What is the difference between a Dual Exhaust vs a 2 Into 1 system in relation to why a 2 into 1 provides more power?
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When looking at Dual Exhaust vs a 2 Into 1, it really depends on how you define power. A lot of information available boasts peak power numbers, these numbers are usually at an RPM range that most bikes rarely see. To really understand how a system performs you need to look at a Dyno graph all the way through the RPM range.
There are a lot of factors that affect where a pipe makes power. Engine size, compression, cam timing, cam overlap, valve size, and intake size are all part of the equation. The biggest factor to consider is at what RPM range the bike will be ridden at consistently. The fact is that pipes designed for race bikes, which are ridden in a very narrow high RPM band, will not perform on a street bike. A general statement that can be made is; longer smaller diameter pipes make low-end power and shorter large diameter pipes make top end power.
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One other design constraint to remember is styling. Everybody has his or her own opinion on what’s going to look good on his or her motorcycle. Drag pipes just wouldn’t be drag pipes if there was a collector stuck on the end of them. With all of this in mind, there are a couple of fundamental differences between 2:2 and 2:1 exhausts when it comes to design. The advantage of a 2:2 is that the pipes are separate so the length can be fine tuned for a specific power band. You can also tune each pipe length per cylinder if necessary.
Also, you have far more styling latitude. The disadvantage is that the power band is narrower. The advantage of a 2:1 is that you tie the cylinders together giving you the ability to take advantage of the natural scavenging affect that occurs between the cylinders during the intake and exhaust valve cycles. This tends to give you a far broader power band and greater overall performance.
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The short and sweet of it. Nice comparison and explanation. I often wonder how many people just buy a set of pipes because they look cool, but are in fact lowering the performance of their bike for the type of bike they have or riding they do. Sort of like the ricers adding a fart can to the back of their Civic.
You did say most people don’t ride their bikes in the RPM that certain pipes are made for. But have you looked at the Victory line up? All of their engines are pretty much the same. However, if you look at their cruiser line up, they have 5 with the exact engine/exhaust. However, for their Hammer S can be fitted with a 2 into one “performance/racing” exhaust. I wonder how it looks on the dino?
I just bought my first Harley this month, got a 12 road king, it has after market pipes, it has the 2 into 1, that I didn’t realize since it has the pipe on the other side two, but it’s blocked, had some on telling me I needed to open that other pipe for better sound and more power but after that article I would saw they are wrong… If I understood it correctly
I just wanted to thank you, you guidance helped me a lot. I just installed V&H 2 into 2 Bid Radius on my 2015 Harley Breakout. Although you don’t have a video on this, your V&H Big Shots install was almost mirror image of what I needed to do. The whole job took me less than 2 hours, all because I followed your instructions. thanks again and keep those videos coming!!
I recently bought a slightly used FXDL Dyna Low Rider. The model came stock with 2 into 2 and this one has just has slip-ons added, stock air box and carbs. I do own a 2 into 1 Samson that will fit. Should I fit it?
Not sure what year FXDL you have. You will have to determine if the exhaust is made for your year & model. http://www.fixmyhog.com/posts/harley-tips/
It’s a 2001. I know it will fit. What I’m asking is whether or not I should mount it. In other words, will a 2 into 1 out perform the stock 2 into 2 (with slip-ons) set up a low rider comes with? It’s a 2001 carburated, no cat exhaust.
Hi, Jay. Best to check with manufacture on expected gains.
You will need to increase air flow and re-jet your carb.
http://www.fixmyhog.com/video/fix-my-hog-reviews-cobra-exhaust-and-more-008361/
http://www.fixmyhog.com/videos/carburetor-rebuild/
http://www.fixmyhog.com/video/performance-carburetor-kit-001427/
http://www.fixmyhog.com/video/custom-21-exhaust-installation-001429/
Also, a correctly tuned set up with a 2 into one will typically out perform a 2 into 2.
We have had better/more success with 2 into 1. Especially Supertrapp.
http://www.fixmyhog.com/posts/harley-tips/
Good article. My ’79 Electra Glide FLH King of the Highway had
true dual exhaust when I got her. Some other mods as well
NOTHING sounds like a well tuned Shovelhead!
I bought D&D 2:1 earlier this year. I love the sound and performance. But man, the ride ability is seriously effected. I cannot lean to the right like I used to without scraping. I’m afraid to push it too far because I have done the bounce, slide and roll sufficiently to suit my needs for some time over the last 30 years. Is anyone else having this problem? Any suggestions on how to address it? Other than putting the dual pipes back on it.
Thanks!
Hi, Newt. We would be happy to assist you; we just need some more information. What is the year and model of your motorcycle?
Thanks for the article! I have a big problem with finding a 2 into 1 that will fit my needs with my 05 deluxe. I sent motor out to bump it up to a 98 and would like to get the most out of it (hence the 2 into 1)…problem is my deluxe is now set up with 4″ stretch bags w cutouts that worked great with my 36″ long true duel fishtails….Not so great for finding a 2 into 1 that is designed for a softail, dumps out before the bags, and still gives me what I am looking for with performance. Can anyone PLEASE give me some help?!?!?
Hi, Matt. You may have to choose- form or function. Our favorite 2 into 1 would be a Supertrapp exhaust.
https://www.fixmyhog.com/post/videos-harley/
Great article.Just one question tho’. Does it make a difference where the join is on a 2:1, with the length of pipe from the head to the join?
Hi Simon. Even small, subtle, exhaust changes will alter the power band when viewed on a Dynomometer graph.
Supertrapp offers the most tunable 2 into 1 exhaust systems.
https://www.fixmyhog.com/videos/electrical/
Does it make any sense to try to create a 2:1 exhaust system by blocking one side of the stock header after the crossover tube. Using slip ons, of course.
Hello Richard,
You will not benefit from that modification. The end result will not have the same flow or back pressure as an engineered 2 into 1 assembly.
https://www.fixmyhog.com/post/videos-harley/
Thanks,
Mark FMH Video Membership
I have short shots on a 2017 Street Bob. I like the sound of the pipes but the performance is terrible.
ok how about a 2 to 1 to 2? BSL makes this pipe im looking at from their outline series, i like the look but i have not found anything quite like this out there yet.
On a Milwaukee 8 is there really a substantial low end torque difference between a good crossover header, say like the RCX Tormentor vs a 2 into 1 exhaust system?
I have the new fat bob and went ahead and put the big swipe I think V and H 0n it. before doing my home work. I have the 114 with cam a low torch red shift. I went with the screaming eagle something big flow air filter all I been told to go 2 into 1 for this particular Milwaukee 8 motor on my bike. I love the V n H stainless pipe they make for it. but it is quite different then lets say the DnD and the bossonni I think I spelt that wrong anyway im looking for more power bc 120lbs of torch just isnt enough. lol. overall I LOVE THIS BIKE. I can dump this thing into a corner like a metric bike. I can. I can keep up with most of those boys. but I gotta say I love it. Altho no front fairing is getting old. im ginghams to try to fit the new sport glide faring on her. I think I can modify it enough to make it look natural. will see. thanks for listening