Turbo Kits and Aux Ports
05-06-2003, 11:28 PM
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Turbo Kits and Aux Ports
Ok, so I've been reading a bit about aux. ports... and some site mentioned that turbo rotaries typically are of the "4-port" variety. Why is this the case, and is this necessarily the case? Will a 6-port high power Renesis engine be able to accept a turbo kit without changing the side housings?
05-07-2003, 09:24 AM
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Yes, in the FC (2nd Gen, the only generation with both NA and turbo engines), the NA engines had 6 ports, and the turbo engines had 4 ports.
This does not mean that putting a turbo or SC on a 6 port engine won't work, or won't work well. One thing to remember is that there is a tradeoff between 4 port and 6 port performance. For an NA engine, a 4 port works better at low rpms (idle/cruise/part throttle), while the 6 port works better at high rpms with a Wide Open Throttle (WOT, stomp on the gas).
When you are optimizing an engine, you do different things between NA and FI (Forced Induction, either SC or Turbo). With an NA, especially with a sports car, you want the engine to flow the best at higher rpms, WOT, for the most peak power. With the Renesis, you can actually have the best of all worlds in that it will only open up ports as the rpms increase. In effect, at higher rpms, all 6 ports are open for the best high rpm/WOT performance, at mid rpms, only 4 ports are open for best performance, and at cruise/idle/low rpms, only 2 ports are open for the best low-end performance.
With an FI engine, you are cramming air in at high-rpms/WOT, so for a normal, street driven FI car, there is little benefit in high rpm performance to having 6 ports vs. 4 ports. With an FI engine, especially with turbos, the engine is not always getting boost. At lower rpms/cruise/idle/part throttle, the engine is actually working as an NA engine, and it can benefit from low rpm performance gains from having 4 ports. So, since there was little benefit in making it 6 port, Mazda made the turbo engine 4 port to give the best low-end/cruise/idle performance. Basically, they traded off a little benefit in high-rpm power for a significant benefit in low rpm power, mileage, and throttle response.
With the variable intake system, there still is a little to be gained by having 6 ports at high rpms on an FI engine, so as long as the variable intake paths are included in an FI Renesis, 6 ports would be optimal.
---jps
This does not mean that putting a turbo or SC on a 6 port engine won't work, or won't work well. One thing to remember is that there is a tradeoff between 4 port and 6 port performance. For an NA engine, a 4 port works better at low rpms (idle/cruise/part throttle), while the 6 port works better at high rpms with a Wide Open Throttle (WOT, stomp on the gas).
When you are optimizing an engine, you do different things between NA and FI (Forced Induction, either SC or Turbo). With an NA, especially with a sports car, you want the engine to flow the best at higher rpms, WOT, for the most peak power. With the Renesis, you can actually have the best of all worlds in that it will only open up ports as the rpms increase. In effect, at higher rpms, all 6 ports are open for the best high rpm/WOT performance, at mid rpms, only 4 ports are open for best performance, and at cruise/idle/low rpms, only 2 ports are open for the best low-end performance.
With an FI engine, you are cramming air in at high-rpms/WOT, so for a normal, street driven FI car, there is little benefit in high rpm performance to having 6 ports vs. 4 ports. With an FI engine, especially with turbos, the engine is not always getting boost. At lower rpms/cruise/idle/part throttle, the engine is actually working as an NA engine, and it can benefit from low rpm performance gains from having 4 ports. So, since there was little benefit in making it 6 port, Mazda made the turbo engine 4 port to give the best low-end/cruise/idle performance. Basically, they traded off a little benefit in high-rpm power for a significant benefit in low rpm power, mileage, and throttle response.
With the variable intake system, there still is a little to be gained by having 6 ports at high rpms on an FI engine, so as long as the variable intake paths are included in an FI Renesis, 6 ports would be optimal.
---jps
05-07-2003, 02:54 PM
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...but there's also the port timing effects of the tertiary ports... i know that with high-pressure aspiration, timing which doesn't overlap any of the cycles much (no cheating before or after TDC/BDC) is better than heavy overlap, because of the tendancy for back-flow to occur (especially with high exhaust timing overlap... ie: slow to close) which only hurts the pumping efficiencies.
referencing rotaryengineillustrated (here, at the very bottom ) i see that all 13b turbo variants never had either of the primary or secondary ports timed any later than 50 degrees After BDC.
in the 6 port NA variants the primary would close at 40 ABDC, with the secondary closing at 30 ABDC, but with the tertiary port above it closing at 80 ABDC (which i think leaves enough delay that the intake port is already starting to open to the next combustion chamber just as the tertiary port closes). this is a major factor in the efficiency of an engine, and could be a reason why turbos and NA 13B engines don't really mix so well.
because it appears that the RENESIS's ports are located lower on the side+int housings, and the exhaust ports are located so that there is literally zero overlap, the timing will probably be different (closures closer to BDC on the intake side) but still maybe not as favourable to a forced induction system as the 4 port motors...??
time will tell
referencing rotaryengineillustrated (here, at the very bottom ) i see that all 13b turbo variants never had either of the primary or secondary ports timed any later than 50 degrees After BDC.
in the 6 port NA variants the primary would close at 40 ABDC, with the secondary closing at 30 ABDC, but with the tertiary port above it closing at 80 ABDC (which i think leaves enough delay that the intake port is already starting to open to the next combustion chamber just as the tertiary port closes). this is a major factor in the efficiency of an engine, and could be a reason why turbos and NA 13B engines don't really mix so well.
because it appears that the RENESIS's ports are located lower on the side+int housings, and the exhaust ports are located so that there is literally zero overlap, the timing will probably be different (closures closer to BDC on the intake side) but still maybe not as favourable to a forced induction system as the 4 port motors...??
time will tell
05-08-2003, 11:24 PM
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you could always just keep them closed... jk. Also though, i think its important to keep in mind because most of the people who will be modding their RX-8's will start from the 6-speed base, which is 6-port. Do you think it will be the case that the 5th and 6th ports will just be retuned to stay closed?
05-08-2003, 11:43 PM
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Originally posted by ProtoConVert
...Do you think it will be the case that the 5th and 6th ports will just be retuned to stay closed?
...Do you think it will be the case that the 5th and 6th ports will just be retuned to stay closed?
---jps
05-11-2003, 09:02 PM
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KISS = Keep It Simple Stupid :D
Since the renesis relocated ports and the statement the engineer made "its made to be fitted for a turbo" then that means the ports should be running....we'll see when someone makes a good turbo or sc system...
Since the renesis relocated ports and the statement the engineer made "its made to be fitted for a turbo" then that means the ports should be running....we'll see when someone makes a good turbo or sc system...
05-24-2003, 11:23 PM
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how do you measure TDC and BDC on a rotary?? On a PIS-TUN engine :D its the highest and lowest point of the PIS-TUN in the SIL-IN-DER. But the rotary doesn't have a linear travel. So how do you measure it in a spirograph setup like the wankel?? Do you measure TDC and BDC by the position of the intake ports full open/full closed or maybe when the rotor just passes over the port?
Spirograph...
05-25-2003, 01:39 AM
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Originally posted by Farsyde
how do you measure TDC and BDC on a rotary??
how do you measure TDC and BDC on a rotary??
BDC is exactly the opposite: it's when the rotor face is furthes from the perhipheral housing, which is 90 rotor degrees (which is 270 e-shaft degrees of rotation) after a TDC event... it's when the rotor is "pointing" down or up... so, really, per rotor revolution, there are two TDC and two BDC events (which is 90 degrees * 4 = 360 degrees) per combustion chamber per whole rotation, just as there are in a 4 stroke piston engine per piston, but the e-shaft goes around 3 whole times, with three whole combustion events, per rotor revolution... pretty cool, i know :D
Last edited by wakeech; 05-25-2003 at 01:48 AM.
07-23-2004, 09:30 PM
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Here's an additional link from Paul Yaw's webpage about port timing (did he fall off the face of the planet too 
?).
http://www.yawpower.com/dectech.html
Is this why quick-spooling turbochargers are the best choice for the 6-port RENESIS? IMO, I wouldn't see any point in high-rpm boost; the opening of the tertiary ports would take care of the top end. Meanwhile, a small-frame turbocharger can take care of the bottom end, which is in need of some power. What about a large turbocharger, such as a T78, or something of that magnitude? Since these turbochargers, I believe, are best for high-rpm apps, its usefulness to the RENESIS wouldn't be much, right? Personally, I don't prefer high-rpm power. I want the best average power gain I can get.
Is it possible to set up large-frame turbocharger to fully spool at midrange? What would the effect be if this was possible? I've said this before in other threads, but what about a new intake manifold, one that utilized long runners for low-end power? Would I have to eliminate the S-DAIS in the process? I know it sounds confusing, but I am trying to explain the best that I can.
?).http://www.yawpower.com/dectech.html
Originally Posted by Sputnik
Yes, in the FC (2nd Gen, the only generation with both NA and turbo engines), the NA engines...With the variable intake system, there still is a little to be gained by having 6 ports at high rpms on an FI engine, so as long as the variable intake paths are included in an FI Renesis, 6 ports would be optimal.
---jps
---jps
Is it possible to set up large-frame turbocharger to fully spool at midrange? What would the effect be if this was possible? I've said this before in other threads, but what about a new intake manifold, one that utilized long runners for low-end power? Would I have to eliminate the S-DAIS in the process? I know it sounds confusing, but I am trying to explain the best that I can.
