Gen 3 Hemi 1/4 mile times VS the stock vintage engines

[Bad B-rad]

My 5.7 is a totally different animal. It's a blast to drive and it's still a Mopar!! 1600 RPM at 70 MPH!!

The rpm at 70MPH has more to do with the 8 speed transmission, then the engine itself.(and the rear end gear, new A8 Chargers have 2.62 or 3.09 rear end gear stock)
Our vintage Mopars would benefit greatly from more then 3 foward gears.
I do not want to cut my car up to stick in a new transmission, and I don't have $4-$8,000 just to spend on a transmission.

I would really love to see or read about some of our cars doing 1/4 mile and 0-60, with only the engines swapped, same rear, same trans.
Make all things equal, so the engines is the only difference.
I am a fan of both the B/RB and gen 3.
I struggle with the idea of pulling my 383, and dropping in the gen 3 I have for my old step side truck.
I would hate to do all that work, spend all that money, just to learn I enjoyed the 383 more, LOL!!

 

[Hey-O]

Truck 545RFE

 

[Bad B-rad]

Truck 545RFE

I am not familiar with the truck side.
But its still a 5 speed correct?
I know they changed the trans names, a 727 became 36rh/37rh, I still say 727, LOL

 

[Darius]

I know you aren't looking for anything BUT the engine but I will post my set up for your info. 5.7, 5 speed Nag1, 294 gear. Body is as stock looking as you can get except for the 17" rims. Ran a 13.777 @ 103.32mph. car weighs 3725 with 1/2 tank and NOTHING else in it. add 195# for my fat *** when I ran that.

 

[Bad B-rad]

I know you aren't looking for anything BUT the engine but I will post my set up for your info. 5.7, 5 speed Nag1, 294 gear. Body is as stock looking as you can get except for the 17" rims. Ran a 13.777 @ 103.32mph. car weighs 3725 with 1/2 tank and NOTHING else in it. add 195# for my fat *** when I ran that.

Great 1/4 time, and a 2.94 rear!!!!!
If I was running a Nag 1, I would be rocking 3.91, to take advantage of the OD.

When I had my Magnum R/T, one of the best mods I did, was the Mopar Transmission, controller, Mancinni racing had it for $220, called it TCM.
I also wanted blue top solenoids, but never got them.

Was the Nag1 a PITA, to install?

 

[Darius]

Had to modify the cross member and raise the "hump" about 5/8". Look at the pics in my build thread "b Body Stiffening" in the "Resto Mod & Pro Touring" forum on this site.

 

[halojumper]

My 5.7 is a totally different animal. It's a blast to drive and it's still a Mopar!! 1600 RPM at 70 MPH!!

People knocking the 5.7. Well guess what you can build the 5.7's and knock the dog snot out of a 392. Hell, I saw a ripp powered v6 challenger pull 425, or 450 on a dyno.

 

[Hey-O]

I am not familiar with the truck side.
But its still a 5 speed correct?
I know they changed the trans names, a 727 became 36rh/37rh, I still say 727, LOL

The 545RFE has an extra taller overdrive, it basically was a the 45RFE which was used on the 4.7, later added a gear and became the 5-speed 545RFE

 

[5.7 hemi]

The 545rfe has 2 2nd gears. It’ll use either 1 depending on load, tps and acceleration. Both 4th and 5th are overdrives.

The 45RFE later became the 5-speed 545RFE.

• Gear Ratios: 1st 3.00:1. 2nd 1.67:1. 2nd Prime 1.50:1. 3rd 1.00:1. 4th 0.75:1. Reverse 3.00:1.
• 545RFE only: 5th 0.67:1.

 

[biomedtechguy]

Once or twice, I have considered a 3G Hemi swap but to me, they just don't have the soul of the classic engines.

THIS!! AGREED!
...and...
Gen 3 issue sample conversation:
"Your Gen 3 was running fine, but now it won't start? Have you checked the code(s)?"
Old school engine, same symptom:
Grab that screwdriver, check air/fuel/spark, and timing if the first 3 are present.
Yeah, I like an old school engine for the purposes I use my car for,
BUT
If I was putting a 70 Superbird clone together I would absolutely want a 392 or larger Gen 3 Hemi, Hellephant or Hellcat, 6 speed manual transmission, best brakes and steering systems available today.

 

[Bad B-rad]

THIS!! AGREED!
...and...
Gen 3 issue sample conversation:
"Your Gen 3 was running fine, but now it won't start? Have you checked the code(s)?"
.

I think its the look when you pop the hood, between the two engines.(gen 3 vs stock )
But the my new 5.7 with stock MDS and no mods besides exhaust, runs 27.5 MPG, on our Carlisle trip,(7hrs on the highway total) and puts down 12.9's in the 1/4.

 

[Bad B-rad]

I have tons of love for the classic engines LA/B/RB/Hemi, and the Gen3, hell even the Magnum 3.9/5.2/5.9 engines, and I am sure the 27.5 MPG on the highway is part the A8 8speed auto, and part the MDS shut down of the 4 cylinders.

When I first got my 2016 R/T it had peg leg 2.62 rear, I changed it out for a Scat Pack 3.09 sure grip. It made a nice difference, but then I found a 3.90 sure grip, from a stick Challenger, and put that in.
Made a huge difference!!!!
I also noticed that with the 3.90's while just cruising, the engine will stay in 4cylinder mode MUCH, MUCH longer then before.
I am guessing with the rear end change (3.90 vs 2.62) it now has the extra power to maintain speed (in 8th) when normally climbing a hill, or incline, I would have to increase rpm to the point it "kicks out " of the 4cyl mode and returns to V8, and now it just pulls the hill in 4cyl.

 

[halojumper]

I have tons of love for the classic engines LA/B/RB/Hemi, and the Gen3, hell even the Magnum 3.9/5.2/5.9 engines, and I am sure the 27.5 MPG on the highway is part the A8 8speed auto, and part the MDS shut down of the 4 cylinders.

When I first got my 2016 R/T it had peg leg 2.62 rear, I changed it out for a Scat Pack 3.09 sure grip. It made a nice difference, but then I found a 3.90 sure grip, from a stick Challenger, and put that in.
Made a huge difference!!!!
I also noticed that with the 3.90's while just cruising, the engine will stay in 4cylinder mode MUCH, MUCH longer then before.
I am guessing with the rear end change (3.90 vs 2.62) it now has the extra power to maintain speed (in 8th) when normally climbing a hill, or incline, I would have to increase rpm to the point it "kicks out " of the 4cyl mode and returns to V8, and now it just pulls the hill in 4cyl.

Could it be that rear gear needs to be programmed in the ecm ? I'm no expert, but it seems like the computer needed some tweaking

 

[Bad B-rad]

Could it be that rear gear needs to be programmed in the ecm ? I'm no expert, but it seems like the computer needed some tweaking

The speed sensor on the 2015 and up is on the front wheels, so rear swaps are super easy on those cars.
I do have a custom engine tune, and trans tune.
One of the TCM programs, the wife ******* about the hard shifts, mainly the down shifts, so I run the softer one 99% of the time.

 

[Bad B-rad]

I actually used two different reputable guys to give me my tunes, tons of data logging, and I had to add the wide band.
Because I have the VVT eagle 5.7, I can run the 6.4 SRV intake, and an MSD window switch to operate the SRV.
They had to add fuel when the SRV opened.
I would love to try and play with when the SRV opens, to see if anything could be gained, but, not enough track time.
Also for my car the 3.70 rear may be a better choice, as now I am running threw the trap at 6100/6150RPM, right at the point where she shifts into next gear, the 3.70 would put me back into the peak power.

I also run street tires, never slicks, I thought about trying a few runs taking off in 2nd gear, to see how she does.

 

[Bad B-rad]

Maybe I should have put it like this, with the 3.90 I CAN get it to stay in 4cyl mode longer.
If you give it any throttle she comes right out of it, just like it should.
But on the highway or cruising around, I CAN get it to stay in MDS mode longer, by being very light on the throttle.

The way I worded it may have misrepresented, what I meant to say.
The car isnt stuck in 4cyl mode, its just that with stock rear gear, it didnt have the nuts to stay in 8th gear, in 4cyl mode at highway speeds and pull every hill, once you hit maybe 15-20% throttle she would kick out, now once at speed, I dont have to go above 15-20% throttle to pull the same hills, so it stays in much longer.

I have read the factory has a built in limit to how long it can stay in 4cyl mode before it has to kick off, for a predetermined time running on all 8.
I have only read this, I do not know for sure.


Photo from Carlisle trip, I was able to get her up to 27.5 before I got off exit.

 

[biomedtechguy]

with the 3.90 I CAN get it to stay in 4cyl mode longer....on the highway or cruising around, I CAN get it to stay in MDS mode longer, by being very light on the throttle....The car isnt stuck in 4cyl mode, its just that with stock rear gear, it didnt have the nuts to stay in 8th gear, in 4cyl mode at highway speeds and pull every hill, once you hit maybe 15-20% throttle she would kick out, now once at speed, I dont have to go above 15-20% throttle to pull the same hills, so it stays in much longer.

And all of that (which I understood your intent the first time) means with the higher numeric rear axle ring and pinion gearset, the 3.70, not only do you enjoy the RIPPING acceleration that the higher number gear ratio provides, BUT you get the BONUS of the engine eco-management keeping it in 4 cylinder mode, which certainly has to help MPG improve, I just am not sure from what you posted if the overall MPG improved with the higher gears. I'm sure that would depend heavily on how long, much, and often it is in 4 cylinder eco mode vs the total trip event.
Cool stuff when you can get the GREATLY improved acceleration of the higher R&P ratio and have similar or even just really good MPG.
It really doesn't matter what kind of MPG my Roadrunner gets, as long as the engine and transmission are happy and performing well!

 

[Bad B-rad]

No the around town MPG has suffered from the rear change.(and highway, when NOT in 4cyl)
I think the avg around town dropped 2-3MPG.
Around town, stop and go, it wont stay in 4cyl mode long enough to see much help.
It's only on the highway, when I can keep it in 4cyl mode that I was able to get the 27.5MPG.
If not in 4cyl mode it gets 18-21 on highway.
We odiously didnt get a Hemi Charger because of gas mileage, it is just a benefit to the overall package.

 

[rolling_Thunder]

Have a stock 6.1L in my 68 Charger - currently getting rid of the factory PCM and going to a stand-alone unit so I can actually tune the thing.

Planning on going with a 6.1 based stroker in the future with some boost but want to work out all the bugs with wiring and fitment now before taking that on. Plus... $$$

 

[Bad B-rad]

Hey rolling_Thunder, are you familiar with HP Tuners?
You can tune the factory PCM, with HP tuners, yourself, or get one from a reputable tuner.
May be cheaper then a stand alone system.
May not.
My buddy with a Scat (now has a built, S/C 6.4 based forged 426) bought an HP tuner system, and loves it.
He got one custom tune, long ago, and now can write his own tunes, took some learning but he loves it.