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Discussion Starter #1 (Edited)
EDIT: Leaving the original text below, but just wanted to write up front that I recently found that my active runners aren't actuating. Will update once I correct the issue.

Hi all. I've recently installed short tube headers and the 392 active runner intake manifold on my 2016 R/T, and the great news for everyone here is that I've got before/after dyno results to share! Please check out the attached photograph which I painstakingly angled to capture a reflection of the car in the glass.

The upper plot shows horsepower while the lower plot shows torque as a function of engine speed. The red curves are the car's baseline performance before the intake and exhaust mods were installed, and the blue curves are after install and tuning on the same dyno. While I only got a few horsepower increase at the peak, the horsepower stays higher beyond the peak and I picked up a ton of power across the low- to mid-RPM range. I spend most of my time in the 2-4K RPM range, so I'm pretty happy with the extra 25-30 horsepower in that range.

For reference, my headers are JBA 1964S-1JS ceramic-coated short tubes and my intake manifold is programmed to actuate the runners at 4600 RPM. I'm also running a Corsa 14985BLK Xtreme catback, but the catback is present in both the before and after runs. Hope this is helpful to anyone considering this modification combo.

Dyno 2020-07-30.jpg
 

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The Pork Wagon (‘14 Cop Charger)
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Very useful before/after comparison, thanks!

If I am reading the data right, it looks like the exhaust upgrade was the most beneficial by far of the 2 mods. As you pointed out, it added performance across the torque band down low, right where the engine spends the majority of its time operating.

The intake’s contribution does appear to be minimal, but I think this is to be expected in this particular application. Its true value as a performance mod would be realized with an upgraded camshaft that helps the engine breath in the 4500+ RPM range.

An upgraded camshaft without the intake upgrade would still run short on breath up top I believe, but that intake’s switch to the short runner design in high RPM operation allows for more breath when it’s needed most by the upgraded cam.

That my understanding of how it all works anyway.

These two upgrades are if particular interest to me BTW, as I am planning on installing a 392 cam in my 5.7L soon. The intake isn’t an upgrade I’ll be doing at the same time, although I know I should. The exhaust was further down the list on future upgrades, but after seeing your Dyno results, I may have to move it up the list a few slots.
 
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Discussion Starter #3
Very useful before/after comparison, thanks!

If I am reading the data right, it looks like the exhaust upgrade was the most beneficial by far of the 2 mods. As you pointed out, it added performance across the torque band down low, right where the engine spends the majority of its time operating.

The intake’s contribution does appear to be minimal, but I think this is to be expected in this particular application. Its true value as a performance mod would be realized with an upgraded camshaft that helps the engine breath in the 4500+ RPM range.

An upgraded camshaft without the intake upgrade would still run short on breath up top I believe, but that intake’s switch to the short runner design in high RPM operation allows for more breath when it’s needed most by the upgraded cam.

That my understanding of how it all works anyway.

These two upgrades are if particular interest to me BTW, as I am planning on installing a 392 cam in my 5.7L soon. The intake isn’t an upgrade I’ll be doing at the same time, although I know I should. The exhaust was further down the list on future upgrades, but after seeing your Dyno results, I may have to move it up the list a few slots.
The last thread I saw you in, I was worried you were trying to talk yourself out of the cam upgrade, glad to see it hasn't worked!

I agree with your assessment, I think the headers gave me most of the low-mid power, but the intake will be a good complement to a cam upgrade that opens up more on the top end. I'd also like to do the camshaft, but I've done a lot in a short period of time and I'm going to need a financial recovery period before I start trying to convince my wife that I need a cam.

Talk to you later!
 

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Thanks for this! I, too have shorties and the AR intake. I’m curious how you landed at 4600rpm (instead of the more standard 4800) for the switch.
 

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Discussion Starter #5
Thanks for this! I, too have shorties and the AR intake. I’m curious how you landed at 4600rpm (instead of the more standard 4800) for the switch.
Seemed like I had read somewhere on here that another member had better results at 4600, but really I don't have a good reason for picking it. At the end of the day the curve is pretty smooth, so we didn't bother trying to adjust the switching RPM.

I have always wondered though, how would I even know if they're actually switching? Suppose your actuator failed one day. Its not like you can see inside the manifold, how would you know when something failed?
 

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The Pork Wagon (‘14 Cop Charger)
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The last thread I saw you in, I was worried you were trying to talk yourself out of the cam upgrade, glad to see it hasn't worked!

I agree with your assessment, I think the headers gave me most of the low-mid power, but the intake will be a good complement to a cam upgrade that opens up more on the top end. I'd also like to do the camshaft, but I've done a lot in a short period of time and I'm going to need a financial recovery period before I start trying to convince my wife that I need a cam.

Talk to you later!
Yeah I started that thread thinking I would get some logical and reasonable support for my position of resisting the desire to upgrade the cam. Ultimately all it took to bring me over to the dark side was one member entwining he had a OE 392 cam still new in the box for sale. It was useless to resist at the point, so I figured why not 🤷

On the subject of your exhaust upgrade, who did the install, you or an auto shop you paid for the labor?

I already know they are a huge pain to install, but anecdotes about much of a pain are still of great interest to me...call me a glutton for punishing stories. 😔
 
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The Pork Wagon (‘14 Cop Charger)
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Seemed like I had read somewhere on here that another member had better results at 4600, but really I don't have a good reason for picking it. At the end of the day the curve is pretty smooth, so we didn't bother trying to adjust the switching RPM.

I have always wondered though, how would I even know if they're actually switching? Suppose your actuator failed one day. Its not like you can see inside the manifold, how would you know when something failed?
I’m not intimately familiar with how the 392 intake switches the runners, but if it’s anything like the dual runner intake that came on the Dodge 3.5L engines, there is an actuating device that bolts to the intake and has a shaft that protrudes slightly into the intake to rotate the valves’ common shaft. That opens and closes all at once and is under tension so if it fails somehow, it will fail in the closed position (long runner design).

The device which actuates the valves has a wiring harness plug and should throw a DTC and illuminate the CEL if it malfunctions for any reason. On the 3.5L Challengers, it would be a P1004 code, but I’m sure that’s different for the 392 intake’s (doubt they use the same code for diff hardware, but maybe they do).
 
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Seemed like I had read somewhere on here that another member had better results at 4600, but really I don't have a good reason for picking it. At the end of the day the curve is pretty smooth, so we didn't bother trying to adjust the switching RPM.

I have always wondered though, how would I even know if they're actually switching? Suppose your actuator failed one day. Its not like you can see inside the manifold, how would you know when something failed?
Yeah, I feel like I’ve seen 4600 somewhere, too, and I’m sure it boils down to if/when it dips, and that depends on so many other things, especially the cam. Your curve is so smooth it makes me want to go try it, but I don’t have access to a Dyno to suss it out. However, I will say on my car I can definitely tell they are closing so I’d suspect I’d feel something negative if it’s too soon with my stock cam. On a side note, one could install a light using the fourth pin (I thought about doing it) but I’m not sure that’s 100% confirmation the runner valve is functional. I’ll post back if I dial it down and report back.
Thanks for the response!
J
 

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Discussion Starter #9
Yeah I started that thread thinking I would get some logical and reasonable support for my position of resisting the desire to upgrade the cam. Ultimately all it took to bring me over to the dark side was one member entwining he had a OE 392 cam still new in the box for sale. It was useless to resist at the point, so I figured why not 🤷

On the subject of your exhaust upgrade, who did the install, you or an auto shop you paid for the labor?

I already know they are a huge pain to install, but anecdotes about much of a pain are still of great interest to me...call me a glutton for punishing stories. 😔
I'm glad you asked! I did the install myself, and now I'll take this opportunity to shamelessly promote one of my older posts! JBA shorties installed on R/T

It was a real pain, but I had the right tools for the job and fairly thin forearms so it was manageable. At the end of the day I got the experience of doing it, so that was worth a lot even if it came with the added anxiety of never really knowing if I did a good job on all of the seals.

A little later I added a wideband O2 sensor to the mid-pipe, and I had to get a guy to weld the bung on for me to do that. The welder ended up being a big MOPAR guy, so that job ended up being well worth the price as I learned a lot chatting with him while he did the work.
 

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Discussion Starter #10
Yeah, I feel like I’ve seen 4600 somewhere, too, and I’m sure it boils down to if/when it dips, and that depends on so many other things, especially the cam. Your curve is so smooth it makes me want to go try it, but I don’t have access to a Dyno to suss it out. However, I will say on my car I can definitely tell they are closing so I’d suspect I’d feel something negative if it’s too soon with my stock cam. On a side note, one could install a light using the fourth pin (I thought about doing it) but I’m not sure that’s 100% confirmation the runner valve is functional. I’ll post back if I dial it down and report back.
Thanks for the response!
J
Right on, thanks man!
 

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The Pork Wagon (‘14 Cop Charger)
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The RPM at which the short runners become more efficient is dependent upon the actual length of both the long and short runners. For these intakes, the lengths put that switch-over RPM somewhere between 4500 and 4800. We could do the math to figure out exactly where it becomes more efficient, but there’s little value in knowing it actually.

The switch-over RPM won’t be as significant in overall power-making (assuming it’s relatively close to the right RPM) since the engine will likely spend such a small amount of time operating in that range at WOT.

If we say the exact RPM is 4789, and you have it set to switch at 4600, that means the engine spins through 189 RPM operating less than most efficiently. But how long, and how much power is made (and therefore lost) in those 189 RPM? Not very much.

So getting it close is good enough...for WOT operating that is. If the car were being raced in a Grand Prix type race or something, that exact RPM might be much more significant to dial in just right.
 
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Discussion Starter #12
The RPM at which the short runners become more efficient is dependent upon the actual length of both the long and short runners. For these intakes, the lengths put that switch-over RPM somewhere between 4500 and 4800. We could do the math to figure out exactly where it becomes more efficient, but there’s little value in knowing it actually.

The switch-over RPM won’t be as significant in overall power-making (assuming it’s relatively close to the right RPM) since the engine will likely spend such a small amount of time operating in that range at WOT.

If we say the exact RPM is 4789, and you have it set to switch at 4600, that means the engine spins through 189 RPM operating less than most efficiently. But how long, and how much power is made (and therefore lost) in those 189 RPM? Not very much.

So getting it close is good enough...for WOT operating that is. If the car were being raced in a Grand Prix type race or something, that exact RPM might be much more significant to dial in just right.
Yeah I think that makes a lot of sense. Just need to be in the ballpark, as you'll fly through the transition pretty fast. Thanks for the insight!
 

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Quick question regarding your intake upgrade: are you running a catch can with it?
 
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Quick question regarding your intake upgrade: are you running a catch can with it?
Yes I am. Of course my line running from the PCV into catch can was the same, but the return line from catch can into manifold had to be redone due to the 392 intake's return hole being in a different place. I think the big loop I made is aesthetically pleasing though.

Finished - right-side view.jpg
 

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Yes I am. Of course my line running from the PCV into catch can was the same, but the return line from catch can into manifold had to be redone due to the 392 intake's return hole being in a different place. I think the big loop I made is aesthetically pleasing though.
Function over form; get it working and then worry about aesthetics if necessary, that’s my philosophy!

Like I said, I’m not intimately familiar with how the 392 intake does the switch from long to short, but I am with the 3.5L intake and how it operates the runners. And those intakes were especially susceptible to the P1004 malfunction after 100K miles or so due to intake buildup from the oily blow by gases coming in from the PCV.

Once enough crud coated the intake’s insides, those runner butterfly valves would be effectively glued in place, and even if they did open, they couldn’t shut completely because of the funk built up, thus setting the P1004 code.

If the 392 intake is similar in how it does it’s thing, I would expect the same general issue to be a possible problem after enough mileage. Running a catch can is the best defense against that though. It kept my 3.5L from repeat P1004 problems, and certainly can’t hurt the 392 setups I would imagine.

Ive run catch cans on almost every engine I’ve had in the last 5 vehicles, but I’m not someone who says they are a necessity for all engines...except for ones with the active intakes. I would not run an active intake without a catch can, personally.

YMMV obviously.
 

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Function over form; get it working and then worry about aesthetics if necessary, that’s my philosophy!

Like I said, I’m not intimately familiar with how the 392 intake does the switch from long to short, but I am with the 3.5L intake and how it operates the runners. And those intakes were especially susceptible to the P1004 malfunction after 100K miles or so due to intake buildup from the oily blow by gases coming in from the PCV.

Once enough crud coated the intake’s insides, those runner butterfly valves would be effectively glued in place, and even if they did open, they couldn’t shut completely because of the funk built up, thus setting the P1004 code.

If the 392 intake is similar in how it does it’s thing, I would expect the same general issue to be a possible problem after enough mileage. Running a catch can is the best defense against that though. It kept my 3.5L from repeat P1004 problems, and certainly can’t hurt the 392 setups I would imagine.

Ive run catch cans on almost every engine I’ve had in the last 5 vehicles, but I’m not someone who says they are a necessity for all engines...except for ones with the active intakes. I would not run an active intake without a catch can, personally.

YMMV obviously.
Excellent points on “a few rpms don’t make a huge difference.”
I also run a catch can, and after seeing how gunked up my 5.7L manifold was, I was glad I had it when I installed the 6.4 intake (I put about 80k on the 5.7 intake b4 I installed the CC).
 

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In regards to the switchover point, if you're running the 8spd it's even less critical due to the minimal rpm drop between gears. Depending on the shift rpm, at WOT you may never fall below the switchover point once you're out of first gear.
 

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Discussion Starter #18
OK, so bad news for me, good news for all of you. I have confirmed that my active runners are not actuating. As a result, the dyno result I posted is significantly more straightforward showing only the benefit of adding the short tube headers.

I know I've seen other R/T dyno's with the 392 intake which showed a big dip in power when they haven't been tuned to account for the extra airflow after they go short mode. I found it odd that I saw no power dip in the baseline run, so I had to investigate. I double checked the wiring and confirmed that I have 12 V, ground, and the actuator wire throwing ground when engine speed surpasses the ON-RPM, so I am confident that the wiring is OK. I ended up sticking a borescope into my intake manifold and just watched the flaps as I changed the ON-RPM setting over and under my idle RPM to test functionality; they're not moving.

I've removed the actuator and I can move the flaps by twisting the knob that the actuator couples to by hand. The flaps move freely, so they're not stuck or anything.

I then plugged the wiring back into the actuator and left it out to watch its behavior. I had to tape the hole on the backside of the intake manifold to turn the engine on, and upon doing so I note that the actuator performs a single actuation cycle when the car turns on, then nothing. The fact that it can always cycle once on startup tells me that my circuit delivers the required current to make it operate, but for whatever reason it is blind to the "actuate now" signal.

I feel reasonably confident that the problem is the actuator, so I'm going to replace it and see if it behaves. It should be ready for pickup on Monday. In the mean time, I'm gonna sit around being pissed at myself for not figuring this out before I paid for the tuning session.
 

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I think what you are seeing is mostly the effects of the intake. If you look the air flow at 4800 for the additional displacement of the 6.4 and the more aggressive cam vs air flow potential of potential of the 5.7 with the milder cam my guess is the air flow of the 5.7 at 5400 to 5600 is about the same as the 6.4 at 4800. Every test I have seen . That is why most are not seeing any major lift on the top end of the 5.7 with the intake. The 5.7 is camshaft limited on air flow! All the benefits everyone is seeing are the longer runner length creating more velocity to fill the combustion chamber down low. My belief is Dodge used the longer runners to clean up the bottom end of 6.4 and the runner switch over and cam to make more power up top. No other reason i can see for the added expense and engineering.

The real test will be when someone runs a 5.7 with a healthy cam and compares the intakes! That is where I believe we will see the big difference! I also have the 6.4 on a 5.7. I drop .3 sec 0-60 with no other changes. The bottom end pick up with the 6.4 intake is probably the best buck. I have run it with and without the runner switch and the 0-60 does not change.

Just my thoughts
 

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OK, so bad news for me, good news for all of you. I have confirmed that my active runners are not actuating. As a result, the dyno result I posted is significantly more straightforward showing only the benefit of adding the short tube headers.

I know I've seen other R/T dyno's with the 392 intake which showed a big dip in power when they haven't been tuned to account for the extra airflow after they go short mode. I found it odd that I saw no power dip in the baseline run, so I had to investigate. I double checked the wiring and confirmed that I have 12 V, ground, and the actuator wire throwing ground when engine speed surpasses the ON-RPM, so I am confident that the wiring is OK. I ended up sticking a borescope into my intake manifold and just watched the flaps as I changed the ON-RPM setting over and under my idle RPM to test functionality; they're not moving.

I've removed the actuator and I can move the flaps by twisting the knob that the actuator couples to by hand. The flaps move freely, so they're not stuck or anything.

I then plugged the wiring back into the actuator and left it out to watch its behavior. I had to tape the hole on the backside of the intake manifold to turn the engine on, and upon doing so I note that the actuator performs a single actuation cycle when the car turns on, then nothing. The fact that it can always cycle once on startup tells me that my circuit delivers the required current to make it operate, but for whatever reason it is blind to the "actuate now" signal.

I feel reasonably confident that the problem is the actuator, so I'm going to replace it and see if it behaves. It should be ready for pickup on Monday. In the mean time, I'm gonna sit around being pissed at myself for not figuring this out before I paid for the tuning session.
Just read this last post........it will be real interesting to see if you get them working if it makes a big difference. I can not see any on my car
 
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