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3 in. exhaust?

10K views 15 replies 7 participants last post by  Gruvin84SS 
#1 · (Edited)
So im looking into doing my exhaust. Im really trying to avoid paying someone to do it for me. My plan was to get long tube headers. Coming right off the header collector would be 3in exhaust cutouts then exhaust tubing to where the stock ehaust comes. 3in cats then straight piping to the rear into 3in inlet and 5in oulet tips. Description might be confusing but tell me what you think if it makes sense. Here's a picture of what I'm trying to do.
 

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#4 ·
I know the stock exhaust is 2.5in. Im gonna be redoing the whole exhaust to 3in. The cutouts will be for track use and show only. And yes, I plan on getting ear plugs. I started my car once with only the headers on and it was loud!
 
#5 ·
I don't think I would lose power with 3in pipes, in my opinion. Wouldn't the exhaust flow better? I figured I would keep the diameter 3in. because thats the diameter of the header collectors. If I put a reducer to 2.5in. wouldnt that cause restrictions to the flow? Im just going on my own logic and my auto mechanics instructor who used to be in racing (I think drag racing) really likes the idea.
 
#6 · (Edited)
3" is a little bit overkill especially with the older 5.7L. I'm doing SRT shorty headers on mine which have either a 2.75 or 3" collector area, to 3" cat-less mid pipes, to 2.75" stock SRT catback on my R/T with the newer 5.7L. From what i've been told even this is a little overkill, but oh well. You should be fine with that setup, however it's going to be LOUD LOUD LOUD all the time.

Bigger exhaust piping isn't always better. It comes a point in time where it's just overkill. Exhaust systems work on scavenging. The exhaust pulses work in such a way that one pulse is used to help pull the other out away from the engine. By needlessly increasing the size of the piping, you are changing the rate at which the exhaust pulses can effectively scavenge and therefor hurting performance in some aspect. Will you make more power with this system compared to stock, the way you have it planned out currently? Yes. Would you make more power with this same setup, but in a 2.5" trim? Probably.

There are times where it is necessary to increase the exhaust diameter, such as instances of larger displacement engines, forced induction, etc.
 
#7 ·
Stock exhaust on your car is actually 2 1/4"



It is 2 1/2" at the mid pipes forward, but from where the mid pipes meet the x pipe (Black arrow) on back, it's 2 1/4"



Unless you have drastically increased the incoming air flow, adding a 3" exhaust will hurt your exhaust's ability to scavenge the charge out of the cylinders, reducing power.

You WILL lose power, unless you are making about 450hp right now...

Stock exhaust cuts down 1/4" after the cats, that's pretty normal for any exhaust. You want your gasses to flow fast enough to suck the fresh charge into the cylinders, but not be impeded. Correct size for the Charger with 350HP works out to.... 2.25-2.5"
 
#8 ·
Well, with where everyone seems to be goin, I'll probably put a 3in to 2.5in reducer after the cutouts. Now with that settled, lets talk cats and X/H pipe. Does it matter the placement of the cats? Are they fine where I have them in the pic I drew or...? And whats the difference between an X and H pipe? Is it really the same thing just different in that one's an X and the other's an H? I forgot to draw it in the pic but I would have an H pipe right after the cats.
 
#9 ·
H and X pipes both basically do the same thing. They equalize the exhaust scavenging of both sides. X pipes are usually a little more efficient at doing so and often give you higher peak HP numbers. Also, X pipes give you more of a raspy race car exhaust note, where as H pipes give you more a deep old school muscle car growl. The chargers come with X pipes from the factory, and that's what I would leave on there since I like the raspy rumble of the X-pipes. The cats you want as close as possible to the header collectors, otherwise they're not going to work that well, and you'll get a catalyst inefficiency CEL. As it is you'll probably get one with longtubes anyway, unless you run a California legal converter and use some oxygen sensor spacers.
 
#10 ·
I did this with an SRT Magnaflow catback. Didnt dyno, but i felt the loss of torque. I countered this loss with a huge MoparCAI intake tube, and replaced the(in my opinion) restrictive Mopar one filter with a Spectre Cone filter, removed the driver's side radiator plastic so that more and colder air would be forced into the filter compartment. Cruised better and got back the torque I had lost as I felt. I thinnk 2.75 would be optimal, 3 inch may prove better for future modding though... let us know whatsup tho!

as for x pipes and whatnot, since u have a daytona version u may have a wider exhaust, u may have the beefy xpipe, i would leave that on. And the resonators
matter of fact go 2.75 all the way to the resos from the x pipe. No drone, smooth sound, and performance
 
#11 ·
as for x pipes and whatnot, since u have a daytona version u may have a wider exhaust, u may have the beefy xpipe, i would leave that on. And the resonators
matter of fact go 2.75 all the way to the resos from the x pipe. No drone, smooth sound, and performance
Sure you don't mean 2.25"/2 1/4"? I don't even think the SRT has 2 3/4" exhaust from the x pipe back.

All information I have points to the mid pipes (cats) being 2 1/2"

I measured them myself.

As far as I know, the Daytonas have a different mid muffler internally ONLY, and different tips. The muffler is a little more free flowing straight through design that was incorporated into all R/Ts around 2008 or so.

Mid pipes/cats: 2.5"



I am unaware of the Daytona having larger exhaust, other than the muffler internals.

If you measure the very tip, which is flared out for looks, THAT may actually measure 2.75"... but it's 2 1/4" pipe from the mid pipes back.
 
#12 ·
The SRT does have a 2.75" exhaust from the X-pipe back. I know this because I had to buy new 2.75" ID exhaust pieces to weld on for the flared out parts that slide over the ends of the mid-pipes because the retard I purchased the exhaust off of decided to slice them open because he couldn't get them off his midpipe when he changed his exhaust. The exhaust after the flared out area that goes over the mid-pipe then goes down in size to a 2.75" OD piping all the way back to the tips that are 3.5" I believe?
 
#13 ·
Where the x-pipe attaches to the mids IS 2.75 on the SRT. That's the coupling, which is stretched to fit the mid pipes (cats). The rest of the x pipe, and exhaust back to the tips are 2.5" (it may flare bigger at the joints where pipes go together, that is not where you measure pipe)

The R/T is 2.5" at the cats, to the x-pipe. The x-pipe is 2.25" and the rest of the system to the tips is 2.25", but the joints may flare larger.

It's possible you bought an aftermarket exhaust, those are bigger than stock...
 
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