Bridge Porting the Renesis
05-26-2009, 01:28 PM
#51
It does seem difficult but it is possible as long as you cut close to the waterjacket..... Not sure how long it would last however but it is possible (in theory according to these measurments). I would think you would also have more leeway earlier in the opening. Thanks Easy E1 for posting the pictures.
1 other thing, it looks as if a bridge port would cause overlap... atleast if you cut the port below the apex seal path. What you guys think?
1 other thing, it looks as if a bridge port would cause overlap... atleast if you cut the port below the apex seal path. What you guys think?
05-26-2009, 01:55 PM
#52
The thing is when you install the Apex Seals the end wedges go on top of the Rotor. The side that's facing you. So the front Rotor has the End Wedge against the Center Cast Iron Plate (Primary intake port). And the rear Rotor gets the End Wedge against the rear cast iron plate (Secondary intake port).
Now porting the exhaust is a whole new can of worms. It has a steel sleeve inside the port. Which I know is very hard. From experience with a Carbide cutting tool. Just bounces off of it.
The problem with the exhaust port besides the insert is again, Where do we enlarge it?
You do not want to make it open any sooner then it does. Why? Picture opening a exhaust Valve on a Piston engine before complete combustion. There goes the power out the exhaust pipe. You want full combustion of the gases to obtain the most power from the AF mixture.
Opening the port sooner would only allow the combustion gasses to escape before complete combustion. Resulting in less Power (HP).
So we can not make it open any earlier than it does. Well you could, but why.
So we're left with making it longer or wider. Well longer is pretty much out too. I think Mazda did a great job on the stock length (duration) opening.
So that brings us to the side like the intake port.
I'm going to sit back and watch where this one goes.
Last edited by Easy_E1; 05-26-2009 at 02:02 PM.
05-26-2009, 02:02 PM
#53
It does seem difficult but it is possible as long as you cut close to the waterjacket..... Not sure how long it would last however but it is possible (in theory according to these measurments). I would think you would also have more leeway earlier in the opening. Thanks Easy E1 for posting the pictures.
1 other thing, it looks as if a bridge port would cause overlap... atleast if you cut the port below the apex seal path. What you guys think?
1 other thing, it looks as if a bridge port would cause overlap... atleast if you cut the port below the apex seal path. What you guys think?
Thank you jfxp for your help in this too. You made me look at some things I hadn't considered.
Now I'm going to have to do this.
05-26-2009, 04:06 PM
#55
Why bridge? If you think about it the purpose of the Bridge for 13B's is to not only increase inlet area but also to increase overlap which will give you a nice higher powerband. "Bridgeing" the Renesis will only yield a very slight increase in area(due to the restrictions that have been outlined on this thread) and there will still be little to no overlap because of the way the exhaust port is carved into the plate.
Plus...the renesis has plenty of inlet area with the way the port is stock compared the exhaust area and the fact that the exhaust gasses hit a wall just as the go through the exhaust ports and are forced to come out at 90 degrees from their flow path.
If I were to build an Renesis with no reservations I would port the intake like I ported my current engine (probably close to the equivalent of a large streetport on a REW engine) and I would drill a 1.0" hole where the casting for the exhaust port of a RX-7 engine is on the RX-8 housings and make two sleeves for these holes and use them as auxiliary exhaust ports. This will add a little over lap and increase the overall flow through the engine since the exhaust will be a little more free flowing.
I think this is where the Reni is limited, not the intake.
Any thoughts on this?
Best regards,
Chris
Plus...the renesis has plenty of inlet area with the way the port is stock compared the exhaust area and the fact that the exhaust gasses hit a wall just as the go through the exhaust ports and are forced to come out at 90 degrees from their flow path.
If I were to build an Renesis with no reservations I would port the intake like I ported my current engine (probably close to the equivalent of a large streetport on a REW engine) and I would drill a 1.0" hole where the casting for the exhaust port of a RX-7 engine is on the RX-8 housings and make two sleeves for these holes and use them as auxiliary exhaust ports. This will add a little over lap and increase the overall flow through the engine since the exhaust will be a little more free flowing.
I think this is where the Reni is limited, not the intake.
Any thoughts on this?
Best regards,
Chris
Last edited by ChrisRX8PR; 05-26-2009 at 04:10 PM.
05-26-2009, 04:39 PM
#56
BHR and Esmeril are on the same page here, and to the extent that we suspect PhillipSA's engine may have had done exactly what you suggest, Chris. We'd like to see the exhaust manifold on SA's engine.
05-26-2009, 04:59 PM
#57
Charles, who is PhilipSA? I am not familiar with his engine?
On another note...I have heard of removing the exhaust sleeves/shields on the two outer.main ports which by itself increases port area significantly and on top of that porting the ports. They did grind inside the plate where the water goes a little to allow more water to gather/flow around the exhaust ports for cooling and they noted that it became necessary to have a larger radiator after this mod was done because the water jacket would be taking more heat than usual due to the shields not being there but the overall results where great.
I have not experimented with this but its sounds like middle of the road solution to the exhaust limits of the engine. They left the center divider on the center port because it keeps exhaust from one rotor from being forced into the other one.
Best regards,
Chris
On another note...I have heard of removing the exhaust sleeves/shields on the two outer.main ports which by itself increases port area significantly and on top of that porting the ports. They did grind inside the plate where the water goes a little to allow more water to gather/flow around the exhaust ports for cooling and they noted that it became necessary to have a larger radiator after this mod was done because the water jacket would be taking more heat than usual due to the shields not being there but the overall results where great.
I have not experimented with this but its sounds like middle of the road solution to the exhaust limits of the engine. They left the center divider on the center port because it keeps exhaust from one rotor from being forced into the other one.
Best regards,
Chris
05-26-2009, 06:36 PM
#59
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Fascinating stuff guys. So this is essentially the way we get a "bigger cam" in our engines. Changing the port adjusts overlap and duration.
What would stop us from welding material onto the port to make it smaller in one area and larger in another? Wouldnt doing this allow us to shift the ports and change the compression of the engine?
What would stop us from welding material onto the port to make it smaller in one area and larger in another? Wouldnt doing this allow us to shift the ports and change the compression of the engine?
05-26-2009, 07:17 PM
#60
Well, Mawnee, you are somewhat mixing your concepts but since you mention piston engines and overlap maybe these analogies will help you visualize the elements unique to the Renesis engine;
1) The port locations of the Renesis can be seen as the lobe centers of a camshaft as their relation to one another defines the amount of available overlap, whether OEM or altered. Most of the discussion on "bridge-porting" has focused on the intake ports with very little discussion given to the exhaust ports.
2) The ports on the Renesis have an "opening" edge and a "closing" edge and these edges are different from one another. Imagine the leading edge of a cam lobe and the trailing edge of a cam lobe. They are usually identical but guess what? New cam technology is exploring the idea that the leading and trailing faces (otherwise known as "ramps") of cam lobes don't NEED to be identical. Neither are the opening and closing faces on the Renesis ports.
3) Side ports open and close quickly much as a roller cam's lobe profile allows the valves in a piston engine to lift off the seat and return to the seat far quicker than a flat tappet cam allows.
4) Enlarging the ports of the Renesis equates greater lobe duration.
5) The greatest impediment to "porting" the Renesis is the proximity the ports have to the water jacket and Mazda didn't leave us much room for error here. That is what Rotarygod discovered when he did my porting for me.
If you take a close look at the Renesis you will see that all Mazda did with the Renesis was apply the past 20 years of piston technology development to the rotary engine. The side ports are, IMO, the rotary version of roller cam development and the side seals being much closer to the rotor face are the equivalent to what the piston engineers did when they raised the top compression ring closer to the piston crown.
1) The port locations of the Renesis can be seen as the lobe centers of a camshaft as their relation to one another defines the amount of available overlap, whether OEM or altered. Most of the discussion on "bridge-porting" has focused on the intake ports with very little discussion given to the exhaust ports.
2) The ports on the Renesis have an "opening" edge and a "closing" edge and these edges are different from one another. Imagine the leading edge of a cam lobe and the trailing edge of a cam lobe. They are usually identical but guess what? New cam technology is exploring the idea that the leading and trailing faces (otherwise known as "ramps") of cam lobes don't NEED to be identical. Neither are the opening and closing faces on the Renesis ports.
3) Side ports open and close quickly much as a roller cam's lobe profile allows the valves in a piston engine to lift off the seat and return to the seat far quicker than a flat tappet cam allows.
4) Enlarging the ports of the Renesis equates greater lobe duration.
5) The greatest impediment to "porting" the Renesis is the proximity the ports have to the water jacket and Mazda didn't leave us much room for error here. That is what Rotarygod discovered when he did my porting for me.
If you take a close look at the Renesis you will see that all Mazda did with the Renesis was apply the past 20 years of piston technology development to the rotary engine. The side ports are, IMO, the rotary version of roller cam development and the side seals being much closer to the rotor face are the equivalent to what the piston engineers did when they raised the top compression ring closer to the piston crown.
Last edited by Charles R. Hill; 05-26-2009 at 07:27 PM.
05-26-2009, 11:10 PM
#63
for NA the reality is the dual side exhaust ports have a substantial area increase over the previous rotary engine, almost 2x. The fact that the flow hits a wall is irrelevant because there is so much area available (high area = low velocity, relatively speaking), which coupled with zero overlap is why manifold/exhaust tuning doesn't come into play for NA, just give it the area to escape is all it needs to accomplish the potential.
The exhaust ports only becomes an issue for FI when the overall engine flow volume goes up, but zero overlap benefits FI so you're in a give/take situation
IMO for NA the way to find power is to accomplish overlap. P porting is a given for accomplishing this despite it's complications and limitations, but a subject for another thread. What individual pictures can't show is the travel paths of the critical seals. Therefore question before us is, can you port in overlap and keep the seals in place?
What this thread has given me is a much greater understanding of how the intake system works. When you consider that the center plate port is the primary low speed intake flow for the engine, the possibility exists that if you can somehow achieve the overlap to occur in the auxillary and/or secondary side plate ports then you can potentially have a rotary engine that not only still maintains a decent low end response, but also a stronger top end. This is due to the fact that the ported overlap won't kick in until the higher revs as those ports open up at their respective high rpm trigger points. Overlap is beneficial at high rpm, but detrimental to low rpm operation. So potentially it's the best of both worlds if it can be had. P Port can't accomplish this without some way to shutter control it relative to rpm, a difficult task to accomplish.
IMO Mazda has built a beautiful system. Throwing aside economy and emissions concerns, is it possible for us to improve upon it for both a higher output and wider powerband to boot?
Overall intake layout (6 port on right, the subject at hand):
Primary center plate port flow:
Secondary (lower) and Auxillary (upper) port flow:
The exhaust ports only becomes an issue for FI when the overall engine flow volume goes up, but zero overlap benefits FI so you're in a give/take situation
IMO for NA the way to find power is to accomplish overlap. P porting is a given for accomplishing this despite it's complications and limitations, but a subject for another thread. What individual pictures can't show is the travel paths of the critical seals. Therefore question before us is, can you port in overlap and keep the seals in place?
What this thread has given me is a much greater understanding of how the intake system works. When you consider that the center plate port is the primary low speed intake flow for the engine, the possibility exists that if you can somehow achieve the overlap to occur in the auxillary and/or secondary side plate ports then you can potentially have a rotary engine that not only still maintains a decent low end response, but also a stronger top end. This is due to the fact that the ported overlap won't kick in until the higher revs as those ports open up at their respective high rpm trigger points. Overlap is beneficial at high rpm, but detrimental to low rpm operation. So potentially it's the best of both worlds if it can be had. P Port can't accomplish this without some way to shutter control it relative to rpm, a difficult task to accomplish.
IMO Mazda has built a beautiful system. Throwing aside economy and emissions concerns, is it possible for us to improve upon it for both a higher output and wider powerband to boot?
Overall intake layout (6 port on right, the subject at hand):
Primary center plate port flow:
Secondary (lower) and Auxillary (upper) port flow:
05-27-2009, 02:28 PM
#65
IMO for NA the way to find power is to accomplish overlap. P porting is a given for accomplishing this despite it's complications and limitations, but a subject for another thread. What individual pictures can't show is the travel paths of the critical seals. Therefore question before us is, can you port in overlap and keep the seals in place?
What this thread has given me is a much greater understanding of how the intake system works. When you consider that the center plate port is the primary low speed intake flow for the engine, the possibility exists that if you can somehow achieve the overlap to occur in the auxiliary and/or secondary side plate ports then you can potentially have a rotary engine that not only still maintains a decent low end response, but also a stronger top end. This is due to the fact that the ported overlap won't kick in until the higher revs as those ports open up at their respective high rpm trigger points. Overlap is beneficial at high rpm, but detrimental to low rpm operation. So potentially it's the best of both worlds if it can be had. P Port can't accomplish this without some way to shutter control it relative to rpm, a difficult task to accomplish.
IMO Mazda has built a beautiful system. Throwing aside economy and emissions concerns, is it possible for us to improve upon it for both a higher output and wider powerband to boot?
Interesting thought though.
05-27-2009, 03:08 PM
#66
Well unfortunately that is not possible. The fact that both ports are open in the chamber at the same time. As the rotor face passes the primary ports it is also passing the secondary ports. If you have overlap in the secondary ports your going to have overlap in the primary ports also.
Interesting thought though.
Interesting thought though.
05-27-2009, 06:34 PM
#68
Now the Lower Intake Manifold does control air flow. But just the secondary porting. (The two end cast irons.) Similar to the throttle body. But there is no way I can see to have over lap with just the secondary ports with out effecting the primary.
Over lap will occur regardless of which intake port/exhaust port is causing it. The fact that exhaust and combustion chambers are open to each other is the factor. It doesn't matter where it happens, just that it happens.
05-27-2009, 08:42 PM
#69
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What about These guys?????
http://www.rotaryheads.com/porting/rx8-porting.html
I know it was brought up on the other topic of the one from over seas but nothing really said about them???
http://www.rotaryheads.com/porting/rx8-porting.html
I know it was brought up on the other topic of the one from over seas but nothing really said about them???
05-28-2009, 12:13 AM
#70
What about These guys?????
http://www.rotaryheads.com/porting/rx8-porting.html
I know it was brought up on the other topic of the one from over seas but nothing really said about them???
http://www.rotaryheads.com/porting/rx8-porting.html
I know it was brought up on the other topic of the one from over seas but nothing really said about them???
They seem to have a Bridge Port listed for the Renesis. But they're not showing any pictures. Not sure what they're doing.
05-28-2009, 01:28 AM
#71
You're incorrect in your cross-chamber overlap analysis. The primary port would be covered by the rotor the same as the original zero overlap alignment. It depends on how and where you port the overlap into the assembly. You made me think about it for a minute though.
Last edited by TeamRX8; 05-28-2009 at 01:41 AM.
05-28-2009, 04:06 AM
#72
The primary port is always open to intake when the engine is running. The secondary port opening on the cast iron face is open to the intake chamber cycle at the same time as the primary port. The auxiliary port (regulated by the SSV) is open to the intake chamber a few degrees behind the secondary port (regulated by the APV). So theoretically if absolutely no intake air is coming through the secondary and auxiliary ports you would have no over lap. If a standard bridge port was implemented in that area. Is this what your saying?
But, if the port design described previously with the Rotor housing being cut back is done there would be an opening to the intake section of the chamber at the same time as the exhaust section of the chamber.
So cutting back the rotor housing is opening the intake cycle to the exhaust cycle. Correct?
So which ever port is open would not matter at this point. The cycles are not separated due to the cut back rotor housing.
There is no seal closing that open area of the rotor housing. It will allow the chambers to meet regardless of which intake port, primary, secondary or auxiliary is open. The apex seal will not close that opening and separate the two chambers at the point.
Overlap will occur.
This is some interesting **** huh?
But, if the port design described previously with the Rotor housing being cut back is done there would be an opening to the intake section of the chamber at the same time as the exhaust section of the chamber.
So cutting back the rotor housing is opening the intake cycle to the exhaust cycle. Correct?
So which ever port is open would not matter at this point. The cycles are not separated due to the cut back rotor housing.
There is no seal closing that open area of the rotor housing. It will allow the chambers to meet regardless of which intake port, primary, secondary or auxiliary is open. The apex seal will not close that opening and separate the two chambers at the point.
Overlap will occur.
This is some interesting **** huh?
