44 LEAN CEL onmy 1990 3.1

Post information about exhaust systems. Either purchased or custom made
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Re: 44 LEAN CEL onmy 1990 3.1

Postby woody90gtz » Wed Sep 14, 2011 9:14 pm

Scavenging is when the exhaust pulse from one cylinder pulls exhaust gas from the adjoining tube like a vacuum. This is how x-pipes and header collectors work. The exhaust pulses might bounce around when they hit the cat, but the cat is not going to pull them through.


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Re: 44 LEAN CEL onmy 1990 3.1

Postby 3X00-Modified » Thu Sep 15, 2011 8:01 am

Money pit Beretta wrote:Ok so you guys think there is no reflection of the pressure waves when it hits the media in the converter? And by that it doesn't happen in the muffler if you have no cat? Or even when you have a straight pipe to the atmosphere? This is very funny!


What your thinking is very funny... You need to read up on exhaust theory, and the function of the components of an exhaust system.

A bit of info...

Hardware
In order to give you a really good idea of what makes up an exhaust system, let's start with what exhaust gas travels through to get out of your car, as well as some terms and definitions:

After your air/fuel mixture (or nitrous/fuel mixture) burns, you will obviously have some leftovers consisting of a few unburned hydrocarbons (fuel), carbon monoxide, carbon dioxide, nitrogen oxides, sulfur dioxide, phosphorus, and the occasional molecule of a heavy metal, such as lead or molybdenum. These are all in gaseous form, and will be under a lot of pressure as the piston rushes them out of the cylinder and into the exhaust manifold or header. They will also be hotter 'n Hades. (After all, this was the explosion of an air/fuel mixture, right?) An exhaust manifold is usually made of cast iron, and its' primary purpose is to funnel several exhaust ports into one, so you don't need four exhaust pipes sticking out the back of your Civic.

Exhaust manifolds are usually pretty restrictive to the flow of exhaust gas, and thus waste a lot of power because your pistons have to push on the exhaust gasses pretty hard to get them out. So why does virtually every new automobile sold have exhaust manifolds? Because they are cheap to produce, and easy to install. Real cheap. Real easy. Like me.

"Ok," you ask, "so now what?" Ah, good thing you asked. The performance alternative to the exhaust manifold is a header. What's the difference? Where a manifold usually has several holes converging into a common chamber to route all your gasses, a header has precisely formed tubes that curve gently to join your exhaust ports to your exhaust pipe. How does this help? First of all, as with any fluid, exhaust gasses must be treated gently for maximum horsepower production. You don't want to just slam-bang exhaust gas from your engine into the exhaust system. No way, Jo-se'! Just as the body of your '94 Eclipse is beautiful, swoopy, and aerodynamic, so must be the inside of your exhaust system.

Secondly, a header can be "tuned" to slightly alter your engines' characteristics. We'll go in-depth into header tuning a little later.

Nextly, exhaust gasses exit from your manifold or header, travel through a bit of pipe, then end up in the catalytic converter, or "cat". The cat's main job is to help clean up some of the harmful chemicals from your exhaust gas so they don't end up in your lungs. In most cars, they also do a great job of quieting things down and giving any exhaust system a deeper, mellow tone. You'll see a lot of Self-Proclaimed Master Technicians (SPMT's) telling people that removing a cat will get you tons of power. There's room for debate on this, but in our experience, removing a catalytic converter from a new car won't gain you much in the horsepower department. It can also get you a $1500 fine if the EPA finds out! If you drive an OBD-II equipped car, you'll also get that damn annoying CHECK ENGINE light burnin' up your dashboard. (And for all you racers concerned with OBD-II's fabled "limp mode", you can put your fears to rest.)

From the catalytic converter, the exhaust gasses go through a bit more pipe and then into a muffler, or system consisting of several mufflers and/or resonators.

Do Mufflers "Make" Horsepower?
The answer, simply, is no. The most efficient mufflers can only employ the same scavenging effect as a header, to help slightly overcome the loss of efficiency introduced into the system as back pressure. But I have yet to see an engine that made more power with a muffler than an open header exhaust. "So," you ask, "what the hell is the best flowing muffler I can buy?"

According to the flowbench, two of the best flowing units you can buy are the Walker Dyno Max and the Cyclone Sonic. They even slightly out flow the straight through designs from HKS and GReddy BL series. Amongst the worst, are the Thrush Turbo and Flow Master mufflers. We'll flow some of the newer mufflers as they become available at our local Chief auto.

Resonators
On your typical cat-back exhaust system, you'll see a couple of bulges in the piping that are apparently mini-mufflers out to help the big muffler that hangs out back. These are called Helmholtz Resonators and are very similar to glasspacks. The main difference is that firstly, there is no sound-absorbing fiberglass or steel wool in a Resonator. And secondly, their main method of silencing is the reflective principle, not absorption. An easy way to tell the difference between a glasspack and a true Helmholtz Resonator is to "ping" one with your finger. A glasspack will make a dull thud, and a true Resonator will make a clear "ping!" sound.



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Re: 44 LEAN CEL onmy 1990 3.1

Postby indyyellow » Thu Sep 15, 2011 12:52 pm

Put in a brand new O2 sensor today. IT was rather easy other then when the thing let loose my arms slammed into the motor, that felt good, ha ha ha.
Took it out and drove it for a bit afterwards. I do see a little better instant MPG readout then I did before I replaced it.


Tim

---2005 Magnum RT -- 116k
---1996 Ford Probe GT (V6/5sp) -- 150k (90k on motor)
---1993 Chevy Silverado Z71 -- 261k

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Re: 44 LEAN CEL onmy 1990 3.1

Postby Money pit Beretta » Thu Sep 15, 2011 8:04 pm

Good news Tim.

Well I have read an old book called Scientific Design of Exhaust & Intake Systems.
By far it's way out of date.
Here is a nice site that I found long ago
http://www.epi-eng.com/piston_engine_te ... nology.htm

But no joke thanks for taking the time to post all that info 3X00!
What I said came out very,very wrong. And I only added to it with my off color and stupid post after the first one. I need to deal with stress in a better way and control/think about what I'm posting before I do.


keep'em flying!

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Re: 44 LEAN CEL onmy 1990 3.1

Postby 3X00-Modified » Fri Sep 16, 2011 8:43 am

Money pit Beretta wrote:Good news Tim.

Well I have read an old book called Scientific Design of Exhaust & Intake Systems.
By far it's way out of date.
Here is a nice site that I found long ago
http://www.epi-eng.com/piston_engine_te ... nology.htm

But no joke thanks for taking the time to post all that info 3X00!
What I said came out very,very wrong. And I only added to it with my off color and stupid post after the first one. I need to deal with stress in a better way and control/think about what I'm posting before I do.


LOL I'm glad you were accepting of what I posted and didn't take it the wrong way.



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Re: 44 LEAN CEL onmy 1990 3.1

Postby Money pit Beretta » Fri Sep 16, 2011 5:45 pm

You were only trying to help a big fool, but it turned out that I'm just a fool.


keep'em flying!


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