4-2-1 Turbo manifold
01-13-2012, 03:05 PM
#41
Former Vendor
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First, firing order is everything, whether it's NA or turbo. You will understand why firing order is critical after you finish reading this, and if you still don't, then I can't help you.
The reason that N/A guys do 4-2-1 is because it alters the RPM where the best scavenging happens. Each time the exhaust valves on a cylinder open, it lets a rush of hot air down that runner, which alters the pressure along the runner and at the collector. However, that rush of air will pull a vacuum on whichever runners are connected to it at the collector.
With a 4-1, that vacuum is spread across three other pipes, and it doesn't do much good. With a 4-2-1, though, you can transfer that vacuum into only one other pipe (at the 4-2 collectors), which means that the scavenging is much more effective. (Pairing is critical, though - if you pair them wrong, one cylinder will act on the other, but by the time the first cylinder is ready to release another charge, the vacuum effect of the second cylinder will be gone. You'll end up with varying VE per cylinder, and it's all bad from there.)
After a certain point, the pulses begin to blend and the effect goes away. Once that happens, you're blending the exhaust gases twice, which isn't as good as just blending them once, so you end up with a little power lost up top. In addition, if you have all four pipes running into the same collector, at a certain RPM (fairly high) you will end up with some of the same effect that the 4-2-1s enjoy in the midrange - as the exhaust pulses begin to pick up in speed, the pressure rises in the collector to the ideal point, and you end up with a little scavenging.
There's one small problem with all of this, though: It's all naturally aspirated theory. Virtually NONE of it translates into turbos. We are pumping all of our exhaust gases into the tiniest of orifices in order to build pressure in the manifold, which is something N/A guys strive to avoid.
What you HAVE seen before is twin-scroll - same kind of idea as a 4-2-1, but for different reasons. When you dump all 4 cylinders into the same turbo collector, the exhaust pulses begin to muddle themselves fairly early on, and you don't get the impact of each pulse acting as effectively on the turbine wheel. If you separate them into proper pairs, the pulses are more directed, and it transfers more of the energy into the turbo itself. The muddling still happens, but it happens at a much higher RPM, and by that point the turbo is wound up and ready to go. If you designed a twin-scroll housing that was the same A/R as a single-scroll housing, it would spool SIGNIFICANTLY faster. Or, you can size the turbo up and get a turbo that will make a lot more power, but still spool like a smaller unit. (The difficulty/cost of proper wastegate control on a twin-scroll setup is why it's not more popular than it is, especially on smaller/cheaper turbos. Supposedly the effect is also diminished on small turbos, but I'm not sure why that is.)
It has almost nothing to do with scavenging or exhaust velocities.
If you look at F1 cars from the 80s, you will see their turbos situated at the ends of a 3" long set of headers. Once you size the turbo to the point where you are actually seeing N/A levels of pressure pre-spool, you can lengthen the headers and get some of that scavenging effect back, or something like that. The complexities of that blend of the two is something that's a little beyond me so far.
One last thing - when I think of an idea that I haven't seen before (like you and your 4-2-1 turbo header idea), I don't immediately think that I am a "great mind" or that the idea is awesome or whatever. My modus operandi is to assume that the idea is stupid, because there are lots of smart people in the world, and if the idea was a good one, it's fairly likely that someone would have already done it. I will then do a little reading to decide whether it has any merit - sometimes it does, and sometimes I will even find the same idea executed in a different platform or at a different level of motorsport (i.e. our Inconel studs, which had never been seen in a Miata before we released them, but had been used in OEM applications, NASCAR, F1, etc. for a while). Usually, in the course of that research, I will either come to realize why the idea is stupid, or realize why it's been done differently.
It's not our job to convince you that your idea is stupid - you should be able to do that yourself. If you're posting it on here, it's your job to convince us that it's NOT stupid.
Last edited by Savington; 01-13-2012 at 03:15 PM.
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01-13-2012, 03:30 PM
#45
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I don't run it because I swapped in a 1.8, and I don't have a track car.
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01-13-2012, 08:08 PM
#46
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Thank you for commenting on my squid intake manifold. It deserves more attention. Tim refused to build it for me because it was too revolutionary. There probably would have been a rush on squid and the koreans and japanese would have run out of snacks.
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01-14-2012, 12:53 AM
#49
You have seen one, or at least a variation on the idea - you just don't realize it.
First, firing order is everything, whether it's NA or turbo. You will understand why firing order is critical after you finish reading this, and if you still don't, then I can't help you.
The reason that N/A guys do 4-2-1 is because it alters the RPM where the best scavenging happens. Each time the exhaust valves on a cylinder open, it lets a rush of hot air down that runner, which alters the pressure along the runner and at the collector. However, that rush of air will pull a vacuum on whichever runners are connected to it at the collector.
With a 4-1, that vacuum is spread across three other pipes, and it doesn't do much good. With a 4-2-1, though, you can transfer that vacuum into only one other pipe (at the 4-2 collectors), which means that the scavenging is much more effective. (Pairing is critical, though - if you pair them wrong, one cylinder will act on the other, but by the time the first cylinder is ready to release another charge, the vacuum effect of the second cylinder will be gone. You'll end up with varying VE per cylinder, and it's all bad from there.)
After a certain point, the pulses begin to blend and the effect goes away. Once that happens, you're blending the exhaust gases twice, which isn't as good as just blending them once, so you end up with a little power lost up top. In addition, if you have all four pipes running into the same collector, at a certain RPM (fairly high) you will end up with some of the same effect that the 4-2-1s enjoy in the midrange - as the exhaust pulses begin to pick up in speed, the pressure rises in the collector to the ideal point, and you end up with a little scavenging.
There's one small problem with all of this, though: It's all naturally aspirated theory. Virtually NONE of it translates into turbos. We are pumping all of our exhaust gases into the tiniest of orifices in order to build pressure in the manifold, which is something N/A guys strive to avoid.
What you HAVE seen before is twin-scroll - same kind of idea as a 4-2-1, but for different reasons. When you dump all 4 cylinders into the same turbo collector, the exhaust pulses begin to muddle themselves fairly early on, and you don't get the impact of each pulse acting as effectively on the turbine wheel. If you separate them into proper pairs, the pulses are more directed, and it transfers more of the energy into the turbo itself. The muddling still happens, but it happens at a much higher RPM, and by that point the turbo is wound up and ready to go. If you designed a twin-scroll housing that was the same A/R as a single-scroll housing, it would spool SIGNIFICANTLY faster. Or, you can size the turbo up and get a turbo that will make a lot more power, but still spool like a smaller unit. (The difficulty/cost of proper wastegate control on a twin-scroll setup is why it's not more popular than it is, especially on smaller/cheaper turbos. Supposedly the effect is also diminished on small turbos, but I'm not sure why that is.)
It has almost nothing to do with scavenging or exhaust velocities.
If you look at F1 cars from the 80s, you will see their turbos situated at the ends of a 3" long set of headers. Once you size the turbo to the point where you are actually seeing N/A levels of pressure pre-spool, you can lengthen the headers and get some of that scavenging effect back, or something like that. The complexities of that blend of the two is something that's a little beyond me so far.
One last thing - when I think of an idea that I haven't seen before (like you and your 4-2-1 turbo header idea), I don't immediately think that I am a "great mind" or that the idea is awesome or whatever. My modus operandi is to assume that the idea is stupid, because there are lots of smart people in the world, and if the idea was a good one, it's fairly likely that someone would have already done it. I will then do a little reading to decide whether it has any merit - sometimes it does, and sometimes I will even find the same idea executed in a different platform or at a different level of motorsport (i.e. our Inconel studs, which had never been seen in a Miata before we released them, but had been used in OEM applications, NASCAR, F1, etc. for a while). Usually, in the course of that research, I will either come to realize why the idea is stupid, or realize why it's been done differently.
It's not our job to convince you that your idea is stupid - you should be able to do that yourself. If you're posting it on here, it's your job to convince us that it's NOT stupid.
First, firing order is everything, whether it's NA or turbo. You will understand why firing order is critical after you finish reading this, and if you still don't, then I can't help you.
The reason that N/A guys do 4-2-1 is because it alters the RPM where the best scavenging happens. Each time the exhaust valves on a cylinder open, it lets a rush of hot air down that runner, which alters the pressure along the runner and at the collector. However, that rush of air will pull a vacuum on whichever runners are connected to it at the collector.
With a 4-1, that vacuum is spread across three other pipes, and it doesn't do much good. With a 4-2-1, though, you can transfer that vacuum into only one other pipe (at the 4-2 collectors), which means that the scavenging is much more effective. (Pairing is critical, though - if you pair them wrong, one cylinder will act on the other, but by the time the first cylinder is ready to release another charge, the vacuum effect of the second cylinder will be gone. You'll end up with varying VE per cylinder, and it's all bad from there.)
After a certain point, the pulses begin to blend and the effect goes away. Once that happens, you're blending the exhaust gases twice, which isn't as good as just blending them once, so you end up with a little power lost up top. In addition, if you have all four pipes running into the same collector, at a certain RPM (fairly high) you will end up with some of the same effect that the 4-2-1s enjoy in the midrange - as the exhaust pulses begin to pick up in speed, the pressure rises in the collector to the ideal point, and you end up with a little scavenging.
There's one small problem with all of this, though: It's all naturally aspirated theory. Virtually NONE of it translates into turbos. We are pumping all of our exhaust gases into the tiniest of orifices in order to build pressure in the manifold, which is something N/A guys strive to avoid.
What you HAVE seen before is twin-scroll - same kind of idea as a 4-2-1, but for different reasons. When you dump all 4 cylinders into the same turbo collector, the exhaust pulses begin to muddle themselves fairly early on, and you don't get the impact of each pulse acting as effectively on the turbine wheel. If you separate them into proper pairs, the pulses are more directed, and it transfers more of the energy into the turbo itself. The muddling still happens, but it happens at a much higher RPM, and by that point the turbo is wound up and ready to go. If you designed a twin-scroll housing that was the same A/R as a single-scroll housing, it would spool SIGNIFICANTLY faster. Or, you can size the turbo up and get a turbo that will make a lot more power, but still spool like a smaller unit. (The difficulty/cost of proper wastegate control on a twin-scroll setup is why it's not more popular than it is, especially on smaller/cheaper turbos. Supposedly the effect is also diminished on small turbos, but I'm not sure why that is.)
It has almost nothing to do with scavenging or exhaust velocities.
If you look at F1 cars from the 80s, you will see their turbos situated at the ends of a 3" long set of headers. Once you size the turbo to the point where you are actually seeing N/A levels of pressure pre-spool, you can lengthen the headers and get some of that scavenging effect back, or something like that. The complexities of that blend of the two is something that's a little beyond me so far.
One last thing - when I think of an idea that I haven't seen before (like you and your 4-2-1 turbo header idea), I don't immediately think that I am a "great mind" or that the idea is awesome or whatever. My modus operandi is to assume that the idea is stupid, because there are lots of smart people in the world, and if the idea was a good one, it's fairly likely that someone would have already done it. I will then do a little reading to decide whether it has any merit - sometimes it does, and sometimes I will even find the same idea executed in a different platform or at a different level of motorsport (i.e. our Inconel studs, which had never been seen in a Miata before we released them, but had been used in OEM applications, NASCAR, F1, etc. for a while). Usually, in the course of that research, I will either come to realize why the idea is stupid, or realize why it's been done differently.
It's not our job to convince you that your idea is stupid - you should be able to do that yourself. If you're posting it on here, it's your job to convince us that it's NOT stupid.
+1 on everything especially the bold part.
<3
-18psi
Last edited by 18psi; 01-15-2012 at 07:33 PM.
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01-15-2012, 03:58 PM
#51
but I'm trying to figure out why I've never seen one.
Edit: Actually I have on a pro-drag SRT-4 making like 1400 hp, so maybe there's something to this.
Some of you guys need to learn to read. I know its not really written properly but its very simple to see that he said he has seen this setup not that he has one.
Why does everyone on this forum jump to bash peoples ideas if they do not include the tried and true? He didnt say the design was better he just asked why more people dont use this design. In my opinion the only reason to even consider this design is for a twin scroll turbo which im sure is used in your friends application.
Edit: Actually I have on a pro-drag SRT-4 making like 1400 hp, so maybe there's something to this.
Some of you guys need to learn to read. I know its not really written properly but its very simple to see that he said he has seen this setup not that he has one.
Why does everyone on this forum jump to bash peoples ideas if they do not include the tried and true? He didnt say the design was better he just asked why more people dont use this design. In my opinion the only reason to even consider this design is for a twin scroll turbo which im sure is used in your friends application.
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01-15-2012, 07:32 PM
#52
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i made a much shorter version for my festiva when it was still 1.6 B6T. ran a 13.2 @112 in the 1/4 with a big 16g turbo attached to it. i blew up the 1.6 so i put a BP in my car and sold the manifold.
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01-15-2012, 09:02 PM
#54
Boost Pope
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Also, Boost Joose, if you're still around, welcome to Thunderdome.
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