So I just thought I'd help out anybody I could here. I'm still new here and just wanted to make the most positive contribution to ToyotaTruckClub.com that I could. I have hand built almost 100 mufflers this year, and built almost as many custom exhaust systems on multiple vehicles. Most of my experience comes from my dad as he has been a welder most of his life. I don't remember exactly how old I was when he first taught me to weld, but I know it was before I was 10 yrs. old. I'm currently 35. The science behind what I create comes from my neighbor. He worked on Thermal Dynamics (rocket exhaust) on the Apollo program. My mufflers are designed by a rocket scientist
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The biggest misconception in the world of performance exhaust consumers is, "an engine needs backpressure to operate properly". Sorry to say that is very general and by itself it is wrong. A more correct statement would be, "an engine needs scavenging to operate properly". 100% percent accurate. You see there is this thing called volumetric efficiency. If you can 'tune' your exhaust system to have efficient scavenging during the peak volumetric efficiency, you will make the most power. With this follows driveability, fuel economy, and just plain fun.
Most manufacturers design an exhaust system to be quiet. That is usually the main priority with the exception of some high end/performance niche markets. Let's touch back on that in a minute. A restrictive exhaust system is not only more quiet than a free flowing system, it scavenges at a much lower rpm. This scavenging at lower rpm causes peak torque to occur at a lower rpm as well. My next few paragraphs will go into this into more detail but: The lower rpm peak torque tricks the average consumer into thinking the vehicle is faster than it actually is.
Here are the main 3 ways to quiet down an exhaust system:
RESTRICTION
This method is the most popular among the mainstream cookie cutter auto manufacturers. This not only robs power, it robs fuel economy. Why do they do this? First and foremost it is the most effective way to quiet down an exhaust system, that is the main priority. Next reason, it's generally the cheapest way to mass produce an exhaust system. Next, as said above, it tricks the consumer into thinking the vehicle is faster than it actually is. Normally this system uses a muffler with multiple chambers and walls that the exhaust pulses have to 'hit' and everytime the exhaust gases have to change direction they slow down. These slower pulses get hit by the next pulse which is forced to slow down, then the next hits the last and etc, etc. Backpressure increases as the rpm's increase, exactly the opposite of what you want to happen when considering power and fuel economy.
REFLECTION
This type of system is used by some aftermarket exhaust manufacturers. The most common set up uses a series of delta's and/or baffles to reflect the sound back into the exhaust system so the next sound wave hits the last and some of the db's are cancelled out. While very effective at making a cool sound on some V8's, and fairly effective at quieting down an exhaust system, this type of system sees an increase in backpressure as the rpm's increase. As said above, everytime the gases have to change direction they slow down considerably and the next pulse hits the last causing backpressure.
ABSORPTION
The misconception with this type of muffler is that it is flow through. While this is true at certain rpm's the statement is only partially true. As said above, the exhaust travels down the exhaust tubing after the manifolds in high pressure pulses. When these high pressure pulses hit the perforations in a properly built 'flow through' muffler they expand into the canister of the muffler, when they expand they slow down. The next pulse hits this slower pulse and slows, then the next and the next, etc. This will create backpressure at lower rpm very similar to the other 2 types of mufflers listed above. But here's the difference: As the rpm's of the engine increase the exhaust goes from pulses to a steady high pressure flow. When the pressure in the canister is equal to the pressure in the exhaust tubing the exhaust gases no longer expand into the canister, they flow straight through, freely In other words, the flow through muffler acts as a restrictive/reflective muffler at lower rpm to promote low end scavenging and torque, but acts much like straight pipes at the top end, where you need it to promote high end torque and hp!
So the above descriptions are very general in order to keep from writing a novel. Most of what I have written has to do with the muffler, but the rest of the system also effects flow similarly. Most things are restrictive, like: Cast iron log manifolds, 'y' pipes, catalytic converters, abrupt step downs (and step ups), going from single to dual exhaust, etc. All of the above scenarios cause backpressure, but more importantly, to the manufacturer, they quiet down the system.
In future posts I will touch on oversizing the tubing, Long Tube Headers cats, 'y' pipes versus 'h' pipes. I will also answer any questions that I can and post up any other info that I feel will be helpful for the many members of this site and to the average web surfer.
.The biggest misconception in the world of performance exhaust consumers is, "an engine needs backpressure to operate properly". Sorry to say that is very general and by itself it is wrong. A more correct statement would be, "an engine needs scavenging to operate properly". 100% percent accurate. You see there is this thing called volumetric efficiency. If you can 'tune' your exhaust system to have efficient scavenging during the peak volumetric efficiency, you will make the most power. With this follows driveability, fuel economy, and just plain fun.
Most manufacturers design an exhaust system to be quiet. That is usually the main priority with the exception of some high end/performance niche markets. Let's touch back on that in a minute. A restrictive exhaust system is not only more quiet than a free flowing system, it scavenges at a much lower rpm. This scavenging at lower rpm causes peak torque to occur at a lower rpm as well. My next few paragraphs will go into this into more detail but: The lower rpm peak torque tricks the average consumer into thinking the vehicle is faster than it actually is.
Here are the main 3 ways to quiet down an exhaust system:
RESTRICTION
This method is the most popular among the mainstream cookie cutter auto manufacturers. This not only robs power, it robs fuel economy. Why do they do this? First and foremost it is the most effective way to quiet down an exhaust system, that is the main priority. Next reason, it's generally the cheapest way to mass produce an exhaust system. Next, as said above, it tricks the consumer into thinking the vehicle is faster than it actually is. Normally this system uses a muffler with multiple chambers and walls that the exhaust pulses have to 'hit' and everytime the exhaust gases have to change direction they slow down. These slower pulses get hit by the next pulse which is forced to slow down, then the next hits the last and etc, etc. Backpressure increases as the rpm's increase, exactly the opposite of what you want to happen when considering power and fuel economy.
REFLECTION
This type of system is used by some aftermarket exhaust manufacturers. The most common set up uses a series of delta's and/or baffles to reflect the sound back into the exhaust system so the next sound wave hits the last and some of the db's are cancelled out. While very effective at making a cool sound on some V8's, and fairly effective at quieting down an exhaust system, this type of system sees an increase in backpressure as the rpm's increase. As said above, everytime the gases have to change direction they slow down considerably and the next pulse hits the last causing backpressure.
ABSORPTION
The misconception with this type of muffler is that it is flow through. While this is true at certain rpm's the statement is only partially true. As said above, the exhaust travels down the exhaust tubing after the manifolds in high pressure pulses. When these high pressure pulses hit the perforations in a properly built 'flow through' muffler they expand into the canister of the muffler, when they expand they slow down. The next pulse hits this slower pulse and slows, then the next and the next, etc. This will create backpressure at lower rpm very similar to the other 2 types of mufflers listed above. But here's the difference: As the rpm's of the engine increase the exhaust goes from pulses to a steady high pressure flow. When the pressure in the canister is equal to the pressure in the exhaust tubing the exhaust gases no longer expand into the canister, they flow straight through, freely
In other words, the flow through muffler acts as a restrictive/reflective muffler at lower rpm to promote low end scavenging and torque, but acts much like straight pipes at the top end, where you need it to promote high end torque and hp!So the above descriptions are very general in order to keep from writing a novel. Most of what I have written has to do with the muffler, but the rest of the system also effects flow similarly. Most things are restrictive, like: Cast iron log manifolds, 'y' pipes, catalytic converters, abrupt step downs (and step ups), going from single to dual exhaust, etc. All of the above scenarios cause backpressure, but more importantly, to the manufacturer, they quiet down the system.
In future posts I will touch on oversizing the tubing, Long Tube Headers cats, 'y' pipes versus 'h' pipes. I will also answer any questions that I can and post up any other info that I feel will be helpful for the many members of this site and to the average web surfer.
