|
i posted this back in 2008 on 6-speed with respect to the RSS version of this 'plenum'. IPD never responded. when an intake system or improvement is DESIGNED versus mocked up & sold as a gimmick, pressure sensors are installed in the runners near the cylinder heads to ensure the intake performs as planned. IPD apparently did not do this; i would gues that pedro didn't, either. bottom line is that i believe these modified feed pipes can actually destabilize the pressure balance present in the factory design:
i'd like to introduce some engineering perspective here. for some background, i designed and tested some intakes on formula SAE cars and used to design subsonic compressible flow networks professionally. there are some things that confuse me about what this 'plenum' supposedly does, and some misconceptions that we can maybe clear up.
first, that IPD piece isn't really a plenum; it's a feed pipe to the two plenums on either side of it. second, the OEM plenum feed pipe on the M96 / M97 motors wasn't designed as a bullnose tee by accident, it was BY DESIGN. it is actually desirable for diffuse rather than laminar flow to supply an intake plenum.
the purpose of the actual plenums in these or any car is to stabilize the pressure at the intake runner heads so that each cylinder has the same supply pressure. a poorly designed intake will cause some cylinders to run rich & others to run lean. this can lead to all sorts of problems.
a well designed intake will ensure equal pressure at the runners. an extremely well designed intake can vary plenum size and runner length to take advantage of the harmonics that allow tuning of the intake system to a specific range of RPM's. porsche's varioram system does the former. varioram effectively increases the plenum size AND bridges two plenums into a single plenum. this allows the intake system to use harmonics to reduce disadvantages of static intake system designs. when designing an intake that does not vary runner length or plenum volume, there are compromises. one must choose whether one wants to use the intake to increase low end grunt or high end power, always sacrificing the other in the process. systems like varioram attempt to have it both ways.
to this point i've been talking about plenums and runners, but haven't really addressed the feed pipe. look at the IPD feed pipe. i believe the y-scoops will cause vortices to form INSIDE the two plenums that they feed. these vortices will occur near the center of each plenum, creating local low pressure areas just in front of the center cylinder in each plenum. in theory, this would cause the center cylinders on each bank to run lean and the outer two cylinders on each bank to run rich. this is not an improvement over the OEM design.
i haven't weighed in on this for awhile because fluid flows do funny things and it's not always easy to predict an outcome without running flow tests. the thing that always through me for a loop are the little pipes that seem to go across the inside of the IPD unit. i thought there might be some magic to these things, but was never really sure.
how 'bout you IPD guys chime in and explain the engineering thought behind this design? how have you verified the performance of the flow networks with and without your part installed in the network? have you actually used sensors in each runner to verify you've maintained or improved the OEM intake network's balance? what types of modeling have you done? any other tests besides dyno runs?
|