Some great information I got from Tial today regarding the Q/QR and the QRJ:
I believe you would be just fine in retaining the QR, but I also think that, if you use the QRJ, and when installed correctly, it will provide a more linear response.
It's perfectly okay to use the -3.0psi spring, as that would also allow the QRJ to be open at idle, to act as a bypass, and if that provides you with the best performance, that's great news. In many other cases, the -6psi spring would provide that same bypass, but the BOV would not respond as quickly. That is exactly why the 'default' part numbers for the QRJ only contain either the -1.5 or -3.0psi springs, then, from there, the springs become an optional item.
Sometimes this just comes down to the specific engine dynamics, and sometimes it's about personal preference, but, again, that's why we offer options.
I am sure that, if there was a suitable demand, we could work with our spring supplier to offer a spring that sits 'between' the current offerings, but that demand has really not been strong. The Q/QR and QRJ actually have some overlap as to spring use, as the required dimensions at the spring cup are identical, but some springs can't be used in some bodies, as they could limit piston travel, etc.
Now, as to why a Q would be more apt to 'flutter' than a QRJ, this really comes down to the design, and as I mentioned, for most applications, I would tend to recommend the QRJ, as it's designed to provide that more linear response, and it's less likely to exhibit 'flutter' than the Q or QR, especially when installed correctly.
The Q and QR tend to be more "on-off-on" in terms of response, where the QRJ has the advantage of that piston/chamber design.
Many times, kit builders choose the Q because it is well-known, robust, and reliable, and has tremendous flow, but in a lot of cases, they would probably benefit from using the QRJ. We try to educate customers as best we can, but in the end, this is precisely why we offer both designs.
That said, I can assure you that for one person that wants to rid the system of any 'flutter', there is an equal and opposite person that actually wants to enhance that very same 'flutter'.
So it does become somewhat subjective.
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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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