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I was very curious why the primary runners of most 4-1 headers for h22a are really long
comparing to a tri-y design.
Is there a reason for this? I was thinking of purchasing a tri-y and using only the primary runners and make it a 4-1. Would there be any disadvantages to doing this besides wasting time and effort?
4-2-1 tri-y design
Attachment 16573
4-1 design
Attachment 16574
4-1 tend to have longer runners so that you can have a higher clearance from the ground at the bottom where the 4 runners blend into 1 outlet.
the longer runners is to make room for ground clearance?
Whilst not disagreeing with you (and other comments) traditionally the two designs were developed to achieve different ends.Quote:
Originally Posted by defect
The 4-2-1 is designed to provide sharper acceleration but lower top end speed; the 4-1 design is usually a more progressive acceleration and higher top end speed.
The 4-2-1 design would be better mated with the smaller capacity engines like the B16A whilst the 4-1 (lazier for want of a better word) design is better suited to the larger capacity engines that make typically more power up high.
Anyone disagree with this summation?
Read this article for more information: Header Dyno Testing & Comparison, Tri Y vs. 4 Into 1 - Performance By Design
If you don't want to read the whole article, here's a summary of their findings:
Dyno Data: Stock vs. Tri-Y 4-Into-1 (Horsepower)
RPM STOCK TRI-Y 4:1
4,000 84 84 85
4,500 101 101 101
5,000 115 116 114
5,500 137 138 134
6,000 150 151 150
6,500 165 167 167
7,000 181 184 185
7,200 191 193 196
7,500 194 199 202
7,700 195 201 204
8,000 191 196 198
8,500 186 192 193
Peter
I know exactly what you're saying and couldn't agree more
why does the 4-1 primary runners stick out so much before the first bend is formed
as to a 4-2-1, the primary runners are pretty short.
is there a reason they are made like this?
i think when one is deciding on what header design to buy or any modification, s/he should choose based on powerband of engine and be consistent in the decision.Quote:
Originally Posted by jdm_b16a
ie. 4-1 header design, larger TB, short length-large bore runners of intake manifold for B16A.
are they made by same company? maybe just different companies do different header design. like smsp / asp.Quote:
Originally Posted by defect
Like I said - so that you can get the appropriate runner length before they bend at the bottom = more ground clearance
the headers arent made from the same company, but if you search for H22a 4-1, there is only one sort of style, which is the one on the right
so basically, your saying, the reason they made the primary runners so long on h22a 4-1 headers is because of clearance only?
how about you the B18c 4-1s, why isn't the primary runners as long as the h22a 4-1 headers?
I'm pretty sure there's more of a reason than just clearance,
if you're making a 4-1 header, you can put a single 2.5" pipe exactly where the oil pan starts, therefore giving more ground clearance instead of 4 smaller primary pipes.
I dont know the theory of it all, I just purchased a H22a tri-y, but I only wanted to use the first piece only and change it to 4-1. Its mainly for clearance issues as the 4-1 that I just posted up earlier is too long and hits my condenser.
Attachment 16598
i think the reason there is only one sort of style is because not many people do H swaps, so plagiarism activity is low.Quote:
Originally Posted by defect
longer primaries in a 4-1 design helps bring out torque earlier in rpm band, sorta like best of both worlds of 4-2-1 and 4-1.
4-1 design + longer primaries would give better torque band everywhere, in theory. *source
i know that all this info is just from one website, so it's rather doubtful how reliable it is.
one thing that i found interesting is that dave from smsp mentioned about larger header exhaust port than head exhaust port to minimize backflow. 1mm larger than head exhaust port. this is also mentioned in Four-Stroke Performance Tuning by A.Bell.