F***! Dual Exhaust
10-14-2004, 10:36 AM
#21
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backpressure does make a difference! Some guys on here will say it is hokey pokey, but they are wrong. Bernoulli's principle, does air move faster through 2" pipe or 3" pipe...2" pipe is the correct answer.
There is a point where you get too much pressure because the volume of exhaust gas produced cannot exit a small pipe as efficiently as a larger pipe.
I would run 2.25" true dual on a mostly stock motor or 3" single. 2.5" is significantly larger than 3" single. The chart on the dynomax website it worth going by, those guys know what they are talking about. I run 3" single, and I know I gained throughout the RPM range.
There is a point where you get too much pressure because the volume of exhaust gas produced cannot exit a small pipe as efficiently as a larger pipe.
I would run 2.25" true dual on a mostly stock motor or 3" single. 2.5" is significantly larger than 3" single. The chart on the dynomax website it worth going by, those guys know what they are talking about. I run 3" single, and I know I gained throughout the RPM range.
10-14-2004, 10:39 AM
#23
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i noticed a huge difference when i changed my truck from just turn downs to piping all the way to the back.2 in 2 out 40 series flow. turn downs gave it a pit truck sound and the low end was gone. keep everything the same except cut off the turn down pipes and ran 2.125 piping to the back with some ss tips. next thing i know, im spinning em off the line again. Through this whole process i never touched the cats. I truely believe that if ur exhaust doesnt match the amount of air the motor is pulling in, then this is the reason for the loss of low end. just my 2 cents.
10-14-2004, 10:46 AM
#24
Originally Posted by jessdog
i noticed a huge difference when i changed my truck from just turn downs to piping all the way to the back.2 in 2 out 40 series flow. turn downs gave it a pit truck sound and the low end was gone. keep everything the same except cut off the turn down pipes and ran 2.125 piping to the back with some ss tips. next thing i know, im spinning em off the line again. Through this whole process i never touched the cats. I truely believe that if ur exhaust doesnt match the amount of air the motor is pulling in, then this is the reason for the loss of low end. just my 2 cents.
If you plan to do any other beneficial modifications, such as mentioned above, I would keep the true dual setup.
10-14-2004, 10:50 AM
#25
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Originally Posted by bodyguard6799
But when you switch to mid or long tube headers dont you have to junk the stock y-pipe???
10-14-2004, 11:02 AM
#26
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Originally Posted by BigKID
I believe the term "backpressure" is being misunderstood and/or misused. What affects the lowend torque is exhaust velocity which is directly proportional to exhaust pipe diameter. You can build an exhaust with very little to no backpressure with smaller diameter pipe that has a high velocity and make great power thruout the rpm range. A true dual 2.5" setup may be too large for a fairly stock 4.8/5.3 because there is not a high enough volume of air to promote a high velocity thru the said flowarea. On the other hand you can have an exhaust too small to flow the output air from the engine in which it 'backsup' in the pipe(s) creating backpressure. This will NOT create more power on low end, it just feels that way because you are loosing power inthe higher rpms because the exhaust cant flow that volume of air but in the lower rmps it is on the edge of its flow capibilities in turn creating a high exhaust velocity. So with this being said, if you still think 'backpressure' is the key, go put some restrictors on you tail pipes with the same diameter piping and tell me if the power output of you truck increases throughout the rpm range.
big pipes don always meen best flow...
10-14-2004, 11:11 AM
#27
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So the stock y-pipe can be reused, I just have to trim em up a bit. Do turn downs really hurt performance?? I really cant see a couple of extra feet making that much difference. And it sounds so much better on a nice lowered truck!!
10-14-2004, 11:36 AM
#28
Unfortunately, I have changed my exhaust too many times, maybe like 4. I have had the best luck with a single in/single out magnaflow. I look at backpressure like tuning, you need to change it as your engine combination changes. For a moderately modded 4.8/5.3, stock exhaust or a muffler change with or without cats is suffucient.
When I went down to the Magnacharger facility in Ventura, they told me that they developed the Radix with the stock exhaust system in mind. This came from the manager in R&D who developed the Radix. He also told me that Detroit as well as almost all other manafactuers spend a ton of money in exhuast design to maximize power and gas mileage. If duals provided the best results with power and mileage, I think they would do it.
When I went down to the Magnacharger facility in Ventura, they told me that they developed the Radix with the stock exhaust system in mind. This came from the manager in R&D who developed the Radix. He also told me that Detroit as well as almost all other manafactuers spend a ton of money in exhuast design to maximize power and gas mileage. If duals provided the best results with power and mileage, I think they would do it.
10-14-2004, 11:49 AM
#29
Originally Posted by Silver2004
I'm hoping to see some other peoples trucks with mid or long tube headers to see how well they tie back into the stock y-pipe. I believe your supposed to retain the stock y-pipe from the cats back. just cut off infront of the cats to mount up to the new longer headers.
10-14-2004, 11:53 AM
#30
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I have the dynatech longtubes.. they come with new cats and a new Y pipe that ties there whole system together into a Y and flanged to mate to the factory intermedate pipe. On my Avalanche it helped with the mid and high RPMs when i had the stock muffler.. I changed to a single/single 3" 40 series and lost some lowend but gained in others.. I am now changing it again to a Magnaflow single 3" inlet dual 2 1/2 tailpipes out the back to add some volocity and pick up the lowend again.