2 into 2 or 2 into 1 exhaust??
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Joined: Jan 2007
Posts: 1,658
Likes: 3
From: NorNev
Best exhaust advice I've read of the forum came from "rounder" in this post.
https://www.hdforums.com/forum/7466823-post18.html
https://www.hdforums.com/forum/7466823-post18.html
Stellar HDF Member
Joined: Mar 2006
Posts: 3,124
Likes: 255
From: From Long Island, now in So. Cal
From the below dyno's
Peak Horsepower (2-2) 63.09 vs. (2-1) 79.86 = about 26.5% difference
Peak Torque.........(2-2) 74.41 vs. (2-1) 79.10 = about 06.5% difference
Not much difference in the % of "peak" torque, but a big difference in the torque curve between the two. The 2 into 1 gives a broader torque curve, and as much as 20% difference between the two in the upper RPM range.
.......
Peak Horsepower (2-2) 63.09 vs. (2-1) 79.86 = about 26.5% difference
Peak Torque.........(2-2) 74.41 vs. (2-1) 79.10 = about 06.5% difference
Not much difference in the % of "peak" torque, but a big difference in the torque curve between the two. The 2 into 1 gives a broader torque curve, and as much as 20% difference between the two in the upper RPM range.
2 to 3 hp difference, is thats a joke? 2-1 makes about 20% more HP and TQ over the 2-2 and I have the dyno graphs to prove it between two identical bikes (wifes and mine) with the same AC, Tuner, Dyno and Dyno operator (stock engine besides the AC and exhaust). 2-2 did not make more HP or tq, what it did make came on early and fell off VERY quickly! Look at the HP curve of the 2-1, its still making HP at red line while the 2-2 is flat and its torque is falling on its face.
Grand HDF Member
Joined: May 2007
Posts: 3,870
Likes: 499
From: Alberta
Personally, I prefer the "stock" look of my 2" Cycle Shacks. The sound is barely illegal, too. They dyno's are good; I've challenged the 2 shops I deal with to guarantee me a significant increase with any 2-1 and they've not taken me up on it...we did try a pair of V&H stepped drags with quiet baffles; lost 10% and had a dip at <3000rpm. Blew the packing out, too.....
Elite HDF Member
Joined: Apr 2007
Posts: 4,919
Likes: 23
From: Seattle, WA
On race engines, drag pipes or a 2-into-2 setup (true dual pipes) actually can be constructed to an optimal length that will render higher top end power, and thus higher speeds/lower elapsed times ....
That being said, the RPM ranges that these engines operate are rarely if ever reached on street bikes ... i.e., they are unusable on most everyday applications ....
What is needed on a street bike is a flat torque curve that plateaus (provides good power at low and mid-range RPMs) and matches the riding conditions faced on a daily basis. For engines designed to operate in these conditions, a 2-into-1 pipe is superior in meeting the requirements ... the exhaust pulse from one cylinder will help to evacuate the exhaust from the other cylinder (known as scavenging) increasing air flow through the cylinders and creating optimum performance on a street bike ....
So, in a nutshell, it may be true that for race applications a 2-into-2 pipe yields superior performance; but, for most of the applications encountered by forum members, the opposite would be true ... i.e., the 2-into-1 head pipe is optimal ....
* * *
Also note: the amount of difference (and where it lies on the RPM range of the torque curve) may not be noticable to many riders ... or may be acceptable to many riders ....
R/
'Chop
That being said, the RPM ranges that these engines operate are rarely if ever reached on street bikes ... i.e., they are unusable on most everyday applications ....
What is needed on a street bike is a flat torque curve that plateaus (provides good power at low and mid-range RPMs) and matches the riding conditions faced on a daily basis. For engines designed to operate in these conditions, a 2-into-1 pipe is superior in meeting the requirements ... the exhaust pulse from one cylinder will help to evacuate the exhaust from the other cylinder (known as scavenging) increasing air flow through the cylinders and creating optimum performance on a street bike ....
So, in a nutshell, it may be true that for race applications a 2-into-2 pipe yields superior performance; but, for most of the applications encountered by forum members, the opposite would be true ... i.e., the 2-into-1 head pipe is optimal ....
* * *
Also note: the amount of difference (and where it lies on the RPM range of the torque curve) may not be noticable to many riders ... or may be acceptable to many riders ....
R/
'Chop
Ultimate HDF Member
Joined: Oct 2007
Posts: 7,562
Likes: 11
From: Palm Harbor fl.
Most will say that the 2:1 will give more hp and tq. A lot of it depends on your setup and how well it is tuned. Either way, I don't think you're talking about a huge difference so you should get the system you like- how it looks and sounds will matter more to you than 2 or 3 hp. Unless you're talking about racing it.
Elite HDF Member
Joined: Apr 2007
Posts: 4,919
Likes: 23
From: Seattle, WA
Is this the 'new normal' ...? LoL
* * *
The Sep 2009 issue of American Iron Magazine Techline by Donny Peterson has an in-depth discussion of exhaust .... I found it to be an excellent article that is informative with regards to the physics and science behind the sound and muffler construction techniques and the performance aspects of pipes ....
Due to the 'stacking' of exhaust pulses and the scavenging effects, benefits and detriments accrue to different exhaust systems depending on their construction ....
Although 2-into-2 'drag pipes' work well to maximize high RPM horsepower, they are not well suited for low to mid-range torque ... which is what most riders want on their street bikes ... also, except for big-inch bikes of over 110 CID, 1-3/4" is the optimal diameter of the head pipes ....
"One exhaust system that I will state is categorically better than others is a properly tuned 2-into-1 header pipe feeding into a collector muffler of sufficient size to have at least 10 times the volume of the swept volume of the cylinders. ..."
Although I 'cherry picked' one sentence of the article, I highly recommend it ... a lot of good stuff there ....
* * *
But, bottom line is that once you make that call, you'll get used to the feel of the performance (whether it's 'optimal' or off by a few) ....
You're gonna love it ... hate it (and change it right away, if you have the resources to throw around like that) ... or feel lukewarm about it (maybe like the looks and disappointed with performance or sound), but it will grow on you ....
R/
'Chop
* * *
The Sep 2009 issue of American Iron Magazine Techline by Donny Peterson has an in-depth discussion of exhaust .... I found it to be an excellent article that is informative with regards to the physics and science behind the sound and muffler construction techniques and the performance aspects of pipes ....
Due to the 'stacking' of exhaust pulses and the scavenging effects, benefits and detriments accrue to different exhaust systems depending on their construction ....
Although 2-into-2 'drag pipes' work well to maximize high RPM horsepower, they are not well suited for low to mid-range torque ... which is what most riders want on their street bikes ... also, except for big-inch bikes of over 110 CID, 1-3/4" is the optimal diameter of the head pipes ....
"One exhaust system that I will state is categorically better than others is a properly tuned 2-into-1 header pipe feeding into a collector muffler of sufficient size to have at least 10 times the volume of the swept volume of the cylinders. ..."
Although I 'cherry picked' one sentence of the article, I highly recommend it ... a lot of good stuff there ....
* * *
But, bottom line is that once you make that call, you'll get used to the feel of the performance (whether it's 'optimal' or off by a few) ....
You're gonna love it ... hate it (and change it right away, if you have the resources to throw around like that) ... or feel lukewarm about it (maybe like the looks and disappointed with performance or sound), but it will grow on you ....
R/
'Chop
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Elite HDF Member
Joined: Apr 2009
Posts: 4,082
Likes: 11
From: Long Island, NY
True, but TQ is fun, and more TQ is even more fun. That's why power is so addictive.
If the OP is thinking about doing work to the motor, I think a good 2-1 pipe is the way to go. If he likes the looks of a 2-2 and doesn't plan on doing much work, then I'd suggest getting what he thinks looks and sounds best.
If the OP is thinking about doing work to the motor, I think a good 2-1 pipe is the way to go. If he likes the looks of a 2-2 and doesn't plan on doing much work, then I'd suggest getting what he thinks looks and sounds best.
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Sep 15, 2005 12:09 AM
