2017: Revisiting 4:2:1 vs 4:1 headers w merge collectors in the modern era

[ptuomov]

Great looking headers!

And look at all that torque from the y-pipe into a single.

[hoffman900]

Calvin does incredible work.

FYI, he uses tubes that size, Y and all on 600+bhp road race engines. It’ll sound incredible as well.

[ptuomov]

Burns wanted stepped 1-5/8 @18" to 1-3/4" @ 18" 4 into 1s with 3" outlet merge collector into single 4" tailpipe,
Engine is gonna hit the dyno with the Elston exhaust soon from 2000-6000rpm and then a chassis dyno, for comparative research

Any update with results?

[54chevkiwi]

Actually no.....
Right before christmas that year my wife at the time dropped the divorce bombshell on me, so, with everything that went along with that, i no longer had the money, and couldnt even stand looking at the car for 2 years...

Only update is i got the engine fired up in the car with that exhaust like september last year, sold that engine in november that year, now im working on a tunnel rammed 421 for the car... i still have this exhaust system but it wont work with the new engine.. it needs 1-3/4 to 1-7/8 primaries, 2.125 secondaries, 30-32” length.

Im in a better spot now so ill likely do this type of test with the 421 for shits n giggles, engines almost finished..
There are two dynos in town and one guys a year out and ones 5 months out, so its gonna take alot of waiting time, everyones super busy nowadays..

I do have some youtube vids of the engine before i sold it so i at least got to hear it... it sounded gooooood, real deep and full, and crisp. really hit you in the chest in person,

[ptuomov]

What I tried in the sim was instead of going from 48mm ID to 60mm ID on the last step
I had a cone that went from 48 ID to 60ID over 375mm:s.
That was better everywhere according to the sim and since my exhaust is modular
I can easily change the last collector to see if it works in the real world to.

Did it work in real world?

[MadBill]

I'm sure there are others (also two strokes of course) but an example of tapered primaries is the Britten 1,000 cc V-twin race bike. The taper is most evident in the last pic here: https://www.carthrottle.com/post/why-th ... ever-made/