurations.
One thing worth noting: The QRJ is designed to be installed with the inlet as the 'side' port, and the discharge as the 'end' port. The unique tapered piston and large chamber that surrounds it lend to the best performance when installed this way. It will still work if installed 'backward' but all of those benefits are lost when this is done. There are sometimes reasons why this doesn't matter, and the design allows this, due to the spacing of the ports.
For a supercharged application, the -1.5psi spring will allow the BOV to act as a bypass for the supercharger at idle and under light-load, which reduces the load on the drive system (usually a belt) and reduces the forces acting against the throttle body, and, of course, prevents odd tuning issues that occur when positive pressure is present in the intake manifold at idle.
I'm personally a big fan of the QRJ, but I also don't own anything that requires the flow rate of the larger devices.
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Fast Intentions "Stage Seb" twin turbo #098- Specialty Z/Tial-Xonarotor/CJM/Ecutek/HKS/KW/SPL/Hotchkis/Rohana/Toyo
700+whp
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