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+--- Thread: 4 into one exhaust header design (/showthread.php?tid=4870)
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4 into one exhaust header design - LakeWylieJoe_imp - 01-08-2020
Has anyone else noticed the header pipes on the 2014 standard, equipped with a four-into-one collector system, are intentionally designed to have uneven lengths?
With a standard crank design of an inline four, a cylinder fires every 180 deg of crank rotation. The most efficient exhaust scavenging would result from headers that were equal length. The pipe for the #1 cylinder, which has the longest run to the collector on the far side of the bike is intentionally made even longer than it needs to be, with an out-of-path bend. #2 has been made longer as well.
In an equal length setup, the #3 & 4 would be bent to add a little length so as to match #1 & 2.
Any thoughts?
RE: 4 into one exhaust header design - Lord Popgun - 01-08-2020
Helmholtz resonator
Sorry, that's all I know about exhaust theory
RE: 4 into one exhaust header design - LongRanger_imp - 01-08-2020
Form, not function.
RE: 4 into one exhaust header design - Frulk_imp - 01-08-2020
I trust the engineers at Honda explicitly. I can’t imagine that they didn’t consider what the impact on performance and reliability the pipe lengths would have on their design. Based on that I’m guessing the impacts were negligible.
RE: 4 into one exhaust header design - GoldOxide_imp - 01-08-2020
If there was a noticeable issue, it would have failed at Design Verification. Maybe it did, but they addressed the issue in one or more best know methods (e.g. popgun's resonator remark).
RE: 4 into one exhaust header design - SportsterDoc - 01-08-2020
Perhaps for oil filter access?
With 0-60 in 3.3 seconds, I would not be concerned.
RE: 4 into one exhaust header design - LakeWylieJoe_imp - 01-08-2020
That's probably the reason, as engine output wasn't the chief goal with the 1100. In any event, the 4 into 1 set is vastly superior in exhaust scavenging compared to the 4 into 2 with a crossover pipe of the other CB1100 models.
RE: 4 into one exhaust header design - SportsterDoc - 01-08-2020
HP was not the prime objective, but overall performance is very pleasing.
Just before I replaced stock tires at 10,579 miles, I did a few hole shots. Above 4,000 RPM, full throttle, the rear broke loose and went a bit sideways...more than once...and the stock Dunlop was not slick...quite a bit of tread left. Hitting over 60 MPH in first gear in 3.3 seconds may not match a crotch rocket, but still a thrill.
86 HP @ 7500 RPM
65.6 ft lbs @ 5700 RPM
0-30 1.2 seconds
0-60 3.3 seconds
0-90 6.8 seconds
0-100 8.6 seconds
1/4 mile 12.11 seconds @ 109.25 MPH
RE: 4 into one exhaust header design - LongRanger_imp - 01-08-2020
Hi Doc, we've missed you. Hope you're doing well.
RE: 4 into one exhaust header design - alprider - 01-08-2020
it can be a desing-construction thing (examp. access to the oil filter)
but
an exhaust is a highly complex matter ( not just in terms of sound)!
different gas pressures or flow velocities resulting from different pipe lengths and shapes....and bringing them together in the right place , like 4into1
or why is the 4in1 considered sportier sometimes (power) ? why for what we have sometimes a "interference tube" at the exhaust, my honda VTX 1300 had it ?
well i cant find a english site...but with the online translater
https://www.motorradonline.de/zubehoer/auspuff-tuning-und-leistungsvergleich-bei-akrapovic-volles-rohr/
and I quickly found no scientific page on gas flows (speeds/pressures) in (exhaust) pipes.....