Does a 2 into 1 exhaust system increase performance

Hi all,
Does a 2 into 1 exhaust increase performance over a twin system? If, so, is at specific rpm ranges?
I believe my T160 benefits from a 3 into 1 but the Norton and Trident engine a very different to each other in their power delivery characteristics.
I guess one advantage of a single exhaust is weight saving and just less physical stuff hanging off the bike but I can’t imagine losing the centre stand off my bike ( I rarely use the side stand.
What purpose does the crossover pipe serve on the standard Commando? I put new headers on my T140V that did not have a crossover pipe (same Dunstal style mufflers) and I’m sure it’s performance picked up considerably. It is louder but I don’t think I’m mistaking decibels for horsepower.
Any thoughts appreciated.
alan

Alan L said:

What purpose does the crossover pipe serve on the standard Commando?

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It's supposed to reduce noise.

Alan L said:

Hi all,
Does a 2 into 1 exhaust increase performance over a twin system? If, so, is at specific rpm ranges?
I believe my T160 benefits from a 3 into 1 but the Norton and Trident engine a very different to each other in their power delivery characteristics.
I guess one advantage of a single exhaust is weight saving and just less physical stuff hanging off the bike but I can’t imagine losing the centre stand off my bike ( I rarely use the side stand.
What purpose does the crossover pipe serve on the standard Commando? I put new headers on my T140V that did not have a crossover pipe (same Dunstal style mufflers) and I’m sure it’s performance picked up considerably. It is louder but I don’t think I’m mistaking decibels for horsepower.
Any thoughts appreciated.
alan

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That’s an impossible question.

A correctly designed 2:1, like the Maney system, can have big benefits on a 360 degree twin, especially in the mid range but also the top end. But it depends heavily on the design of the exhaust as well as things like cams and cam timing etc.

However, I would hazard a guess that the vast majority of 2:1s marketed over the years were detrimental to performance.

Stock Norton headers with stock Norton peashooters actually work rather well on Nortons, which kinda made life hard for after market 2:1 makers !

Ask Al he knows all about 2:1, he knows everything.

Back in 1982 when I converted my 850 Commando to a Featherbed frame I got my new exhaust headers made up for the Featherbed frame from my local exhaust shop that had a mandle bender and a experienced operator, made without the balanced pipe, he made the pipes straight through to the rear where I cut them down to where I wanted my short open mufflers with very little baffles mounted, just enough to keep it quiet but open enough for performance wise.
As Nigel has said it depends on what work is done to the motor, what cam and head work has been done, restricted mufflers will affect performance no matter what system you use, my set up works very well with my cocktail shakers mufflers with very little baffles and have been using similar mufflers since 1982, the quicker my exhaust gases get out the better my Norton performs, but my motor is not stock, built for the Featherbed frame with cam and head work, mine is set up for mid range performance where my power is used the most, but my motor will rev very freely and will rev past 8000 rpm if you let it but I like to keep my motor together in one piece and know when to back off lol, ignition system, carb set up and jetted right as well exhaust system all play a part in performance, get it wrong and could make your bike slower.
My set up work very well for what I use my Norton for and I am using the same set up to this day since 1982 and the same headers that were made back then, been through a few mufflers since.

Ashley

No guarantee of improved performance by just putting a 2 into 1 exhaust on. Actually can have the opposite effect if your tuning skills aren't up to snuff. I've never used a Maney 2 into 1. I doubt he has any for a P11. lol

I replaced a good working shorty dual exhaust that I low sided on and destroyed with a Bub 2 into 1. Getting any kind of pipes in the SF bay area in California for a P11 was difficult for me in the late 1970's, so I had Bub make me one. He was a small operation at the time. The Bub pipe did not like Amals tuned for the dual exhaust very much. No top end but usable low and mid-range if I didn't want to ever ride over 60 mph. I parked it for a decade or more and rode dirt and modern bikes. I got it working in the early 1990's using Mikuni carburetors and a bunch of engine work. My experience is probably not typical for a Commando owner however. I'm still using the 2 into 1, but I made a few changes to it and my engine and carburetion is not standard Norton. No limits on where the engine works in the RPM range as long as I don't lug the engine and ride in the right gear.

The problem with my Mk2 850 is it just keeps going so my actual desire to change anything is low though another few hp would be nice to offset my middle (old) age spread
Best thing I did was put new Premium Amals on it

Are the new Premium Amals set up right for your motor, jetted right, right size piolet jet, needle setting, timing set right etc.

Alan L said:

The problem with my Mk2 850 is it just keeps going so my actual desire to change anything is low though another few hp would be nice to offset my middle (old) age spread
Best thing I did was put new Premium Amals on it

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Thoughts from an old guy that has had a Norton a long time and added noticeable HP to one: Adding significant HP to an old Norton is expensive, and a lot of work. If you enjoy spending money and doing the work, it can be rewarding. However, I'm thinking sticking with your lack of desire to change anything is a good plan. A stock 850 with new Premiers would probably be a nice ride. If it aint broke, don't fix it.

ashman said:

Are the new Premium Amals set up right for your motor, jetted right, right size piolet jet, needle setting, timing set right etc.

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I was told by Classic Bike Spares in Australia that they were set up for an 850. I stuck them on, it started first kick, idled perfectly and I haven’t touched them since. The original Amals had worn slides and I couldn’t get the idle speed below 2000rpm. The fuel consumption has improved dramatically. In brief, I paid the money and got what I paid for.

Alan L said:

I was told by Classic Bike Spares in Australia that they were set up for an 850. I stuck them on, it started first kick, idled perfectly and I haven’t touched them since. The original Amals had worn slides and I couldn’t get the idle speed below 2000rpm. The fuel consumption has improved dramatically. In brief, I paid the money and got what I paid for.

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Never mind, shit happens! Think of all of those joyful hours you could have spent setting it all up. Better luck next time.

My 74 850 @ 4,000 miles came with cross over pipes and aftermarket Dunstall mufflers. For some reason, I found a no name 2 into 1. I installed that, sans center stand and it was useless for more performance. I think it restricted performance. Currently running straight pipes into fishtails. I think they are 1 3/4 ID. I used a copper plumbing fitting to step them up and a baffle for some backpressure.

Years ago for the 96 EVO FXSTC Harley, I found a set of Patriot Defenders. 2 into 1. All stainless. They had a different feature. A flapper at the end of the muffler. My HD ran best 7/8 open, ran like shit fully closed. A great set of 2 into 1.

The usual thing which is done to improve performance is fit a hotter cam which usually has more radical timings. What usually happens with a large capacity vertical twin, is the power comes on stronger at about 4000 RPM and finishes at about 7000 RPM - A megaphone exhaust magnifies the bump in the rev range where the power comes on. A two into one exhaust system usually cuts a bit off the top of the rev range, makes the transition from almost no power to a lot, much smoother and stronger. It does not matter much what exhaust system you have on a Commando. The cam is already a race cam, and the motor is big enough and the stroke is long enough to make the power transition gentle. The low crank balance factor probably stops the motor from revving easily. With my 850 motor, I immediately raised the balance factor so the motor would rev easily. I advanced the cam timing to make the exhaust system work harder. If the exhaust valve opens earlier, what happens to the resonance in the exhaust is stronger, but the noise level increases, and if you use petrol as fuel - everything probably becomes hotter.
Some people seem to believe that more horsepower is always to go, but on both public roads and race circuits there are usually corners. Big horsepower on long straights is good, but around corners strong and gentle are better. In a corner, if you get a message from the bike, you will always back-off.
One of my previous race bike was a 500cc Triton which was made out of 650 parts. With megaphone exhausts, it was impossible to ride. A two into one pipe lowered the top of the rev range from 10,500 RPM to 9500 RPM - by changing the gearing, I could choose where I was going to lose a race. Being balked in corners was a nightmare. With high gearing I was not usually passed at the ends of straights, but I was slower in corners. I did not usually race with low gearing on that bike. A Z900 Kawasaki is not fast in corners.

I suggest that what 2 into 1 exhaust system actually does is, it makes what power your motor delivers become smoother, so more usable. If you are proceeding at 60 mph into a bend which requires braking as you enter it, the 2 into1 exhaust system helps the transition from braking to accelerating to be much safer, so in effect - you become faster. If a motorcycle is light in the front, at the transition point, it will usually send the rider a message to back-off. The two into one exhaust does the reverse of that. Two-stroke motorcycles are usually light and have neutral steering. Care must always be taken at the transition point, a better way to ride them is always very smooth in corners at fairly constant high revs. The bump in a power-band, can cause a two-stroke to swap ends. A Commando can be faster in corners. In racing where you are faster or slower can make a difference, depending on the circuit. If you come out of corners faster, you do not need so much power and acceleration when you are on the straights. On a race circuit, you do not usually get penalised for speeding.

Why the hell is Al flagged?

What does "flagged" mean and why is it applied?

MexicoMike said:

What does "flagged" mean and why is it applied?

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It means Jerry is currently approving his posts before they should show on the forum due to complaints about content.

As a 74 year old rider on a 51 year old bike the stock performance is just right. I had a few Suzuki back when I was immortal. If you need to go faster you probably can buy a used GSXR for less that the 2 into 1 exhaust.