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Discussion Starter · #1 ·
Just owondering, the VRIS system is designed for the normal aspirated engines to get the extra power by tuning or channelling the air flow using the 2 butterfly valves... so what happens if you throw on a turbo or SC? Seems to me I'd want to remove it because it would be restricting the airflow of the FI system. Am I right or wrong?
 

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The VRIS is designed to lengthen and shorten the effective volume of the intake manifold plenum and by extension, the runners. Doing so at the right times, it can use the same resonance effect of a tuned "wind" instrument to get a minor ram effect, enhancing torque.

With a blower, several things change. First, with such a huge increase in the pressure inside the manifold, the natural frequency of the system goes up, rendering the OEM VRIS points pretty much useless. Second, with a compressor forcing air into the plenum, the actual path taken (long versus short) is of little importance. If the manifold is pressurized to, say, 8PSI, the whole manifold is, including the space in front of and behind the VRIS #2 plates (if they were closed.) The compressor, if properly sized, would be able to maintain enough flow through the "long-passages" (above and below the #2 plates) so that opening the #2s wouldn't net any gain.

As well, most turbos I've seen are peaking in power between 5500 and 6000RPM, during which time the PCM is holding the VRIS plates open anyway; removing them won't produce much peak gain. Even at 6250 when the #2s close, I can't see there being a big pwoer hit.

Some think that removing the plates may aid in turbo spool and reduce lag and I suspect there may be some truth to that, though I also think the effect will be small.

If it were me, being the geek that I am, I'd use a Hobb's switch to cause the VRIS #2 to open when the manifold pressure went above 1 or 2 PSI. That way, the VRIS stays intact during times when boost is low and is "out of the way" when boost is online.
 

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Discussion Starter · #3 ·
What about AFMlink?

He He Geek! I knew you'd come through for me Mike! Thanks for the knowledge, then there shouldn't be much difference (if at all) between the ZE manifold and 03 manifold conserning the VRIS... (I'm planning on getting the ZE manifold) another question... have you ever used the AFMlink? From what I understand you can eliminate the MAF because this unit uses vaccum/pressure to monitor and adjust fuel flow, plus adding a turbo later will make this a must in a way.
 

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A ZE manifold using a KL03 PCM in normally aspirated conditions will experience torque deficits at 3250, 4250 and 6250 because the 'ZE manifold has different VRIS resonance points than the 'O3. With a turbo, these concerns are pretty much nullified.

As for the Link, no I haven't used it though I (think I) know of two people who have: Fortier and Andrew Brownsword (93 PGT Turbo). Andrew can answer better than I (hope he will) but I'm guessing it didn't work for him due to the weirdly nature of the output signal of the VAF on the V6. If it did work, methinks Andrew wouldn't be the going through the pain of trying to re-program his car's PCM to work with a MAF sensor.
 
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