Facts About Exhaust Systems
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Comments
2 1/2 inch diameter mandrel bent pipe is the minimum appropriate size for four cylinder engines.
2 1/4 and 2 3/8 inch diameter pipe is TOO SMALL.
Only Iperformance publicly posts dyno tests of their products.
Iperformance exhaust system are completely and totally made in the United States of America.
Your local custom exhaust shop does not have mandrel pipe bending equipment.
2 1/2 inch diameter mandrel bent pipe is the minimum appropriate size for four cylinder engines.
Extensive dyno testing has proven that naturally aspirated four cylinder engines of 1.6 liter displacement and larger, especially 2.2 liter and 2.4 liter displacement, benefit most from 2 1/2 inch diameter mandrel bent exhaust pipe, producing more low range torque and horsepower, more mid range torque and horsepower, and more high range torque and horsepower than any smaller diameter pipe. In all cases and in all tests, the 2 1/2 inch diameter pipe outperformed all smaller sizes of pipe at every single point between engine idle speed and redline. While many companies who offer and people who use exhaust systems with smaller diameter pipe, and they may make bold and convincing arguments about loosing low and mid range torque, none of these arguments are based in fact and none of these companies or these people can provide even a single dyno test to back up their assertions.
Iperformance did the dyno testing and we made our decision of what size pipe to use in our exhaust system based on that dyno testing, we use 2 1/2 inch diameter pipe because it results in more power from your engine.
2 1/4 and 2 3/8 inch diameter pipe is TOO SMALL.
Extensive dyno testing has proven that, for naturally aspirated four cylinder engines, 2 1/4 and 2 3/8 inch diameter pipe restricts low range torque and horsepower, mid range torque and horsepower, and high range torque and horsepower. In all cases and at all engine speeds, 2 1/2 inch diameter pipe outperforms 2 1/4 and 2 3/8 inch diameter pipe at every engine speed from idle speed to redline.
Other companies may use 2 1/4 and 2 3/8 inch diameter pipe with their exhaust systems and may even try to convince people that they chose that size pipe because they did testing which they claim showed the smaller diameter pipe to produce more power. However, they will never provide any documentation of that testing to anyone to see so that they may verify for themselves the validity of the claims these companies make. The fact is that all of the dyno testing done comparing pipe diameters proves something very different, that 2 1/2 inch diameter pipe is the minimum appropriate size for four cylinder naturally aspirated engines. The truth of the matter is that these companies made their decision of what pipe diameter to use in their exhaust systems based on the lower price per linear foot of the smaller diameter pipe, the reduced cost of manufacturing because it is easier to bend smaller diameter pipe, and the reduced cost in quality control because they do not have to be as careful concerning fit beneath the car with a smaller diameter pipe that does not require the same level of manufacturing precision as larger diameter pipe.
Iperformance did the dyno testing and we made our decision of what size pipe to use in our exhaust system based on that dyno testing, we use 2 1/2 inch diameter pipe because it results in more power from your engine.
Only Iperformance publicly posts dyno tests of their products.
None of the other company's offering headers or exhaust systems for these vehicles posts any dyno tests at all, not dyno tests they have conducted themselves, and not dyno tests conducted independently by their customers. Meanwhile they will consistently make claims that their product "makes this much power" without ever providing any documentation to back up their claims.
Only Iperformance has the courage to put their money where their mouth is and post not only dyno testing done in house, but also dyno testing that has been submitted by our customers who have already paid for the products they purchased and have absolutely no alternate motivation or incentive to provide those tests to us. These are completely and totally independent and unbiased tests and provide the absolute highest level of genuineness.
The single greatest influence on exhaust tone and exhaust sound is the diameter of the pipe used in the exhaust system.
The diameter of the pipe used in the exhaust system determines the sound pitch and tone of the exhaust sound made by the engine of an automobile. This is part of the physics of sound and those who are familiar with stereo system and speaker box design or architectural acoustics are probably already familiar with this. The exhaust pipe acts like a port on a speaker box, and the diameter and length of the port of a speaker box can be changed to alter the resonant frequency of the speaker in that box. With exhaust systems, the length is not as much a variable as the pipe diameter. The larger diameter that the pipe is, the lower the tone made by the exhaust flowing through that pipe, because lower tones have longer sound waves. A smaller pipe diameter will not let sound with longer wavelengths pass, and this results in a higher tone. This is why 2 1/4 inch diameter exhaust systems sound higher in pitch, often like a weed whacker or a chain saw, while 2 1/2 inch diameter exhaust systems will produce much deeper toned exhaust sound that is more highly sought after among car and performance enthusiasts.
2 1/2 inch diameter exhaust systems have a deeper tone than 2 1/4 inch diameter exhaust systems.
Iperformance exhaust system are completely and totally made in the United States of America.
Some other exhaust manufacturers are making their products in Mexico while others are having their products made in South East Asia. There is nothing inherently wrong with Mexico or any of the countries in South East Asia, but none of those places are known as hot beds for performance parts manufacturing, for high technology manufacturing abilities, or for their high quality standards. These places are, however, known as the cheapest places available for manufacturing products which may or may not be of even the lowest acceptable quality level.
Iperformance headers and exhaust systems are completely and totally manufactured and assembled within the United States of America, with manufacturing facilities in Seattle, Washington and St. Louis, Missouri, both cities which are noted for their long history of commercial and aerospace manufacturing as is indicated by the fact that Boeing and the former McDonnell Douglas companies are based in these two cities. Iperformance takes advantage of the aerospace subcontractors in both these cities to provide raw materials and manufacturing quality that is second to none in the industry.
Crush or compression bent exhaust systems will never flow as much as or result in the same or even similar performance improvement as mandrel bent exhaust systems.
"Compression bent" is the new and increasingly popular name for crush bending. This name has been coined or invented by the industry of local custom exhaust fabricators who do not have access to mandrel bending equipment to trick performance enthusiasts into believing they are getting something that is "almost as good as mandrel bending". Mandrel pipe bending maintains the cross sectional area of the inside of the pipe through bends by placing a tool within the pipe while it is bent to keep the sides from crushing or compressing in. Crush or compression bending allows the pipe to compress in and reduce the cross sectional area of the inside of the pipe. As an example, a 2 1/2 inch diameter pipe that is bent at a 45 degree angle will still have outer dimensions of 2 1/2 inch both across and perpendicular to the angle of the bend in the pipe. A compression or crush bent 2 1/2 inch diameter pipe will have a measurement of 2.55 inches across a 45 degree bend and 2.25 inches perpendicular to the bend. This is a rather significant reduction in the inside area of the pipe for such a mild bend, and 90 degree compression or crush bends result in even further reductions in the interior space of the pipe.
For proper and efficient exhaust flow, it is important to keep a consistent pipe diameter for the entire length of the exhaust system. Narrow places and widened places cause turbulence in the exhaust flow and reduction in the speed of the exhaust flow. Each compression or crush bend in an exhaust system represents a bottle neck in the flow of exhaust through that exhaust system, and each bottleneck causes an increase in back pressure and a reduction of both efficiency and engine power output. How much of a reduction in power? A 2 1/2 inch compression or crush bent exhaust system will dyno only one half to two thirds the performance gain of even a 2 1/4 inch mandrel bent exhaust system, or one third to half the performance improvement of a 2 1/2 inch mandrel bent exhaust system.
Your local custom exhaust shop does not have mandrel pipe bending equipment.
The most basic mandrel pipe bending equipment starts in the price range of a quarter million dollars, and the computerized equipment used to make the Iperformance products costs several times more than that. Small, custom exhaust shops simply do not have the kind of money it takes to buy mandrel pipe bending equipment, and this equipment is found almost exclusively in the shops of header manufacturers. Local custom exhaust shops, with very few exceptions, use crush bending machinery which they may call "compression" bending (see above). They may claim they do mandrel bending hoping that you will never look under the car yourself to see, or claim that their crush or compression bending is "just as good as mandrel pipe bending". Ask to see a sample of their bending and measure for yourself and if they claim that their crush or compression bending is "just as good as mandrel bending", ask to see a dyno test comparing their crush or compression bent exhaust to true mandrel bent exhaust. If they can't or won't provide a sample and a dyno, you know exactly where there concern is, and that concern is not to provide you with the very best performing product for your car.
