PhillipM

Although the port area is smaller your might want a slightly larger header pipe anyway to help prevent reversion from turbulance from the shape of the centre ports.

Brettus

iTrader: (2)

wish someone would try RGs idea - maybe in another 5 yrs or so ......

OpTiCaL

What exactly do you mean by turbulance? From my understanding of fluid dynamics (which is quite limited), the gas will enter the smaller pipe at the same velocity as its leavin the port causing a more consitant flow... if you go instantly to a larger pipe than port size you will lose some velocity due to the venturi effect.

correct me if i'm wrong, but mazda made the center port smaller for a reason... not sure why, but i would think the higher velocity would have something to do with it...

OpTiCaL

yup, got measurements today! hoping to pound out some type of protype in the next 2-3 weeks...

rotarygod

If you could see a port in person you'd see that they've pretty much got this feature built into them. There is a huge lip on the bottom of the exhaust port that you can not get rid of without cutting into the water jacket and then repairing. I have yet to be successful at repairing this and I've tried. The damn cast iron like to crack when welding. Even when welding slowly with pre and post heating of the part. It sucks.

rotarygod

They actually did it for a very simple and non scientific reason. Space. There isn't much and they didn't widen the center housing to make more. They just made due with what little area they had. I wish it were for some other good reason but it's not.

Rotr8

iTrader: (2)

speacking of 5yrs or so when the F is RB gonna publish the release of thier header,,, I ve emailed them over the last two years about this and we keep get developement dates, Ithink the last Iheard was the end of July so july has passed and anyone else hear anything...

OpTiCaL

ah, ok, so all pipes off the header will be the same size... kinda shitty reason tho

rotarygod

The center port could be one size smaller but once you take a round pipe and form it into a rectangle, you end up using too large of a pipe. The proper way to do it would be to machine a piece that transitioned the shape for you but maintained the area of the runner. This is what RB is doing with their flange and they did it on their Miata header too.

TeamRX8

iTrader: (25)

The Renesis has no relevance to the MX5 engine. With zero overlap it's a wasted effort except for marketing to people who really don't understand what's going on with this engine ...

olddragger

iTrader: (3)

We live in America --Team.
Headers may help a little with us FI guys--proper headers that is.
Now you can get a little with na headers but it will be too expensive for most. And for those it is not--they already have the means.
OD

PhillipM

You absolutely must prevent as much reversion from the centre port as you can though - otherwise it compromises any benefit you gain from the pulse tuning on the outer ports, given they are open at the same time - and we're not talking huge gains to start with.
So, a step to interupt any reverse flow is beneficial so and then slowly transition to the correct size pipe to keep gas flow speed up for the same reasons, the step won't harm the centre port flow much as the main disruption is in the port itself, the low-pressure wave it would create would have little effect as it would be too high frequency, and centre pipe gasses still have huge amounts of energy even 4-5ft down the system in the LCB header so plenty of energy to pick the gas speed back up with.

I can't see what you're grumbling about Team - no one sells one, so how can marketing come into it?

OpTiCaL

Team sounds a little miffed off... so let me ask you guys this... what are they doing for the RX8s that they race?

rotarygod

I hate to say it but the rotary is nothing special in relation to any other engine. Each engine works the exact same way using the exact same principles following the exact same airflow rules and the exact same laws of thermodynamics. Whether it has a piston or rotor is irrelevant as air and heat have no idea which is which. They are each 4 cycle internal combustion engines which makes them the EXACT same thing! Saying that, the thing that matters is the lack of port overlap. Maybe nothing will work better than anything so far but don't be so quick to claim nothing will. You're a smart guy which is why I've always been confused about your absolute certainty that nothing can do better even though you haven't tried it. You can not make that claim with ANY degree of certainty until you've tried everything and directly proven them to not work. Until everything is tried and disproven (and it all may very well be disproven), there is always hope and the possibility that something may give a positive result. You shouldn't give up until you've tried everything you can think of. Don't be satisfied with mediocrity. Just remember, innovation isn't usually accomplished by those who reach definitive conclusions based on partial information.

rotarygod

It's already compromised in relation to the outer ports.


I found on 13B's that the most important thing in the exhaust was velocity. Anti-reversion is a good thing but not if it means using a larger pipe than necessary. You can flare out the end of a pipe or get creative in other ways to accomplish the same thing but just using a larger pipe isn't a good idea. It's a compromise. You are reducing one benefit to gain another.

r0tor

iTrader: (1)

The other large difference between the MX5 engine and this besides the overlap is the exhaust pulse itself... piston pulses or even peripheral port pulses are much more sharply shaped then renesis pulses (due to the relatively slow opening and closing of the port) and dont have a giant hunk of interference in the port leading to more effective resonance tuning

PhillipM

Hence bringing the pipe size back down afterwards

TeamRX8

iTrader: (25)

I only get miffed when n00bs spout off without doing a proper search, and hence are completely uninformed about what they're spouting off about

WRT the rest of the replies, I rest my case ...

OpTiCaL

n00bs... since when is RG a n00b?

kind of a general statement that doesn't target the issue...

TeamRX8

iTrader: (25)

anybody can talk the talk, you must be greener than fresh grass since you're not aware that I'm one of the exclusive few here who has walked the walk with posted the results to back it up ...

OpTiCaL

yeah i pretty much am... maybe you can point me in the directions of your results

I would search for it, but i'm not exactly sure what i would be searching for...

rotarygod

Look up his header thread. Neat design. It's a very easy and simple 50+ year old design that's still common on hotrods today but then again my proposal is nearly that old too as siamesed ports were common on engines back then. Everything seems to come back around again at some point. In many ways people were more creative back then.

You only need results to back up things when you make claims. I state ideas complete with disclaimers that it may or may not work, tell people how I'd try it and then hope someone who is interested in potentially learning something actually does try it. If it works, great. If not, that's still good info too as you can definitively say it doesn't work. I am not a person that will discount every single potential design idea before anyone has even tried it. I'm well past the point where I have anything to prove to anyone anyways. Besides, I make no claims. I just share info and my train of thought with the challenge to others to either prove me right or WRONG! I'm cool with it either way.

I want everyone to learn. To do this I'd like to see others get involved in the process which means everyone should have the information to experiment with ideas that they may not have thought of should they choose to. I want multiple brains to think about these things as there may be different perspectives on a topic. I think of rotary knowledge kind of like open source software. At least it should be. It's shareware and everyone should be able to expand on, play with, improve, disprove, alter, aspects of it as they choose and then share the results with the whole world. It should be well understood that ideas are just that and nothing more. There are no promises made with those ideas. Theory is fine. Hunches are fine. Proof is what happens when someone does it. Only then is it a conclusion where a claim can be made. I do think general trends can start to be seen over time though and up to this point we definitely have an exhaust trend to follow.

PhillipM

Well, it certainly doesn't hurt power going by our results, just need to get hold of a stock manifold for comparison.

OpTiCaL

So i take it you already have one made? Whats it look like... pics plz!

PhillipM

It won't fit in an RX-8 engine bay as it's in an off-road buggy, sorry