Exhaust manifold cylinder pairing
12-31-2008, 12:26 PM
#1
Honda-Tech Member
Thread Starter
Exhaust manifold cylinder pairing
i have noticed the short tube tri-y headers normally pair cylinders 1 and 4 together, and the long tube versions pair cylinders 1 and 2 together.
what are the performance benefits of pairing the cylinders one way vs. the other?
what are the performance benefits of pairing the cylinders one way vs. the other?
01-02-2009, 10:18 AM
#3
FSAE
Re: Exhaust manifold cylinder pairing
Our Honda 4 cyliners have a fire order of 1-3-4-2, so for the complete cycle of all four cylinders firing, it looks like 180*-180*-180*-180*.
Therefore, a exhaust pairing of 1 & 4 would have equal 360* combustion separation. This separation is ideal for exhaust scavenging, as cylinder 4 will have an equal pull of exhaust gasses from the exhaust stroke of cylinder 1, and cylinder 1 will have an equal pull of exhaust gasses from the exhaust stroke of cylinder 4. The same is true for cylinders 2 & 3.
A 1 & 2 pairing would have 180* and 540*, which would yield a single strong exhaust scavenging effect from cylinder 1 on cylinder 2. But the combustion event from cylinder 2 will have no scavenging effect on cylinder 1.
How does this effect manifold design? Well that is where the black art comes into play. Basic theory would tell you the 2-1 merge collector would need to be bigger with a 180* and 540* pairing due to the one large scavenging event. The 2-1 merge for 360* pairing could be smaller to allow for the same volume of exhaust gases to pass at an given point in the engine cycle. There are many other physical characteristics that affect scavenging timing, like the size and number of steps in the primary exhaust tube, length of primary exhaust tube, length of secondary tube... Some others
Therefore, a exhaust pairing of 1 & 4 would have equal 360* combustion separation. This separation is ideal for exhaust scavenging, as cylinder 4 will have an equal pull of exhaust gasses from the exhaust stroke of cylinder 1, and cylinder 1 will have an equal pull of exhaust gasses from the exhaust stroke of cylinder 4. The same is true for cylinders 2 & 3.
A 1 & 2 pairing would have 180* and 540*, which would yield a single strong exhaust scavenging effect from cylinder 1 on cylinder 2. But the combustion event from cylinder 2 will have no scavenging effect on cylinder 1.
How does this effect manifold design? Well that is where the black art comes into play. Basic theory would tell you the 2-1 merge collector would need to be bigger with a 180* and 540* pairing due to the one large scavenging event. The 2-1 merge for 360* pairing could be smaller to allow for the same volume of exhaust gases to pass at an given point in the engine cycle. There are many other physical characteristics that affect scavenging timing, like the size and number of steps in the primary exhaust tube, length of primary exhaust tube, length of secondary tube... Some others
01-02-2009, 11:43 AM
#4
Honda-Tech Member
Thread Starter
Re: Exhaust manifold cylinder pairing
sounds like a solid theory
would the scaveging effect be more important on a short tube design w/ less primary length before the merge vs a long tube design with more primary length before the merge?
i have heard that a long tube design is a must when making 280+ whp, but the long tube designs i have seen pair cylinders 1/2 together.
would the size of the motor come into play when determining what the best cylinder pairing would be?
would the scaveging effect be more important on a short tube design w/ less primary length before the merge vs a long tube design with more primary length before the merge?
i have heard that a long tube design is a must when making 280+ whp, but the long tube designs i have seen pair cylinders 1/2 together.
would the size of the motor come into play when determining what the best cylinder pairing would be?
03-02-2009, 05:09 AM
#6
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Re: Exhaust manifold cylinder pairing
well on a h22 im going to be doing dyno desting
a camp1320 header it is a 1/2 pair up,, runners small ond long
vs
a hytech style tri-y 4-1 pair up,,, shorter runners and fatter
this test is going to be done on a 12.0.1 motor ported head,euro r im,70 mil tb, stage 2 cams ect....
a camp1320 header it is a 1/2 pair up,, runners small ond long
vs
a hytech style tri-y 4-1 pair up,,, shorter runners and fatter
this test is going to be done on a 12.0.1 motor ported head,euro r im,70 mil tb, stage 2 cams ect....
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