Torque.......2 into 1 or 2 seperate pipes?

[Pacman]

Another question.......I'm going to be using a Honda VTR1000 *V-twin ........... stock it has 2 mufflers.... the header pipe comes off the 2 cylinders and joins under the engine and then splits off into 2 separate pipes going up each side of the rear of the bike.
For the best torque from this engine should I run 2 mufflers..... or reconfigure the header and run only one? My plan is to run Supertrapp style mufflers so * torque can be messed with somewhat by changing the number of disc's.......So what's everyone's opinion! *

[Bugpac]

the more back pressure the more torque....Not sure on that motor, but on the gixxers torque is hard to find, so you got to do all you can to get it....I probbaly would suggest sticking to factory configurations....But then again, i have a hard time doing what i should, compared to what i think...

[rxpo]

Get Doug Heims opinion on the exhaust. *He is running a RC51 (1000cc V) with dual pipes and trick mufflers. *This thing is a beast. *You should hear it roar even a 1/4 mile away. *Damn thing almost popped my eyeballs out when he started it. *

I don't know if the performance would be degraded much if he went to a 2 into 1, all I know is this thing is a earth shredder in all gears.

[Pacman]

Stock engine is 68 - 78 ft/lbs. @ 7000 RPM......depends on which web site you look at!

[s_c_engineering]

i personally ride one of these bikes, id stick with two pipes unless your gonna step up the single exhaust in size. it has tons of torque and pulls all the way from idle. *if you go smaller than the exhaust already is your gonna loose top end. *and yes this is one of the gnarliest sounding engines there is imo. *you will definately enjoy it and will have the "v8" of minibuggies.

[bdkw1]

The reason the bikes have 2 mufflers is noise control versus space. A 2 into 1 with a properly sized muffler will give the best results.

[yoshi]

There's a myth (that I too use to believe) that engines need backpressure to make more torque. This is incorrect. Backpressure is resistance when you really want the least resistance possible....




1 of many things I found on the net when doing a search:

"Destroying a myth.

Some say that "an engine needs backpressure to work correctly." Is this true?

No. It would be more correct to say, "a perfectly stock engine that cannot adjust its fuel delivery needs backpressure to work correctly." This idea is a myth. As with all myths, however, there is a hint of fact with this one. Particularly, some people equate backpressure with torque, and others fear that too little backpressure will lead to valve burning.

The first reason why people say "backpressure is good" is because they believe that increased backpressure by itself will increase torque, particularly with a stock exhaust manifold. Granted, some stock manifolds act somewhat like performance headers at low RPM, but these manifolds will exhibit poor performance at higher RPM. This, however does not automatically lead to the conclusion that backpressure produces more torque. The increase in torque is not due to backpressure, but to the effects of changes in fuel/air mixture, which will be described in more detail below.

The other reason why people say "backpressure is good" is because they hear that cars (or motorcycles) that have had performance exhaust work done to them would then go on to burn exhaust valves. Now, it is true that such valve burning has occurred as a result of the exhaust mods, but it isn't due merely to a lack of backpressure.

The internal combustion engine is a complex, dynamic collection of different systems working together to convert the stored power in gasoline into mechanical energy to push a car down the road. Anytime one of these systems are modified, that mod will also indirectly affect the other systems, as well.

Now, valve burning occurs as a result of a very lean-burning engine. In order to achieve a theoretical optimal combustion, an engine needs 14.7 parts of oxygen by mass to 1 part of gasoline (again, by mass). This is referred to as a stochiometric (chemically correct) mixture, and is commonly referred to as a 14.7:1 mix. If an engine burns with less oxygen present (13:1, 12:1, etc...), it is said to run rich. Conversely, if the engine runs with more oxygen present (16:1, 17:1, etc...), it is said to run lean. Today's engines are designed to run at 14.7:1 for normally cruising, with rich mixtures on acceleration or warm-up, and lean mixtures while decelerating.

Getting back to the discussion, the reason that exhaust valves burn is because the engine is burning lean. Normal engines will tolerate lean burning for a little bit, but not for sustained periods of time. The reason why the engine is burning lean to begin with is that the reduction in backpressure is causing more air to be drawn into the combustion chamber than before. Earlier cars (and motorcycles) with carburetion often could not adjust because of the way that backpressure caused air to flow backwards through the carburetor after the air already got loaded down with fuel, and caused the air to receive a second load of fuel. While a bad design, it was nonetheless used in a lot of vehicles. Once these vehicles received performance mods that reduced backpressure, they no longer had that double-loading effect, and then tended to burn valves because of the resulting over-lean condition. This, incidentally, also provides a basis for the "torque increase" seen if backpressure is maintained. As the fuel/air mixture becomes leaner, the resultant combustion will produce progressively less and less of the force needed to produce torque.

Modern BMWs don't have to worry about the effects described above, because the DME (car's computer) that controls the engine will detect that the engine is burning leaner than before, and will adjust fuel injection to compensate. So, in effect, reducing backpressure really does two good things: The engine can use work otherwise spent pushing exhaust gas out the tailpipe to propel the car forward, and the engine breathes better. Of course, the DME's ability to adjust fuel injection is limited by the physical parameters of the injection system (such as injector maximum flow rate and fuel system pressure), but with exhaust backpressure reduction, these limits won't be reached.

- Adapted from Thomas V. "

[Bugpac]

I would say on a v-8 car with 500lbs of torque back pressure would not matter, for us with minimal torque and trying to find every bit we can, a wide open exhaust is not the key...IMO...

[yoshi]

Originally Posted by Bugpac\";p=\&quot

I would say on a v-8 car with 500lbs of torque back pressure would not matter, for us with minimal torque and trying to find every bit we can, a wide open exhaust is not the key...IMO...

Wide open is not correct either.

Another quote from a physics guy..


Here is bernoullis law of flow fluid dynamics...
Bigger diameter=higher pressure, smaller velocity.
Smaller diameter=smaller pressure, higher velocity.
Bernoulli's principle 101!

This same principle applies with our GA16s exhaust flow.
We have to find a piping that balances the pressure as well as the velocity of the exhause gas. *If the pressure and the velocity is not balance correctly then we get a bad flow of exhaust gas.

Now as you guys all know. *Air always wants to go from the high pressure to low pressure. *So we have to make the exhaust air "want" *to flow out of the car to the low pressure area.

Now a bigger diameter piping would do this...BUT! Hell the velocity in that thing is slow! *The air would reach there eventually but at a slower rate. *Think of a house hose, make it *a very big diameter now. *What happens? *The water in the hose will come out a lot slower! *And if you held it out to water the plants, the water would most likely *drop on your foot instead

A smaller diameter piping creates faster velocity in fluid flow as well as lower pressure...BUT!!! *The pressure in it would be extremely small. *This means that the Force/Area of the air flow would be small, meaning the acceleration(not velocity) of the gas would be slow! *This makes sense, because gas would want to leave a low pressure zone slower than a high pressure zone! *Also, if you decrease the diameter of the piping, it would be like your car breathing through a straw!

Ok so for the exact diameter of the piping we need something that balances the pressure of the exhaust gas as well as the velocity of flow of the exhaust gas! *We need a correct diameter that balances out both! *This is why you can't have a too big diameter piping or a too small diameter piping!

[Bugpac]

Ok so backpressure is not always the answer, and is not always the bad guy either...I will agree 100% it depends on the specific motor at hand...

http://www.bigcitythunder.com/pages/und ... xhaust.pdf

My stock gsxr 600 can not adjust its own air/fuel mixture, so i chose to run a supertrap, the power band seems lower than stock with the increased back pressure, i can adjust the disks to compensate...

http://www.bigcitythunder.com/pages/und ... xhaust.pdf