Resonator Sizes

[rorn]

I have an Apexi Dunk Catback with 60mm piping and the Jackson Racing Supercharger on my 98 Prelude.

I need a new resonator but I cant find anyone who carries the Ractive 60mm (2.36inch)resonator. I called Carline and they said they only carry 2.25 or 2.5 inch resonators.

Should I get a resonator that is too big or too small?

I was told that a supercharger does require some back pressure. But I also heard that a larger diameter area will cause a low pressure zone and cause exhaust gases to slow down.

What do you guys think?

Rorn

[youngbex]

LOLOLOLOLOLOLOLOLOLOLOLOLOLOLOLOL


what fucking idiot said that a supercharger need exhaust back pressure, it has nothing to do with exhaust at all it is belt driven

[RickDaTuner]

any car that runs Forced induction will benefit more from a free flowing exhaust, really if i were you i would be going for a 3" catback rather than a 2.36" exhaust wich would benefit a N/A


everyone needs to disspell the whole Exhaust gass back pressure theory, any and all forms of exhaust gas back pressure hinder performance even in a N/A engine

[schmooot]

Originally posted by RickDaTuner



everyone needs to disspell the whole Exhaust gass back pressure theory, any and all forms of exhaust gas pressure hinder performance even in a N/A engine

really, can you explain this better for a N/A engine? I assumed that in order for an n/a engine to dispell exhaust at an optimum level it requires a lower pressure area in order to draw the gasses out and an exhaust pipe that is too large won't have that low pressure area. Whereas a FI engine doesn't rely on atmospheric pressure at all because air is forced. By all means correct me if I'm wrong

[RickDaTuner]

Well the way that I remember Learning about Back pressure is that you need to think of a Rifle a well Tuned Riffle Barrel that will allow the projectile to achieve maximum Velocity at the point of Exit.

Any and all forms of back pressure are bad!

When you think of designing a cars exhaust system, your main goal would be to make the best free flowing medium so that exhaust gasses can exit freely. If a car engine was basically one big gas flowing machine it would be easy. Just make one straight pipe and the jobs done!

But since the modern automobile has multiple Cylinders, it’s not such the easy story.

So we know that basically most inventions that man has created work on waves of resonance, such as the watch, the computer, the TV, and a car engine.
In a cars engine, reciprocating waves are created by the process of Burning a mixture of fuel and air which drive the pistons down through a cycle and are then expelled out an exhaust pipe. In a four cylinder engine the pattern of which the cylinders are fired at would be 1-3-2-4 or 1-4-2-3 depending on the engine.
The firing order is relevant to exhaust systems because this is what I am referring to when I speak of resonance.

So basically to make a simple exhaust system you need a header and a exhaust pipe. And in order to get the most performance you need a

-Header
That is fabricated to allow the smooth consistent Flow of the Spent gasses. This can be achieved by,
Making smooth nicely rounded Pipes, which are arranged to meet together in the sequence of normal combustion to allow the gasses smooth non Turbulent flow,
-Pipes
which are in a tapered patter which start off at one Diameter size and finish with a slightly larger opening

Now allow me to explain each attribute and how they work to allow your car to make more power

Smooth piping... well I think this is the most obvious one, smooth air flow = low turbulence, when it comes to performance and going fast you want to eliminate or reduce, all and any forms of turbulence

Properly sequenced piping... this is an important factor to under stand and is really only relevant to naturally aspirated Engines. The arrangement of the header pipes at the exit point is very crucial because it basically creates a smooth flow of gasses; this is the point that is trying to be brought about when after market parts manufactures design 4-2-1 headers.

Tapered piping... this is incorporated into the design of a header to allow the exhaust to achieve as much velocity as possible, Burning fuel and air are still very much expanding when they enter the header. So by having a pipe that has a gradually increasing diameter the still expanding gasses increase speed as they exit by pushing against the pipe!

So in a more or less vague description of the header those are the basics of how it works.

Now to the exhaust pipe

in order for you to get maximum performance out of your exhaust system if you were to design your own. You need to understand Fluid Dynamics, and the laws of expanding gasses, I personally am not a NASA engineer and don’t fully understand this, but well ill try to explain what I know, or how I remember it.

All good exhaust systems rely on the Delta V which can be explained as
Delta is the change in speed of a Gas
V is the speed of which the gas is traveling.

Going back to my example of a riffle we put this into use.

Gas will always want to be equal with the surrounding gasses this is why a balloon will deflate itself if you don’t pinch the opening, a lame example but you get the Idea,
When you think back to car exhaust and how when it’s exiting its still expanding you put this into play

A compressed gas traveling through a pipe will travel at its maximum, velocity given a few things.

1. Un interrupted flow
2. Properly sized piping
3. Smooth resonance

As in the design of the header, nicely rounded curves and piping allow a gas to travel in a nice non turbulent manner.

Pipe Sizing is the single most important attribute of a good exhaust system. You need a pipe that isn’t to small that will restrict the flow of the exhaust, but a pipe that not so big that the exhaust, instead of being released will, begin to pool in the pipe
so to achieve this there is an equation which for the life of me I cant remember but basically it calculates the maximum diameter a pipe can be, to allow a said a mount of gas to exit a given length of pipe while maintaining its Velocity without creating Turbulence.

I know I am missing few things here, but I hope this helps and yeah just to make it so that I mentioned it Back pressure is bad...


we has a little bit of a disscusion on this a little while ago

http://forums.beyond.ca/showthread.php?s=&threadid=37385

[GTS Jeff]

Originally posted by RickDaTuner



we has a little bit of a disscusion on this a little while ago

http://forums.beyond.ca/showthread.php?s=&threadid=37385 The article you posted doesn't support your argument man. It clearly states that "proper" sizing is needed on exhaust piping, not as big as possible.

[RickDaTuner]

Originally posted by GTS Jeff
The article you posted doesn't support your argument man. It clearly states that "proper" sizing is needed on exhaust piping, not as big as possible.

your right, a big exhaust on a FI engine is not always better, too big and you would get exhaust gas pooling, i suppose i should have been more carefull in my post:thumbsup:

but then again i never said go big or go home:dunno:

[GTS Jeff]

Originally posted by RickDaTuner


your right, a big exhaust on a FI engine is not always better, too big and you would get exhaust gas pooling, i suppose i should have been more carefull in my post:thumbsup:

but then again i never said go big or go home:dunno: Well you kinda did here:


Originally posted by RickDaTuner
any and all forms of exhaust gas pressure hinder performance even in a N/A engine

Exhaust gas "pooling" happens in both NA and FI engines. It's just that with FI engines each pocket of exhaust that gets shot out of the engine is bigger, necessitating a larger exhaust.

[RickDaTuner]

[i]

everyone needs to disspell the whole Exhaust gass back pressure theory, any and all forms of exhaust gas back pressure hinder performance even in a N/A engine [/B]

haha my poor typing skillz own me