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I was playing around with my SRT 392 A8 yesterday in the paddle shift mode, really fun! I was curious about what RPM range it's best to operate in for max acceleration with this car? I noticed if I shifted too early or too late, the car would feel a little doggish or I wouldn't have enough RPM's left in the power band to get anything out of that gear.
 

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It makes sense. A lot of people think u should shift at redline & that really doesn't make any sense as if an engine makes the most of its self at that point. It some point u stop making power as well at torque & at that point u are just wasting your time. I've been wandering the samething because I have a 392 6 speed (because I like rowing threw gears lol) & have been looking at the shift points. I always forget to hit the dyno setting when I'm at a dig to see where everything starts to fall off.

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I'll be the smart @ss that says, use the same shift points the A8 does when in automatic sport mode. It knows best :)

A Guy
 

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I'll be the smart @ss that says, use the same shift points the A8 does when in automatic sport mode. It knows best :)

A Guy
Lol possible but his gear rate is probably different as well as he has a few more transmission gears then I. Lol. Also he can set his shift points as well so its probably not where they need to be from the factory let alone if they have been changed.

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In my 2014 SRT with the A5 transmission I have found shifting in the 6,300-6,400 rpm range works best for me at the track. I data log all my runs so I can compare things like actual shift point, rpms at launch etc.. to see what makes for my best quarter mile times. But one thing you have to keep in mind is you can't wait until the tack says 6.300 as the rpms are rising so quickly that by the time your brain and hand perform the shift you will be well past that number. Therefore you have to shift when you see the rpms going past say 5,900 ( I just picked that for demonstration, you would have to play around a bit with it to see what works for you) in order to have the car shift at the desired rpm.

With all that said while I feel the A8 cars would benefit from an increased over stock shift it is my understanding that the car goes through the gears so fast on launch that it's pretty difficult to shift manually. Possible a better solution might be to get a reprogrammed TCM that has increased shift points in it.
 

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392 / 6.4 ratings (2015+)

HP peak is @ 6,100 rpm
Torque peak is @ 4,200 rpm

So you'd want to initiate the shift just as you start to get to 6K - the other thing is the look at what given speed you're at and on the upshift you start around the torque peak.

For max acceleration you want to be in that sweet spot 4,100 - 6,100 rpm as the torque plateaus and the hp is still building up.

Spinning the engine to 6,400 rpm (stock engine) isn't going to gain anything - power starts dropping off and you're going to hit the rev limiter.
 

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what I've observed in the track tests that various publications used, the majority of the time letting the transmission do its own shifting yielded the fastest times
 

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Discussion Starter #9 (Edited by Moderator)
392 / 6.4 ratings (2015+)

HP peak is @ 6,100 rpm
Torque peak is @ 4,200 rpm

So you'd want to initiate the shift just as you start to get to 6K - the other thing is the look at what given speed you're at and on the upshift you start around the torque peak.

For max acceleration you want to be in that sweet spot 4,100 - 6,100 rpm as the torque plateaus and the hp is still building up.

Spinning the engine to 6,400 rpm (stock engine) isn't going to gain anything - power starts dropping off and you're going to hit the rev limiter.
Thats the answer I was looking for! Thank you. And I know the computer probably knows best but it's still fun to use the paddles.
 

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Thats the answer I was looking for! Thank you. And I know the computer probably knows best but it's still fun to use the paddles.
My experience with my Hellcat is while I can use the paddles I can't reliably time my shifts to the optimum shift time.

Ideally the shift wants to happen just short of red line. The reason is an up shift drops RPMs down. By shifting at just short of red line the engine RPMs when they drop still end up at a higher and better RPM level than the RPMs would be if the shift was made at an RPM level any distance below red line.

The purpose of the 8-speed is to provide as little RPM drop as possible from shift to shift to keep the engine in its sweetest spot in terms of power output and thus acceleration.

If I just want to play F1 driver I use the paddles. While I might apply full throttle I up shift at some RPMs below red line. The few times I have hit red line the car slows as if I had applied the brakes so I know in order to maximize acceleration I can't shift the transmission manually but must let it shift itself.

So, if I want to maximize acceleration I leave the transmission in D and hammer the throttle down and hold on. (Certainly starting from a stop I have to pedal the engine to minimize tire spin, so it is not just shove the pedal to the carpet and hold on.) The engine controller upshifts just short of redline and as a result acceleration is as good as it can be. And consistently so.
 

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I wasn't suggesting you don't use the paddles, just that the computer will tell you the shift points :) Hal had better info

A Guy
 

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392 / 6.4 ratings (2015+)

HP peak is @ 6,100 rpm
Torque peak is @ 4,200 rpm

So you'd want to initiate the shift just as you start to get to 6K - the other thing is the look at what given speed you're at and on the upshift you start around the torque peak.

For max acceleration you want to be in that sweet spot 4,100 - 6,100 rpm as the torque plateaus and the hp is still building up.

Spinning the engine to 6,400 rpm (stock engine) isn't going to gain anything - power starts dropping off and you're going to hit the rev limiter.

Great post. I've been experimenting with my manual challenger and it supports what your'e saying. Shifting above that range doesn't help.
 

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Here's a good video on the topic.

 

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Find a dyno graph of a stock 392 to find out when to shift. Rear end gear ratio can also play a factor too. Doesn't apply in ur case with the A8, but let's just say if the gears were really long, if the car holds power or barely drops off after the peak, it may be better to rev a little higher so when it shifts to the next gear it's not falling down below ~4k rpm. Basically what I'm saying is it's not always best to shift at peak power and in a lot of cases you'll be faster shifting a little over peak.
Same concept as higher average hp>higher peak hp
 

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Here's some related info that I came across some time ago. A lengthy thread but some parts can probably be skimmed over.

It's about torque vs horsepower but does discuss power bands & shift points.
 

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FWIW, I use the paddles...a lot. If I'm looking for "optimal", I'm in Track, I've pulled a paddle to get to manual, and I just hold the throttle to the floor and let the car shift. My reactions and choices will not do better than the ZF and associated programming will.
 

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the reason to shift at or close to redline though is better explained if you know the gear ratio's of the gear your going from and the gear your going to. The gear ratio's are just torque modifiers. You cant say shifing at the peak of one gear at 1 rpm is the best for every gear. racers normally shift at or close to redline because that normally puts you in the middle of the peak in the next gear. Shifting at the same rpm for each moves you around the power band of the next gear. the next gear also puts less torque to the wheels than the one currently in so losing a bit of power at the higher rpms is still more wheel torque then you get with the peak of the next gear so its almost always better to stay in a lower gear for more time then shifting to the higher gear quicker.
There was somewhere on the internet I found ounce that did the math and you plugged in your gear ratios and power output and it told you what rpm was best for what gear. This was maybe 10-12 years ago though.
this is also why the 8 speed is faster then the 6sp. Since the ratio's are closer you are not losing a large amount of wheel torque going to the next gear so the car pulls harder in each then jumping larger ratio's the 6sp manual does or even the 5sp auto.

Ron
 

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Well not to create an argument but I stand by my results that at least for me my best quartermile times came from elevating to a bit above the stock shift point. Now I do have an aftermarket tune which may effect the power curve, but I've got well over 200 passes on my car experimenting with about every combo of set up for launch rpm and shifting I could think of and I consistently get better times when shifting at the higher rpm. When I had my R/T for example I purchased a Mopar TCM and swapped that in, it gave me good solid 6,200 rpm shifts which in turn gave me better quarter mile times. Lots of folks said at the time that 6,200 would be above the optimal shift point for the 5.7, quite possibly it was but my car seemed to benefit from it nonetheless. I know there were some old threads on this forum where this was discussed before and there was at least a few of us that felt we were getting better results by increasing shift rpm. That was if I remember right all A5 transmissions, may not apply to A8 guys, I haven't had a chance to play much with one of those yet.
 
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