olddragger

iTrader: (3)

me too
OD

TeamRX8

iTrader: (25)

not that it won't work, but rather the overall effectiveness

Renesis + common header theory =

OpTiCaL

Yeah, i kinda get what you are saying... not so much the common header theory is bad, but the application of any single header theory.

Why cant the exhaust have multiple paths to take based on RPM... the intake is based that way, so why not the exhaust as well!!?!?!

TeamRX8

iTrader: (25)

no overlap = no scavenging potential

the frequency resonance on the intake side can still be taken advantage of though

OpTiCaL

FALSE!

Unless you are saying this is a total lie then too!?

rotarygod

Considering the Renesis is so much more efficient over the 13B due to exhaust port timing even though the 13B has overlap and the Renesis doesn't, I'm going to have to laugh at the scavenging comment and just say it's incomplete information. There is a certain point where overlap is beneficial. However, you do not need overlap to make power which means that scavenging does not mean power production and lack of it does not mean no potential power.

BTW: Resonance occurs on the exhaust side too. It's effect is stronger on the exhaust side than the intake side.

BTWII: I have yet to see ANYONE "think outside the box" when it comes to Renesis headers.

olddragger

iTrader: (3)

its gets confusing for me to address this in a driveability sense. At one time I actually was wondering about an expansion chamber(and still I am curious), but know I think that NO back pressure is basically the way to go. Straight pipes--I mean straight pipes --no curves--especially more inches in lenght from the ports than the currently available products . So fitment will be tricky.
Does R32 mean anything to anyone?
olddragger

Benjamz

I'm trying, can't wait to see it on the dyno. Reference "PM"

OpTiCaL

As a matter of fact, the old guy at the mazda dealer mentioned something about an expansion chamber... not really sure tho. I think i am going to go back and talk to him this week with the new information i have.

rotarygod

I know what you're trying but you know that already. It wasn't really directed at you.

alnielsen

iTrader: (4)

RG didn't think much of my expansion camber idea when I brought it up 2 yrs ago.

https://www.rx8club.com/showthread.p...ight=expansion

rotarygod

If you are thinking in terms of a 2 stroke exhaust design, it won't work. A plain expansion chamber can be made to work on a 4 stroke as it is designed to a certain set of criteria. There are other ways to try it though.

olddragger

iTrader: (3)

exactly RG i dont mean like a 2 stoke expansion chamber like you see on the bikes etc.
olddragger

olddragger

iTrader: (3)

thread revival.
Pictures of Teams original header is on page 7 and RG has an interesting concept posted within--sorta like one I posted about later in the years.
I am going to build an exhaust system for my car and I am researching everything I can find first.
That is the reason I revived this thread. It has a LOT of great information in it.

Rote8

I have often wondered about a vacuum for the exuast side to force scavenge.

PhillipM

Yep, that works, the Renny never fully discharges all the exhaust gases, in fact it deliberately hold some of the gases towards the rear of the chamber as an EGR cycle, you can pull a vacuum on that, extract more of it and obviously if you time it right that results in more intake charge in the chamber. You don't need overlap to be able to scavenge, it's just more effective the more overlap you have.

bse50

Finally somebody had the guts to admit that. I really admire your hands on work and results Phil.

TeamRX8

iTrader: (25)

You are misinformed about the force available vs the force required to accomplish such a feat

olddragger

iTrader: (3)

that is also my question--exactly how could this be done in an effective manner?
I have been aware of the retained gases in the CC, but has anyone discovered how much is retained?
What volume is there to improve on?
There is one question in this old thread that I would like to ask again.
What is the purpose of the exhaust gasket and header ports being so much more bigger than the exhaust ports? It is a very noticeable difference. I believe the primary ports are approx 26 mm and the header port is 38mm with the steel gasket being MUCH bigger? I am speaking with Jack Burns on Monday ( hopefully) and I am trying to get as many facts together as possible.
Is it for cooling?

bse50

Phil posted pictures of his setup elsewhere. Just look at how the collectors merge.
Apparently there are gains that ignorant people just don't want to aknowledge.

HiFlite999

iTrader: (2)

In the discussions about "negative-pressure-reversion-waves" helping to pull out exhaust gasses, nothing at all has been said about their corresponding positive-pressure-reversion-waves! In a resonant system, one can't simply take the (-) of the pressure wave without considering the (+). What prevents the wave from reaching the exhaust port at maximum positive pressure?? Over the range of loads/rpms there are going to be times when this happens resulting in power loss.

Hence, the big step. Much of a pressure wave will bounce against that step rather than reach the port itself. It may reduce the maximum of any scavanging effect but avoid holes in the hp curve.

First few posts of this discuss it. http://www.seatcupra.net/forums/showthread.php?t=319359

or: http://www.rx7club.com/naturally-asp...0/#post9116049

but don't expect 50 hp gain w/o overlap ...

olddragger

iTrader: (3)

Thanks and I have seen Phils pic--its a pretty good set up. I am also thinking on extending the primary pipe length--but I am also still researching and talking to people before I do. I have accepted that the usual exhaust theories really doesnt mean as much to us. I am also trying not to overthink it.
I really dont think there is a magic formula/part anywhere to be found--except maybe "zoomies"
Close attention to transitions may be more important than anything else--excluding the obvious stuff.

Most commercial headers I have seen seem to have more restriction to flow in the pipe that handles the rear rotor. The pipe has to be shaped to clear everything. i realize that, but I am thinking that the front and the rear rotor primary pipes really dont need to be equal in length. Instead more emphasis needs to be placed on the bends in the primaries? I am thinking that it may be more important to keep a straight path from the port for as long as possible and to have the least radius of turns as possible? Damn the turns etc needed to make them all equal and make sure both rotors can move the exhaust the same?
Is this just another OD crazy thought? I am open to all ideas and discussion for and agaisnt.
Please remember I am running a supercharged engine.

PhillipM

Any force above a net zero will accomplish it.

olddragger

iTrader: (3)

what is wrong with a header like this for a supercharged engine? Dont judge the collector--just the flange and pipes
https://www.rx8club.com/attachments/...nifold-002-jpg

X7rotor

iTrader: (2)

2stroke exhaust designed have expansion chambers that help the motor gain compression in the powerband. Once the air and fuel mixture goes through.resonence really isn't needed for the most efficient power due to different ports in a two stroke cylinder. But tuning a rotary like a two stroke doesn't seem to beneficial as a expansion chamber exhaust on a rotary would probably do close to nothing.