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In the interest of science, and stimulating argument, I would like those here who feel so inclined to post here.
The premise:
It has been widely regarded as truth that the Renesis side exhausts are, eh, sub-optimal.
For either more HP, or better power through the gear, or a streetable combo of both.
If you had the ability and the resources, how would you change them? If you could cast or machine your own irons, or modify stock irons to whatever shape you wanted?
You must keep the same drastic 90 degree bend, side ports only, and a stock exhaust manifold must be able to bolt up. ( I know it is not the best for power. Just for consistency of argument. ) Stock rotors and seals, and seal "tracks".
The reason I am asking is that there has been a lot of back and forth on this over the years, and a lot of thought also.
I am hoping to get some good input, maybe something that no one has thought of yet. Maybe something we can eventually use?
Fire away, fellas!
Last edited by kevink0000; 08-27-2020 at 08:57 PM.
Why are you saying "you can do whatever you want" but then limiting it to the side exhaust ports? I'd rather have fancy rx7 billet plates cut for the rx8 intake and use rx7 housings and see what happens. That said, I doubt it does much considering nobody is doing hybrid builds anymore. How about using a first gen rx7 center plate? Get rid of the troublesome siamese port, then play with the porting characteristics again from scratch.
A couple of things:
- widen the intermediate iron and/or place the siamese ports above one another rather than side by side to give the turn a gentler radius and widen the port itself. Adjust outer ports to match.
- cut a second exhaust port in the iron face for egr and overlap, controllable via a valve. Analagous to the aux intake ports. This gives you exhaust timing control similar to VVTLi. I don't know if it ultimately helps power but it could help emissions/driveability. EGR may be bad for deposits though.
Why are you saying "you can do whatever you want" but then limiting it to the side exhaust ports? I'd rather have fancy rx7 billet plates cut for the rx8 intake and use rx7 housings and see what happens. That said, I doubt it does much considering nobody is doing hybrid builds anymore. How about using a first gen rx7 center plate? Get rid of the troublesome siamese port, then play with the porting characteristics again from scratch.
Ok, well thank you for your input. But what would you do with the side ports to improve them, like I asked above?
A couple of things:
- widen the intermediate iron and/or place the siamese ports above one another rather than side by side to give the turn a gentler radius and widen the port itself. Adjust outer ports to match.
- cut a second exhaust port in the iron face for egr and overlap, controllable via a valve. Analagous to the aux intake ports. This gives you exhaust timing control similar to VVTLi. I don't know if it ultimately helps power but it could help emissions/driveability. EGR may be bad for deposits though.
Can't think of any way of improving them given the boundaries you set . The fact that they work pretty well up to double N/A mass flows is testament to how good the existing design actually is. As an example ..... my turbo 8 makes the same or better power than an REW with same sized turbo at same boost all the way up to 400whp. After that it's game over however.
If the centre iron could be wider and have an insert the same as the outer port ...that's an obvious improvement . But you said same manifold so ....no dice on that idea.
Now lets look at my results with a GT35r 1.01AR . I've actually dynoed my setup many times over four different dynos so may as well post from each dyno so there is no suggestion of my dyno being too optimistic.
1/PPRE 396whp @ 13psi
Note: this was first ever dyno when setup was very restricted as compared to now . To get max. power I needed to rev the engine out to higher rpm than the other dynos.
First .... just to quote myself to show what Team actually called me out on : "As an example ..... my turbo 8 makes the same or better power than an REW with same sized turbo at same boost all the way up to 400whp. After that it's game over however."
Analysis :
As I mentioned , after 400whp it's game over for the Renesis due to port timing issues I've gone over in previous threads. The above results suggest it's pretty even up to slightly over 400whp. After that we know the REW starts to really shine. What is really interesting is the numbers in the 10-13psi range. This is where the Renesis is really happy and can actually outshine the average REW engine.
Yes ...that's what I said and that's what I meant. It's called comparing apples with apples. But just for you here's a modern turbo as well at same boost level. Bit of an unfair comparison with a bigger turbo but it still stacks up
EFR8374@14.5psi ....402whp
Also, lets not gloss over the thread topic and why I even mentioned the above. The point being , up to a certain mass flow the Renesis exhaust ports aren't as bad as people think.
Point made ...now stop squirming Team .
It looks like the 450 whp limit theory is going to be put to the test soon too.
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Are you talking about Landspeed with the massive turbo on e85 and nitrous ? If you think that setup breaking 450 is a valid test of my theory then you really are out of touch with reality.
Getting back on topic.
Kevin : this is something I tried a couple of years ago. As my turbo setup utilised the siamese port to work with the wastegate I was able to evaluate whether it actually flowed more than stock. I found that the boost creep I was getting reduced by 1.5-2psi at peak rpm. So conclusion is ...it does flow better than stock. Whether that would make any difference in an NA scenario .... don't know.
If you think what you’re doing the last several years compares directly to 13 years ago on a 10 year older factory vehicle is apples to apples then you’re out of touch with reality. Even the last 5 years or so have been very transformational wrt rotary turbo achievement.
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Apple to apples is comparing a gt3582 with a gt3582 .... What reality are you talking about?
And the only point of the post with dynos etc was defending my initial comment ...which, unless your head is so far up where it shouldn't be that you can't see it, I did . Comprehensively.
The Renesis can’t get past 270 - 280 bhp no matter what you do to the intake. So obviously there’s an exhaust limitation nobody has been able to get past. Simply throwing peripheral exhaust port housings on won’t do it.
Even doubling the center iron size wouldn't add as much flow as the extra exhaust port on the housing, which as you said won't do it. In that case, what happens if you just eliminate the side exhaust in favor of periphreal? What happens if you dramatically change the side exhaust timing? Would either of those have more of an effect than just increasing flow on the current ports?
So I’ll just go ahead and spill it; imo the biggest issue with the siamese port is that it’s not actually sealed separate between the two rotors. To do that with the standard width center iron would have made the center discharge ports even smaller. Mazda did a good job trying to keep them two sides as separate as possible, but it’s not entirely possible with a single sleeve like that. It may not seem apparent why that’s an issue, particularly wrt backpressure. There’s more to it than having the divider plate to prevent blowing superheat exhaust gasses at the opposing rotor/side seal.
I have to say I'm really disappointed. I guess part of me hoped that maybe you knew something interesting that would be helpful.
I'll just say this straight up ... there is no cross contamination issue. There are other issues with the Siamese but that's not one of them.
How do I know this ?
1/ The Renesis makes great power N/A ...more than any other before it (in stock trim)
2/At double atmospheric pressure (under boost) the Renesis makes double the power it makes NA .... if there was a cross contamination problem ..would this happen?
3/ As evidenced in the above dyno charts the Renesis does just as well as a stock REW engine under boost (up to the point it falls over). If there was a cross contamination problem ..would this happen?
4/That thing you seem to think you don't need to figure this stuff out : Experience (oh wait ...you saw something in a Mazda video .....chuckle)
Did you know i've tested :
The sleeves pictured above
Sleeves with no divider (yes none , zero , nada , nothing)
Sleeves with every flow path to the opposing chamber sealed off (except for the one to the manifold of course)
Maybe four or five other iterations of Siamese sleeve trying to find some majic.
A completely blocked off Siamese port
The only time I've EVER seen a REDUCTION of power was when the entire Siamese port was blocked off. You may recall that my first turbo manifold did this (until the wastegate opened) . There was a perceptible loss of power (not much , but enough to notice) before the wastegate opened. I rectified this by changing the design to allow the gas to escape into the manifold rather than backflow into the combustion chambers.
Other than that I've never detected a decrease (or increase) in power due to any of the tests I've done. Edit : I did see a very small loss with no divider at all ...barely measurable.
So other than a video where you see a glimpse of the opposing rotor through the exhaust port (because there wasn't a sleeve there). Have you got anything to support your theory?
Some tests maybe? Some reason to suspect there actually is some kind of issue there?
I have to say I'm really disappointed. I guess part of me hoped that maybe you knew something interesting that would be helpful.
I'll just say this straight up ... there is no cross contamination issue. There are other issues with the Siamese but that's not one of them.
How do I know this ?
1/ The Renesis makes great power N/A ...more than any other before it (in stock trim)
2/At double atmospheric pressure (under boost) the Renesis makes double the power it makes NA .... if there was a cross contamination problem ..would this happen?
3/ As evidenced in the above dyno charts the Renesis does just as well as a stock REW engine under boost (up to the point it falls over). If there was a cross contamination problem ..would this happen?
4/That thing you seem to think you don't need to figure this stuff out : Experience (oh wait ...you saw something in a Mazda video .....chuckle)
Did you know i've tested :
The sleeves pictured above
Sleeves with no divider (yes none , zero , nada , nothing)
Sleeves with every flow path to the opposing chamber sealed off (except for the one to the manifold of course)
Maybe four or five other iterations of Siamese sleeve trying to find some majic.
A completely blocked off Siamese port
The only time I've EVER seen a REDUCTION of power was when the entire Siamese port was blocked off. You may recall that my first turbo manifold did this (until the wastegate opened) . There was a perceptible loss of power (not much , but enough to notice) before the wastegate opened. I rectified this by changing the design to allow the gas to escape into the manifold rather than backflow into the combustion chambers.
Other than that I've never detected a decrease (or increase) in power due to any of the tests I've done.
So other than a video where you see a glimpse of the opposing rotor through the exhaust port (because there wasn't a sleeve there). Have you got anything to support your theory?
Some tests maybe? Some reason to suspect there actually is some kind of issue there?
Brett,
Interesting.When you tried the siamese port (conjoined to be PC) with no divider, or a limited divider, did you try it NA as well as FI?
But I wonder if without the deflector, one chamber would blowtorch the rotor of the other at some points in the cycle. So maybe a longevity issue was resolved with the port insert deflector? It seems obvious that could occur.
Last edited by kevink0000; 08-30-2020 at 11:22 AM.
Interesting.When you tried the siamese port (conjoined to be PC) with no divider, or a limited divider, did you try it NA as well as FI?
But I wonder if without the deflector, one chamber would blowtorch the rotor of the other at some points in the cycle. So maybe a longevity issue was resolved with the port insert deflector? It seems obvious that could occur.
No ..never tried it NA . Actually on reflection , I'd like to ammend that by saying ...with no divider there was no major loss of power . I actually do remember seeing a very small loss in one iteration where the divider did not fully cover the line of sight between the chambers ...barely measurable. I didn't leave it that way long enough to see if there were long term effects as I suspected there would have been.
This is an example of where you haven’t fully visualized what is going on properly. It wasn’t blocked off in the true sense. The flow output was blocked from exiting into the manifold, but the siamese connection path between the two rotors not only still existed, blocking the outlet exacerbated the situation with the result you noted.
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DUH ! of course that was why it lost power ... I didn't think I had to spell that out for you !
I've actually never seen you squirming so hard as you are right now. But I know there is no way to get anything past your armour plated noggin so it's pointless taking this discussion further. You are making assumptions based on no information. When you do have something definitive, do come back and put me straight.
Having results and fitting a theory to them is a common mistake. It’s just like taking a different manufacturers turbo and manipulating the inputs on the Borg Warner Matchbot program until you finally get the output that matches what you perceive to believe your non-BW turbo setup is doing. Your turbo does not have either the BW compressor or turbine configuration. The program is entirely based on those configurations though. Simply manipulating things until you get the observed results to match a conjectured theory is bad science in it’s worst form.
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That's like saying . Newtons' theory of gravity was based on apples ...don't ever try it with bananas because it wont work!
Do you think I just blindly plug numbers into that program without considering the differences that might be present between the two brands?
08-27-2020, 08:53 PM
The perfect 13bmsp exhaust port
you crack me up man, do you even hear yourself? No, that comment wasn’t necessary at all.
