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Revisting what seems to be an old 2-1 controvery

Old 04-24-2015, 10:20 AM
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Revisting what seems to be an old 2-1 controvery

So...I want to start off by saying in no way shape or form am I a Honda Engineer.

Here's what I've gathered thus far through my investigations.

Concerns :

Reduced back pressure causes a drop in Torque.
Piping Size may not be big enough when going to a single outlet
The "flow diverter" in the pipe is necessary for back pressure.


So my thoughts on the situations are as follows.

If you were to have a new collector installed that removes the left u bend using the same size piping as stock with a single D&D slip on (which is what I have) would you not be creating a close to adequate amount of back pressure without the use of the u bend and second can?

If the back pressure is the concern then using a stock sized pipe at the collector to goto the single pipe would give you some of that back correct?
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Old 04-24-2015, 12:49 PM
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You can try, many have though I have never seen acceptable results.
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Old 04-24-2015, 12:52 PM
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I just can't see how there is that much pressure loss when many of the slip on cans are straight through setups...It's not like you're removing a catalytic convertor or anything.
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Old 04-24-2015, 01:04 PM
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Its no
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Old 04-24-2015, 01:05 PM
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Its no what?
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Old 04-24-2015, 01:11 PM
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Lol sorry my phone fucked up

Its not just back pressure, pulse timing and scavaging play a huge part in exhaust performance...
The honda engeneers didnt get it wrong in this department.
Can it be improved, yes... 2-1? Maybe, but youd need a dyno gas analyzer and a whole lot of scrap pipe and welding skills to figure it out
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Old 04-24-2015, 01:14 PM
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They made it 2 into 2 for a reason.

Use Vulcan logic Captain & the KISS theory - shouldn't fail U now...
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Old 04-24-2015, 01:14 PM
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LOL all good.

Well i bought a spare header pipe and just so have an uncle and dad who are welders for a living.

I mean you do always apply the standard "the more air you let out the more you have to let in"

But all the research i've done in regards to setups people have done in the past they all claim the back pressure is the main concern.

I am in need of gaining much knowledge in the jetting and carb adjust area so I may end up taking it somewhere after getting the exhaust mod done to have it tuned and see what they think.
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Old 04-24-2015, 01:17 PM
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Originally Posted by nnjhawk02 View Post
They made it 2 into 2 for a reason.

Use Vulcan logic Captain & the KISS theory - shouldn't fail U now...
See the thing is its 2 to 1 to 2.

And the loop in the exhaust I believe was put there to equal out the exhaust flow correct?

So what happens to the flow if you remove the loop and go to a single exit?

I am by no means an expert or nor do i claim to know anything about it.

Just trying to utilize simplistic knowledge of exhaust and its operation to maybe justify removing the left can LOL
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Old 04-24-2015, 08:50 PM
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I made w 2-1 a few years back , it worked to a degree , gave better too end power but lost out at the bottom ,it also moved the the torque/bhp cross over 1000 rpm higher .
The only real advantage for doing it is weight saving and **** the locals off as its much louder
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Old 04-25-2015, 12:48 AM
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Originally Posted by bewsted View Post

I am in need of gaining much knowledge in the jetting and carb adjust area so I may end up taking it somewhere after getting the exhaust mod done to have it tuned and see what they think.
Sounds like an expensive way of trying to solve a problem that really doesn't exist on a bike that's not really worth that much. Hope you have an expert tuner in your area who a) wants to even be bothered messing with it and b) who is actually good at this sort of thing considering most sportbikes went to fuel injection 15-20 years ago. I'd imagine taking it to any dealer will be a complete and total waste of your hard earned money. For example a GM dealer (or most any other shop) pretty much has no interest in working on say any 90's car with regards to tuning or electronics nor do most any of them have the knowledge or equipment to do it. Nevermind tuning a quadrajet or messing with ignition points... And did you ever wonder why most every big v-twin sportbike from this era came with dual mufflers? I can't imagine it was just for looks. All the AMA and World Superbike RC51's all had dual mufflers too after a short try at 2:1 which they obviously found wasn't the way to go. Again it just seems like a really expensive and frustrating way to shed a few pounds off the bike, especially considering you'll be relying on someone else to "get it right" for you. Don't see it as much of a "controver(s)y" I think the consensus is it's a huge p.i.t.a. that requires someone with alot of tuning knowledge and proper equipment and time to sit around and trial and error the exhaust design and also the carb tuning. Best of luck if you're bent of doing it...

Last edited by captainchaos; 04-25-2015 at 01:03 AM.
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Old 04-25-2015, 12:55 AM
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--------------------------------------------------------------------------------

Quoted from Rogue on RC51forums.com

The 2-1 exhaust fad

I disagree with the entire premise of this more midrange power with a 2-1
update: the dyno charts are proving me right...

I have seen many 2-1 systems yield better topend hp & weaken the mid-range like on the Erion Superhawk & numerous Hawk GT systems. That's not to say that with enough piping & tubing you could get just about any result ya want, but it will most likely be a point of diminishing return as the overall power output will most likely be significantly lower (if you were to purposely build an exhaust just to prove a point)

I firmly believe that on the HRC Superbikes that the extra length of piping is taking the jerk out of the mid-range making it a less powerful hit of power & thus more useable, but not "more" mid-range power. Along with that I suppose that top-end may be suffering some, but with 190hp on tap I guess you could stand to lose a couple here or there.

Either way I think alot of people are going to be dissapointed when the final product comes around & it doesn't give you this miraculous mid-range power gain that you have all been dreaming about.

Several manufacturers are currently working on 2-1 exhaust for the RC51, once some of them are on the open market & we can test them then I may need to revise this page, but until I am proven wrong I will stick to what I learned over the years.

Update 06/05/02: The Erion 2-1 full exhaust on the 02 bike is producing dismal power curves even worse than stock & has several issues with overheating the motor as well as scorching the single cannister.

Update 07/18/02:dyno charts of the Erion 2-1 with a terrible mid-range dip

Jardine has admitted that they are having problems with the mid-range with their 2-1 system & Arrow is being very tight lipped about their 2-1 after having made a big showing of the prototype many months ago which to me is most likely indicative of their failed attempts or at least performance issues stemming from the design.

UPDATE: Jardine has released their 2-1 full system & the performance numbers aren't bad, nothing spectacular, but no major drops in performance either. A few owners have commented that it leaves a flat spot in the mid-range, but overall with a price tag of $499 it sounds like a pretty good deal for those that want more performance than stock, less weight (credible reports have it at a whopping 19lbs of weight savings & a price tag of $390) & something fairly unique dyno chart for Jardine 2-1 another dyno chart for Jardine 2-1 supplied by an actual owner (the mid-range dip is pretty severe on this one). There have also been numerous issues of the welded tab breaking off on them as seen here 2-1 Jardine broke.
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Old 04-25-2015, 12:59 AM
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If companies who win championships and build exhausts for a living like Erion and Jardine couldn't get it right...
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Old 04-27-2015, 12:23 PM
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Well i have a spare header to screw with....Or will soon...
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Old 08-12-2015, 05:30 AM
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Are you tuning for every last smidgen of horse power? Have you looked at the collector on the stock exhaust? Not optimal. The so called 2 to 2 exhaust is really 2 to 1 to 2. Simply for aesthetics. Exhaust lay out is just packaging the engineers had to deal with. Anything power wise you may lose in going to a 2 to 1 configuration you'll probably make up for in weight loss.
Remember, exhaust tuning is scavenging as much combustion by-productout of the cylinder as possible before the intake charge so as to not pollute it.
I'm going to a 2 to 1 system and I'm not going to concern myself with backpressure as I am head pipe be as close to equal as possible and the collector to make as much use of pulse timing as I can.
Remember why exhaust wrap came about? It was designed to keep heat in strategic areas of the exhaust to keep velocity up to increase scavenging. That's the opposite of backpressure.
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Old 08-12-2015, 10:40 AM
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Originally Posted by ratchetman View Post
Are you tuning for every last smidgen of horse power? Have you looked at the collector on the stock exhaust? Not optimal. The so called 2 to 2 exhaust is really 2 to 1 to 2. Simply for aesthetics. Exhaust lay out is just packaging the engineers had to deal with. Anything power wise you may lose in going to a 2 to 1 configuration you'll probably make up for in weight loss.
Remember, exhaust tuning is scavenging as much combustion by-productout of the cylinder as possible before the intake charge so as to not pollute it.
I'm going to a 2 to 1 system and I'm not going to concern myself with backpressure as I am head pipe be as close to equal as possible and the collector to make as much use of pulse timing as I can.
Remember why exhaust wrap came about? It was designed to keep heat in strategic areas of the exhaust to keep velocity up to increase scavenging. That's the opposite of backpressure.
The Superhawk's header is not a 2-1-2 simply for aesthetics as you say. It's designed this way for a reason. Here's s a quote from 8541Hawk:
Then lets look at the stock header. Yes it has "merge collectors" ...and also has multiple bends in the rear primary to "trick" the system into thinking the primaries are approx. the same length.

We then come to the part that most folks get wrong. when the pipe splits back into 2 the normal comment is "look at that restriction" Honda left in the pipe. What is really going on is that "restriction" is tricking the exhaust into thinking it is single sided at low RPM (that is why the right pipe stays cool at idle) and then as the RPMs (and exhaust pressure) rise it then flows as a dual exhaust system.

So what I see on most single sided set ups is that the left pipe is removed.
Now IMHO that is the side that should be seeing the exhaust pressure at low RPM. Routing the gases to the right side has now shortened the exhaust system. Without re-timing the cams you will loose power (the same way adding high mounts loose 1-2hp by making the exhaust system longer). Then at high RPMs you will have an increase in back pressure, which, ...is not good for power.

While the mod can work for some folks, IMHO it is not the "Hot Set Up" and has limited applications.
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Old 08-12-2015, 11:24 AM
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Honda engineers are amazing. That's all i'm gonna say...

James
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