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I had installed a SI/SO magnaflow system gaining MPGs and power. Then I got ahold of an AT3030. I cut out the magnaflow adn welded in the 3030 keeping the front resonator and Magnaflows tail pipe and tip. Now with the 3030 in I ran it to Dallas and lost about 2-3 MPGs. Also it wasn't as strong as the stock set up let alone the Magnaflow. I drive the same 140 mile route regularly so I have a fairly reliable basis for comparison. I took a trip to Tulsa and really noticed a difference. I got curious while in Tulsa about ht edifference and started pokinbg around. I think that I can feel some air from the REAR of the 3030 to tailpipe seam. Is it possable that an exhaust leak could cause these issues? Thanks for the insight. MJ
'06 Ram QC SLT Hemi 4X2 Lone Star Edition -Mopar Drop in Bed Liner, Chrome Nerf Bars, Black Bed Rail Caps, Chrome Bed Rails, Bed Wheel Well Fillers, Mud Flaps -Helwig 1-1/8" Rear Sway Bar -Magnaflow SI/SO Res-Back System w/ 4" Tip -Access Vanish Tonneau Cover -WeatherTech Digital-Fit Floor Mats |
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FYI, backpressure is something you dont want for power, dont matter what any myths anyone might inform you of. A leak after the muffler will not harm performance. A tailpipe is a leak in a sense.....
 My cammed hemi http://www.youtube.com/watch?v=hw1lDSLSKgc JOHNNYHEMI Stu cam 218/218 112LSA spartan max, 6.1 rods, 6.1 springs,Tuned, Hedman Longtubes, Dual 3" dynomax bullets, NO cats, SRT-10 rear axel swap D-60 LSD,4.10 gears srt-10 dual piston vented rear brakes SHARADON STAGE III VALVEBODY, Lincoln 18" E-Fan,TransgoHDReprogram SHift Kit with resistor, Taylor Shorties,mcgaughys 2/4 drop, Custom painted bumpers, shaved and painted grille shell, rumble bee grille inserts, Debadged, |
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From my understanding there is such thing as not enough back preassure though.
At any rate, the leak being on the back side of the muffler really makes the idea of lost back preassure hard to swallow. The only reason I am thinking this is because I don't have any other mods to the truck so it isn't balanced with air in. Make at least a litte sense? Me either.  '06 Ram QC SLT Hemi 4X2 Lone Star Edition -Mopar Drop in Bed Liner, Chrome Nerf Bars, Black Bed Rail Caps, Chrome Bed Rails, Bed Wheel Well Fillers, Mud Flaps -Helwig 1-1/8" Rear Sway Bar -Magnaflow SI/SO Res-Back System w/ 4" Tip -Access Vanish Tonneau Cover -WeatherTech Digital-Fit Floor Mats |
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I agree with Johnny. You don't want any back pressure. That is why the better header systems have a scavenging effect on the exhaust ports.
SRT10 undersprung rear axle with 4:56 gears, Mcgaughy's 2" drop spindles and Belltech 2" drop coils, supermaxx longtube headers and hi perf cats, Edge Evolution gauge pack, Fiberglass hood with functional shaker ram air, and Airaid CAI, 180 Jet stat Flexalite E fan, Diablo tuner |
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"Jordan" |
 As long as your truck is N/A, the idea is to reduce backpressure. This is why drag/race cars run open headers. Not much backpressure there._____________ 2004 QC 2WD Comp 268 cam, 6.1L valvesprings/pushrods, Pacesetter Jet-Hot coated LT's/ORY, K&N intake, Taylor shorties, Borla XR1 dumped, 3.92/posi rear, SCT tune by Hemifever, short belt for the track, 15% tint, 2" drop shackles, debadged except fenders |
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Its not really loosing backpressure that causes loss, its going too big compared to your engines displacement and flow that takes effect My cammed hemi http://www.youtube.com/watch?v=hw1lDSLSKgc JOHNNYHEMI Stu cam 218/218 112LSA spartan max, 6.1 rods, 6.1 springs,Tuned, Hedman Longtubes, Dual 3" dynomax bullets, NO cats, SRT-10 rear axel swap D-60 LSD,4.10 gears srt-10 dual piston vented rear brakes SHARADON STAGE III VALVEBODY, Lincoln 18" E-Fan,TransgoHDReprogram SHift Kit with resistor, Taylor Shorties,mcgaughys 2/4 drop, Custom painted bumpers, shaved and painted grille shell, rumble bee grille inserts, Debadged, |
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 HTC.com Audio Consultant  |
exactly, going too big you loose exhaust velocity, you got to get a balance between high flow and velocity witch might take a couple of tries.
 Black 2004 Qc 4X4, Superchips,comp 260 cam,home ported & milled heads,6.1 spring and pushrods, PSC1, Taylor Thundevolt 50, Edelbrock TES headers, true duals with Magnaflow, K&N C.A.I., Innovate LC1, MarkVIII E Fan, 180* t stat,Hellwig RSB, 6 X HID,sport running boards and bed accents,lund rool pan, Kenwood KNX7100 nav., R camera, 80G hard drive, 9" flip down monitor, Phoenix gold Tantrum 600.4 for Diamond Audio 4.5" dash and R.F. 5" R doors, Orion Extreme 500.4 for HCCA 6S comps front door, Precision Power DCX 1500.1 for 2 X 10" RE Audio SE, Oxygen Audio 20 Farad cap, Rammat sound deadner, tons of wires |
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Going too big wouldn't be terrible, but having it at the right size is best. Like sppb said, you loose exhaust velocity, which in essence, is a vacuum in the exhaust system. When the vacuum is at its best, when the valves overlap, that vacuum will actually increase suction on the intake which helps performance obviously. Of course, this is more important on HIPO race engines. Not so much on a daily driver. So if you absolutely need the performance then do the research, but if you just want a nice exhaust system that will give you a few more horse and a nice tone on your daily driver, I wouldn't worry too much. Just don't do something radical in size. At the very least, just match the pipe size to the collector size. I think that makes sense. But then again, I'm in no way an exhaust expert. I'm only an expert on eating food lol
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