header lenth
11-10-2006, 10:23 PM
#2
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RE: header lenth
I read somewhere that it should be as short as possible....but I would wait to hear from others on that. I left mine the length it was when purchased (2.5") and I really think it slowed the boat down, so I cut it just long enough to mount the tuned part to it.
11-11-2006, 08:03 PM
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RE: header lenth
It will act as a muffler, nothing more.
Tuned pipes work by the rear cone reflecting the unburnt charge back into the cylinder before the piston closes the exhaust port. Too long and the port is already closed resulting in no gain! Too short and it meets the incoming charge not allowing the proper filling of the cylinder with fresh fuel mix. It is a balancing act.
Tuned pipes work by the rear cone reflecting the unburnt charge back into the cylinder before the piston closes the exhaust port. Too long and the port is already closed resulting in no gain! Too short and it meets the incoming charge not allowing the proper filling of the cylinder with fresh fuel mix. It is a balancing act.
11-11-2006, 08:15 PM
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RE: header lenth
I've never heard it said like that. Thank you for that! That is something I can understand.
Is there a chart that tells the length in accordance with size motor? And by length we're talking about the first weld mark or crease where the expansion chamber starts correct?
One more thing, is there anything about the size of the expansion chamber? I know some are just a double cone, then some expand for a couple inches then taper down, and then again some expand and stay that large all the way to the end where it abruptly closes.
The latter is what I've heard is working best at this point.
Thanks.
Is there a chart that tells the length in accordance with size motor? And by length we're talking about the first weld mark or crease where the expansion chamber starts correct?
One more thing, is there anything about the size of the expansion chamber? I know some are just a double cone, then some expand for a couple inches then taper down, and then again some expand and stay that large all the way to the end where it abruptly closes.
The latter is what I've heard is working best at this point.
Thanks.
11-11-2006, 08:37 PM
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RE: header lenth
Length, volume, engine size, RPM range and exhaust temp all factor in. Different people measure length differently but basically if you measure to the start of the rear cone the placement is ussually within 1" of each other. Most of the pipes on the market are of similar diameter and rear cone angle. If you look at a Hanson RPM pipe (no band) and a MidWest 2" band pipe both will tune with the rear cone at the same length. So the 2" band pipe will need a 2" shorter header! The rear cone determines the the tuned length, front cone is just a funnel.
The odd one out is Cooper pipes, they are smaller diameter and shorter cone angles, the will tune shorter and the length is critical for best performance.
The odd one out is Cooper pipes, they are smaller diameter and shorter cone angles, the will tune shorter and the length is critical for best performance.
