Some of you don't know that I'm sort-of a rebel. I don't take anybody's word for anything. I question everything. Convention should be challenged. I'm not an engineer, but I easily could have been. So, two decades ago when I installed my first Thorley header I followed the conventional thought that pipe sizing needed to be 2.25" behind a 22RE. I always thought that was over-kill for these engines. As I learned about such things as "exhaust scavenging" I really started to question the wisdom of 2.25" exhaust on a 22RE.
Of course Google is your friend, most of the time, and I went into this with an objective, analytical mind. One table has made it's rounds, and you can find it here: How To Calculate Muffler Size and Exhaust Pipe Diameter | Exhaust Videos. Another good site was this Exhaust Size Calculator, Exhaust Size Calculator.
Now get real people, there is no way in Hades our trucks are making anything much over 130hp, regardless of modifications. If you are, then show me the dyno, and try to justify how friendly your truck is driving around town, or how it does crawling. If you are getting screaming HP our of your 22RE it's not going to be in a form that will be low RPM friendly.
What did I do? Last month I found huge rot in my Flowmaster 50, so it had to go. A year ago I had the cat replaced, so it had to stay, 2.25" and all. When I went to the muffler shop I told the fella that I wanted to keep the 2.25" from the cat to the muffler, but I wanted a 2" tail pipe. He thought I was nuts. I was going to install a Flowmaster 50 SUV, but he talked me into a Magnaflow instead. The Flowmaster was removed, and I went with a Magnaflow #12245, 5"x8"x18". Frankly, I don't want to hear the engine anymore. It's still louder than I would like, especially when I get into the throttle, but it's nicer cruising than before.
I can tell you I have noticed no difference with power getting on the freeway, or any other loss of power. It also seems to be easier pulling off from stops and overall friendlier around town (minor difference), likely due to improved scavenging. I won't have any seat time in low range for another month, but I highly suspect it will be better behaved crawling around. I also have a road trip coming up so I'm curious how it does on the freeway, how it does dropping from 5000 feet elevation to sea level, and if my mileage changes. Of course the design differences between the Flowmaster and the Magnaflow could account for an improvement in fuel economy.
Of course Google is your friend, most of the time, and I went into this with an objective, analytical mind. One table has made it's rounds, and you can find it here: How To Calculate Muffler Size and Exhaust Pipe Diameter | Exhaust Videos. Another good site was this Exhaust Size Calculator, Exhaust Size Calculator.
Now get real people, there is no way in Hades our trucks are making anything much over 130hp, regardless of modifications. If you are, then show me the dyno, and try to justify how friendly your truck is driving around town, or how it does crawling. If you are getting screaming HP our of your 22RE it's not going to be in a form that will be low RPM friendly.
What did I do? Last month I found huge rot in my Flowmaster 50, so it had to go. A year ago I had the cat replaced, so it had to stay, 2.25" and all. When I went to the muffler shop I told the fella that I wanted to keep the 2.25" from the cat to the muffler, but I wanted a 2" tail pipe. He thought I was nuts. I was going to install a Flowmaster 50 SUV, but he talked me into a Magnaflow instead. The Flowmaster was removed, and I went with a Magnaflow #12245, 5"x8"x18". Frankly, I don't want to hear the engine anymore. It's still louder than I would like, especially when I get into the throttle, but it's nicer cruising than before.
I can tell you I have noticed no difference with power getting on the freeway, or any other loss of power. It also seems to be easier pulling off from stops and overall friendlier around town (minor difference), likely due to improved scavenging. I won't have any seat time in low range for another month, but I highly suspect it will be better behaved crawling around. I also have a road trip coming up so I'm curious how it does on the freeway, how it does dropping from 5000 feet elevation to sea level, and if my mileage changes. Of course the design differences between the Flowmaster and the Magnaflow could account for an improvement in fuel economy.
. Also I'm from Quito, so I'm driving at very high altitudes, does anybody thinks this would be a good setup for me? 
