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Custom Dodge Ram Performance Mods - Engine - 5.7 HEMI V8 Discuss modifying your Dodge Ram with Performance Parts and Accessories!
Factory Spec: 5.7-liter HEMI® V8 engine - 390 horsepower, 407 lb-ft of torque.


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  #1  
Old 07-17-2010, 09:43 PM
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Default Exhaust Back-pressure

does anyone know if the Hemi rams need backpressure or if it is better to have very little exhaust backpressure
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Old 07-17-2010, 09:47 PM
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You need some so don't go too large on your muffler inlet/outlet size or the tailpipe diameter.
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Old 07-17-2010, 09:54 PM
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I have a Cat bat system S/I, S/O with 3in. pipeand wanted to get new headers but didn't know about what effect that would have on backpressure and if it needs backpressure
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Old 07-17-2010, 09:55 PM
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3 inch is fine. With the headers stick with your stock cats and you'll be good.
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Old 07-17-2010, 09:58 PM
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In the Hemi powered cars, I'd say the less the better but in a heavy truck you want a little to help make that low end torque.
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Old 07-18-2010, 09:42 AM
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Thanks, and I was also wondering if anyone had tried the BBK shorty headers
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Last edited by age525; 07-18-2010 at 03:47 PM.
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Old 07-19-2010, 12:16 AM
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ya i would stick stock cats to create back pressure i didn't i mean i guess i got obx and magnaflow dual exhaust
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Old 07-19-2010, 08:40 PM
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Actually you don't want any backpressure power wise. The problem is when it's gone, it tends to swing the bell curve of the tq upwards in the rpm range. Overall you'll make more power but some feel you've lost it because it's moved up the scale. Key is to gear properly. If you're not willing to gear up, seat of the pants will feel better w/ the lower power numbers.
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Old 07-20-2010, 02:02 AM
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our trucks need tq to get them moving...unlike cars where more open is better (for hp)....just need a good exhaust that promotes efficient scavenging... I kinda went the best of both worlds by runnin 3" true dual exhaust (almost sounds too big but with my setup I need it) to 3"DI/3.5"SO, i went single out to get a little back pressure back..
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Old 07-20-2010, 09:49 AM
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All the scavenging is done long before the main exhaust system. Not much past the header collector your done (thus why header extensions on open headers typically boost power). By increasing backpressure you're lowering the power it could be making and simply boosting the low end only (total under the curve is less) and it just feels quicker because it scoots off the line better w/ the wimpy gearing and stall speed.

The biggest issue is these are trucks and owners still want to use 'em as trucks. Has nothing to do with cars vs. trucks as a car "feels" faster w/ more low end too. It's just easier to crutch past that with less GVM. Most I've seen that are drag racing the trucks really don't have them optimized for the strip. That requires more stall, deeping gearing, really free flowing exhaust, etc. This typically swings the bell curve up the rpm range and kills a little low rpm tq (the power under the curve over the whole range goes up though...there's a difference). Not optimal for towing a trailer at low rpm though so ya gotta decide what part of the rpm range you want to spend the most time in. A truck WILL be faster with a low backpressure exhaust but you have to be willing to turn a little more rpm for it to happen. Can't eat your cake and have it too.
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