2015 auto or manual trans?

[SnoKing]

In my tow test today when accelerating up an on ramp it was taching 2700-2800 or there abouts, so the question is where is max HP? HP makes speed, torque starts a load moving. The 385 HP is at 2800 RPM, that is why they let is rev to those RPM's.

SNOKING

 

[Newsa]

In my tow test today when accelerating up an on ramp it was taching 2700-2800 or there abouts, so the question is where is max HP? HP makes speed, torque starts a load moving. The 385 HP is at 2800 RPM, that is why they let is rev to those RPM's.

SNOKING

Power = force x speed.

Rotational (angular) HP = Torque x RPM (with a correction constant in it for units)

 

[Newsa]

I never let mine go over 2300 RPM. And that's rare

 

[Newsa]

I never let mine go over 2300 RPM. And that's rare

I bought a truck. Not a Maserati

 

[Doubleclutch]

When accelerating up a hill from a stop or onto an interstate with a 20,000+ poumd load, i saw a video with the Aisin having shift points at 2600-2800 (above 3rd gear) RPM. That's not peak torque.
That's 1000 RPM above peak torque.

Would you want the transmission to shift AT peak torque, or ABOVE peak torque such that the new gear pulls through to peak torque?

 

[RVTRKN]

I've ran my C&C up the south bound Grapevine at 2900 RPM in 4th gear at 22K pounds, it didn't skip a beat. But it sure didn't feel like a Maserati, it didn't even feel like a Porch. That's the problem with a 3:73 diff and an AE G56, 5th would have bogged it and 4th at 2300 would have put me into the slow truck lane at 5mph behind a heavy semi.

 

[Newsa]

Would you want the transmission to shift AT peak torque, or ABOVE peak torque such that the new gear pulls through to peak torque?

Above peak torque, but 600-700 RPM above peak torque. Not 1000-1100 RPM above peak torque.

My statement was originally that you spend more time at higher RPM if the automatic is shifting for you. I (like photowrite) prefer to keep our CTD in the 1500-2300 RPM range. It is where the cummins was designed to perform. It is a mock down of a semi engine. It was not designed to be hooked up to an automatic. A ford powerstroke V8 doesn't get low end torque and is designed for an automatic transmission

 

[SnoKing]

Well I am not taking mine back! The Aisin at this point seems well behaved. It shifts into 6th gear if you turn TH off. Snoking

 

[RVTRKN]

The Aisin has proven itself with the C&C series before they put them in a 3500 pickup. They are huge next to a 68rfe, Dodge can't change their software or even the shifting strategy. I missed the boat in 07 when I equipped my C&C with a little known G56, over a little known Aisin Auto. If I was looking into a SRW truck, it would be a 3500 with the Aisin, then have the Dealer install a 4:10 diff. But when I get my 07 C&C with a NV5600, my truck will be a stout pulling machine.

 

[cerberusiam]

When accelerating up a hill from a stop or onto an interstate with a 20,000+ poumd load, i saw a video with the Aisin having shift points at 2600-2800 (above 3rd gear) RPM.

That is about right for peak TQ with stock programming, where the TQ and HP curve is the most efficient. Peak TQ is never going to happen at 1600-1800 rpms in the higher gears and you will never see anything approach peak in the lower gears. G56 is no different, would totally destroy the DMF if it ever applied the de-rated TQ at anything less than 2500-2600 rpms, Both drive train configurations need the rpms to survive the TQ rise on shift points or they won't last long.

in the 1500-2300 RPM range. It is where the cummins was designed to perform. It is a mock down of a semi engine.

Not under a load, power is de-rated under 1800-1900 rpms. No mock down of a semi engine comparison makes sense, the bore and length of stroke is what determines where the engine will make power effectively, aside form tuning. Big difference between a 6.7 and 10 liter engine.

 

[gsbrockman]

Guys.....just give up.

The way I see it......if one wants to stay within the powerband, that powerband is between peak torque RPM and peak horsepower RPM.

If one only wants to go 600 to 700 RPM above peak torque....so be it (and probably not a bad idea due to the input torque the G56 is limited to handle based on internals AND clutch).

Dyno run of a 2013 RAM 3500 SRW Aisin 385 / 850 truck (332/765 at the rear wheels)
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Not too shabby of a graph for an engine hooked to automatic although "It was not designed to be hooked up to an automatic."

http://www.cumminsforum.com/forum/2013-general-discussion/584835-2013-6-7-332-765-a.html

http://cumminshub.com/67.html

The paragraph below the Cummins 6.7L w/G56 6 speed manual sums it up best :
http://www.dieselhub.com/news/2013-cummins.html

 

[CMgoFast]

Even at 2800 rpm you're still pulling around 600 ft lbs. Which is enough to pull anything these trucks will pull.

 

[Cummins12V98]

Just put the pedal to the floor and let the truck do it's thing.

 

[Newsa]

Not under a load, power is de-rated under 1800-1900 rpms.

So When Ram/Cummins advertise peak torque between 1500-1700 RPM, they are reporting wrong numbers? I think not. They are honest about the derating of the G56 equipped Cummins & 68RFE. So they are accounting for derating in their numbers. It is actually torque-managed almost every where else except they also derate at slow speeds.

 

[Newsa]

Even at 2800 rpm you're still pulling around 600 ft lbs. Which is enough to pull anything these trucks will pull.

True 600 ft lbs has proven to be plenty for me. But if you are in tow haul and the transmission up shifts at 2800, your RPM'S will ALWAYS be above 2100 when accelerating and when you need the most torque

 

[SnoKing]

Like gsbrockman says, we need to just give up! SNOKING

 

[SnoKing]

http://www.cheatsheet.com/automobil...cience-behind-car-performance.html/?a=viewall

 

[cerberusiam]

So When Ram/Cummins advertise peak torque between 1500-1700 RPM, they are reporting wrong numbers?

Not wrong numbers, just not applicable numbers. Is and always has been Cummins tests the engines on an engine dyno with ALL the TQ management and safeties off. That is NOT as installed a Ram platform. This has been discussed many times and the answer has been the same for years, platform performance does not mimic advertised engine numbers. Look at the posted dyno sheet, there is no appreciable TQ rise until after 1900 rpms and the peak is in the 2100-2220 rpm range and relatively flat out to 2800. The shift points on the auto trans are defined by throttle position and will be at a high enough rpm with high APPS to limit the hit of the TQ rise on shift points.

Even the manual units are derated as soon as you clutch it for a shift. One can get by short shifting on an empty\light loaded truck but do that frequently under a heavy load and it just beats the trans to death and kills the DMF. So replace the DMF with a clutch that holds and problem moves to the bearings and gears in the trans. Simply too small to take the hit without lots of TQ management and derated power levels. Autos will live longer and use the power band better because they lock and unlock the TC to limit the hit.

 

[Newsa]

Not wrong numbers, just not applicable numbers. Is and always has been Cummins tests the engines on an engine dyno with ALL the TQ management and safeties off. That is NOT as installed a Ram platform. This has been discussed many times and the answer has been the same for years, platform performance does not mimic advertised engine numbers. Look at the posted dyno sheet, there is no appreciable TQ rise until after 1900 rpms and the peak is in the 2100-2220 rpm range and relatively flat out to 2800. The shift points on the auto trans are defined by throttle position and will be at a high enough rpm with high APPS to limit the hit of the TQ rise on shift points.

Even the manual units are derated as soon as you clutch it for a shift. One can get by short shifting on an empty\light loaded truck but do that frequently under a heavy load and it just beats the trans to death and kills the DMF. So replace the DMF with a clutch that holds and problem moves to the bearings and gears in the trans. Simply too small to take the hit without lots of TQ management and derated power levels. Autos will live longer and use the power band better because they lock and unlock the TC to limit the hit.

The shown torque curve is not proof of torque management below 1900 RPM. That is a dyno of a truck who's wheels were turning slowly at first. There is torque management when the speed of the rear wheels is below 35 mph. So the low performance of the torque just hapoened to be when the wheels were turning slowly. A run that was done to investigate real engine torque at a high enough speed in a high enogh gear would show usable torque at the 1500-1700 RPM level. I can feel that torque in my G56 in 6th gear. It is not limited there..... once the turbo is fully spooled, it accelerates best in those RPM's

 

[Newsa]

My guess is a dyno of a g56 equipped CTD from 45 mph to 60 mph in 6th gear would look different at those RPM's?