Regarding 5.7 torque curve (1 Viewer)

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I don’t understand this power curve. Does anyone know the sweet spot for the 5.7 v8 torque curve? Like what’s the rpm to shoot for for being in final gear (.59 in the 6 speed I think) on the highway?
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Think horsepower. HP is what does work at the end of the day, and what gets rigs and loads to the top of hills.

From that lens, the sweet spot for the 5.7L is 5600 RPM, although it's tractable everywhere.

It's because torque doesn't really mean anything without RPM when it comes to doing work. The two combined is the definition of HP.

Saying the quiet parts out loud -

A truck with lots of torque (makes a lot of HP at low RPM) has strong grunt off the line and tractable pulling power.

A truck with a lot of horsepower (continues to make a lot of torque into higher RPMs) is what wins races to the top of hills.
 
The lowest rpm that will still lock the torque converter against your aero and friction losses.
 
Based on that graph I’d guess whatever the gear ratio was and rpm at 57mph is your target
 
310 HP at the wheels and at 4,400 ft elevation? Impressive for 381 at the crank at standard atmosphere.

FWIW, On a 'built' 200, I've found the 6spd hard to keep locked in 6th with anything other than a very light throttle. So flat road, no headwind, etc. I typically keep mine in manual 5th to prevent the wear from constant lock/unlock 6th or 6-5-6 hunt. Only when I know the conditions are right to I allow 6th.
 
310 HP at the wheels and at 4,400 ft elevation? Impressive for 381 at the crank at standard atmosphere.

FWIW, On a 'built' 200, I've found the 6spd hard to keep locked in 6th with anything other than a very light throttle. So flat road, no headwind, etc. I typically keep mine in manual 5th to prevent the wear from constant lock/unlock 6th or 6-5-6 hunt. Only when I know the conditions are right to I allow 6th.
What size tires on your built 200 w the 6 speed that hunts gears?
 
What size tires on your built 200 w the 6 speed that hunts gears?
285/70R17 is all, so 33s. Build image is in the avatar.

True 'hunting' of gears is probably not the right term unless on a long highway grade. It's more the frequent lock/unlock in 6th. Transparent to most users, but it's a wear cycle with each event, no mater how small. And unlocking 6th happens with not a lot of added pedal pressure. But even around town I've found that the trans is biased to economy (aren't they all?) and achieves 6th too early, only to go back to 5th when traffic changes speed, slight inclines, etc. So rather than add the wear from all those cycles I just use manual 5th as my default and then push it up to 6th only when conditions warrant. Less delay when needing power is helpful too. Admittedly, I'll probably never see the benefit from this driving technique, but maybe the next owner will.

With the 8sp on the 570 I do similar. Out of the driveway is always manual (technically 'sport') 6th unless conditions warrant. For most 'local' highways I'll allow 7th. Only on interstates above say 70 do I allow 8th and even then only if it's open, steady-speed traffic.
 
285/70R17 is all, so 33s. Build image is in the avatar.

True 'hunting' of gears is probably not the right term unless on a long highway grade. It's more the frequent lock/unlock in 6th. Transparent to most users, but it's a wear cycle with each event, no mater how small. And unlocking 6th happens with not a lot of added pedal pressure. But even around town I've found that the trans is biased to economy (aren't they all?) and achieves 6th too early, only to go back to 5th when traffic changes speed, slight inclines, etc. So rather than add the wear from all those cycles I just use manual 5th as my default and then push it up to 6th only when conditions warrant. Less delay when needing power is helpful too. Admittedly, I'll probably never see the benefit from this driving technique, but maybe the next owner will.

With the 8sp on the 570 I do similar. Out of the driveway is always manual (technically 'sport') 6th unless conditions warrant. For most 'local' highways I'll allow 7th. Only on interstates above say 70 do I allow 8th and even then only if it's open, steady-speed traffic.
I think it’s less the wear from the 6-5-6 (or 8-7-8) shifting or torque converter locking and unlocking, but more from the heat being generated with the TC unlocks and that heat getting dumped into the fluid
 
Looks like I didn't answer the right question. Reading again, final engine speed on the highway depends on overall gearing, tire size/rolling resistance, and loads in terms of aero, weight and/or towing. The dyno graph only shows how tractable and flexible the 5.7L is, but won't answer what engine speed you need.

The transmission ECU is going to try to lock-up if wheel torque required to hold speed is sufficient. If it needs a bit more torque, it will unlock the torque converter to get a slight gearing advantage along with a bit more engine RPM. If torque demand is still not met, it will downshift with more engine speed again. There isn't necessarily one single value to shoot for and will depend on your mods and power required to hold speed.

Looking at this chart, a point of reference for a stock vehicle at 75MPH will be 1930 rpm for the 6-speed and 1866 rpm for the 8-speed. So somewhere in that range is maybe your answer. You can see how tire size impacts that rpm not for the better, making it more likely to unlock/hunt. Pair that with more aero loads still, and using sport mode or a regear maybe the answer. I will say there's margin at those engine speeds to hold the gear with some minor load/grade.

As an upper data point and more extreme example, when I tow my 8k trailer with rounded corners on 37s, I need about 2600 rpm at 65mph for the transmission to stay locked in gear. There's margin in that too though and 2300 rpm maybe all I need if I had a gear to get to that engine speed.

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I think it’s less the wear from the 6-5-6 (or 8-7-8) shifting or torque converter locking and unlocking, but more from the heat being generated with the TC unlocks and that heat getting dumped into the fluid
Good point on the additional heat. I think it's probably both. Each actuation event, be it TC lock or shift solenoid, causes some non-zero amount of wear. An those wear particles end up in the fluid. The hard part is determining the net effect. Am I extending the life from 600k miles to 700k miles? If so, it's probably pointless. OTOH if I happen to have the nth percentile trans and extend the life from 150k to 250k then there's benefit. I suppose it's no different than 3UR OCI's at 5k vs 10k; the average owner will never see the gain. But that also doesn't negate that it's the best practice, with 'best' is defined as what is optimal for the truck we love.
 
This chart is more representative of what the actual torque curve looks like vs that one in the first post. You will have to do the unit conversion from kW and Nm.

1740684524072.jpeg
 
I think the chart from the OP was with a tune.
Yes but the chart is kinda dumb since it looks like they didnt even start the pull at a low enough RPM to be useful, and show it in MPH instead of RPM. We dont even know what gear they used. Looks like they didnt start the pull until >3500 rpm.
 

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