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Exhaust operation and the back pressure myth "Or" Ask Uncle Otto about exhaust

Old 03-11-2011, 04:14 PM
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Trying to figure what Muffler I want. What a chore. Not like shoes, I cant just try them on. 2011 F150 Super Crew Lariat 5.0L single exhaust. Love the rumble and throat but don't want it overwhelming at 1500 RPM doing 70mph. Want to stay single pipe. Always liked Flowmaster. Any opinions out there for the new guy? Thanx
Old 03-12-2011, 12:00 AM
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I have a 2006 4.6L V8. I recently installed 2 SI/SO super 44 flowmasters with turndowns right after the muffler. The pipes are 2.25 diameter. They installed an H pipe about 8 inches in front of the mufflers (several feet from the cats). I am really really unimpressed with the sound. I can barely hear it on startup or outside the truck.

I am now planning on installing high flow cats and changing the turndowns to pipes out of the back to increase the sound. What should I do about the H pipe? It seems awfully close to the mufflers to even do any good.
Old 03-21-2011, 04:37 PM
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the easiest proof that backpressure is a myth...

we have a 700 HP dirt track racecar that has nothing but headers coming off each side and are only about 3 feet long... no cats, no mufflers, not x,h or y pipes... runs like a champ
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Old 03-21-2011, 04:51 PM
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This has me really wanting to take my flowmasters off and go with something else. I love the sound but crap... I didn't know it did NOTHING for power. I have an intake and tuner, but maybe I can scrape by with a few more ponies with an inline (non chambered) exhaust system instead. I hate all show and no go so I kinda hate myself a lil now. Thanks ha ha
Old 03-21-2011, 05:05 PM
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Hooker Aerochamber =D
Old 03-24-2011, 04:52 PM
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Doesn't the 09 and up F-150 already have a straight through muffler?
Flowmasters are no good, they just make a signature sound. Straight through is the way to go.
Old 03-24-2011, 05:06 PM
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I know the 2009+ trucks have the "hybrid" type muffler. I consider it a hybrid because while you can see through it, it still has the chambers that do the sound deadening. The stock systems have come a long way from what they use to be, but still aren't perfect.
Old 03-24-2011, 09:06 PM
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so basically, trucks with a sport side exhaust, like mine, are pretty much choking itself out with less pipe? ive noticed that when i want to pass someone and i press the accelerator to downshift that it kinda feels like its stumbling, or falling on its face before it catches up. almost like the engine is bogging out. i put the exhaust on 60 g's ago and dont know whats been causing it. just got the pcm updated from the dealer too. still has the same stumble i guess. since im about to hit 100,000 ive been wondering if its just spark plugs, COPS, or even my torque converter. or if it could just be my damn exhaust. lol
Old 03-25-2011, 12:17 AM
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Originally Posted by JorgeRod54
so basically, trucks with a sport side exhaust, like mine, are pretty much choking itself out with less pipe? ive noticed that when i want to pass someone and i press the accelerator to downshift that it kinda feels like its stumbling, or falling on its face before it catches up. almost like the engine is bogging out. i put the exhaust on 60 g's ago and dont know whats been causing it. just got the pcm updated from the dealer too. still has the same stumble i guess. since im about to hit 100,000 ive been wondering if its just spark plugs, COPS, or even my torque converter. or if it could just be my damn exhaust. lol
The original tires on that were 31.1 inches tall, and now you have 35`s. Did you change the gear ratio?
Does it really Stumble, or does it just take a long time to get up to speed?
Is your exhaust the stock pipe, with duals back from the muffler?
I have had plugs take a crap before 100k.
Old 03-25-2011, 09:16 AM
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nope, I'd only change the gears if i went to 37s. it doesnt necessarily stumble and shudder, just seems to bog out for half a second, then finally pick up speed. exhaust is SI/DO sport exit.

but so the thread doesn't get off hand, this is a great wealth of info. awesome write-up bro!

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