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Discussion Starter · #1 ·
I see lots of V-Twin motors running short, seperate dump pipes, and some inline twos running them as well. I was wondering if there's much of a performance difference between running a split exhaust or a joined exhaust on an inline two cylinder four stroke motor?

(I know exhaust system design is ultra critical on a two-stroke engine....but is it a big deal on four strokers?)

My old Honda "350" chop ran a two-into-one header and was a real beast for it's size. A few guys told me that the header was a BIG part of the reason that the old Honda ran so good.

(Doing a Trumpy now...and I wondered if it should get a header, or if two kinda short "dump tubes" would work out okay without hurting the power output much?)

It's a long way from needing pipes, but I'm trying to get the overall design nailed down in some crude sketches before I get into cutting and stuff!

What's the word on two cylinder exhaust systems for street warriors???
 

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No dyno experience to back it up, but I had a Beezer Lightning, a couple Triumphs, and a Norton 750 Atlas and had different pipes on them all at different times. The Norton liked longer, smaller diameter pipes. The Beezer and Triumphs seemed to like shorter open pipes. Carbureted old iron-head Sportsters and Big Twins seem to like short open pipes, can't say about Evo's. I had a 2-into-1 setup on a Sportster and it really didn't like it. All depends on the tune, I'm sure. All these bikes were running on the rich side but back then mileage wasn't a concern.
 

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Discussion Starter · #3 ·
Thanks for the insight, DosTrumps...I was wanting to run two short "dump pipes", but didn't know if that would kill the motor's pull off the line or not.
 

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Ive got drags on my 750 Bonnie and it gets it like a raped ape off the line , I am soon to be adding a 2into 1 using the drag pipes mated to a 2into 1 "muffler" Hope it works ok
 

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Busted Knuckles said:
Ive got drags on my 750 Bonnie and it gets it like a raped ape off the line , I am soon to be adding a 2into 1 using the drag pipes mated to a 2into 1 "muffler" Hope it works ok
Personal opinion, I don't like to run 2-into-1 on a twin the size of a Trump. The pulses are much stronger than a 4-cyl 750, and I think you can get interference from one cylinder to the other at certain RPM's, unless the lengths are just right (like a true header). That seemed to be the trouble with my Sportster's 2-into-1, which was clearly not an equal length set-up for both cylinders. Sportsters have some queer fuel-ratio zones anyway, because of their firing pattern, and it seemed to really make that worse in the 3,000 to 4,000 RPM range, a huge flat-spot.

If you look at the factory pipes on Triumphs, they had a crossover right near the head, never down under the bike. But if you are connecting only at the muffler, it might not have any "tuning effect" being so far from the engine (which I mean would be a good thing).
 

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DosTrumps said:
.

If you look at the factory pipes on Triumphs, they had a crossover right near the head, never down under the bike.
I believe that balance pipe was used in an attempt to dampen a particularly loud and annoying,"pulse" that occured in certain RPM ranges. Stahl Engineering used a similar setup on their 180 degree headers(as did Chrysler on their Hemis)back in the mid to late 60's.It had something to do with the velocity of the pulse(or shock wave)traveling back and forth in the pipes if I remember correctly.
 

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I run a two into one Exhaust on my V twin motor. Tuned length no sharp angles. It runs very very good. It all really depends on the motor type. Some pipes work better on particular motors. My 750 commando had dual upswepts and was faster then hell.
 
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