Attention: TDR Forum Junkies I've looked at every thread I could find regarding the 51" Donaldsons. One question remains, as I have read conflicting opinions regarding sound. I believe the consensus is that the M100580 (5" in/out) has way better flow (Donaldson's web site clearly shows that) than the M090544 (4" in/out). So here's my goals (keep in mind this is a 04. 5 with factory exhaust, including cat and 4" in/out muffler):
1) Max flow improvement
2) Sound levels that resemble stock at cruise speed (in the cab at least, don't care about what's behind me!), including towing, but I have no problem with louder wide-open throttle characteristics.
# 1 seems clear based on a lot of posts ... the 5 inch rules. #2 has been said to be A) significantly louder than the 4" at W. O. T. (fine with me) but quiet cruising, or B) quite a bit louder than stock in all realms of operation, or C) reasonably quiet but with an annoying freeway drone.
I know some of the variables could include trucks with and without cat, as well as some carrying 5" all the way aft to the exit. But does anybody have a clear idea of whether the better flow of the 5" will be livable with my sound criteria on the otherwise stock 04. 5 exhaust system?
The Nelson 86131M (4" in/out) also made my short list. It's supposed to be identical to the Donaldson M090544, except the Donaldson has a cone-shaped baffle inside. Any major sound/flow differences between these two?
Finally, there was one thread where a truck similar to mine was dynoed with and without cat. There was zero difference in the h. p. and torque numbers. I don't think there was a statement regarding fuel economy differences. Why would you bother removing the cat (or cleaning it out, thru-piping, etc. ) if there are no gains to be had? In my case, I would need a removable test tube to swap for NV emissions once a year, so I need some hard evidence to sway me. I'd say 1/2 to 1 mpg improvement might do the trick ... anybody think I would see that?
1) Max flow improvement
2) Sound levels that resemble stock at cruise speed (in the cab at least, don't care about what's behind me!), including towing, but I have no problem with louder wide-open throttle characteristics.
# 1 seems clear based on a lot of posts ... the 5 inch rules. #2 has been said to be A) significantly louder than the 4" at W. O. T. (fine with me) but quiet cruising, or B) quite a bit louder than stock in all realms of operation, or C) reasonably quiet but with an annoying freeway drone.
I know some of the variables could include trucks with and without cat, as well as some carrying 5" all the way aft to the exit. But does anybody have a clear idea of whether the better flow of the 5" will be livable with my sound criteria on the otherwise stock 04. 5 exhaust system?
The Nelson 86131M (4" in/out) also made my short list. It's supposed to be identical to the Donaldson M090544, except the Donaldson has a cone-shaped baffle inside. Any major sound/flow differences between these two?
Finally, there was one thread where a truck similar to mine was dynoed with and without cat. There was zero difference in the h. p. and torque numbers. I don't think there was a statement regarding fuel economy differences. Why would you bother removing the cat (or cleaning it out, thru-piping, etc. ) if there are no gains to be had? In my case, I would need a removable test tube to swap for NV emissions once a year, so I need some hard evidence to sway me. I'd say 1/2 to 1 mpg improvement might do the trick ... anybody think I would see that?
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