Has anyone that has installed any of these mandrel bent exhaust kits noticed an improvement (or worsening) of their gas mileage? I am considering buying a Diamond Eye 3.5" single exhaust and installing on my crew max.
To my understanding a more free flowing exhaust and intake decrease the velocity of air going in and exhaust traveling out at the lower rpm's. This is why people usually see a decrease in power/torque in the lower rpm range when doing such mods. However when you get into the upper rpm's you no longer have a restriction and the power is increased. Lower rpm power is what gets you moving from a stop and decreasing the power there would decrease the engines efficiency under normal driving conditions.
The Corsa catback I have on my 2010 uses 3 inch pipe.Went from 16.5 to 16.1 MPGs, but I'm rarely in 'D' these days. I like to shift for myself most of the time,probably not as fuel effecient but, I DON'T CARE.:biggrin1:I don't notice enough botton end loss to bother me,if any at all.
No disrespect to a Marine but I disagree. There are several exhaust systems and cold air intakes that increase both hp and gas mileage. You will need to do your research on which one is best for both. If hp and mileage is going to help in your decision, then ignore the sound, because yes, there are systems out there that sound great, but will reduce your hp and mileage. Typically, if the pipes or the intake produces more hp, it should produce better milage as well. You are making the engine breath easier both on intake and exhaust which makes it more efficient. However, depending on the amount of miles you drive a year, it could take 3 to 5 years to pay for itself. My picks so far are the AFE Stage 2 intake, I'm on the fence about the Banks Monster exhaust, and am now considering the Doug Thorley long tube headers. I will let you know my results if I choose any or all. Also, if you are looking for more mileage, consider a hard tonneau for the bed (do not remove the tailgate for mileage).
unless you change out the exhaust manifolds for some long tube headers, keep the stock tubing. You'll be sorry if you don't. Since it's dual until the muffler there could be some benefit to cutting out your muffler and installing 2 flow through mufflers in its place, but again keep the stock tubing and make sure the muffler is the same i/d as the stock tubing. It would also be beneficial to install a crossover or 'H' pipe as close to the front as possible.
Borla, Gibson, Corsa, Bamufflers are all good mufflers. The important thing is you don't want any baffles in the mufflers. Just one baffler will screw up your flow. Some mufflers have a 'v' in them, or chambers. This is only for sound and robs lots of power. The sound that you get with a flow through muffler is second to none and will actually produce power.
There is a good write up on the link above regarding this subject.