Nice. What is the 0.995 correction factor?
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1. Great work, Brett. Fun to see someone pushing the envelope and trying to innovate.
2. So the siamese is the ultimate restriction on renesis power? |
Originally Posted by BigBadChris
(Post 4856880)
1. Great work, Brett. Fun to see someone pushing the envelope and trying to innovate.
2. So the siamese is the ultimate restriction on renesis power? It only becomes a problem at this power point though .... Anything less and the problem is just the 10:1 compression ratio ...... which is an easy fix. |
Originally Posted by 9krpmrx8
(Post 4856879)
Nice. What is the 0.995 correction factor?
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have you already ported the exhaust ports and sleeves?
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Originally Posted by rotarenvy
(Post 4856924)
have you already ported the exhaust ports and sleeves?
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Would it assist the Siamese port spill over if the center runner of the manifold was also divided so the gases had to go farther before they could spill over? Or separated all the way to the turbo housing? (not getting into the complexities of making a manifold that way)
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Originally Posted by northzone
(Post 4856998)
Would it assist the Siamese port spill over if the center runner of the manifold was also divided so the gases had to go farther before they could spill over? Or separated all the way to the turbo housing? (not getting into the complexities of making a manifold that way)
If you imagine a pipe with a restriction in it ....everything before the restriction is at a higher pressure than everything after it . This is what we have at the Siamese sleeve except we also have ,BEFORE the restriction, a direct path around the sleeve to the opposing rotor. There is no way to effectively block the path without a total redesign of the iron ...yes I have tried ! To understand this you really need to look at a sleeve inside the port and think about where the restriction actually is. The port itself is not a restriction at all ...the sleeve is. |
I did an approximate calculation that found the size of the port itself is more than DOUBLE the size of the passage in the early part of the sleeve . In this latest engine I made a few changes that got that down from 2x the size to about 1.4x the size . This was what I was hoping would lead to a breakthrough .................... It has helped a little, but it has not solved the issue.To do that would require that ratio be reduced to less than 1:1 (you still have the problem of trying to turn the gas 90 degrees which in itself will create backpressure) ...or total separation .
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I know this is probably out of everyone's reach, but then again, internet advice is worth every penny you pay for it. REC (Rotary Engine .Com) has remade their own 20B center iron. I assume we would have to go that far to fix this issue, making a completely new center iron?
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Originally Posted by BigBadChris
(Post 4857034)
I know this is probably out of everyone's reach, but then again, internet advice is worth every penny you pay for it. REC (Rotary Engine .Com) has remade their own 20B center iron. I assume we would have to go that far to fix this issue, making a completely new center iron?
There was a reason Mazda did such a shit job of designing that middle iron . To make it work any better they would have needed to lengthen the engine to get better exhaust flow from the middle , make a new longer eccentric shaft and possibly even fit a center bearing . Not only making the engine heavier and hugely expensive , but also not really increasing the power much over what they had already achieved by just making a few changes to existing patterns. But to answer your question ...YES .... IMO. |
Can you share pics of your exhaust port modifications?
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Originally Posted by rotarenvy
(Post 4857042)
Can you share pics of your exhaust port modifications?
This is for the outer ports ....the thickness of the felt pen line is exactly how much I took out ,I also rounded the edge underneath .At the other end I just removed the ridges ...... pretty standard . https://cimg9.ibsrv.net/gimg/www.rx8...3da8dfa9e3.jpg |
did you modify the port inserts? how did you get 0.6 more port area from the siamese insert?
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At the siamese end ....... I used a 4port plate instead of a 6 port plus I modified the sleeve to make it flow better .
See the difference in port size here .... https://cimg5.ibsrv.net/gimg/www.rx8...5994efa983.jpg Soooooo ... Yes I made the Siamese exhaust ports SMALLER and got a better result ! I believe that if I could have made them even smaller still ,about half the size of the 4 port ports ...the problem would be solved for the most part . |
so you force more exhaust to use the outerports.
I can't see this flow reversion happening to the same extent on an SC car as the flow will take the easiset path and vent to close to atmospheric rather than do a 180deg flip and go into the next chamber. |
No ... I think you missed the key thing here . The Siamese port can be less than half the size it currently is and still flow the same amount of gas . That's because the port isn't the restriction ... the sleeve is .as far as the sc goes ... I don't believe there is any advantage .., because you actually need to make probably an extra 70-80 hp at the engine just to match what a turbo can do . At that level even though you are dumping to atmosphere..., you still have enormous restricton at the sleeve and reversion will still happen . |
so the restriction is at the point of minimum cross section. still reversion will only occur when either chamber has a lower pressure than exhaust back pressure. yes it will probably will still occur on a sc engine but at what level and duration?
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Originally Posted by rotarenvy
(Post 4857062)
so the restriction is at the point of minimum cross section. still reversion will only occur when either chamber has a lower pressure than exhaust back pressure.
I know this because I've seen what happens as I have reduced backpressure over the years ..... it should have had a much more profound effect than it actually did .
Originally Posted by rotarenvy
(Post 4857062)
yes it will probably will still occur on a sc engine but at what level and duration? |
Originally Posted by Brettus
(Post 4857064)
It still will get reversion, because how much backpressure there is isn't as important as how much pressure there is BEFORE the restriction. ...
Originally Posted by Brettus
(Post 4857064)
Who knows ............... but we will never see a 400+whp Supercharged Renesis so the point is moot ! If you want to give it a go , make sure you have funds ready for the rebuild ;)
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Originally Posted by rotarenvy
(Post 4857065)
this is the bit I'm not getting. so your saying when the sleeve is saturated the exhaust flows around the sleeve between the chambers to create the reversion?
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ok now I get you. porting makes this worse. blocking the air injection and a tighter fitting custom sleeve might help tho.
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Good discussion on exhaust restriction. Any idea on ideal boost pressure to get the most benefit from the system. I have the hymee supercharger and I managed to get 200kw at the wheels with 8psi boost.
Possibly looking to increase the boost to 10 or possibly 12psi. I assume that these boost levels should be ok? |
Originally Posted by rotarenvy
(Post 4857067)
ok now I get you. porting makes this worse. blocking the air injection and a tighter fitting custom sleeve might help tho.
I have tried a tighter fitting sleeve (professionally inconel welded) ... it beat itself to death and I ended up with both a dead engine and a dead turbo ! I have also vented the air injection hole to the exhaust . Bit late now ..but this might help others get what I'm talking about : https://cimg1.ibsrv.net/gimg/www.rx8...98f705b396.jpg |
Originally Posted by skc
(Post 4857068)
Good discussion on exhaust restriction. Any idea on ideal boost pressure to get the most benefit from the system. I have the hymee supercharger and I managed to get 200kw at the wheels with 8psi boost.
Possibly looking to increase the boost to 10 or possibly 12psi. I assume that these boost levels should be ok? The ideal boost pressure for maximum power from a particular system is : the pressure that still gives you the same incremental increase in power that you got for the first say 5-6psi . For my setup ... 13-14whp per pound of boost . When that starts dropping ... don't go any further. However your system is more likely to be limited by the SC than anything going on at the Siamese. |
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