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Gene,
I read that you exited the exhaust before the rear tires. In your calculation would a 3.5 stock straight pipe from the turbo to about mid cab and then going to 5"(because the pipe was free) with manderal bend exiting before the rear tire flow better than a 4" from the turbo to the stock exit location behind the rear tires w. muffler. The reason that I ask is if as I have read elsewhere bends and length cost flow. Do these bends, the extra length, and muffler(though a "performance" muffler) add up to enough additional restriction to offset the benefit of 4" ehaust over my setup? I'm interested in the flow properties but don't have the math skills. If it doesn't make a difference or much difference I probably won't save up the coin to go 4". I've also heard that 5" exhaust doesn't make any difference than 4" (mabe even worse)if you are not going extreem because of flow factors such as exhaust gas cooling, tumbling because of reduced velocity, etc... Is this true?
My intent is to use my F350 within the factory load ratings and where I live it is flat....flat....flat so I don't have to work the engine as hard as those in the mountains. Above that I don't intend to play as hard as allot of the others(drag racing and such) just the occasional romping it around (considering the cost of fuel). Mostly I'm trying to save fuel by any improvement in efficiency possible.
Well with the whole exhaust system design being a balancing act (for different eng types and sizes) I would think that for a non-tubro gas 360 ford engine a 2 1/4 is about the right size tube. "ernesteugne " do you concur?
Given your goals, 4 inch might help, but 5 inch is not worth it. For a primarily stock setup, you're not going to lose much through the mandrel bends... the loss can be calculated, but you'll never see it in your MPG numbers because there are so many other factors influencing that reality.
Yes... I know the thread is old. Just trying to answer Karl's questions from a 30,000 foot perspective.