Lasse wankel header
12-27-2007, 02:01 PM
#76
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12-27-2007, 02:16 PM
#77
with overlap...the in hole is open when the out hole is open...
zero overlap...the in hole is open when the out hole is closed...
suck on a closed hole all you want...
savvy?
12-27-2007, 02:21 PM
#78
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Your sucking the exhaust gases out, it's called scavenging, normally with overlap you get more effect because you can also help pull in some inlet mixture, you can't do this on the renesis but you can still help with the exhaust gas scavenging, savvy?
12-27-2007, 02:29 PM
#79
not saying do not do this...but setting a realistic expectation that this modification is not the same as in a piston engine where the gain is significant.
12-27-2007, 02:31 PM
#80
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I agree, but there is some gain to be had, removing more combustion gases will also help draw in more intake charge when the chamber gets around to the intake port.
Slight gains, but gains all the same.
Slight gains, but gains all the same.
12-27-2007, 02:39 PM
#81
If your into racing...and I'm talking about hardcore racing...your probably going to be fabing your own header anyway...
This type of product in the other markets is aimed as a low cost easy NA mod with "butt-dyno" gains...
As much as I love aftermarket support for our cars, this is one market which has a very hard sell in the one argument that matters most...bang vs. buck...
12-27-2007, 02:56 PM
#85
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Also, if you're bored Team explain in more detail why multi-tube is worthless.
-Fil
12-27-2007, 02:57 PM
#86
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right but there exists a maximum theoretical gain to doing this on this type of engine...and in this case due to the design of the engine itself, the amount of possible gain is further reduced.
not saying do not do this...but setting a realistic expectation that this modification is not the same as in a piston engine where the gain is significant.
not saying do not do this...but setting a realistic expectation that this modification is not the same as in a piston engine where the gain is significant.
12-27-2007, 03:22 PM
#88
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There is most certainly a benefit to "scavenging" with a zero overlap engine! I know it's been stated many times that you can't get scavenging without overlap. You definitely can't get scavenging without collecting exhaust pipes such as true duals on a 13B but scavenging you can get with no overlap.
But how? When we think of scavenging, we think of the exhaust velocity pulling on the intake during overlap through the benefit of the low pressure wave behind it. Obviously we can't utilize this low pressure wave if there is no overlap. Or can we?
This low pressure wave, at vertain points in the rpm range depending on tuning, can in fact leave the chamber below ambient outside pressure. This means that when the intake ports open, there is a greater pressure differential than normal and the air in the port gets "moving" at a faster rate. Higher intake velocity helps cram more air into the engine. Keep this trend going and it will also help as the port closes. It will raise the average air speed velocity through the port which increases efficiency. Yes it can be done!
The downside to trying to do this is the evil siamesed center exhaust port. It completely messes up tuning in this manner. No matter how long your equal length header tubes are, there will always be an interference wave where the center ports come together which will off set what we are trying to accomplish with header length. There may be a way to "trick" this interference wave into becoming a positive effect wave however and you can't do it with 3 equal length pipes and only 1 collector.
On some old 4 cylinder engines, the original Mini Cooper comes to mind, there were only 3 exhaust ports. These engines had the 2 middle valves dump into a siamesed runner in a similar fashion to the Renesis center ports. I know someone is going to complain that the firing order of a 4 cylinder through these 2 ports isn't even and this is true but all we care about is acoustic resonance of the system and not so much how often pulses run through. The reality is that an even stream of pulses such as with the Renesis actually works more in our favor.
These older engines and cars did get raced. Keep in mind the Mini wasn't the only engine with a siamesed center section. It's just the only one I can think of right now. The race cars had some very creative exhaust designs to deal with the siamesed center ports. The most successful setups ever used on these engines utilized unequal length runners and dual collectors. The 2 outside exhaust runners were equal length as each other and collected with each other only. The center port was deal with in one of two way. One of them just being an addition to the other. The first way was to make this pipe anywhere from 30%-50% longer than the outer pipes and collect them downstream of the first collector at a second one. The length of this center pipe being the critical item to tune. You first figure out what the optimum header pipe length is and then base the outer pipes around this length. The center pipe length was then tuned. It MUST be collected farther downstream though as lengthening it and collecting it at the same point does NOTHING! RB tried this.
The other setup which was a variation of the above added a "dead leg" pipe to the center immediately after the port left the head of the engine. It gets tee'd off right at the entrance to the center runner. This pipe was the exact same length as the outer pipes but plugged off at the end.
Each of these setups tried to take advantage of acoustic resonance to help with a scavenging effect. Since sound waves are also energy, it was the hope that these acoustic waves, which are known to tune very well, would offest the negative waves that cancelled out the fact that the center ports were siamesed. Hymee proved in a dyno a few years ago that the center port has much more energy in it as it was the first to glow brightly in a dyno session. This is proof enough that the center needs to be treated differently.
However, NO ONE had addressed the center port in a different way. Until someone does, none of them will have any more spectacular results than any other setup. I don't care if it's cheap ebay crap or has RE-Amemiya stamped on it. None of them will give more than 4-5 additional hp. I don't care what they claim. The reason they gain anything at all is through additional flow. It has nothing to do with tuning. I know team has claimed that his works best but he won't say how it is designed. Until then I'm raising the bs flag. I'll keep it up after I see it if the center port isn't addressed uniquely from the rest too. He also says mine won't work. Maybe it won't. I don't know yet. I do know that I am the only one to address the center ports being siamesed and that gives it the greatest probability of success. That doesn't mean it will work any better though. One thing is for sure that a downside to my design is the space required to do it.
The reson I feel this has the most validity is that it isn't a new problem and that it has been solved in the past. That's a good place to start with a design for this engine. Only when someone tries it and proves that it doesn't work will I agree that NO header design out there will do anything other than any other. Up to this point, they don't. There are only a few more designs to eliminate. Mine included. It might not work. We'll find out someday I guess.
But how? When we think of scavenging, we think of the exhaust velocity pulling on the intake during overlap through the benefit of the low pressure wave behind it. Obviously we can't utilize this low pressure wave if there is no overlap. Or can we?
This low pressure wave, at vertain points in the rpm range depending on tuning, can in fact leave the chamber below ambient outside pressure. This means that when the intake ports open, there is a greater pressure differential than normal and the air in the port gets "moving" at a faster rate. Higher intake velocity helps cram more air into the engine. Keep this trend going and it will also help as the port closes. It will raise the average air speed velocity through the port which increases efficiency. Yes it can be done!
The downside to trying to do this is the evil siamesed center exhaust port. It completely messes up tuning in this manner. No matter how long your equal length header tubes are, there will always be an interference wave where the center ports come together which will off set what we are trying to accomplish with header length. There may be a way to "trick" this interference wave into becoming a positive effect wave however and you can't do it with 3 equal length pipes and only 1 collector.
On some old 4 cylinder engines, the original Mini Cooper comes to mind, there were only 3 exhaust ports. These engines had the 2 middle valves dump into a siamesed runner in a similar fashion to the Renesis center ports. I know someone is going to complain that the firing order of a 4 cylinder through these 2 ports isn't even and this is true but all we care about is acoustic resonance of the system and not so much how often pulses run through. The reality is that an even stream of pulses such as with the Renesis actually works more in our favor.
These older engines and cars did get raced. Keep in mind the Mini wasn't the only engine with a siamesed center section. It's just the only one I can think of right now. The race cars had some very creative exhaust designs to deal with the siamesed center ports. The most successful setups ever used on these engines utilized unequal length runners and dual collectors. The 2 outside exhaust runners were equal length as each other and collected with each other only. The center port was deal with in one of two way. One of them just being an addition to the other. The first way was to make this pipe anywhere from 30%-50% longer than the outer pipes and collect them downstream of the first collector at a second one. The length of this center pipe being the critical item to tune. You first figure out what the optimum header pipe length is and then base the outer pipes around this length. The center pipe length was then tuned. It MUST be collected farther downstream though as lengthening it and collecting it at the same point does NOTHING! RB tried this.
The other setup which was a variation of the above added a "dead leg" pipe to the center immediately after the port left the head of the engine. It gets tee'd off right at the entrance to the center runner. This pipe was the exact same length as the outer pipes but plugged off at the end.
Each of these setups tried to take advantage of acoustic resonance to help with a scavenging effect. Since sound waves are also energy, it was the hope that these acoustic waves, which are known to tune very well, would offest the negative waves that cancelled out the fact that the center ports were siamesed. Hymee proved in a dyno a few years ago that the center port has much more energy in it as it was the first to glow brightly in a dyno session. This is proof enough that the center needs to be treated differently.
However, NO ONE had addressed the center port in a different way. Until someone does, none of them will have any more spectacular results than any other setup. I don't care if it's cheap ebay crap or has RE-Amemiya stamped on it. None of them will give more than 4-5 additional hp. I don't care what they claim. The reason they gain anything at all is through additional flow. It has nothing to do with tuning. I know team has claimed that his works best but he won't say how it is designed. Until then I'm raising the bs flag. I'll keep it up after I see it if the center port isn't addressed uniquely from the rest too. He also says mine won't work. Maybe it won't. I don't know yet. I do know that I am the only one to address the center ports being siamesed and that gives it the greatest probability of success. That doesn't mean it will work any better though. One thing is for sure that a downside to my design is the space required to do it.
The reson I feel this has the most validity is that it isn't a new problem and that it has been solved in the past. That's a good place to start with a design for this engine. Only when someone tries it and proves that it doesn't work will I agree that NO header design out there will do anything other than any other. Up to this point, they don't. There are only a few more designs to eliminate. Mine included. It might not work. We'll find out someday I guess.
12-27-2007, 03:30 PM
#89
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That's what I was trying to put across but nowhere near as eloquently.
I'd quite like your opinion on ours in regard to that though, as you can see the two outer ports run a far different exhaust length than the centre port and the centre port joins 2 inches further down the collector than the outer ports.
I'd love to weld the centre ports up and run a pair of small peripherals in their place, along with the outer side ports, but can't justify the cost at the moment.
I'd quite like your opinion on ours in regard to that though, as you can see the two outer ports run a far different exhaust length than the centre port and the centre port joins 2 inches further down the collector than the outer ports.
I'd love to weld the centre ports up and run a pair of small peripherals in their place, along with the outer side ports, but can't justify the cost at the moment.
12-27-2007, 05:09 PM
#90
That's what I was trying to put across but nowhere near as eloquently.
I'd quite like your opinion on ours in regard to that though, as you can see the two outer ports run a far different exhaust length than the centre port and the centre port joins 2 inches further down the collector than the outer ports.
I'd love to weld the centre ports up and run a pair of small peripherals in their place, along with the outer side ports, but can't justify the cost at the moment.
I'd quite like your opinion on ours in regard to that though, as you can see the two outer ports run a far different exhaust length than the centre port and the centre port joins 2 inches further down the collector than the outer ports.
I'd love to weld the centre ports up and run a pair of small peripherals in their place, along with the outer side ports, but can't justify the cost at the moment.
12-27-2007, 07:16 PM
#92
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Hey, RG. Is it possible to create a center pipe with a divider that is extended to match the center port divider. In essense creating four ports with four pipes. The center two just happen to be siamessed.
Not really work?
Too hard to mass produce?
Not really work?
Too hard to mass produce?
12-27-2007, 07:34 PM
#94
12-27-2007, 07:42 PM
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But having things CNC milled is fairly cheap if you do the CAD program yourself, I've had exhaust manifold plates milled before for less than 10 per unit, fortunately I have both a program and a CNC mill these days.....
12-28-2007, 10:02 AM
#96
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RB tried a center divider and made a 4-1 header. I posted pictures of it a couple of years ago. The conventional 3 pipe header made about 4 hp and the 4-1 made about 5 hp. Little difference. I would like to see this tried but instead collecting it into 2 separate pipes. 1 for each rotor. Then adjusting it's total length. I don't like the idea of 1 collector. Even trying 2 separate pipes all the way out would be an option. The 13B guys call this a true dual system and it works better on engines with less overlap than more. It would be interesting to see how it works with no overlap.
Phillip I think your header looks great. Very nice work. I don't think the short collector distance difference that you have is going to do anything though. You do have some good distance to play around with though so you could actually try many different things and learn what works best. I can't wait to see your project when it's done.
Phillip I think your header looks great. Very nice work. I don't think the short collector distance difference that you have is going to do anything though. You do have some good distance to play around with though so you could actually try many different things and learn what works best. I can't wait to see your project when it's done.
12-28-2007, 10:19 AM
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Aye, if there's one thing we have it's room!
Hopefully the shorter pipe length will make the difference if I've done the maths right - it's actually joining 10" before the outer pipes, even though it doesn't look it, if not I'll try the centre section and dual pipes you've suggested.
And if that doesn't work the housing is going on the milling machine.
Hopefully the shorter pipe length will make the difference if I've done the maths right - it's actually joining 10" before the outer pipes, even though it doesn't look it, if not I'll try the centre section and dual pipes you've suggested.
And if that doesn't work the housing is going on the milling machine.
Last edited by PhillipM; 12-29-2007 at 07:28 AM.
12-28-2007, 12:45 PM
#99
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The problem with 2 stroke theory as applied to a rotary is that 2 stroke tuning not only helps pull gasses out of the chamber but also push some back in near the end of the cycle. We don't want that.
