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Discussion Starter · #1 ·
I'm sure this question has been asked before but the search function was of no help.

What kind of realistic horsepower and torque numbers would I be looking at if I added the following to my 2016 SRT 392:

  • Fastman True 84mm throttle body
  • Ported 392 intake
  • Hellcat airbox and filter
  • 1 7/8" long tube headers and high flow cats
  • Stainless Works 3" exhaust
  • 93 octane tune

My best guess is around 450 wheel? Considering these cars do about 405 to 420 to the wheel on a Mustang dyno in stock form.

Man, it's annoying that the Mustang guys can squeeze 70 to 80 more WHP with similar mods for less money on that 5.0 Coyote, and match or exceed the 392's torque at the same time. Why do our Hemis not take to mods as well when we have so much more displacement?
 

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... Why do our Hemis not take to mods as well when we have so much more displacement?
Airflow and RPM. Double the valves, Zero pushrods.
From what I can find the intake ports flow relatively comparable CFM and have close to the same overall valve area, (5.0 is much smaller, but there are 2 of them)
Add in all the advantages of having 4 camshafts and zero pushrods, both in high RPM and variable timing, that all makes up for the difference in size.
Speaking of size, those smaller 5.0s are huge in the engine bay. That new pushrod 7.3 Ford truck engine is a torque monster and MUCH smaller, that will be a dream swap in older cars/trucks now.
 
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Hemis not take to mods as well when we have so much more displacement?
The 6.4 has been pretty much optimized in terms of compression ratio to survive on pump gas. These are not like engines back in the day where CR was low. For example, I have an early 70's 460 BBF that had a terrible CR of ~7 to 1 and bumping that up to 9 to 1 gave considerable boost in power and was fairly cheap to do.
 

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Discussion Starter · #4 ·
Airflow and RPM. Double the valves, Zero pushrods.
From what I can find the intake ports flow relatively comparable CFM and have close to the same overall valve area, (5.0 is much smaller, but there are 2 of them)
Add in all the advantages of having 4 camshafts and zero pushrods, both in high RPM and variable timing, that all makes up for the difference in size.
Speaking of size, those smaller 5.0s are huge in the engine bay. That new pushrod 7.3 Ford truck engine is a torque monster and MUCH smaller, that will be a dream swap in older cars/trucks now.
Yeah, I thought the Hemi was a large engine until I saw a 5.0 and the 5.2 up close. Monsters!

They don't have the same low end torque but man do they pull once you start to spin up the RPM's. I think if Dodge ever seriously considers bringing back the Cuda, or some other pony car/sports car, they should use an aluminum DOHC V8.
 

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Discussion Starter · #5 ·
Airflow and RPM. Double the valves, Zero pushrods.
From what I can find the intake ports flow relatively comparable CFM and have close to the same overall valve area, (5.0 is much smaller, but there are 2 of them)
Add in all the advantages of having 4 camshafts and zero pushrods, both in high RPM and variable timing, that all makes up for the difference in size.
Speaking of size, those smaller 5.0s are huge in the engine bay. That new pushrod 7.3 Ford truck engine is a torque monster and MUCH smaller, that will be a dream swap in older cars/trucks now.
That all makes sense. I'm still curious what kind of power numbers I'd be looking at though. Maybe they're not worth doing on their own, but worth it as supporting mods for either a cam or a supercharger.

I was surprised to see the 7.3 wasn't putting out much power for its displacement, the 6.4 BGE from Dodge puts out 420 horsepower while the 7.3 puts out 410. But I'm sure that it'll be easy to hotrod.
 

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I was surprised to see the 7.3 wasn't putting out much power for its displacement, the 6.4 BGE from Dodge puts out 420 horsepower while the 7.3 puts out 410. But I'm sure that it'll be easy to hotrod.
I read a very interesting article about the 7.3, it is actually designed to be a economical gas engine. For something like towing/hauling with constant moderate load, a large displacement comparatively smaller valve arrangement engine operates more efficiently at the constant mid range loads. Then in a crate engine 500+ torque/hp ain't bad for a drop in cheaper engine compared to a 5.0.
I bet it would be a gas pig in a car with around town driving, but for HD trucks going down the road, it was actually an improvement.
 

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Discussion Starter · #7 ·
I read a very interesting article about the 7.3, it is actually designed to be a economical gas engine. For something like towing/hauling with constant moderate load, a large displacement comparatively smaller valve arrangement engine operates more efficiently at the constant mid range loads. Then in a crate engine 500+ torque/hp ain't bad for a drop in cheaper engine compared to a 5.0.
I bet it would be a gas pig in a car with around town driving, but for HD trucks going down the road, it was actually an improvement.
Makes sense
 

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I think the other reason the 5.0 makes good power is RPM. It is tuned to spin.

The 6.4 certainly rev's (better than a 5.7 for sure), but I think it tuned to make low end torque at the same time and was built to balance both low end and top end.

I've heard the 5.0 is kind of soft on the bottom end.

Might be worth looking at the torque curve rather than just peak numbers.
 

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Discussion Starter · #9 ·
I think the other reason the 5.0 makes good power is RPM. It is tuned to spin.

The 6.4 certainly rev's (better than a 5.7 for sure), but I think it tuned to make low end torque at the same time and was built to balance both low end and top end.

I've heard the 5.0 is kind of soft on the bottom end.

Might be worth looking at the torque curve rather than just peak numbers.
That and the valve train on the 5.0 is built to handle that kind of spinning. With the right manifold, it can be modified to spin to a little past 8000.

It takes a lot to build up the 6.4 to spin faster and higher, but such is the way of things with pushrod engines.

I'm told that the latest gen 3 Coyotes have comparable torque curves, combined with more aggressive gearing and a lighter car, as well as a 10 speed auto. It does 0 to 60 in 3.9 seconds. Dodge better catch up!
 

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Discussion Starter · #11 ·
They could if they were to make the chassis as small and light as the mustang.
Well I don't want the car to shrink that much, some weight savings would be nice but I mostly meant they have to increase the power on the 392.
 

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Dodge better catch up!
Unfortunately, sales would seem to suggest that Dodge is fine just like it is, and if sales ever falter, I would worry that the Challenger would just go away all together.

The reality is, they are just different cars. You can fit real humans in the backseat of a Challenger and carry real luggage, and if you want to keep up with a new Mustang they sell the Hellcat for that. If you want fast enough and be able to take your wife and teenage son with you then a Scat Pack does the job pretty well. If you want maximum speed and don't care who or what you leave at home then maybe a Mustang is the better option.

I understand your desire, I too wish I could have the best of both worlds. But I don't really like the look of the new Mustangs and can't stand to sit in a Camaro let alone drive one, so I accept that my Challenger R/T isn't the fastest on the street and enjoy what I have while daydreaming and planning to make it faster or sell it and put a bunch of money in my Duster to further modernize it.

In a lot of ways, a modernized old car is probably the best way to get the best of both worlds. Drop 600 pounds and keep the same horsepower and maybe even save a little money. But you give up ABS/ECS/soundproofing/etc. And you have to build the whole thing yourself.
 

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Well I don't want the car to shrink that much, some weight savings would be nice but I mostly meant they have to increase the power on the 392.
Wish I could find the quote, but I remember reading when the 6.4 came out that the engineers at SRT said they could have give it more power, but they felt they gave up way too much low end torque and lost the feeling of power when they did. They said it was a much more enjoyable motor to drive this way.

If I am remembering that right, doubt the 6.4 will change much and if more N/A power is needed it will require a different motor rather than changes to the existing 6.4.
 

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Discussion Starter · #14 ·
Wish I could find the quote, but I remember reading when the 6.4 came out that the engineers at SRT said they could have give it more power, but they felt they gave up way too much low end torque and lost the feeling of power when they did. They said it was a much more enjoyable motor to drive this way.

If I am remembering that right, doubt the 6.4 will change much and if more N/A power is needed it will require a different motor rather than changes to the existing 6.4.
I read that too, but a Mopar guy I know of said that problem could be solved by a slightly different cam profile and a redesigned intake manifold AS LONG AS it's accompanied by some weight savings, and maybe a little more aggressive rear gears, like a 3.30
 

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Discussion Starter · #15 ·
Can anyone tell me if my power estimate for full bolt ons is accurate?
 

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Can anyone tell me if my power estimate for full bolt ons is accurate?
Pretty accurate on 93 from multiple cars I've seen. 450-460ish
 

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I'd say more like 15-20ish RWHP. Thing is, tunes usually desensitize the knock sensors a little allowing less timing to be pulled. Tweaking VVT can net a few ponies.
 

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Wish I could find the quote, but I remember reading when the 6.4 came out that the engineers at SRT said they could have give it more power, but they felt they gave up way too much low end torque and lost the feeling of power when they did. They said it was a much more enjoyable motor to drive this way.

If I am remembering that right, doubt the 6.4 will change much and if more N/A power is needed it will require a different motor rather than changes to the existing 6.4.

The 392 was originally rumored to hit 500 horsepower (though Allpar was always more conservative and predicted 450-480 hp). Tom Langston noted that Kraig Courtney, SRT engine design supervisor, had addressed these rumors in Mopar magazine (March/April 2011), saying that they had improved the area under the torque curve at the expense of peak numbers:

We were pretty confident that we could get 500 hp, but ... the prototype 392 was strong up high, but as you accelerated, it didn’t give you that kick in the butt we expected- a kick in the butt approaching that of the muscle cars of old. ... The first 6.4 just wasn’t as strong feeling as the numbers said it should be. So we took a look at the intake that’s being used in our trucks right now, it’s an SRV dual-runner intake that we can run short runner or long runner. Obviously, you run short runner for power and long runner for torque. So we made up some manifolds and ran them in a car and it felt a lot better. Not as much horsepower, but the area under the torque curve was far bigger. ... We can go out and, quite honestly, take on some of the competition’s cars that are more powerful according to their numbers.
 

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I was around 505rwhp for an uncorrected dyno run (haven't see the official dyno sheet yet.) I have the following:

  • BBK 90mm throttle body
  • 650 FIC injectors
  • E85 conversion
  • JLT CAI
  • 180 T-stat
  • Kooks LT 1 7/8" headers
  • Kooks catless mids
  • Unlocked PCM
  • Muffler/Resonator delete
  • Motor/transmission tune
Putting in a cam in the next couple of weeks.
 

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Discussion Starter · #20 ·
I was around 505rwhp for an uncorrected dyno run (haven't see the official dyno sheet yet.) I have the following:

  • BBK 90mm throttle body
  • 650 FIC injectors
  • E85 conversion
  • JLT CAI
  • 180 T-stat
  • Kooks 1 7/8" headers
  • Kooks catless mids
  • Unlocked PCM
Putting in a cam in the next couple of weeks.
Not bad! I personally wouldn't do E85 for fuel mileage and availability reasons. How much of that power do you think that E85 contributed?

Also, what kind of cam are you putting in? Who made it?
 
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