Weird question/thought about PCM's

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Chief115

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Has anyone swapped pcms from an older 3rd gen to a newer one? I read that the later models introduced the "multi displacement system".

In theory since it's still a 5.7 hemi, couldn't you swap to an 07 or 08 pcm and get the multi displacement?

With that, those who have it is it worth it? Is it passive where you don't know whether have your cylinders are dead, or active like gm's where it'll tell you when it's killed your cylinders?

Just a random bourbon thought
 

justin13703

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No, MDS also involves internal parts of the engine. You can't just put a different pcm in the truck and have mds. Also, the trucks that have mds (06-up) also use the Can-bus system which is not something that will work with an older truck.
 
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Chief115

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No, MDS also involves internal parts of the engine. You can't just put a new pcm in the truck and have mds. Also, the trucks that have mds (06-up) also use the Can-bus system which is not something that will work with an older truck.



This is extremely disheartening lol. Sounds like I shoulda sprung for the 06 or 07.

Is it worth it? The mds I mean
 

justin13703

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This is extremely disheartening lol. Sounds like I shoulda sprung for the 06 or 07.

Is it worth it? The mds I mean

A lot of people will tell you no, but I personally love the mds and it is the reason why it's possible for me to get 21mpg on the highway, at least before I got my 35's. A lot of people with the pre-mds trucks talk about getting 14-15mpg on the highway. This is extremely dependent on driving conditions though.
 

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Well said Sir .

Sent from my SM-G900V using Tapatalk
 
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Chief115

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I read on some forums about combinations of mods along with tunes that can potentially get 23 mpg. Does anyone know if that's true?
 

justin13703

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I read on some forums about combinations of mods along with tunes that can potentially get 23 mpg. Does anyone know if that's true?

It may be possible, but it would require an extremely light foot, some very flat roads, and possibly some drafting.
 

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I read on some forums about combinations of mods along with tunes that can potentially get 23 mpg. Does anyone know if that's true?

Not possible, even with an 80 MPH tailwind, on a HEMI truck. Maybe for a 4.7L (doubt that too) or one of the V6 trucks but it's questionable in my mind. The trucks are just to heavy and not aerodynamic enough to get there given they are pretty brick like when it comes to design.
 

justin13703

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Not possible, even with an 80 MPH tailwind, on a HEMI truck. Maybe for a 4.7L (doubt that too) or one of the V6 trucks but it's questionable in my mind. The trucks are just to heavy and not aerodynamic enough to get there given they are pretty brick like when it comes to design.

It very well may be possible but it would not be something you could do every day. When my truck was all stock I could get 21mpg on long flat road trips, so with an economy tune and the right wheel/tire setup and driver mod, 23 could be doable with a well maintained truck and ideal conditions. At least on a truck with MDS. No MDS, yeah it's not gonna happen lol. Honestly, the hemi would be the only chance at hitting 23 because it is the only motor with mds.
 
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blackbeautyhemi

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I read on some forums about combinations of mods along with tunes that can potentially get 23 mpg. Does anyone know if that's true?

I achieved 23 mpg on a beach trip when my truck had just a leveling kit on with factory sized tires on factory 20 inch wheels. At the time I just had a canned tune, exhaust and cold air intake installed.
 
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Chief115

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Interesting haha. That's is all great information. What's the best consistent mileage you guys typically get?
 

blackbeautyhemi

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Interesting haha. That's is all great information. What's the best consistent mileage you guys typically get?

Since I've lifted it my average stays in the 14's and that's mostly around town. On a highway trip I can hit 18-19 mpg.
 
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Chief115

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Since I've lifted it my average stays in the 14's and that's mostly around town. On a highway trip I can hit 18-19 mpg.



What kind of life do you have? I was thinking about getting a rough county 5in suspension lift, but i don't know if that'll be overkill. It's not so much for going mudding. More so just getting to tough places
 

justin13703

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Since I leveled mine and put on the 35s I get around 16-17 highway.
 
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