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Discussion Starter #1 (Edited)
I was listening to an episode of *****in' Rides recently and was amazed at the difference between the 1973 340 'Cuda and the 2015 Challenger Hellcat that they compared. The 'Cuda had been punched out to a 416 and the two cars received exhaust cutouts. But with the exhausts open or closed, it was unanimous, both to Dave Kindig and his cohort Kevdog (and to me as well), that that Cuda sounded like angels singing compared to the modern muscle.

So I 'm sitting here wondering: why? I know a lot about engines, but not so much about just what creates the harmonics of sound.

The two engines sounded different in a number of ways, with the Cuda sounding, as Dave put it, more "Gnarley." But another thing that stood out on the show confirms something I've thought about many times before:

Why is our modern HEMI so slow to return to idle when ya take your foot off the gas? What's going on with the fuel system that causes this?

IT SOUNDS ALMOST LIKE THE THROTTLE IS NOT BEING FULLY RELEASED.
 

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A few thoughts: did the Cuda have headers? Did the Hellcat? Did the Hellcat still have cats? Both those things will dramatically affect the sound. So will a big cam, which I’m assuming the Cuda had.

As for the revving, there are probably a couple things at play here. One is the flywheel (or flexplate if it’s auto) may be much heavier on the Hellcat. More rotating mass means a slower revving engine. It could also be programmed by Dodge to rev down more slowly for drivability. I’m not an engineer, but it seems logical that if it loses RPM too fast, it will get out of its optimum power band more easily.
 

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I bet the "slow throttle return" is programmed in to cut down on the amount of raw gas going through the exhaust. I could be wrong. Also remember ours are limited to a dead rev of 4k, the old ones are not and rev higher and sound meaner, also the exhaust acoustics may be affected by an X pipe differently than they are by an H pipe, but that would only affect the sound with the cutouts closed.
 

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I bet the "slow throttle return" is programmed in to cut down on the amount of raw gas going through the exhaust. I could be wrong. Also remember ours are limited to a dead rev of 4k, the old ones are not and rev higher and sound meaner, also the exhaust acoustics may be affected by an X pipe differently than they are by an H pipe, but that would only affect the sound with the cutouts closed.
I think you are probably right about the slow throttle return. Likely an emission's thing. The new cars sound just fine to me.
 

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The delayed return to idle is as pallen stated to reduce emissions. It goes back to the 70's where cars had mechanical idle delay solenoids or some other mechanical means. Once ECU controlled engines became the norm the delay was programed into the ECU.
 

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Man, those were the days! Beautiful car! Sounds awesome.
 

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Discussion Starter #8
A few thoughts: did the Cuda have headers? Did the Hellcat? Did the Hellcat still have cats? Both those things will dramatically affect the sound. So will a big cam, which I’m assuming the Cuda had.
Pretty sure neither had headers, that the cats were still onboard the Hellcat, and the the 340 did not have a big cam. I don't think it had the lumpy idle that Cuda 340's sample video depicted.
 

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Pretty sure neither had headers, that the cats were still onboard the Hellcat, and the the 340 did not have a big cam. I don't think it had the lumpy idle that Cuda 340's sample video depicted.
Oh.....I wouldn't be so sure about the 340 vs 412 and cams one wild/ one not.

The 340 STROKED to make 412ci will sound less radical with the same cam profile due to displacement. the 412 could actually have a very carzy high lift/long diuration cam and sound very tame vs the small displacement motor.

I run a stroked 383 SBC ithe cam I'm running sounds pretty healthy but it's not even close to as racy sounding as it will sound in a 350. If it could be used in a 327 or even really old school 283 it'd be an EXTREME fender shaker.

Roller cam profiles vs flat tappets are part of this sound thing too. The ability of a roller cam to open higher and lengthen duration with less overlap between exhaust and intake is another reason newer engines can make the same or even more power without sacrificing the vacuum at idle so plainly obvious when you hear that truly racy cam.

The old engines sound racy because they are.......they stumble and shake at low RPM because it's been sacrificed entirely to make peak power newer engines don't struggle to make and they don't have to give away all the bottom end to make top end power.

I miss the sound too.......but I don't miss the horrid MPG or the very short power band that won't get started in a small block at much less than 3000RPM.
 

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Check out the exhaust sound on this 340 'Cuda. Music to my ears!


1970 Plymouth Cuda Exhaust Black Widow - YouTube
Yeah that's the sound. Gulp air through a carb and exit it through headers and a free flow exhaust......with no extra frills or attempts to clean anything up in the way of sound or emissions.

No new car sound this good unless it's been made pretty much illegal for use on the street. You could get this out of a new car.......but it's gonna require a really big cam and off road exhaust with no cats and steel long tube headers.
 

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Discussion Starter #12
The 340 also had a "rasp" to the exhaust note right after the driver let off the gas pedal. He was simply blipping the throttle in the driveway for the camera. As the engine began do decelerate in RPM, it made this raspy sound that was totally absent in the Hellcat.

Many have commented here on the sound of the idle. That too was different, but the majority of the differences between these two motors occurred as the driver was revving the engine.

I'm not sure if the Hellcat exhaust sounds just like other HEMIs or not. Also not sure if the motor decelerates at the same rate as other HEMIs, or if the flywheels are the same. But it did seem like it took forever for the engine to return to idle.
 

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The 340 also had a "rasp" to the exhaust note right after the driver let off the gas pedal. He was simply blipping the throttle in the driveway for the camera. As the engine began do decelerate in RPM, it made this raspy sound that was totally absent in the Hellcat.

Many have commented here on the sound of the idle. That too was different, but the majority of the differences between these two motors occurred as the driver was revving the engine.

I'm not sure if the Hellcat exhaust sounds just like other HEMIs or not. Also not sure if the motor decelerates at the same rate as other HEMIs, or if the flywheels are the same. But it did seem like it took forever for the engine to return to idle.
That's the exhaust/ healthy cam and a carb "talking".......it's NOT Chrysler 340 specific. I get tbe same basic sound out of a larger displacement SBC with long tube hooker headers, the same size 2.5 inch exhaust and Flowmaster chambered mufflers. No Cats, long tue headers and the chambered mufflers make this sound on most every older V8 you put them on that has enough cam to produce it. The fast return to idle is no doubt all about the carb vs computer directed fuel management.
 

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Discussion Starter #14
When I was growing up, my best friend's dad had a 1965 396 El Camino. He ordered the highest performance 396 they had. We used to plant ourselves against the back of the cab, rub down the bottom of our tennis to make sure they "stuck" to the bed, and see who could be the last one to hit the tailgate when "Uncle Don" as I called him, stomped on it in first and second. I remember well, how that engine would "bark" as you put it, through the Cherry Bombs he had on it, every time he let off the gas, especially at higher RPM's. As I recall, that rascal got something like 6 or 7 mpg. Seemed like the exhaust was louder on decell than it was during acceleration.

The 340 Cuda I listened to did this same thing, but not as "pronounced."
 

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I remember well, how that engine would "bark" as you put it, through the Cherry Bombs he had on it, every time he let off the gas, especially at higher RPM's. As I recall, that rascal got something like 6 or 7 mpg. Seemed like the exhaust was louder on decell than it was during acceleration.The 340 Cuda I listened to did this same thing, but not as "pronounced."

I had a friend who owned a 1970 Dart Swinger 340. It had a 4-speed and Cherry Bomb mufflers and was super loud. When he wound it out at night, you could hear his car from 1/2 mile away!


It looked exactly like this:





 

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I had a friend who owned a 1970 Dart Swinger 340. It had a 4-speed and Cherry Bomb mufflers and was super loud. When he wound it out at night, you could hear his car from 1/2 mile away!


It looked exactly like this:





These days chambered mufflers are the way to go.......better on all levels and just as loud when you "stand on it".

Cherry Bombs are a nostalgic name from the past but Glass packs in general are THE WORST.....poorly designed mufflers you pay dearly for with HP loss. They have no place on any car today. New or Old.
 

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Discussion Starter #19
Nothing sounds better than a old mopar music to my ears
Listening to that 340 on that show was indeed music: what a symphony. That Hellcat could certainly annihilate the old Cuda in the quarter, but if all we had to go by was their sound as they sat in the driveway that day, there was no comparison. They sounded as different as night and day: the Cuda was the KING.
 

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