Best exhaust for a Briggs Opposed twin? (Straightpipes)

Best exhaust for an opposed twin? i thought about stacks, but i dont particularly care for those. im thinking about doing it down and out the sides, or maybe out the back, or maybe shooting it out in front of the tires, or doing both cylinders into one, shooting it out the right side, and putting a glasspack muffler with an elbow on the end to shoot the exhaust out right in front of the rear tire?

I cant decide. ive heard oppys dont like having both run into one. the pipe i have is a few sections of 3 inch automotive pipe, some bike frame pieces for the bends( 1 inch to match where it comes out of the engine i want to gradually work up from there. i have some 2 inch pipe as well)

any suggestions are greatly appreciated

Ive been told 2in is about the max.
On another forum, a discussion about using an oppy for a racing mower it was suggested and agreed upon about making a 2 into 1 exhaust would be good.

Ill be building a dual exhaust for my "craftsman thing" one of these days... Thers a couple ive seen on youtube with dual exhaust and they sound pretty mean.

For exhaust there is a rule of thumb here to follow- the exhaust port is what you base pipe size from. 1 pipe per cylinder, you need to keep the same pipe size to the end or will hurt engine performance. 2 into 1 would be, pipes off motor are same as exhaust port size, then where they come together around a 25% increase in pipe size is favorable to the end. Duels are good for high rpm where 2 into 1 is good for low end power. Exhaust systems don't care what motor you put them on, to take advantage of the exhaust system you need to follow the rules.

2 inch and 3 inch pipe would not help any and would hurt performance but would make a favorable tone.

I been building complete exhaust systems for many years for cars, trucks, mini bikes, gocarts and it's all the same.

so running 1 inch pipe all the way down, running both cylinders into this, and then maybe putting a 1.75 inch cherry bomb on the end would give me both good low end and nice tone? the smallest cherry bomb ive seen is 1.75, maybe i could find 1.5 inch and then weld it up there. that way, i keep the same pipe all the way through and just have a cherry bomb on the end

i dont need ridiculous preformance, but this opposed will be governorless and itll probably run in the neighborhood of 46 or 4700 rpm, as far up as maybe 5. ive seen these things do 6 stock, but i dont want to push it that far. i will be doing oil mods too, so that i dont burn up the upper cylinder. i know these are notorious for having upper cylinder lubrication problems

Yah, 1 inch pipe coming off cylinders to a collector that changes to 1.5 inch pipe. Any bigger would slow down the exhaust too much to not help anything. If you just have the right size pipe, then make your own cherry bomb with steel wool for packing, real easy to make.

TheGreenHornet wrote:

ive heard oppys dont like having both run into one.

I really cannot imagine who would say this, or why. a 2 into 1 system can take full advantage of exhaust scavenging, and actually improve performance. I've seen some hackjob 2-into-1 rigs that look pretty restrictive, so that may have been the issue.

so, if i hook the main pipe to the left cylinder, and for the right cylinder, run the pipe into the main one at an angle so it flows with the current of the exhaust instead of beating straight down and pushing against the other, would that work?

I've never done it myself, but I think you run them both into a collector so the exhaust pulses will help pull the other one out or something like that

AllisKidD21 wrote:

I've never done it myself, but I think you run them both into a collector so the exhaust pulses will help pull the other one out or something like that

You got the right idea.

The pipes need to run parallel with each other  so when the exhaust reaches the collector, the velocity of the exhaust creates a suction for the other pipe when it goes through the collector. The collector is it's own section in the system and needs to be coned shaped. Plus, me saying the pipe after the collector needs to be about 25% bigger then the primary pipes (pipes off the motor), will expand the exhaust gas a little and slow it down, this gives it flow direction through the pipe and help with the suction too. Ofcourse, if the motor has more cylinders, this pipe section of pipe will be bigger accordingly (secondary pipe). Then comes the muffler, then tailpipe.

A V shape where the 2 pipes come together won't have as much suction then the pipes running parallel with each other going into the collector, but if room prohibited it, then do what you need to do, shouldn't heart anything.

Great! thanks for all of your help. I will come back and reference this when i begin building my speed build (they dynamark) as it will have an oppy on it. My ranch king however, which i originally started this thread for, began experiencing issues. The oppy on it has major wear on both cylinders, the upper cylinder more specifically, and it has valve issues. both valves in the upper cylinder are terribly loose, so i am going to call it parts for my other 2 oppys, and swap a vtwin in or something. So now...does anybody have any ideas for a Briggs vanguard vtwin ohv? the exhaust ports are on the bottom, and i have headers for it. they came from a briggs intek that had the rectangle exhaust cube in the front, and both pipes curved down to it. the king has a space there, where i can run these headers and they will end up right in open space, if that makes any sense at all. If you need a better description, ill try to get pictures and illustrate what i mean

Sounds cool, can't wait to see 'er!

I want to put dual shooters out the back because right now it just shoots out the front and it way too loud i have 2 old chrome tips form uan old exhaust that i found

We got a opposed we might drop onto on of mowers.

There is a very good chance we are doing a set of WRX style uneven length headers.
(because boxer rumble is life)