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SRT Exhaust conversion with Dual In - Dual Out Muffler

15K views 41 replies 8 participants last post by  Strongjeff 
#1 ·
I have a 5.7L Hemi that I'm in the process of changing the rear bumper to the SRT and installing a center exhaust and I'm considering a true dual setup from the cats back. Does anyone have experience with cutting the y-pipe right after the cats and attaching a dual in - dual out muffler?

I have been researching sound clips for the Magnaflow 12599 muffler but I'm not sure if converting the factory y-pipe to a true dual out would decrease back pressure and hurt performance. Please chime in if you have any experience with this conversion and let me know your thoughts.

Much appreciated.
 
#2 · (Edited)
With a dual inlet muffler the muffler will equalize the pressure. True dual is when each side is independent with two mufflers... Which is really hard to do considering the space we have to work with between the frame and rear driveshaft. The only good way to true dual is to remove the rear tire and put a couple mufflers back there. You will lose back pressure no doubt going with a dual exhaust setup... I would probably go with 2.25 duals if your engine is stock, since the stock mid pipes are around 2.25 also.
 
#3 · (Edited)
Thank you for the feedback. I misused the term "true dual" exhaust since my intention is to have a setup like the OEM SRT exhaust...one muffler for both outlets. Tire will be removed to allow for center exit. I have the Overland model and didn't realise the mids were only 2.25 in diameter. Long term goal is to add the SRT manifold and mids since I've read that is where the biggest choking point is with the 5.7L. My goal is similar to what you have already done with yours.

Thanks again for your input/advice.
 
#4 ·
I have a set of srt8 manifolds... Mid pipes... And full srt8 cat back if your interested. I bought another set of manifolds for backup and was going to go the total srt8 route... But now I think I want to go with a 3.5 or 4 inch pipe. Pm me if your interested and ill email you some pics.
 
#5 ·
PM sent.
 
#6 ·
Would it be possible to cut the OEM Y-pipe off right after the O2 sensor and simply adapt an X-pipe to the end of the 5.7 mid-pipes to allow for a dual-in, dual out muffler? This would allow me to install and retain a permanent "cat-back" setup until funds allow me to later add the OEM SRT manifolds and mids to compete the setup.

 
#8 ·
I would save yourself a lot of aggravation trying to mate an x pipe to your mid pipes and just get a y pipe, turn it around and you will instantly have two outlets to put into your muffler. The x pipe will cost more money to install and most likely give you marginally better performance. The o2 sensor on the passenger side looks like it is pretty close to where you are cutting for an x pipe, and the pipes kind of do some funky angles to clear the transmission cross member. Plus with the y pipe you are basically only cutting the flange off your mid pipes so if you ever want to go back it will be easier.
 
#9 ·
Did you use the M8x30x1.25 flange bolts to attach the manifolds to the heads? Also, is there a gasket needed between where the manifolds attach to the midpipes?
 
#10 · (Edited)
Well, my patience paid off. I found a set of SRT manifolds and SRT midpipes and I'm in the process of gathering all the hardware to take on this project. Here a few photos of the parts I acquired. A HUGE thanks goes out to DannyVtCA and Viking757 for all their knowledge and experience they've shared with me so far taking on this project.

SRT8 mid pipes



SRT8 exhaust manifolds



I found the manifold gaskets from an '09 5.7L and they match up perfectly to the "D-shaped" ports of the SRT manifolds.
The gaskets are made by Fel-Pro. Part # MS970 and I found them at rockauto.com. The backside have the cushioned gasket material that mates with the surface of the manifold that you can't see in the photo.



Marking up the EGR port and extra bolt hole using the gasket as a template.



The faces of the manifolds are a bit corroded so I dropped them off at a milling shop yesterday to have the faces resurfaced.
The first machine shop I took it to informed me that the steel was so hard it was difficult to refinish them with standard rotary disks so they referred me to another milling shop that had the milling lathe. This is truly the best way to resurface the faces.

Here's an example of how they looked when I dropped them off.
I'll post photos of the resurfaced faces on Friday when I pick them up.



Here's an example of the milling machine that is being used to resurface the manifolds.



Stay tuned for more info.
 
#11 ·
Looks good man! I'm subscribed, hope you have better luck with those damn mid pipes than I did. Remember you have to drop the cross member 2 inches. Also, when mating the muffler flanges to the mid pipe flanges you need to drop the hangers over the axle.... Because you are dropping the mid pipes 2 inches the hangers are too high and the muffler flanges don't mate up very well and leak.
 
#12 · (Edited)
I haven't have a problem with my manifolds... I just wire brushed them really good. Resurfacing them may be overkill. Plus if they remove too much surface your going to have problems mating the mid pipes up because they would have essentially made the distance between your manifold outlets narrower. Cleaning the surfaces of your heads is going to be pretty tricky.
 
#13 · (Edited)
Fortunately, the faces aren't warped so they won't have to remove much material. Good point about the alignment of the mid pipes if they are slightly narrower. I'm not sure what to do yet if they are off a bit. I'll have to cross that bridge when I get there.

I'm temporarily going to either find a used OEM SRT exhaust or purchase an SRT pre-made catback exhaust so all the flanges will line up at the mid pipes. I figure the exhaust shop can then put the support hangers wherever they need them.

I'm not sure what I'm getting myself into but this should be a fun learning experience. Thanks again for the support. I definitely need it.
 
#14 · (Edited)
If your motor is completely stock I think your going to get a lot of low end torque loss with the mids and dual exhaust setup.... You will gain with the manifolds... Then lose so much with all that pipe. So you will be doing this for aesthetics and noise. The stock exhaust you have on is spot on when it comes to diameter of the mids and catback for the stock motor....The log manifolds are the problem. I hope you plan on the doing the cam, and save some money and do it yourself. It's not that bad, hardest thing is wiggling the radiator in and out... Other than that its a piece of cake with the right amount of time and tools. What does everyone else think? If he stays stock cam should be go 2.25'' or 2.5'' duals?
 
#15 ·
It is completely stock right now. I'd like to get more feedback from others about the loss of low end response. You've got me thinking that until I do the cams and CMR tune maybe I should temporarily add a Y pipe after the SRT mid pipes and do a 2.5" single-in, single-out muffler in the meantime. (???)

I'll be installing an OEM SRT intake tube in place of my stock resonator box this weekend and I have a throttle body that will be ported to 85mm as well.

Any thoughts would be appreciated.
 
#16 ·
Your opening up a can of worms with the srt8 mids. They have major hurdles to get them to work. Your cheapest and probably best bet would be to cut the flanges off them, mate them to your current mid pipes and install the srt8 manifolds. Then get a pre made 3'' cat back of your choosing that will bolt right up. You will only be paying the shop for the manifold install and flange weld work. Putting a pre made cat back on is simple. If you wanted to improve your performance a little more cut the stock y pipe out and install the magnaflow dual 2.5'' inlet, single 3'' outlet y pipe and mate that to your stock mids and pre made cat back. This setup would be more than sufficient for most cams, and in the end you will save major money. I know it is a shame to chop up those srt8 mids, but in the end you will have a jeep that runs stronger.... The mids aren't what is holding you back. You would have to pay a metal working shop probably more money than those mids cost you to fabricate special flanges to mate to your srt8 manifolds. Only two people have successfully installed srt8 mids.... Viking and myself.... And I can say that they fit like garbage. I don't like how close they come to the tranny and how low you have to drop the tranny cross member.... It does not make for a lot of confidence driving around with a low cross member and a 1200 degree cat rubbing your tranny pan. The dual exhaust dream on a wk hemi is somewhat of a stretch... Without expensive run flat tires your asking for trouble.
 
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#17 ·
If your hell bent on duals, here is my future plan. Cut this vertical support section out of your rear bumper support to snake dual pipes out the passenger side. But, my advice is just use a single inlet dual outlet muffler.
 

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#18 · (Edited)
I am going to scrap my srt8 mid pipes at some point and use the flanges to fabricate a set of high flow custom mids... probably 3''... that go into a dual inlet dual outlet flowmaster muffler I already have... But when i do im going to awd dyno and get a custom tune to go along with such a large exhaust. I'm going to cut that vertical section of the bumper support to get the duals out the passenger side. I am opening up a can of worms also because getting two 3'' pipes to clear the tranny support is a stretch also.... My plans are to probably convert the pipes to oval to snake them through. I don't really want to spend another grand on exhaust right now when mine is fine. But with this setup I will have to uninstall for smog testing. I expect to lose low end with oversize mids... But pick up massive top end power. I had jeep srt8 magnaflow mids which are 3'' on for a month right after my cam install... And they really touched tranny pan bad...And my god I have never accelerated so quickly from 35-100mph, it was running into that dual 3'' inlet dual 2.5'' outlet muffler and 2.5'' pipes exiting where the spare is.
 
#19 ·
I did this mod 2 years ago to my 09 GC..... excellent bang for the buck considering used srt8 is pretty reasonable. Spare tire needs to go so maybe get a donut size one and put in the back??? My setup had the rear reso's cut out so there is some drone but not too bad. I think mabe the gains will be better using the eagle heads as the exhaust ports are perfectly matched the srt8. But with 93 octane predator tune and K+N intake it completely kicks ass over the stock 5.7 by a huge margin...... 14.18 I the quarter in hot Florida heat..... This thing runs up to 140 easy and was still pulling but that was enough for me. I have been sitting on a 6.4 VCTvcam for a whil and need to get it in and tuned..... 13's should be easy...... For a relatively stock 5.7 the srt8 exhaust is the best choice. Stock logs and suitcase muffler choke the crap out of our great hemi motors!!! TBF
 
#20 · (Edited)
Did you keep your mids or swap in the srt8 mids Tampa bay? If so, how the hell did you get them to fit? I tried for hours and could only get about 1/10 of an inch clearance with the tranny pan.. And when everything heated up I saw contact. I dropped the tranny support two inches.... I found... The further you keep dropping the tranny support, the more clearance you get with the tranny pan. Someone has mentioned denting the tranny pan, but it is a risky move since the area where it is rubbing is very close to the spin on filter. And in the end you can only orient the mids down so much before they will start leaking at the manifolds.
 
#21 ·
Does anyone have photos of the completed SRT manifold and SRT mid pipe install they could share? I can't seem to find any photos of it done anywhere. I'm particularly interested in how the tranny support looks dropped and how low it hangs.
 
#22 ·
Sorry man, I didn't take any photo's... Because I wasn't too proud of it. There is a lot of power and stress on that cross member, just make sure you use hardened washers... And yes you can move the outer longer bolts to the inner bolt holes, so you only have to buy 4 super long bolts. Pull one out and go to Home Depot, they have the bolt size guide hanging the the fastener section... Then measure the bolt and add at least 2'' to be safe when ordering. I was preliminary pricing them out before I called it quits... They are probably $10 to 15 per bolt since they are metric, need to be a certain hardness, and special order from Massachusetts or somewhere... Maybe it was bolt depot that had them... Not sure. The tranny cross member is pretty visible without dropping it 2'', I just knew that I could never get away with it at smog time with all these washers glaring the smog tech straight in the face. There is also some trimming of metal/rubber bracket that is sandwiched between the tranny and the cross member, but nothing too bad, just the metal edge of it.

Food for thought... You can open up your stock cats to whatever size pipe you want, I've seen ram guys fabricate 3'' mids with the stock cats.
 
#23 · (Edited)
There's probably a reason only you and a couple of other guys have done this mod. I'm beginning to doubt if this project is even worth the headache. If anything, I'll talk to an exhaust shop about cutting the flanges off the SRT mid pipes so they'll mate up to the manifolds and then adapt them down to the stock WK mid pipes. At the y pipe I'll use your recommendation of using a single in, dual out muffler and then exit out the center of the bumper.

I'm still waiting for my rear bumper claim to be processed. After a month of waiting, excuses about delays due to weather, and so on, Greyhound Express informed me they have lost my rear SRT bumper which I wanted to have installed before doing anything with the exhaust. Unbelievable I know. This just gives me more time to think about the right approach to the mid pipe/crossmember issues.

On a positive note I got the manifolds back from the machine shop yesterday and they turned out great. At the recommendation of the machine shop they drilled the extra bolt hole next to the EGR port in an oblong shape to avoid any alignment issues. The hole in the manifold gasket that you use as the template is also oblong so it was better to be safe than sorry.





Oh, and I had some fun with a wire wheel on the manifolds last night. Oooh, Shiney!

 
#24 ·
Hey rock, I am 99.9% sure that there is no bolt hole where the machine shop put the oblong hole in your manifold... Ill check my old heads later to make sure...
 
#25 · (Edited)
It is my understanding that there are nine bolts on the passenger's side manifold. The slotted hole I had drilled should be for this slotted section that the 6.1 manifold doesn't have.



Are you confusing it with the driver's side which only needs 8 bolts?

 
#26 · (Edited)
Yup, your right man... Checked my old head and there is a nine hole... My bad... Been a year since I installed mine. I definitely didn't drill that hole, maybe that is why I get an egr low flow code.
 
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