This has been a nice informative thread. My Rebel is also my DD. I know the age y pipe is $$$ but that and shorties would keep my ok here in IL and I wouldn’t need to tune so it fits my needs although I know it’s not as great as long tubes.
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Correct, and good on you for taking that out of this thread and not coming to any conclusions that shorty > LT just because it Fits this application!
Remember, the original 1 5/8" LT Mopar headers along with 2 1/2" mid pipes, high flow cats and Borla dual 2 1/2" exhaust was a well designed, Efficient system for stock to 500WHP on the 5.7 3rd gen Rams and Better fuel economy. (1-2mpg)
So everyone should be looking to that as the "model" and then making decisions based on their personal use of their trucks.
Also remember;
Race truck 1/4 mile = gains Above peak TQ come into play
Tow vehicle/ DD = gains Below peak TQ come into play
So complete opposites as far as exhaust requirements.
The JBA 1 5/8" shortys should give a nice gain that should be noticeable while regular part throttle driving as well as high end power and slightly better fuel eco if rest of exhaust is kept to the parameters of the "model" above.
Primary tube diam defines the peak TQ rpm, so the 1 5/8" OD header pipe keeps peak TQ down low where you want it for a tow/DD vehicle.
Pipe Length defines which side of peak TQ is going to be TQ biased. Shorter pies = bias Above peak TQ, Longer pipes = bias Below peak TQ.
eg. If you take our "model" exhaust from above and replace the 1 5/8" Mopar LT headers with the JBA 1 5/8" shorty's, what's going to happen?
Side by side dyno will show that the Mopar LT's would have greater TQ below peak TQ than the shorty's, they would meet at about the same peak TQ rpm, then the shorty's would begin to out TQ the LT's in the mid to upper rpm.
Either way, Both trucks would retain Great drivability, the LT's would get slightly better fuel eco because of added TQ Below peak TQ rpm.
eg #2
Someone does the JBA 1 5/8" shorty's and adds 3" Y pipe and full dual 3" exhaust.
Result = anything from no change to lost some low end and fuel eco. Step on it Full Throttle and you will feel some gains up top, but nothing you want in a Tow/ DD 5600+lb truck.
In this scenario, the only Saving grace is the 1 5/8" headers! 1 3/4" = Worse, 1 7/8" = Brutal!
My Ram is a DD/ Tow vehicle and always will be. Every mod I do is for added performance Plus better eco which Proves you are making things more Efficient!
So all of my gains will be focused on Below peak TQ rpm! (and keeping peak TQ as low as possible!)
