TeamRX8’s Renesis Header Theory Thread
01-02-2018, 07:50 PM
#26
are you saying that pipe ID has no bearing or relationship to WHP and no direct effect on where power is made?
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03-10-2018, 01:20 AM
#28
Alright, since this has been quiet for while, I'm going to ask what may be a dumb question.
You mention a 12° race collector. Excuse my ignorance, but is 12° optimal for some reason or another? Is it to reduce the turbulence between the merging pipes/exhaust flows?
If so, would there be any benefit to smoothing the transition between the engine exhaust ports and the header ports, like what the racing beat flange seems to do? The transitions appear to be smoothed, albeit fairly sharply. Would there be any benefit to making the transition more gradual? CNC-ing individual ports to fit like your longtube mockup shouldn't be too much of an issue. Space may be a concern, depending on how tall the transition ends up being. Cost may become prohibitive as well, but if you want to get yourself a perfect match for your baller 22ga iconel build, it'd be a way to do it.
Of course if there's no benefit, the whole thing is cost prohibitive from the jump.
You mention a 12° race collector. Excuse my ignorance, but is 12° optimal for some reason or another? Is it to reduce the turbulence between the merging pipes/exhaust flows?
If so, would there be any benefit to smoothing the transition between the engine exhaust ports and the header ports, like what the racing beat flange seems to do? The transitions appear to be smoothed, albeit fairly sharply. Would there be any benefit to making the transition more gradual? CNC-ing individual ports to fit like your longtube mockup shouldn't be too much of an issue. Space may be a concern, depending on how tall the transition ends up being. Cost may become prohibitive as well, but if you want to get yourself a perfect match for your baller 22ga iconel build, it'd be a way to do it.
Of course if there's no benefit, the whole thing is cost prohibitive from the jump.
03-12-2018, 07:26 AM
#30
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I think the idea is to reduce turbulence as much as possible. The smaller the collector angle, the less turbulence. Obviously, after a certain point, you get into diminishing returns.
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03-12-2018, 10:34 AM
#31
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https://www.rx8club.com/series-i-tec...10/#post154360
I am sure you have read Rotarygod's thoughts on a custom header back in the days.
Is this something you could try with your "modular" prototype?
"...figuring out the perfect header primary pipe length and then making the 2 outer pipes collect at this distance. The center pipe does not collect here. Take the length of the primary runners and multiply it by 3. This is how far down after the first collector that the 3rd runner will collect at."
I am sure you have read Rotarygod's thoughts on a custom header back in the days.
Is this something you could try with your "modular" prototype?
"...figuring out the perfect header primary pipe length and then making the 2 outer pipes collect at this distance. The center pipe does not collect here. Take the length of the primary runners and multiply it by 3. This is how far down after the first collector that the 3rd runner will collect at."
Last edited by Marton Fabian; 03-13-2018 at 08:09 AM.
03-14-2018, 07:27 PM
#32
Originally Posted by TeamRX8
In a nutshell, modern exhaust header theory is based on engines with port/valve timing overlap where both are open to the chamber at the same time. This is important because pulse theory dependent on stored and actual fluid momentum. If you have pressure in a closed chamber (stored energy) and you open a port to allow it to exhaust it will just blow out until equalization occurs. You can’t flow out anymore than equalization without beginning the vacuum process, which requires a lot of energy to accomplish. In theory if the pressure was high enough and could be released quickly enough it could pull some small magnitude of vaccum with it before bouncing back, but the reality is the magnitude is so small as to be irrelevant from an engine oerformance impact.
Originally Posted by TeamRX8
In summary, no overlap = no exhaust tuning
Beyond this is all my reasoning, someone more versed please let me know if I've gone wrong somewhere.
The chamber has the highest pressure, when it opens, it equalizes into the atmosphere along the path of the exhaust. Since there isn't any overlap, there's no way to create a low pressure zone behind the front expanding down the tube. The gasses are simply diffusing into a larger container. So you get an ever decreasing pressure gradient as the pulse moves along the exhaust, but never a "wave" of high pressure then atmospheric. Just varying degrees of higher than atmospheric pressure throughout the exhaust system.
God I hope this is at least kinda right...
Anybody have any thoughts on my question about smoothing the transition between the engine and the header (square to circle)?
03-16-2018, 04:30 AM
#33
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I think we can all agree on this. The point would be calculating the perfect timing of the pulses for a given rpm range and trying to assist that with the header design, as much as possible, right? In my understanding, RGs recommendation would be aiming for the same by collecting the pulses from the siamese ports later. It might produce some great tones in the meantime! 
03-16-2018, 03:28 PM
#35
That’s a fair assessment, but often in practice they’re never truly equal and then also the crossover turbulence of the un-separable siamese port makes that a moot point imo. I’d refer you to take another look at my original racing manifold design and compare it to your comment.
03-22-2018, 02:51 PM
#36
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https://www.rx8club.com/series-i-tec...10/#post154360
I am sure you have read Rotarygod's thoughts on a custom header back in the days.
Is this something you could try with your "modular" prototype?
"...figuring out the perfect header primary pipe length and then making the 2 outer pipes collect at this distance. The center pipe does not collect here. Take the length of the primary runners and multiply it by 3. This is how far down after the first collector that the 3rd runner will collect at."
I am sure you have read Rotarygod's thoughts on a custom header back in the days.
Is this something you could try with your "modular" prototype?
"...figuring out the perfect header primary pipe length and then making the 2 outer pipes collect at this distance. The center pipe does not collect here. Take the length of the primary runners and multiply it by 3. This is how far down after the first collector that the 3rd runner will collect at."
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bwilk (03-22-2018)
03-22-2018, 04:06 PM
#37
By "flat out rejected it" do you mean via this thread or via other discussions? I think Team was poo-pooing the idea in the thread that Marton quoted, albeit in a somewhat obtuse way to the uninitiated or less knowledgeable users.
03-22-2018, 04:24 PM
#39
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General question. I went to my local muffler shop today and asked him to order me a midpipe to get rid of my cat. However...he suggested that he could just cut the cat off and weld a pipe to existing midpipe and put what he called a bung in it to screw the o2 sensor in. I already have a borla system from cat back. So my question is will what he suggested work? Or should I buy a aftermarket midpipe without cat? His would only be around $25.
03-22-2018, 04:28 PM
#40
General question. I went to my local muffler shop today and asked him to order me a midpipe to get rid of my cat. However...he suggested that he could just cut the cat off and weld a pipe to existing midpipe and put what he called a bung in it to screw the o2 sensor in. I already have a borla system from cat back. So my question is will what he suggested work? Or should I buy a aftermarket midpipe without cat? His would only be around $25.
Leave the stock resonator in place if you do this ...unless you like the sound of a chainsaw that is .
03-22-2018, 11:58 PM
#43
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Hey RG, both of those points suck... You've got a lot of very helpful info on here.
By "flat out rejected it" do you mean via this thread or via other discussions? I think Team was poo-pooing the idea in the thread that Marton quoted, albeit in a somewhat obtuse way to the uninitiated or less knowledgeable users.
By "flat out rejected it" do you mean via this thread or via other discussions? I think Team was poo-pooing the idea in the thread that Marton quoted, albeit in a somewhat obtuse way to the uninitiated or less knowledgeable users.
03-23-2018, 09:22 AM
#45
I've always been an RX-7 guy and still have one. I've never owned an RX-8 so I never had a car to try the idea on. It might not have worked but since it was never tried, we'll never know. Team thought the idea was a waste of time and wouldn't work so he just rejected the concept entirely having not even tried it. I'd love to know for sure either way. I've learned a bit about rotary port timing since then but primarily on the 13B so I'm not sure what new info I could suggest for the Renesis.
03-23-2018, 11:03 AM
#46
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Yeah I know. I'm just not motivated to work on cars anymore. My RX-7 has been on jack stands for a few years. It's sad considering I have everything necessary to get it running. I just haven't taken the time. I did start working on it again this week but I typically do that for a few days and then not touch it again for months. If this were 20 years ago, it would be running in a weekend.
03-28-2018, 03:57 PM
#47
Again, the whole premise of that argument is based off of a theory for an engine with overlap timing where none exists on this completely unique situation of the Renesis, which is an engine with no overlap timing. It’s an apple hypothesis for a watermelon application.
Instead of evaluating the unique situation of not having any timing overlap and trying to understand and work a solution from that fundamental basis people are instead just blindly taking what they already know for a completely different application and throwing that at it instead. Putting into terms you might better relate to; I don’t know any respectable engineer who would consider that to be a rational approach to the situation.
.
Last edited by TeamRX8; 03-28-2018 at 04:07 PM.
08-25-2019, 03:20 PM
#49
I was able to influence turbo spool significantly by opening the side exhaust ports before the siamese . I wonder .................. if the same thing done on an NA engine with an equal length header would it have any affect ??????????????????
Last edited by Brettus; 08-25-2019 at 03:37 PM.