Turning off 4cyl mode on the 392?

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Ben_

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If I use the manual gear selector and set 8th as highest in my RAM it kills the annoying VVT 'Eco' mode. Not sure it would work the same in a Wrangler 392 but worth a shot.
When I switch to Manual mode, I'm only able to shift up to 2nd gear while at a stop. Otherwise I get "Shifting Not Allowed" displayed in the dash when trying to shift to up past that. Once I start driving, I'm only able to shift up a gear or 2 above where it thinks I should be.

If I'm at speed and have it in 8, as I slow down it downshifts, but then stays in that gear if i accelerate again. So it doesn't look like I can just kick it into manual mode in M8 and let it auto shift.
 

crazyjas

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The shameless plug solution is, if you get a PCM unlock, tuner, and bypass cable from Livernois Motorsports, we absolutely can disable it for you. Better yet, our 392 is in transit, and ready for us to start tearing into it for upgrades!
Quote please
 

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When I switch to Manual mode, I'm only able to shift up to 2nd gear while at a stop. Otherwise I get "Shifting Not Allowed" displayed in the dash when trying to shift to up past that. Once I start driving, I'm only able to shift up a gear or 2 above where it thinks I should be.

If I'm at speed and have it in 8, as I slow down it downshifts, but then stays in that gear if i accelerate again. So it doesn't look like I can just kick it into manual mode in M8 and let it auto shift.
"Paddle" shifters are there for this reason.
 

JJMalone

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When MDS is active the pushrod is partially disengaged, the roller is still in contact with the cam but a solenoid moves a part of the pushrod out of the way to prevent the valves from opening. Oil still gets to the moving parts as needed. My old Ram gave me no troubles and I hardly noticed any significant difference in exhaust note (although I was still stock). I can imagine a Tazer for the 392 is in the works that can prevent MDS and probably already exists for other models with Hemi engines.

Mechanically, you shouldn't be worried over the MDS.
To clarify how MDS works:

The deactivation cylinders have different lifters with 2 oil ports that serve the lifters, whereas non-MDS lifters have one oil port serving them. In normal operation, solenoid valve delivers oil to MDS lifters to operate normally. When MDS is activated solenoid valves deliver only one port (I believe it is the lower one) that allow an internal spring in the lifter to follow the cam and not move the pushrod. This is to prevent pumping losses. Couldn’t find out which cylinders are deactivated. Firing order is 1-8-4-3-6-5-7-2 so it will be either 1,4,6 and 7 or 8,3,5 and 2 as either of these orders will yield a 180 degree firing sequence (running on 8 yields a 90 degree firing sequence).

PS. After further research it appears 1,4,6 and 7 are the deactivation cylinders if they are the same as the 5.7.
 
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Billet Wilson

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Has anyone been running Livernois tunes? Pulling the trigger but want to make sure everyone's happy with the experience.
 

BobT

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I am mixed with a tune that unlocks the pcm(I have a spare 2016 Scat Pack Shaker that may or may not be interchangeable) and the Tazer.
Bit too new of Jeep to pull the trigger for me ATM.
 

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Has anyone been running Livernois tunes? Pulling the trigger but want to make sure everyone's happy with the experience.
A little bit of an update, was able to make it to the track, only made one pass, and the DA was over 3000', but still happy with the only pass under it's belt. This was on our new flex fuel tune, but with 93 in the tank.

PXL_20210811_142500102.jpg
 

oldcjguy

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How often do the cylinders deactivate in city/suburban driving?
Almost never. If it's like the Challengers you need to be over 60 mph and have very litle load on the motor.
 

Livernois Motorsports

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Almost never. If it's like the Challengers you need to be over 60 mph and have very litle load on the motor.
I experienced the exact opposite, mine was almost constant. MDS starts at as little as 14mph, can be active as high as 3800rpm, and can be up to about 1/3 pedal. it all depends on load, but these are in it more aggressively than most other applications.
 

oldcjguy

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I experienced the exact opposite, mine was almost constant. MDS starts at as little as 14mph, can be active as high as 3800rpm, and can be up to about 1/3 pedal. it all depends on load, but these are in it more aggressively than most other applications.
So... not like the Challengers ;)
 

Livernois Motorsports

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So... not like the Challengers ;)
The challengers aren't too much different. pretty much the only difference is that they don't activate until about 27 mph, and will disable at about 5% lower torque than the Jeep does. I am sure if you are aggressive it may not happen often, but it definitely happens a fair bit on the cars too.
 

Beer

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I use a Range Technology disabler device on my Zo6 and Denali. It plugs into the obd2 port and it always stays on eight cylinders when installed. I don't know if they make one for the Jeep. You can contact them at 888-997-6515. I hope this doesn't go against forum rules and if it does I apologize. Also it doesn't leave any codes on the computer.
 

2nd 392

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I use a Range Technology disabler device on my Zo6 and Denali. It plugs into the obd2 port and it always stays on eight cylinders when installed. I don't know if they make one for the Jeep. You can contact them at 888-997-6515. I hope this doesn't go against forum rules and if it does I apologize. Also it doesn't leave any codes on the computer.
Range technology is for GM&some F150’s only.They are missing out on a large mopar/Jeep sales.
 

WOwen

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A little bit of an update, was able to make it to the track, only made one pass, and the DA was over 3000', but still happy with the only pass under it's belt. This was on our new flex fuel tune, but with 93 in the tank.

PXL_20210811_142500102.jpg
Saw video on FB. Killer time for a big box! Curious to see how much HP corn will make. I know SP's with the 6.4 and just bolt ons are running 11's. Yes different vehicle but close to 500whp. So will Livernois be working on a CAI and possible exhaust system? Coming off the right side of the block that 90° turn can't be good for airflow.
 
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