Helmholtz resonators: Which one(s) and where do you install? [2019 SHO PP + MRT]

[studio460]

MRT axle-backs:

Hey, all! I just got my MRT axle-backs in Black Ops-black and was wondering where to put the Hemholtz resonator: Which ones will fit and where exactly do they go? Also, do I need one or two?

Currently, the exhaust on my 2019 SHO PP is 100%-stock. Note that I live in California and I can't remember if they do under-vehicle visual-inspections or not. There's even traffic signage in my area which flash, "increasing the sound of your exhaust is illegal." So, third-CAT deletes are probably not in the cards (though, the resonators themselves are likely a dead-giveaway to the more observant).

Someone posted photos of their resonatored, SHO-exhaust, but can't find them at the moment. Uber-anxious to get to the muffler shop and slap the MRTs on, but definitely want to add the resonator(s) at the same time.

Givens:

A. MRT axle-back already purchased/delivered.
B. Exhaust 100%-stock.

Goals:

1. Off-the-shelf, 2.5" Hemholtz-resonator.
2. Weld-on/clamp-on, off-the shelf X-pipe (even if just a short 'X' "connector"). Which brands to look for?
3. Add adapters where necessary to increase pipes to 2.5" (unsure if the MRTs came with 2.25" or 2.5" pipes).
4. Drone: Moderate drone-abatement (though, some drone not a deal-breaker).
5. Desired sonic-signatiure: Deep, throaty-sound (obviously!).

An all-in-one X-pipe/Hemholtz-resonator solution in 2.5" would be ideal: Brands, options?

Thanks!!!

 

[kryptto]

So I have been working on my exhaust. Living in FL I have no inspections. Backpressure on the turbos is the number one issue for exhaust performance.

Once I pulled the downpipes out I am going to pull out the third cat.

I was pro putting in MRT axle backs and removing the stock resonator and third cat as an entire section, running straight pipes back to the MRT.

I am scratching that idea, someone here posted their stripped down exhaust to MRT mufflers (search mrt) and it was very loud - had loud cabin drone - and started to sound like that fapfapfap of what the kids like nowadays. I prefer grumbling sound - I do understand with turbos that is hard to achieve.

Back to you and the reason for my side tour through my decisions I am making - go to some of what you are trying to qualify.

KEEP the stock resonator - it does what you are asking for in keeping the noise from the turbos down. Just put in the MRT, like the videos on the MRT website. IF you want some backpressure relief have a shop cut out the third cat. It's not monitored - good luck finding a shop. You will need to find a guy who can do that work. It will relieve some pressure - won't need any tuning - keep resonator to keep drone to a minimum, and save some cash. Install the MRT axle backs.

That's my two cents. Keep in mind the car has a 3rd cat cause when ford went to pass emissions with the fed government they failed with the two downpipe cats. SO if you remove it you might fail the California emmission testing. TBH the third cat was added more than likely cause of CA emmision standards.

I really like the MRT on stock exhaust, sounds better than other brands.

Keep it simple and you will save money and state regulators.

Found those link here in the forums:

Thread 'MRT axle back' https://shoforum.com/threads/mrt-axle-back.140597/

Resonator suggestion link and exhaust discussion:

Thread 'Mild exhaust improvement' https://shoforum.com/threads/mild-exhaust-improvement.145108/

More comments about removing resonator:

Post in thread 'Exhaust Options/Advice' https://shoforum.com/threads/exhaust-options-advice.143847/post-1583334

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[studio460]

Hey, kryptto—thanks for that very detailed reply! I was pretty impressed with MRT's YouTube demos, so I'm inclined to follow your recommendations. Good to know that the third-CAT delete/straight-pipes or glasspacks wasn't the way to go. So the thrid-CAT has no sensor and won't throw a code? Great!

I had a CAT go bad on my Marauder and the muffler guy just drilled it out—no problem! Anyway, thanks again for all the advice! Now, to get my ass to the muffler shop!!!

 

[kryptto]

Hey, kryptto—thanks for that very detailed reply! I was pretty impressed with MRT's YouTube demos, so I'm inclined to follow your recommendations. Good to know that the third-CAT delete/straight-pipes or glasspacks wasn't the way to go. So the thrid-CAT has no sensor and won't throw a code? Great!

I had a CAT go bad on my Marauder and the muffler guy just drilled it out—no problem! Anyway, thanks again for all the advice! Now, to get my ass to the muffler shop!!!

Thanks for the compliment, now I am no kid and play with YT all day so they are sideways, I know, here are two videos - really audio of my SHO - PPE cattless DP's STOCK 3rd cat, resonator and mufflers.

One how it sounds starting up - second revving.

 

[studio460]

Sounds great! Looking forward to mine.

 

[studio460]

X-pipe: Yea or ney?

Going back and forth on whether or not to add an X-pipe. Still looking for 2.5" X-pipes but unsure which ones will fit. I also recall someone on the Marauder forum claiming they lost power after installing their X-pipe (4.6L DOHC V8). I'm mainly installing it as a presumed drone-abatement measure and unsure of any performance improvements to be had (I assume, minimal to none, or even possibly slightly less).

 

[kryptto]

First off there is a process called scavenging- the way pressure not only pushes its way out of the exhaust system, but also those pulses pulls exhaust gasses out of the system. There is a science to pressure, and I am no engineer.

The truth is I haven't found an aftermarket turbo exhaust system using an H or X pipe, that traditionally aspirated engines seem to use them.

I wouldn't add something to the system that the manufacturer hasn't engineered. If you can find an actual credible source that shows a similar ecoboost with dual exhaust and x pipes.

I am not saying it couldn't help, just saying show me the proof it will help. I am sure there are others with more knowledge. Hey I am just going back to your ask up top. Are you removing all your cats?

I did find on the ecoboost website the following fastest sho.... however is that what are you going for? Drag racing?

802SHO 2010 Build - Page 19

802SHO 2010 Build - Page 19

www.ecoboostperformanceforum.com

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[Mazuroo]

I had to get some work on my 2015's exhaust (flex pipes were rusted away, she will turn 100k tomorrow..). I had him delete the rear exhaust while he had it in the air, re-using the stock tips. Sounds awesome, but yes the drone is a real bummer around 2300RPM. I am going to have 2x J Pipes but on (helmholtz), there are a bunch of calculators online; the drone on a 6'er is the worst from 2100 to 2500, which equates to about 34 inches or so of pipe.

 

[kryptto]

X-pipe: Yea or ney?

Going back and forth on whether or not to add an X-pipe. Still looking for 2.5" X-pipes but unsure which ones will fit. I also recall someone on the Marauder forum claiming they lost power after installing their X-pipe (4.6L DOHC V8). I'm mainly installing it as a presumed drone-abatement measure and unsure of any performance improvements to be had (I assume, minimal to none, or even possibly slightly less).

OK maybe you could have this magnaflow installed. There are others that used them in place of the 3rd cat...

Tru-X Universal Pipe - 2.25 inch Inlet/Outlet | MagnaFlow

Universal pipes and exhaust components are designed to make custom exhaust fitments easier and last longer. Part 10790 has an Inlet/Outlet diameter of 2.25 inches.

www.magnaflow.com

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[studio460]

Thanks, kryptto! A quick Google-survey revealed a lot of "No!" replies on installing X-pipes on twin-turbos; citing the application is only meant for N/A-engines. Virtually all reported that an X-pipe will notably attenuate exhaust-sound.

Then I stumbled on this interesting post on a Porche 996 forum here:

"Exhaust Review: Speedtech 2.5 X-Pipe

" . . . I have had the exhaust for about a month and have driven around 1500 miles. The car has an APR ECU flash and a Sachs 2.5 clutch, but is otherwise stock . . . I did a lot of research and watched a lot of videos before I purchased my exhaust. I was initially going to buy a used twin-can design, but fell in love with the exotic sound of the X-pipe design.

" . . . Before the exhaust was installed, I was worried that it might be too quiet for my tastes. I was pleasantly surprised. I should have known an exhaust with no real muffler would not be quiet, even with 100 CEL cats. The cold-start is mean, with a crackle and pop that settles into a low rumble not unlike a large displacement sport bike.

"The overall sound is louder than I expected, given the smaller 2.5 design over the 3.0. That is a good thing. There is no real drone, but the sound is greatly amplified and not quiet at lower revs. It is not quite as loud as my NSX, but few things are.

"I was very surprised at how exotic and high-pitched the sound is at certain RPM. As with my NSX, it plays a beautiful high-note at around 2700 RPM and sustains and raises it until around 3500 RPM.

" . . . It sounds far more like a naturally-aspirated 911 than I could have imagined possible. I love the ability to hear the turbos as they spool [emphasis added] . . . at full throttle there is a nasty bark and the expected monstrous whoosh.

"My butt-dyno can feel a decent increase in power as to be expected with such a free-flowing exhaust and 100 CEL cats. I would estimate that with the APR tune the power is something in the range of 530hp/540tq at the crank. It certainly feels like a car that could run mid 11s and trap in the low to mid 120s.

"A friend of mine came over last Saturday for a car play-date, as my wife likes to joke. He has a long-hood 912 and a 996 C2. I took him out in the NSX and then the Turbo, letting him drive each after a short ride. He had a great time and was very impressed with each's . . . "

[Listen to YouTube video here (skip to 00:26):]

 

[studio460]

. . . There are others that used them in place of the 3rd cat.

Hmmm . . . now wondering if I can get away with deleting the third-CAT (and replacing it with the X-pipe), and still pass inspection. How tight are things under there? Is there room enough for both?

 

[kryptto]

Funny you ask me, I was wondering the same. It's not a large cat, but very possible their small xpipe from Magnaflow might just fit. My research much like yours tells me xpipes are better on naturally aspirated engines.

I am getting my car put up on a lift today. Let's see if I can get a tape measurement.

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[Ta2dResqr]

Hmmm . . . now wondering if I can get away with deleting the third-CAT (and replacing it with the X-pipe), and still pass inspection. How tight are things under there? Is there room enough for both?

As far as a check engine light, yes. The third cat is after all sensors. If they use a sniffer, you may not pass emissions. The other issue is making it look factory if they do visual inspections. Without cutting one open, it appears to be similar to an X/H pipe. Both banks feed into the third cat and two pipes exit. I started doing a little research about eliminating the third cat. I also found from a performance aspect, NA are better with the X/H pipe and twin turbo is better without. We do not have emissions checks here. I am currently planning to use two individual straight pipes to make the car a true dual exhaust.

 

[kryptto]

As far as a check engine light, yes. The third cat is after all sensors. If they use a sniffer, you may not pass emissions. The other issue is making it look factory if they do visual inspections. Without cutting one open, it appears to be similar to an X/H pipe. Both banks feed into the third cat and two pipes exit. I started doing a little research about eliminating the third cat. I also found from a performance aspect, NA are better with the X/H pipe and twin turbo is better without. We do not have emissions checks here. I am currently planning to use two individual straight pipes to make the car a true dual exhaust.

@Ta2dResqr so you are with me - no X - H pipe is better for turbo.

What about the drone? I was going to have the 3 CAT deleted - and run 2 pipes to the resonator? Thoughts?

I also found from a performance aspect, NA are better with the X/H pipe and twin turbo is better without. We do not have emissions checks here. I am currently planning to use two individual straight pipes to make the car a true dual exhaust.

 

[studio460]

tl;dr: keeping factory-resonator.

Took my SHO and MRTs to the muffler shop today and got a look under the car (doh! totally forgot to take a picture!). The third-CAT is really small, up near the front. The factory-resonator, to the rear. The MRTs I received don't exactly fit:

1. Shop needs to add about a 30° elbow since the factory pipes aren't horizontal.
2. Hangers aren't in the right place. Shop needs to de-weld the MRT hanger and add a hanger on the other side; MRT hanger puts the tips too far inward of the bumper-cover cavity by about two inches.

So all that's gonna add some extra labor, damnit. WTF, MRT? Too much to do this afternoon (plus, I'm having them install the Whiteline anti-roll bar), so will bring it in tomorrow morning.

Decided against replacing the third-CAT since the shop says California does do visual-inspections (been driving electrics on my commute to work since 2014 and my Marauder hadn't been running for a while, so I have no idea what current smog-inspections entail). If I were to delete the third-CAT, I would go with straight-pipes; the CAT is only about 12" long, if that. Also keeping the factory-resonator for now.

So, I will have a 100% factory-exhaust up until the MRT axle-backs. Just finished spray-paining the mufflers in high-temp matte-black, since only the welded-on MRT tips came in "Black Ops." The tips do look great though and appear beefier than the Ford tips. Also, I had hoped the Black Ops tips were black-chromed—appears they're powder-coated (though, a very nice job).

 

[kryptto]

I will bet after they get them fitted it will sound better. I am gonna have the 3rd cat cut and straight piped.

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[studio460]

Another option, which is what another shop did on my Marauder, was to simply drill-out the CAT. After drilling, the Marauder passed smog multiple times (surprisingly), and never threw any codes. Also, since the SHO's lacks any sensors, I may have them do that if it doesn't add too much to the bill; I'd guess you'd get near the same benefit as a CAT-delete, but without any visible changes (i.e., since the CAT is modified only internally, it should pass visual inspection). In fact, if they sold "empty" CATs, that would be an attractive option. During my last smog-check (more than five years ago), I don't recall seeing them use a sniffer. All they did was plug into the OBD-II port. If fact I don't recall seeing anyone insert any probes into my exhaust for some time.

 

[thenewguy]

You can try 2 options, one is what i have, vibrant resonators in place of the mufflers

If you want it louder, you can take off the resonator and 3rd cat and put a resonated magnaflow x pipe in its place, if you still want it louder, remove mufflers and keep the magnaflow x pipe

 

[Ta2dResqr]

Another option, which is what another shop did on my Marauder, was to simply drill-out the CAT. After drilling, the Marauder passed smog multiple times (surprisingly), and never threw any codes. Also, since the SHO's lacks any sensors, I may have them do that if it doesn't add too much to the bill; I'd guess you'd get near the same benefit as a CAT-delete, but without any visible changes (i.e., since the CAT is modified only internally, it should pass visual inspection). In fact, if they sold "empty" CATs, that would be an attractive option. During my last smog-check (more than five years ago), I don't recall seeing them use a sniffer. All they did was plug into the OBD-II port. If fact I don't recall seeing anyone insert any probes into my exhaust for some time.

SHO has sensors, they are before the primary cats and after the primary cats (Kind of misleading, there are 2 primary cats and the "third" cat is a mutual secondary). As far as gutting the cat, that is a very common option. You can either pull it off and beat all the material out in small chunks (pain since it is all one assembly on our car), or another popular option is to drop it down, cut the top open with a plasma cutter or cutoff wheel, remove the core, and weld it back up. Both can cause bad drone as you now have a big empty chamber. If you wanted to get real fancy, while it is open, you could install straight pipes inside.

 

[CCXVI]

Helmholtz resonators are huge in the Q60 world, where I am now. They make an incredible difference when done right. As to the X pipe question I'll put in my experience, on the SHO I had the exhaust exit behind the front wheels for a while. It went from cats to X to 90° bends and out just behind the wheels, and had no drone at all while cruising. I tried similar when I went back to stock, but had to add a muffler and resonator to tame all the rasp. It seems like the longer the pipe, the more drone you have, but a couple people had said when I told them there was no drone on the side exit that the X pipe was a big reason why.