Header design theory
 

Moved/Merged thread. -RG

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i just talked to mr amemiya him self and hes say hes getting 10whp from his header and he also thinks that racing beat shouldnt really have that hard of time to get the 7 -8whp they said they seen

not untrue, not the complete story either. I'm far from an expert at the deep technical levels, but...

The pulse cycling in a 2-stroke piston engine and a 4-stroke piston engine is quite different. I'm pretty sure that I've read that the 2-stroke and rotary have some similarities (not the same). Probably moreso with peripherial ported rotaries. In 2-stroke piston engines a "chamber" is used to aid in scavenging.

Two-stroke header design is very different than rotary applications, especially for the Renesis since it has zero overlap.

^^ where does it say same in my post? I am aware that rotary headers don't employ a chamber for scavaging. I didn't say that the header designs were the same. I said that the pulse cycling would seem to be more similar between 2-strokes and rotaries than 4-strokes and rotaries. Doesn't it specifically say above that it would apply more to PP rotaries that the Renesis? Not trying to bite your head off, but you kinda missed my point...

Two-stroke header design differs from rotaries in that:

-the pulse spacing per degree of crank rotation is different
-the manifold pressure signature (pressure at a location per degree of rotation) is different

But you are right that two-stroke theory is closer than piston 4 stroke theory when talking about a full perhipheral port motor. So yeah, I guess I did miss your point

2-stroke or 4-stroke, you're still talking reciprocating piston engine, like I said the rotary is different :dunno: nor did I claim it was the whole story :confused:

^^no, but as tuj has pointed out now, two-stroke theory is closer to rotary theory than 4-strokes. Not the same. I brought up two-strokes to point out that just piston vs rotary dangerously oversimplifies things as we can see in the differences between two-strokes and four-strokes. Side-ports in the Renesis change things, but let's not "throw out the baby with the bath water".

Header theory:
 

Since another thread started getting into this topic, I decided to bring the discussion to a new thread. Any header design comments, questions, theory, etc can be debated and discussed here.

Thanks - this is my favorite readings while on the forum :)

So, the only thing holding us back, is the Siamese center port, correct? Is the Renesis the first rotary to have this setup? I most likely will only be asking questions.

First rotary to used siamesed exhaust ports? Yes. First engine to? No. Just to add some fuel to the fire, it is also not the first engine to successfully use zero overlap. This too has been tried and while not in any production cars, it is known to work. OK everyone, get studying and come up with some neat ideas! I've told mine a long time ago.

RG...what is port timing of the center ports....when do they open...and close compared to the side ports?? Also..what is the best theory for pulse tuning with the exaust?? I know this is a bit vague...but in general are we looking to propagate even pulses...or have pulses that vary with intake cycle to allow for better filling during intake?

not exactly, please explain you longer siamese pipe theory :angel:


BTW, I have an Re Anemiya header in hand, they seemed to have dropped the center siamese port divider plate shown in their website photo

why not copy over the discussion from the other thread, no sense repeating ourselves, I gave one theory there ...

I have a photo of an RX-8 header that appears to be made from Titanium :SHOCKED: I've been meaning to scan it in and see if somebody can do a japanese translation on it

As far as header flow, the stock header is a bus-type of flow, whereas the RE or OBX ones are hubbed + equal lengths that arranges the flow to not overlap. I think this is beneficial for every type of engine, especially the high revving ones. I still don't know what kind of gains we're looking at since no one has formally installed and dynoed one.

no, neither is equal length,, the closer pipes are swung around some to increase their length, but they aren't equal

OK it's been added here. Unfortunately the way I did it, it's added at the beginning.

The rotary is a 4 stroke otto cycle engine. That is all that matters. It makes no difference if it has valves or not. It makes no difference if it has pistons or not. It is absolutely not similar to a 2 stroke nor is it closer to a 2 stroke than a 4 stroke in any way. If you use a 2 stroke exhaust design on a rotary, you will lose power. I'll let that one be debated a while before I chime in with the answers as to why this is so.

wow,
a tread that i tried to start to move an argument turned into a productive header thread....

cool!

beers

There is no debating the fact that the combustion cycle is a 4 stroke otto cycle. I don't think that was what any of us were really debating. We were looking at things from what the header sees... exhaust pulses. One rotor making one complete crankshaft (E-shaft) revolution vs One cylinder/one piston making one complete crankshaft revolution. No denying even if they are both otto cycle, the piston and the rotary aren't producing the same thing. Maybe I was way off target by bringing in the two-stroke, however, I didn't say to use a two stroke exhaust design on the rotary. I did say that negating your header idea based upon the it coming from piston engines and this is being a rotary is flawed as two-stroke and four-stroke piston engines are both piston engines, but very different and use very different header designs.

I see where you are coming from now. It has been surmised in the past that 2 stroke exhaust theory would work on a rotary but after studying it, it can't any better than on a traditional 4 stroke.

My way of thinking is based purely on acoustics and what is going on inside the pipes. The idea is inspired by exhaust technology of an older siamesed 4 cylinder engine but it should apply as both are 4 cycle engines. That's really all that matters. The effects of rotary vs piston will only affect total length in relation to each engine.

Again I'm guessing because you're still being coy with sharing the details of your idea, but IMO this will only serve to disperse the total pulse energy of a given rotor, resulting in a net reduction in scavenging ability. Attempting to phase in the center port pulses with a longer pipe (I assume 50% longer for inter-phasing purposes) only negates the total rotor exhaust pulse energy potential. The siamese port in in the Renesis is not at all similar to the model you are attempting to use as the basis for your theory. In that model a rotor/cylinder pulses entirely through the siamese port, it does not pulse through both an individual and shared siamese port simultaneously, thus splitting up the energy. IMO the center siamese port energy will be substantially weaker than the individual port energy for a given rotor pulse and won't be capable of the desired effect.

Is there anything that can be learned from the people that hotrod the flathead Ford V8? I believe that had a siamese center port.

in those situations the siamese port is larger to handle flow from both cylinders, the usual performance fix is weld in a center divider and split them apart from each other

the Renesis is different as described in my previous post, not to mention that the siamese port is not larger yet uses a divider plate to keep from blasting hot gases into the cojoined port of the other rotor, it can get away with this because it most likely flows considerably less of what it's non-siamesed port does, hence my previous argument

if I could get my hands on the port cycle timing and flow rates a flow model analysis and header design could be readily generated; the info is easily obtainable with the right equipment and parts, but it's not likely that anyone would just hand it over ...

am I the only one that thinks exhaust resonance tuning on a rotary is a bit of a waste of time?

It seems to me that with how the exhaust port gradually opens and closes you do not get nicely defined exhaust pulses like in a piston engine where the valve pops off its seat and the cylinder discharges rather uniformly and then gets abruntly cut off with the valve closing.