Hi all! I am new to Rams, but have other modded cars. I have an '03 4.7 with a flowmaster 44 in place of the stock muffler (came on the truck). I am also in CA, so I have 3 cats rather than just one. Would doing a 3" catback with a y-pipe to duals with no mufflers cause any loss of back pressure? Or do the CA cats give enough back pressure not to lose torque? Any gains by straight piping or just sound?
Newbie questions
- Thread starter Vytasb
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Back pressure is a misnomer. What you are referring to is exhaust scavenging. As gases exit the pipe they draw the gases behind along outward. So if you go too large a diameter your engine now has to not just pump the pistons, but the exhaust stroke has to work harder to push the exhaust out. That being said, you're not going to get improved performance from pulling the muffler (or reduced low end for that matter).
Make sure you are actually seeing catalytic converters (with heat shields and/or O2 sensor bungs) and not counting factory exhaust resonators as cats--I can't remember when Dodge started with the resonators on RAM trucks or if they used the same exhaust on all engines, but resonators would be inline after the muffler.
For the RF Trolls out there (you know who you are), this example is over simplified I realize, but helps to advise the OP what he's really trying to avoid.
Yes, cats and muffler and resonator, and length of pipe all have an impact on scavenging. TOO free flowing exhaust can be a problem for an naturally aspirated (N/A) vehicle, but staying CARB legal in Corruptifornia should be your larger concern--you have to pass smog . In your case anything you add needs to be Corruptifornia Air Resources Board (CARB) approved for street use or you'll have to strip it all off at inspection time.
Taking the muffler off isn't going to contribute to speed or torque, just tailpipe noise, and the Commissars of the People's Republic of Cali don't like noise. A lot of jurisdictions still carry decibel meters in their patrol vehicles specifically for the purpose of harassing and impounding (J/K), okay, ticketing and collecting contributions to the government trough from those with noisy exhaust.
So, since its not a performance issue with a 4.7L, if you want duals or just better sound, as long as your cats aren't shot, adding a CARB certified CAT-back system or as little as a 2.5" -3 " single-in, with 2.25" dual-out muffler with pipes to the rear bumper, or even turned down after the axle will give you the sound you want, without all the activist-government headaches. If your cats need replacing, well then that opens up more possibilities, but more $$$ needed.
Make sure you are actually seeing catalytic converters (with heat shields and/or O2 sensor bungs) and not counting factory exhaust resonators as cats--I can't remember when Dodge started with the resonators on RAM trucks or if they used the same exhaust on all engines, but resonators would be inline after the muffler.
For the RF Trolls out there (you know who you are), this example is over simplified I realize, but helps to advise the OP what he's really trying to avoid.
Yes, cats and muffler and resonator, and length of pipe all have an impact on scavenging. TOO free flowing exhaust can be a problem for an naturally aspirated (N/A) vehicle, but staying CARB legal in Corruptifornia should be your larger concern--you have to pass smog . In your case anything you add needs to be Corruptifornia Air Resources Board (CARB) approved for street use or you'll have to strip it all off at inspection time.
Taking the muffler off isn't going to contribute to speed or torque, just tailpipe noise, and the Commissars of the People's Republic of Cali don't like noise. A lot of jurisdictions still carry decibel meters in their patrol vehicles specifically for the purpose of harassing and impounding (J/K), okay, ticketing and collecting contributions to the government trough from those with noisy exhaust.
So, since its not a performance issue with a 4.7L, if you want duals or just better sound, as long as your cats aren't shot, adding a CARB certified CAT-back system or as little as a 2.5" -3 " single-in, with 2.25" dual-out muffler with pipes to the rear bumper, or even turned down after the axle will give you the sound you want, without all the activist-government headaches. If your cats need replacing, well then that opens up more possibilities, but more $$$ needed.
Last edited:
ramportin1
Sickest member here
to answer your one question, you will get zero gains from running no mufflers
Vytasb
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- 2019
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- 5.7 eTorque
Thanks all! I've never been a fan of flowmaster, but I don't think I want to spend money on exhaust work if I won't gain anything but sound out of it. I'll probably go for a tune next. I read the predator doesn't work on 03 4.7's, but I read the next best one is the superchips. Or any other recommendations?
