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2015 SRT392 A8 in white pearl coat
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Discussion Starter #1 (Edited)
Seat of the pants dyno: a Challenger FEELS faster?

I let my cousin drive my SRT a while back, and when he came back, he told me something that I just wasn't expecting to hear. He said that the Scat Pack with the manual transmission was WAY quicker than my SRT. I had assumed that he'd never ridden in any kind of muscle car, and was surprised at his comment. So I asked how he knew this: and he replied that he'd rented a Scat Pack with the manual, and in his opinion, it was much quicker. Ha... I didn't even know that you COULD rent a Scat Pack.

I didn't say much, just commented that I hoped he enjoyed himself; but it made me wonder... why would he say that? This forum has confirmed that the 392 with the 8 speed auto is no slouch. His opinion was based on his "seat-of-the-pants" dyno, and today I decided to do a little research.

Seems that this organic dyno, though mistaken, is based on some very real experience. I was reading an article from Road and Track about this "butt dyno" and a comparison between the Scat Pack and the Hellcat. (see below)

CLICKY HERE

They commented that not only did the 392 Auto FEEL much closer to the acceleration of the Hellcat than it could actually achieve, it pulled harder than the manual Hellcat -- briefly -- in each of its first 5 gears.

I've not had the chance to ride in any other Challenger but my own, so personally I wouldn't know. Nor would I care as I don't race the car. But my experience with my cousin and the subsequent research I've done leads me to ask...

For those of you who've driven manuals and automatics, or Hellcats and 392's, what says the seat of your pants dyno?
 

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If your cousin is anything like mine......He’s f*cking with you......and it sounds as if your taking the bait. Rent a “manual” Scat pack? Where? I want proof.
 

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Several rental companies rent cars like Challenger Scat Packs, and yes, they do have manuals available. Not available everywhere of course, and depends on actual car availability. A Guy
 

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100% agree with your cousin a manual will always FEEL faster. The goal of an automatic is to deliver as much power smoothly as possibly , always keeping it in power with no downtime. If your shifting through gears and arent as fast as an automatic transmission, your going to get launched every gear you hit with torque at the pedal.
 

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2015 SRT392 A8 in white pearl coat
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Discussion Starter #5 (Edited)
If your cousin is anything like mine......He’s f*cking with you......and it sounds as if your taking the bait. Rent a “manual” Scat pack? Where? I want proof.
You could not be more wrong sir, on all three points. Had you done a simple google search for rental Scat Pack, you would have found this: CLICKY
 

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You could not be more wrong sir, on all three points. Had you done a simple google search for rental Scat Pack, you would have found this: CLICKY
You're right. You can rent performance cars. My friend was on a business trip, last week, and he rented a 2018 Camaro SS (455 hp) from National in Jacksonville, FL.
 

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2016 Scat Pack Shaker
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The buttometer is notoriously inaccurate. My own needs re-calibration, last trip to the drag strip my bottometer thought the slowest run was quickest. In the hands of most drivers the A8 is significantly quicker than the M6 0-60, 1/8 mile and 1/4 mile per many posts on this forum.
 

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Keep in mind that this is the same uncalibrated device that has people spending hundreds on intakes, and dropping in K&N filters for "more powa".

Salt. Grains. Something something...
 

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Butt dyno- subjective and often poorly calibrated. Who cares? The only thing that matters is how it feels to you.
 

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Keep in mind that this is the same uncalibrated device that has people spending hundreds on intakes, and dropping in K&N filters for "more powa".
Agreed. I have looked at intake and exhaust bolt ons many times and remain unconvinced that they provide any return for the investment.
 

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Unless your a track guy - does it really matter? Both are quick cars pushing the exact same amount of HP. The manual just lets you control that power and torgue. That's about it. To each his own - its a personal thing.
 

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On the stock tune, cars can actually feel quite different base don how their adaptives have been built over time. if you drive like a grandma, your car will perform sluggishly. Crack the whip! ;)
 

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On the stock tune, cars can actually feel quite different base don how their adaptives have been built over time. if you drive like a grandma, your car will perform sluggishly. Crack the whip! ;)
Absolutely agree with you! I drive my cars hard - not all the time but I definitely put the car to work some days and have always found your philosophy to be true. The car does adapt and learn your driving style and it seems to affect its personality/ability.
 

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2020 Dodge Challenger Hellraisin Scat Pack
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Butt dyno's are notoriously unreliable.

Have not driven a manual Scat Pack or a Hellcat but an A8 Hellcat is quicker then even a manual Hellcat. There's a nice YT video of a "shootout" between a manual Hellcat and an A8 Hellcat.

The problem with a manual equipped muscle car is one gets big G's at launch -- if the tires hold -- and one gets pushed back in his seat and this feels impressive, is impressive. This is my experience with my 996 Porsche Turbo (413hp) and my 2006 Pontiac GTO (400hp). Acceleration is to put it mildly impressive as all heck. And the Turbo rear tires at 11" wide hook up though it takes some careful clutch work to avoid over stressing the tires.

Then comes time to shift from 1st to 2nd. One gets thrown against the seat belt almost as hard as one got pushed into the seat as the car's acceleration slows down as one shifts. Now given the cost of a Porsche Turbo transmission (approx. $12K) and I don't think I ever knew how much a new GTO 6-speed transmission would cost to replace I didn't speed/power shift but I shifted it as quick as I could. Still there's a big fall off in acceleration.

But as one might expect after the shift and the throttle is reapplied the acceleration is back.

As an aside not long after I bought my 996 Turbo I was down in Redwood City having just pulled off the freeway and sitting at a stop light waiting to make a left hand turn. Along side of my car comes a new Lambo -- I could not tell you the model. The light changed. There was no "race" involved but both the Lambo driver and I accelerated away with some enthusiasm. The Lambo was equipped with some kind of auto transmission and the speed at which the driver went up through the gears was impressive. Compared to how fast I was able to shift my Turbo -- and the Turbo was a nice shifting car the best of all the cars I've owned (save the Boxster which shifted very very quick, quicker then the Turbo) -- the Lambo made my Turbo's shifting speed seem glacial by comparison. It really drove home how much "performance" a manual equipped performance car left on the table, so to speak, with a manual transmission. It was at that point I decided the next Porsche I bought would if possible be equipped with a PDK. (I have since driven loaner vehicles with a PDK and it is an impressive automatic transmission.)

As a second aside I have to mention how my butt dyno really liked the Boxster's acceleration. With around 217hp and 192ftlbs torque the Boxster engine didn't match up with the Turbo's 413hp and 420ftlbs torque but the Boxster's lighter 5-speed shifted so quick it was nearly as quick as the A8 in my Hellcat. It was a real blast to when possible start out and run the Boxster up through the gears. With a 7200 RPM red line and an engine that pulled all the way to red line the Boxster gained speed at a rate that was deceptive for the size of the engine (but the car only weighed in at around 2850lbs) and because of the light weight, good engine and fast shifting transmission the car delivered an acceleration experience that was quite exceptional. I had to tell myself the numbers don't lie: 0 to 60mph in 6 seconds for the Boxster vs. 0 to 60mph in 4.2 seconds for the Turbo so no way the Boxster was as fast as the Turbo but my butt dyno loved the Boxster all the same. So did the rest of me.

And yet a 3rd aside, I might mention my new Mini JCW with its 6-speed manual brings back Boxster memories. The JCW's 6-speed shifts very very quickly and the JCW turbo charged engine with 228hp and 236ftlbs torque coupled with a weight of around 2850lbs so the JCW gains speed under hard acceleration very fast. As with my Boxster, my butt dyno loves the JCW.

Anyhow, first with my R/T Scat Pack and more recently with my Hellcat, both with the A8 automatic, launching is much easier -- start out in 2nd gear and either manually up shift which I do because with the engine still in break in miles I don't take RPMs up to red line -- or the favored and tested and proven technique is to start out in 2nd and once underway move the shift lever over to automatic mode and then let the transmission controller up shift at red line while you keep the pedal mashed to the carpet. This technique produces the quickest elapsed time, the highest trap speed, and is repeatable over and over again.

I've never yet done the 2nd technique -- engine break in considerations as I mentioned above -- but the 1st technique I've done a few times to give the engine some workout as part of the break in process and the acceleration is impressive. There is just a small interruption in the car's acceleration when the transmission up shifts. The car quickly -- in just 3 seconds or so -- gets into illegal speed territory and if that wasn't a concern the car pulls like one can't believe even as the car's speed climbs to <static> mph and beyond.

Another style of acceleration I've done is similar to what happened with the Lambo and my Turbo. I start out from a stop light or from turning onto a freeway on ramp and with a clear road ahead give the engine some throttle, nearly full throttle but not enough to break loose the rear tires then before red line is reached use the paddle to up shift. The acceleration is awesome made so in no small part by how quickly the automatic up shifts. As I do this either I have a big smile on my face or I am laughing out loud. This acceleration is a feeling/experience that I don't think will ever get old.

Anyhow, to wrap up: I think your cousin's butt dyno needs a recalibration or maybe it as landoawd said: "Salt." "Grains." "Something something..."
 

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Doesn't the Manual Scat Pack come with a higher geared differential than the automatic?
 

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Doesn't the Manual Scat Pack come with a higher geared differential than the automatic?
No...the rear ends the same.

The auto actually has much lower(higher ratio) 1st and 2nd gears then the manual.

Also, the auto's start in 2nd gear when in default mode. At least the SRT 392 does. Just assuming the Scat Pack's the same.??? Almost forgot, that's when the "ECO" mode has been selected.
SRT 392 Transmissions.jpg
 
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2015 SRT392 A8 in white pearl coat
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Discussion Starter #17 (Edited)
Doesn't the Manual Scat Pack come with a higher geared differential than the automatic?

No...the rear ends the same.

The auto actually has much lower(higher ratio) 1st and 2nd gears then the manual.

Also, the auto's start in 2nd gear when in default mode. At least the SRT 392 does. Just assuming the Scat Pack's the same.??? Almost forgot, that's when the "ECO" mode has been selected.
View attachment 891409

I'm guessing you guys read the article for which I provided a link in my initial post? It spoke of the gear ratios of the Scat Pack and the Hellcat, saying that the Scat Pack auto shifts into fourth before the manual Hellcat gets out of 2nd. Any truth to that?

Gary
 

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I can only speak for the A8 Hellcat, but you can set the car up multiple ways. So depending on how you have it set will depend on how quick it "feels".

Leaving it in default mode will definitely feel slower than putting it in Sport Mode or Track Mode.

Probably the quickest "feeling" set up for the A8 Hellcat would be setting it to Track Mode and completely turning off the traction control and electronic stability. The transmission will stay in a gear longer and shift very hard at high RPM.
With a good set of drag radials on the rear, I cannot imagine the SP or 392 "feeling" quicker.

My custom setup:
 

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I'm guessing you guys read the article for which I provided a link in my initial post? It spoke of the gear ratios of the Scat Pack and the Hellcat, saying that the Scat Pack auto shifts into fourth before the manual Hellcat gets out of 2nd. Any truth to that? It spoke of the gear ratios of the Scat Pack and the Hellcat, saying that the Scat Pack (auto) shifts into fourth before the manual Hellcat gets out of 2nd. Any truth to that?

Gary
I wouldn't know the answer to that. But I would have to assume, based on my read of the article, that he based that statement on the fact that he ran the HC up to 90 mph in 2nd and I'm guessing he had to run the SP up to 4th gear to reach the same speed.

I don't think that article should say, "the automatic Scat Pack briefly pulls harder in every one of its first five gears than the manual Hellcat does." I guess that would be true if you compare gear to gear. But based on the above statement the HC would still be in 1st or 2nd gears when the SP is up in 3th and 4th gears, thereby the HC would be in those higher torque gears while the SP's is using gears with a lot less torque.

Looking up and thinking about the fact that the engines have their highest torque values well below their redlines, makes me wonder why/if the auto goes close to redline when shifting. I'll have to try it out. When at the track, a couple of times last fall, I was too busy looking straight ahead.

EDIT: Just looked back at Booky's video and got my answer. I think the HC has a little lower redline then the SP.
 
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