REC CNC Rotary Porting Services
12-29-2019, 04:09 PM
#1
REC CNC Rotary Porting Services
Hey 8Club!
Great video with tons of information. Very cool shop and definitely recommend checking out some of their other content posted. CNC is a pleasure to watch and take the time to check out the complete video if you can. Exhaust port machining begins around the thirteen minute mark.
Enjoy!
Great video with tons of information. Very cool shop and definitely recommend checking out some of their other content posted. CNC is a pleasure to watch and take the time to check out the complete video if you can. Exhaust port machining begins around the thirteen minute mark.
Enjoy!
12-30-2019, 02:54 PM
#4
https://www.rx8club.com/series-i-maj...orting-267889/
Have yet to see even a single dyno that backs up the talk. The Renesis is unique among all modern day engines in that there’s no overlap between intake and exhaust timing events. If you think opening the exhaust port earlier only and sending unused work energy out the tailpipe; without anything occurring later in the timing to offset it, is the way do do it then be my guest. Even if the claim of 35% exhaust flow increase is true rather than just pulled out of a hat, it’s pointless if it’s not flowing it at the correct exhaust timing point.
there’s people on here with the mod. They talk about visceral stuff like it ‘sounds racy’, Butt dyno approves, etc. Well if you’re sending burning combustion into the exhaust system early it likely will sound cool. We all know Butt dynos tend not to be calibrated very well either. They never post an actual dyno output graph though. My feeling is there’s a reason why. If you can afford to do this then a few dyno runs for $125 is peanuts. So it’s not a cost issue. It might be a reality issue though, but maybe somebody will provide further information to reach a confirmed conclusion. The one person I trust the most claims 10bhp max is the best he has ever seen on his *engine dyno* with a ported NA Renesis.
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Have yet to see even a single dyno that backs up the talk. The Renesis is unique among all modern day engines in that there’s no overlap between intake and exhaust timing events. If you think opening the exhaust port earlier only and sending unused work energy out the tailpipe; without anything occurring later in the timing to offset it, is the way do do it then be my guest. Even if the claim of 35% exhaust flow increase is true rather than just pulled out of a hat, it’s pointless if it’s not flowing it at the correct exhaust timing point.
there’s people on here with the mod. They talk about visceral stuff like it ‘sounds racy’, Butt dyno approves, etc. Well if you’re sending burning combustion into the exhaust system early it likely will sound cool. We all know Butt dynos tend not to be calibrated very well either. They never post an actual dyno output graph though. My feeling is there’s a reason why. If you can afford to do this then a few dyno runs for $125 is peanuts. So it’s not a cost issue. It might be a reality issue though, but maybe somebody will provide further information to reach a confirmed conclusion. The one person I trust the most claims 10bhp max is the best he has ever seen on his *engine dyno* with a ported NA Renesis.
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Last edited by TeamRX8; 12-30-2019 at 03:09 PM.
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NotAPreppie (12-30-2019)
12-30-2019, 03:55 PM
#5
If you think opening the exhaust port earlier only and sending unused work energy out the tailpipe; without anything occurring later in the timing to offset it, is the way do do it then be my guest. Even if the claim of 35% exhaust flow increase is true rather than just pulled out of a hat, it’s pointless if it’s not flowing it at the correct exhaust timing point.
12-30-2019, 04:42 PM
#6
Agreed. I always felt like that was a mistake, but Mazda claims they only added those siamese ports for emission reasons, but they also didn’t want to make an entirely new wider/heavier center iron putting full ports in. However when you study the timing between both sides the one siamese side is open though closing with low pressure as the other side is opening with high pressure gases blasting out.
The crappy little divider plate helps, but I’ve always felt that the heat and gas crossover there is one of the pitfalls of why there have been so many engine issues. Not using the full depth RX7 apex seal design is another less than optimum choice too imo. The Renesis rotors fully support the deeper apex seals when modified in the aftermarket. Factory rotating assembly balance on the Renesis is also know for being fubar; another durability issue.
There were many things to learn from, not sure they actually see them all if they ever proceed with the 16x or some future derivative.
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The crappy little divider plate helps, but I’ve always felt that the heat and gas crossover there is one of the pitfalls of why there have been so many engine issues. Not using the full depth RX7 apex seal design is another less than optimum choice too imo. The Renesis rotors fully support the deeper apex seals when modified in the aftermarket. Factory rotating assembly balance on the Renesis is also know for being fubar; another durability issue.
There were many things to learn from, not sure they actually see them all if they ever proceed with the 16x or some future derivative.
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Last edited by TeamRX8; 12-31-2019 at 01:28 PM.
01-03-2020, 10:41 AM
#7
Agreed. I always felt like that was a mistake, but Mazda claims they only added those siamese ports for emission reasons, but they also didn’t want to make an entirely new wider/heavier center iron putting full ports in. However when you study the timing between both sides the one siamese side is open though closing with low pressure as the other side is opening with high pressure gases blasting out.
The crappy little divider plate helps, but I’ve always felt that the heat and gas crossover there is one of the pitfalls of why there have been so many engine issues. Not using the full depth RX7 apex seal design is another less than optimum choice too imo. The Renesis rotors fully support the deeper apex seals when modified in the aftermarket. Factory rotating assembly balance on the Renesis is also know for being fubar; another durability issue.
There were many things to learn from, not sure they actually see them all if they ever proceed with the 16x or some future derivative.
.
The crappy little divider plate helps, but I’ve always felt that the heat and gas crossover there is one of the pitfalls of why there have been so many engine issues. Not using the full depth RX7 apex seal design is another less than optimum choice too imo. The Renesis rotors fully support the deeper apex seals when modified in the aftermarket. Factory rotating assembly balance on the Renesis is also know for being fubar; another durability issue.
There were many things to learn from, not sure they actually see them all if they ever proceed with the 16x or some future derivative.
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Also, these are the guys I'm looking at to rebuild my engine, as I don't want to go across the US border and they're in Alberta. The guy who runs the shop was nice enough via email and provided some rough estimates as well as a bit of troubleshooting for me.
01-03-2020, 10:57 AM
#8
REC seems like a very respectable company. I just don’t agree with the mod for the stated reason and have generally downplayed Renesis porting over the years. The NA hp claims which have pretty much proven to be a bust. That mod might be good for a turbo though. I thought you were previously doing an MZR swap or something. What happened?
01-03-2020, 11:18 AM
#9
I think you might have me confused with someone else, or I was talking nonsense at the time. I'm building random things for my 8 while the winter goes on, but nothing like that. My dream RX8 would be something in the 300-350HP range, but I don't have the capital to achieve it. I'm looking at stuff I can do for fun while tracking my car 1-2 times per year. That's currently a splitter (one for me and one for my DSP buddy), maybe a flat bottom. I don't race, so rule-sets don't really matter to me.
I do remember your sig had a quote about bridgeporting being like taking a pile of cash, putting it in the ditch, dousing it in lighter fluid and striking a match. Or maybe I'm confusing you for someone else now.
I do remember your sig had a quote about bridgeporting being like taking a pile of cash, putting it in the ditch, dousing it in lighter fluid and striking a match. Or maybe I'm confusing you for someone else now.
01-03-2020, 11:27 AM
#10
I would also just like to point out that as a result of this service you are rebuilding your engine, if you didn't elect to do this service while the motor was already apart to be rebuilt. It's pretty difficult to say where the power increase came from, the rebuild or the porting? I believe you are much better off spending money on machining the rotors for taller seals and balancing complete rotating assembly.
01-03-2020, 04:00 PM
#11
Would have a very limited benefit for a turbo as well ......... IMO . The problem when turboing isn't port size ...it's port close timing.
Not sure if you were aware or not , but I ran a four port center plate on my turbo setup at one stage ...mainly to try improve spoolup. The 4 port exhaust ports are quite a bit smaller than the 6 port ones. I found zero difference in top end with those in place . They flowed just as much as the 6 port plates.
That experiment (even though it was limited to the siamese) is what made me realise that port size (intake or exhaust) had nothing to do with the issues, anyone that has tried to find the limits of the engine, has encountered.
Not sure if you were aware or not , but I ran a four port center plate on my turbo setup at one stage ...mainly to try improve spoolup. The 4 port exhaust ports are quite a bit smaller than the 6 port ones. I found zero difference in top end with those in place . They flowed just as much as the 6 port plates.
That experiment (even though it was limited to the siamese) is what made me realise that port size (intake or exhaust) had nothing to do with the issues, anyone that has tried to find the limits of the engine, has encountered.
Last edited by Brettus; 01-03-2020 at 04:47 PM.
09-19-2020, 02:51 PM
#12
Guess I never saw this reply. I’d disagree some on that point. The 13B peripheral exhaust port opens 25 deg sooner than the Renesis. That’s essentially what they’re trying to do with this porting mod. Bleeding off the pressure sooner is going to benefit a turbo engine. The problem is it’s too small and also it comes into the port at almost 180 deg opposite of the port direction, and then has to try and go back in the other direction around a sharp point or very minimal radius. The mod definitely isn’t going to help an NA engine at all. The only dyno I ever saw with it was with a newly rebuilt NA engine by the same company and it only made 180 whp on a Mainline dyno.
Because of the way Mazda rephased the intake ports to be close to TDC of the intake stroke, where the exhaust stroke is at minimum volume, is why most porting mods aren’t working on the Renesis. The new positions of the primary and secondary port being near rotor TDC is what prevents extending the closing of the exhaust port. Being near TDC with minimum chamber volume, if there is any overlap at all, then as soon as the intake port opens that compressed pressure suddenly expands into the intake ports. On the 13B, the intake ports are phased a lot further away from TDC. The chamber volume has opened as the rotor is moving towards the intake stroke, allowing the gasses to expand and have less pressure. When the intake port opens, it doesn’t impact the incoming flow as much due to the decreased pressure.
This is why bridgeporting and other attempts to add overlap don’t work on the Renesis. I just went through and explained all these timing events in another thread within the last week. You need to find and read two separate posts there. It also ties in with why the exhaust manifold tuning doesn’t work on the Renesis. Mazda recognized all this in the Renesis turbo patent from several years ago, but the modifications proposed there are very specifically intended for forced induction and not applicable for NA at all. If you have the full translation for the patent they explained it all well enough.
They added an additional wide x narrow peripheral exhaust port with a valve to open close it. At high loads they open it, but that added port goes to atmospheric pressure separate from the higher turbo manifold pressure. They use overlap with the incoming turbo pressure to force exhaust gasses out of the chamber into that port so it won’t carry over and contaminate the intake charge. The port is narrow and wide to provide a lot of area, but within a very precise rotor timing range. Because of the pressure differential and only being used under high load, the flow can only go out and not come back in. It’s forced scavenging. It requires intake pressure to force the process.
So the one attempt I saw trying to duplicate it; first, it was NA so there’s no intake pressure to flush anything out. It just adds overlap and that simply doesn’t work with the intake port timing for NA on a Renesis due to where the intake ports are positioned. Even with a turbo, the area of one hole is too small and if the diameter is too big then the excessive timing isn’t going to be beneficial either. In that same thread where I laid out all these port timing differences, I also covered why adding 13B rotor housings with peripheral exhaust port (hybrid Renesis) will never work for NA and may only work with a huge turbo, like an EFR 9180.
It all comes down to how Mazda changed the port phasing to be different on the Renesis. If you don’t have or come to the understanding of those differences, then you’re never going to understand why the Renesis is different and what will work and what won’t work relative to the previous 13B engines. My experience in general is that most people on the forum don’t have that understanding. That lack of understanding is manifest in all the years of arguing over long tube headers and other such topics.
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Because of the way Mazda rephased the intake ports to be close to TDC of the intake stroke, where the exhaust stroke is at minimum volume, is why most porting mods aren’t working on the Renesis. The new positions of the primary and secondary port being near rotor TDC is what prevents extending the closing of the exhaust port. Being near TDC with minimum chamber volume, if there is any overlap at all, then as soon as the intake port opens that compressed pressure suddenly expands into the intake ports. On the 13B, the intake ports are phased a lot further away from TDC. The chamber volume has opened as the rotor is moving towards the intake stroke, allowing the gasses to expand and have less pressure. When the intake port opens, it doesn’t impact the incoming flow as much due to the decreased pressure.
This is why bridgeporting and other attempts to add overlap don’t work on the Renesis. I just went through and explained all these timing events in another thread within the last week. You need to find and read two separate posts there. It also ties in with why the exhaust manifold tuning doesn’t work on the Renesis. Mazda recognized all this in the Renesis turbo patent from several years ago, but the modifications proposed there are very specifically intended for forced induction and not applicable for NA at all. If you have the full translation for the patent they explained it all well enough.
They added an additional wide x narrow peripheral exhaust port with a valve to open close it. At high loads they open it, but that added port goes to atmospheric pressure separate from the higher turbo manifold pressure. They use overlap with the incoming turbo pressure to force exhaust gasses out of the chamber into that port so it won’t carry over and contaminate the intake charge. The port is narrow and wide to provide a lot of area, but within a very precise rotor timing range. Because of the pressure differential and only being used under high load, the flow can only go out and not come back in. It’s forced scavenging. It requires intake pressure to force the process.
So the one attempt I saw trying to duplicate it; first, it was NA so there’s no intake pressure to flush anything out. It just adds overlap and that simply doesn’t work with the intake port timing for NA on a Renesis due to where the intake ports are positioned. Even with a turbo, the area of one hole is too small and if the diameter is too big then the excessive timing isn’t going to be beneficial either. In that same thread where I laid out all these port timing differences, I also covered why adding 13B rotor housings with peripheral exhaust port (hybrid Renesis) will never work for NA and may only work with a huge turbo, like an EFR 9180.
It all comes down to how Mazda changed the port phasing to be different on the Renesis. If you don’t have or come to the understanding of those differences, then you’re never going to understand why the Renesis is different and what will work and what won’t work relative to the previous 13B engines. My experience in general is that most people on the forum don’t have that understanding. That lack of understanding is manifest in all the years of arguing over long tube headers and other such topics.
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Last edited by TeamRX8; 09-19-2020 at 02:54 PM.
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yomomspimp06 (09-21-2020)
09-19-2020, 03:30 PM
#13
"Would have a very LIMITED BENEFIT for a turbo as well ......... IMO ."
Kinda sounds like you are agreeing 100% to me . 
Guess I never saw this reply. I’d disagree some on that point.
The problem is it’s too small and also it comes into the port at almost 180 deg opposite of the port direction, and then has to try and go back in the other direction around a sharp point or very minimal radius.
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The problem is it’s too small and also it comes into the port at almost 180 deg opposite of the port direction, and then has to try and go back in the other direction around a sharp point or very minimal radius.
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09-21-2020, 02:20 PM
#14
my apology if it wasn’t clear, I’m thinking it’d be a bit more than I had interpreted the magnitude of your reply based on the exhaust opening timing difference between the REW and MSP. It’d likely be more help at the lower end of the rpm range, but as flow increases and the available port open-close time decreases with escalating RPM, then in that upper rpm range I’m thinking along the same line as yourself. So depending more on what size turbo and the intended power-band range is going to influence that outcome. Say in comparison to my proposed 4-port engine as compared to what you, Curt, and Slash are doing.
The turbo side of the modification is getting off topic for this NA thread though and I probably shouldn’t have taken it there except to explain the difference. Which I don’t see it helping an NA motor at all despite all the racy sound it might achieve dumping burning fuel early into the exhaust manifold. I do see that potentially benefiting turbo spool up though.
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The turbo side of the modification is getting off topic for this NA thread though and I probably shouldn’t have taken it there except to explain the difference. Which I don’t see it helping an NA motor at all despite all the racy sound it might achieve dumping burning fuel early into the exhaust manifold. I do see that potentially benefiting turbo spool up though.
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09-21-2020, 10:23 PM
#15
for those who don't want to search:
Ok, so now let’s take it to the next level. In summary of the previous post I made regarding Renesis port timing relative to the 13B REW, Mazda mostly advanced the phasing of the intake and exhaust ports in the combustion cycle.
Where the REW exhaust port closed at 48 deg ATDC, on the Renesis it closes at 3 deg BTDC; advanced 51 deg
Where the REW primary port opened at 45 deg ATDC, on the Renesis it opens at 3 deg ATDC; advanced 42 deg
Where the REW secondary port opened at 32 deg ATDC, on the Renesis it opens at 13 deg ATDC; advanced 19 deg from about 4000 rpm and up
Just for clarity, the Renesis APV port opens at 38 deg ATDC
Let’s start with the unmodified Renesis engine. It has no overlap between the exhaust port closing at 3 deg BTDC and the primary intake opening at 3 deg ATDC; a 6 deg separation. Whereas the REW port closes at 48 deg ATDC and the primary intake opening at 45 deg ATDC; 3 deg overlap. The one critical aspect of this that’s different between the two is the position of the rotor. When Mazda advanced the intake and exhaust phasing on the Renesis, it now occurs right around TDC; where the combustion chamber of the rotor is at it’s minimum volume. Whereas on the REW and earlier 13Bs it’s happening about 45 deg later when the volume is expanding for the intake cycle to take place. This is a big deal, especially for forced induction.
So think about a turbo REW which at some point is going to have exhaust back-pressure. Even though the exhaust port stays open for 48 deg past TDC, the rotor combustion chamber is expanding as the exhaust port opening is becoming smaller. So the net combustion chamber pressure is decreasing at the point the primary intake port is opening, helping to minimize back-flow into the intake system.
On a Renesis though, this same event is taking place right around TDC when combustion chamber is at a minimum and pressure is highest. Even though there is zero overlap, any remaining pressure in the combustion chamber when the exhaust port closes will be released into the primary intake port 6 deg later which for all basic purposes is still TDC. The pressure is not relieved into an expanding volume like on the REW. On the Renesis, it will instead be immediately released into the primary intake port.
Those of you who understand my Renesis exhaust manifold theory can perhaps better grasp why I had stressed that it was best to get the exhaust gasses out with the least amount of resistance/back-pressure. You can’t scavenge a closed chamber; the Zero Overlap condition, and the exhaust port closes slowly at the end with an every decreasing opening area. Some people theorized you could pulse tune a wave to hit at the closing, but because of the actual conditions that will never work. It can only occur if the port could be instantaneously shut from below ing widely open right as the pulse hits. Even then it’s still trying to pull a vacuum on a closed chamber. They don’t understand the difference between the energy of the pulse and the energy required to pull a vacuum. It simply can never happen. Nobody was listening when they were told that.
So that’s NA. What about FI on the Renesis? Well it’s the same thing. Any back-pressure that’s trapped in the combustion chamber when the exhaust port closes is immediately released into the primary port 6 deg later. Even if you think a way around that is to fill/block the primary port, the secondary port opens only 9 deg later. The rotor has progressed around some towards the intake cycle, but is still so close to TDC that it won’t be a huge difference, but it might offer an advantage. I had thought with a blocked primary port maybe combined with modifying the UIM to allow limited flow from the primary port runner over to the secondary runner, which would then transition to full secondary runner flow when the SSV opens, might be worth investigating. Still unsure on that though.
However, once we pair 13B rotor housings with Renesis plates to form a hybrid the impact is huge, as noted before. Not only is the exhaust port still open when the primary port opens at 3 deg ATDC, the secondary port opens only 9 deg later from 4000 rpm up, and even the APV has some overlap too from 6000 rpm up. Even though the combustion chamber is expanding, both the intake and exhaust ports are open at the same time for a very long period. There’s a lot of combustion gas dilution and back flow into the intake because of too much overlap too early in the intake cycle and imo all the results bear this out. This is why I stated previously that using a big turbo with a large A/R turbine housing and higher rpm range is the only way 13B housings with Renesis plates will ever work. That’s pretty much how it’s done with a P port intake and forced induction on a rotary.
Where the REW exhaust port closed at 48 deg ATDC, on the Renesis it closes at 3 deg BTDC; advanced 51 deg
Where the REW primary port opened at 45 deg ATDC, on the Renesis it opens at 3 deg ATDC; advanced 42 deg
Where the REW secondary port opened at 32 deg ATDC, on the Renesis it opens at 13 deg ATDC; advanced 19 deg from about 4000 rpm and up
Just for clarity, the Renesis APV port opens at 38 deg ATDC
Let’s start with the unmodified Renesis engine. It has no overlap between the exhaust port closing at 3 deg BTDC and the primary intake opening at 3 deg ATDC; a 6 deg separation. Whereas the REW port closes at 48 deg ATDC and the primary intake opening at 45 deg ATDC; 3 deg overlap. The one critical aspect of this that’s different between the two is the position of the rotor. When Mazda advanced the intake and exhaust phasing on the Renesis, it now occurs right around TDC; where the combustion chamber of the rotor is at it’s minimum volume. Whereas on the REW and earlier 13Bs it’s happening about 45 deg later when the volume is expanding for the intake cycle to take place. This is a big deal, especially for forced induction.
So think about a turbo REW which at some point is going to have exhaust back-pressure. Even though the exhaust port stays open for 48 deg past TDC, the rotor combustion chamber is expanding as the exhaust port opening is becoming smaller. So the net combustion chamber pressure is decreasing at the point the primary intake port is opening, helping to minimize back-flow into the intake system.
On a Renesis though, this same event is taking place right around TDC when combustion chamber is at a minimum and pressure is highest. Even though there is zero overlap, any remaining pressure in the combustion chamber when the exhaust port closes will be released into the primary intake port 6 deg later which for all basic purposes is still TDC. The pressure is not relieved into an expanding volume like on the REW. On the Renesis, it will instead be immediately released into the primary intake port.
Those of you who understand my Renesis exhaust manifold theory can perhaps better grasp why I had stressed that it was best to get the exhaust gasses out with the least amount of resistance/back-pressure. You can’t scavenge a closed chamber; the Zero Overlap condition, and the exhaust port closes slowly at the end with an every decreasing opening area. Some people theorized you could pulse tune a wave to hit at the closing, but because of the actual conditions that will never work. It can only occur if the port could be instantaneously shut from below ing widely open right as the pulse hits. Even then it’s still trying to pull a vacuum on a closed chamber. They don’t understand the difference between the energy of the pulse and the energy required to pull a vacuum. It simply can never happen. Nobody was listening when they were told that.
So that’s NA. What about FI on the Renesis? Well it’s the same thing. Any back-pressure that’s trapped in the combustion chamber when the exhaust port closes is immediately released into the primary port 6 deg later. Even if you think a way around that is to fill/block the primary port, the secondary port opens only 9 deg later. The rotor has progressed around some towards the intake cycle, but is still so close to TDC that it won’t be a huge difference, but it might offer an advantage. I had thought with a blocked primary port maybe combined with modifying the UIM to allow limited flow from the primary port runner over to the secondary runner, which would then transition to full secondary runner flow when the SSV opens, might be worth investigating. Still unsure on that though.
However, once we pair 13B rotor housings with Renesis plates to form a hybrid the impact is huge, as noted before. Not only is the exhaust port still open when the primary port opens at 3 deg ATDC, the secondary port opens only 9 deg later from 4000 rpm up, and even the APV has some overlap too from 6000 rpm up. Even though the combustion chamber is expanding, both the intake and exhaust ports are open at the same time for a very long period. There’s a lot of combustion gas dilution and back flow into the intake because of too much overlap too early in the intake cycle and imo all the results bear this out. This is why I stated previously that using a big turbo with a large A/R turbine housing and higher rpm range is the only way 13B housings with Renesis plates will ever work. That’s pretty much how it’s done with a P port intake and forced induction on a rotary.
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