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4.7L Exhaust upgrade help!

23K views 62 replies 8 participants last post by  sconnie89 
#1 ·
Hi everyone just looking for some input from those who have upgraded their exhaust on the 4.7L 2002 Quad cab. I want to do dual exhaust but I'm not strictly after sound only, would like to gain a little from the money spent. I like the sound and look of the Flowmaster 50 series but not sure how it compares to the 40 series or the Magnaflow. I'm kinda lost and don't know where to start! I have been reading that a Y pipe with single in and dual out is a good route for this truck to avoid losing low end torque?? Really just need a good setup with a deep tone and a few pony gains coupled with a CAI. Any input is greatly appreciated! -Chris
 
#2 ·
You aren't really going to gain much out of just an exhaust. The difference between Magnaflow and Flowmaster will be very minimal, especially on a 4.7. I'd honestly go with whatever you think sounds better.

Magnaflow will flow slightly better because of it's straight through design while the Flowmaster will be louder because of it's chambered design. IMO the 50 Series HD muffler is a great choice. Nice and loud when you get on it, but no highway drone at cruising speed.
Swapping out the Y-pipe is also a great idea since the stock one is very restrictive. IMO just swap that out and then get a cat back dual exhaust system. I had the Flowmaster American Thunder system on my 4.7 and it sounded great (came with a 50 Series HD muffler). There's a sound clip linked in my signature below if you're interested.
 
#3 ·
I have the Magnaflow dual exhaust kit on my 2013 4.7, the truck lost precious bottem end torque,it gets it back above 4,000 rpm till it short shifts itself at 5600 rpm,but how often do you drive at those rpm's.
I'd do as suggested above,a decent single in/single out muffler on the stock 3" pipe.
3" pipe is lots big enough for a 4.7,the muffler leaves a bit to be desired though.
I've looked at swapping the Y pipe as it is a bit crushed.
Not sure there's enough exhaust flow from the little 4.7 to make the y-pipe a restriction though
I have the AirRaid CAI and a ported 78mm throttle body on mine,can't say as i'd spend the money again.
If i was doing it again,i'd knife edge the stock throttle body and build a ram air kit for the stock airbox,and keep close to a 1,000 bucks in my pocket,but that's only my personal opinion
 
#5 ·
With duals you want either 2.25" or 2.5" max diameter. For single do at least 2.5" and 3" max. I have 2.5" duals to 3" single on my 4.7 and didn't lose any power anywhere. Also didn't gain 100hp but feels stronger all around, and sounds great. I recommend a straight through muffler, I find chambered to be "tinny" and annoying sounding.
 
#6 ·
Are they the stock head pipes Sean,if so,they're only 2.25" to the 3" single.
I'd avoid dual 2.5" pipes,that's what mine are with the Magnaflow kit,and i honestly don't think the truck would spin the back tires on ice.
I lost a pile of torque under 4,000 rpm,truck pulls like gang busters after that for 287 cubes,but man waiting for it to get to 4,000 rpm takes forever,lol.
After 4,000 it puts a smile on my face though:smileup:

Come this spring i'll probably put the stock pipe back on with a decent Magnaflow muffler instead of the Magnaflow dual exhuast kit.
Truck does sound really good though,wife loves it,lol
 
#7 ·
Stock is 2.5" before the cats and 2.25"(roughly, it's actually not exact) after the cats then after the y pipe it's 3" single.

Right now I have a short section of 2.25" after the cats, then 2.5" dual to 3" single with cats. Redoing the whole exhaust friday will be similar but no cats and all 2.5" before the y.
 
#8 ·
I'll be damned,you're right.
Figured it was nice enough today to finally put my drain hose on my Moroso catch can,figured while i'm under the truck i'd check up on you,lol
I had measured my pipes after the cats awhile ago,but had never reached up and measured before the cats.
Lad you impress the hell outta me,you know these trucks pretty good,lol:smileup:
Rick
 
#9 ·
lol I did the opposite, when I ordered pipe I measured before the cats and not after. It was quite a shock when I held the new 2.5" pipe to weld in there and it was a different size. That was one of those "OH F*CK" moments lol. So we made "ghetto" collectors by cutting slots int he larger pipe and hammering it down on the smaller pipe, then welding it all up(needed the truck the next day). One of the main reasons I want to redo it.

That's the only reason I happen to know that so well lol
 
#10 ·
LMAO,i know what you mean.
Worst thing is then you're madder then hell at yourself.
I've called myself a few dumb-ass names over the years:i_rolleyes:.

I'm really curious how your exhaust turns out,keep us posted.
Now you got me thinking about mine too,aw crap,lol:shy:
Rick
 
#11 ·
Will do, I'll probably post pictures sunday. I'll have some of my buddy's z28 as well, we are redoing his exhaust too. That's a pretty fun car.

Only thing I'm worried about is if my O2 non fouler trick will work. I've read alot of people have trouble with it on the 4th gens. Not sure what to do if it doesn't work, only other option I can thing of is custom tune but no way I'll give up the superchips. So prob just live with the light... Let's hope the non foulers work...
 
#12 ·
Awright,are you using mandrel bent tubing?

I've heard of the non-foulers,but just what exactly are they.
I've never seen a pic or even a discription of what they entail.


Back when i was playing with my supercharged Buick Regal,the trick was to splice a 100 ohm 1/4 watt resistor inline with the back O2 when you dumped the cat,letting a constant low voltage feed through the 02.
I'm not sure if these O2 sensors work the same though with the grounding circuit.
 
#13 ·
Yeah all 409 SS, mandrel bent. I am eliminating the cats, and instaling non foulers (see attached pic), and will have the whole exhaust be 6 pieces. dual pipes before the muffler in 4 pieces. The muffler (22" magnaflow dual 2.5" in, singel 3" out) another piece. And stock tailpipe the 6th piece. My current exhaust is nice but the collectors suck(as said above), I used aluminized pipe which is ok but he welds were mild steel, and I wish I made it in more pieces for easier removal/trans removal.





 
#15 ·
Thanks Sean.

Looks like the idea is move the orginal sensor out farther so it runs cooler.
I'm assuming they work on a temperature differential if thats the case.
Could a guy plug the hole and attach the sensor right to the outside of the pipe.
I wonder if a guy could weld a stand-off reciever to the pipe and screw the sensor into it.
Rick
 
#16 ·
Or, you can do what I did and just get rid of the Y pipe and get a dual in/dual out muffler. Looks, sounds and works great!
That's actually what I am doing, I'm replacing my y pipe with a dual in/single out muffler :)

Thanks Sean.

Looks like the idea is move the orginal sensor out farther so it runs cooler.
I'm assuming they work on a temperature differential if thats the case.
Could a guy plug the hole and attach the sensor right to the outside of the pipe.
I wonder if a guy could weld a stand-off reciever to the pipe and screw the sensor into it.
Rick
I'm pretty sure the way they work is they take a reading outside the pipe and inside the pipe and compare oxygen content (have no idea exactly HOW) and the way this trick works is by spacing the sensor out of the exhaust stream it somehow keeps it within it's range to not throw a code/CEL. Some people also pack steel wool in the spacers.

I've heard of the electronic resistor simulator trick too.

Supposedly computers are getting more difficult to "trick". So we'll see how it goes... It worked on my s10 like a charm though.
 
#17 · (Edited)
HMM,that's interesting.


If they're checking oxygen content they will be harder to fool.
I thought maybe they might work on a temp differential,but i gotta admit,i'm behind the times on these new ones,lol.
This is the first computor toy i've tinkered with since my old Regal,and it was 10 years ago since i was playing with it,things have changed somewhat since then:thk:

Do you know who's exhaust is that in the picture?
Somebody done a nice job on that system
 
#24 ·
Moved this post up from the ARH headers thread

Thanks Sean.
I started going through your 80 pg build (holy crap,lad,lol),and had picked up the port spacing differances.

I only picked up the pic of a stock manifold and an earlier header though,but it damn near looks like a guy could cut and slice the flanges to work,but it'd take some tube reworking to make the modded flanges work.
And i don't think the gains would be worth the labour and cost though.

Has anybody tried porting the stock manifolds.
Is there enough wall material in the stock manifolds to get any gains from porting them.

Been looking at the 02 sensors,i'm tempted to start probing wires,they might sense oxygen content,but they still use an electrical signal to the computor.
I'm thinking there's gotta be a way a guy can duplicate the closed loop electrical signal to the putor .
Rick
 
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