Intake Design Exploration

[RICE RACING]

When I was helping a student do his Thesis (I was operating the engine dyno and doing the mapping) for SAE intake manifold runner length experiments he was tossing up to use 1st or 2nd order waves for packaging reasons.

It would be nice to use (at lesser effect) the later orders to allow a shorter more direct manifold. Have you looked into that?

It's a bit like the header discussions from old people who used to race 13B P.P.'s fitted to a prototype mid engine set up. No way could you use the long header but the later order waves allowed a much shorter version and the power differences were in favor of the short through less system length and pipe friction losses.

Keep up the good work.

[vex]

Originally Posted by RICE RACING

When I was helping a student do his Thesis (I was operating the engine dyno and doing the mapping) for SAE intake manifold runner length experiments he was tossing up to use 1st or 2nd order waves for packaging reasons.

It would be nice to use (at lesser effect) the later orders to allow a shorter more direct manifold. Have you looked into that?

It's a bit like the header discussions from old people who used to race 13B P.P.'s fitted to a prototype mid engine set up. No way could you use the long header but the later order waves allowed a much shorter version and the power differences were in favor of the short through less system length and pipe friction losses.

Keep up the good work.

When I saw you posted in this thread, I was a little nervous that I made a mistake somewhere.

I have actually avoided working on the intake runner length problem for some time as I didn't have a good grasp on the physics or math of what was going on (not to mention the time I didn't really have to devote to it). I may revisit them today and better take into account the various order waves/harmonics you reference--and if I'm feeling adventurous I'll even put in pipe/friction losses. As always I'm glad to have input on matters that I don't have any experience in.

As an aside I no longer have access to CFD to verify diffuser geometry or even flow distribution (as the latest update to Autodesk's suite of CFD solvers requires more resources than my little laptop can handle). I hope to remedy this situation in the coming months; but we'll see how it all plays out.

Edit: Looking back over some of the Helmholtz equations for a tuned resonator I can't seem to locate any 'simple' references to what wave number enters into the calculations. Thinking over the physical process of how the intake runners work and tune I'm debating on if I need to even progress down this road. Rotarygod already did a majority of the simplification for the combined area of the stock intake runner port size. Ideally I would like to just adjust the posted forumula to account for a different runner area (combined primary and secondary ports), but if I do any more detail than that I think I would just be wasting time. Maybe I'll put this all on the back burner for awhile...

[j9fd3s]

neat thread! i've not much to contribute except that i've read a lot of SAE papers and Mazda has published a lot of rotary specific info.

particularly 831010 which is the 6 port intake system. the 90032 rotary P port modeling paper. also the S2000 paper is good, although isn't rotary specific. there is an S5 paper too.

the crib notes, we know about the lengths, i think, shorter = higher rpm peak.

they have a graph of plenum size vs VE, and due to the 270 degree cycles the rotary has what they call a tournament effect, when one rotor closes it uses the reflection to charge the other rotor. Mazda found a smaller plenum increases this effect. honda actually found the same, which is why the S2000 has a teeny plenum.

with the Rx8, all the runners (primary, secondary, thirdinary, corollary, arbitrary, and fred), have tuned lengths AND diameters.

from the info provided it really looks like Mazda made something that they could easily change the lengths on, and then they just tried a bunch, easier to do on a P port.

mike