Building for torque vs. horsepower?

[Uncle Jesse]

I have a few questions on this topic.

#1: how much can tuning effect torque? In essence, can you tune with the goal of more torque gains rather than focusing on horsepower gains?

#2: obviously torque will be just as hard or harder on your drive train as horsepower. So, it seems to be a general consensus that a stock ally can handle up to 100 hp over stock, what about torque? People seem so concerned with hp numbers and completely ignore a diesels biggest strength, torque, why?

#3: now building a puller is going to be different from building a drag truck, so, what are the typical steps taken in each build, and what would be the best course of action to incorporate those steps into a daily driver geared towards towing (campers, toys, cars, nothing commercial or oversized)?.

I hope these don't come across as stupid questions. Your knowledge and info will be greatly appreciated.


Keep 'er 'tween the ditches

 

[Dirtymaxx03]

Torque is all in the tuning.

Torque is what breaks parts, not the horsepower.

 

[LWATSON]

The Allison can handle about 200 ft lbs over stock.

 

[durallymax]

Torque is twisting force, it is what breaks things. Horsepower is work done over time and is calculated off of an engines torque and RPM. This is why an 8.1 will beat a duramax to the top of the hill pulling a trailer. More horsepower. It's also what wins drag races and other competition events. Horsepower is how fast you can do the work, the faster person to do the work wins.

So why not use a 500hp honda civic to do the same work as a 500hp semi? Efficiency. The civic is making 500hp@8500RPM while the semi is making it down near 1500rpm. The way the calculation for horsepower works, the higher torque of the semi gives its the high power but at a lower RPM. In this case the semi would have 1,750ft-lb of torque at 1500RPM with the power at 500hp. The civic is only making 310ft-lb.

Both can do the same amount of work in the same amount of time (500hp). The issue is efficiency and reliability. Running an engine tuned like that civic is will be very inefficient and will not last long. Slow RPM's are more efficient and more reliable.

T=Torque
R=RPM
H=Horsepower

If you know your engines torque and RPM and want to find the horsepower at that RPM:

(T*R)/5252=H

For a stock LB7 at peak torque this would be.

(520*1,800)/5252=178

If you know Horsepower and RPM and want to know Torque at that RPM

(H*5252)/RPM=T

For a stock LB7 at peak HP this would be:

(300*5252)/3,100=508


Assuming you add exactly 100hp at the same RPM as the peak hp before. You can also just multiple the previous torque by the same percentage hp change since everything else is staying the same. In this case 33%.

(400*5252)/3,100=678


All transmissions are rated for their torque input, nothing else. The original Allison 1000 5spd behind the LB7 was rated for 620ft-lb. Torque on its own is not necessarily what breaks stuff, its the shock loads with the torque behind them that break things. That why a 1000hp truck can survive sometimes while a 500hp truck grenades things.


Tuning can change a torque curve to a certain extent but you are still limited by the engines hard parts.

 

[Uncle Jesse]

So if I understand this correctly:

-horsepower equals speed

-torque equals efficiency

-tuning can manipulate the torque curve but can't really change your engines hp to tq ratio. Only increasing the engines stroke length can do that.

-the equation you posted is based on the fact that hp and tq meet at 5,252 rpm correct?

So to conclude, horsepower is how fast the engine does it's job, and torque is how efficiently it does it.

I did not know that transmissions are rated for their torque capacity. Thank you for your input, it is very clear and easy to understand.


Keep 'er 'tween the ditches

 

[x MadMAX DIESEL]

Hp and torque as always equal at 5252 no matter what

 

[durallymax]

So if I understand this correctly:

-horsepower equals speed

-torque equals efficiency

-tuning can manipulate the torque curve but can't really change your engines hp to tq ratio. Only increasing the engines stroke length can do that.

-the equation you posted is based on the fact that hp and tq meet at 5,252 rpm correct?

So to conclude, horsepower is how fast the engine does it's job, and torque is how efficiently it does it.

I did not know that transmissions are rated for their torque capacity. Thank you for your input, it is very clear and easy to understand.


Keep 'er 'tween the ditches

1 horsepower is 33,000 ft-lb/min. The higher the horsepower number, the more work being accomplished in a given amount of speed whether the amount of work is being done due to more force (torque) or speed (RPM).

Torque does not equal anything other than twisting force. Efficiency can mean many things, it does not mean one specific thing even though in this case you are likely referring to fuel efficiency. Generally speaking a high torque low RPM engine will be more efficient than one running high RPMs, but not always and there are many other factors to consider.

Changing the engines stroke ratio can change the engines power and torque curves as well as their relation to each other. Longer stroke with smaller bore equals higher torque and lower RPMs, short stroke with large bore equals high rpm low torque. Generally speaking. Again many other variables to consider.

5252 is the constant in the equation yes. It comes from dividing 33,000 by 6.2832 which is the circumference of a one foot circle. Horsepower and torque will ALWAYs meet at 5252. No way around that. An engine will peak power above 5252RPM will make less torque than it does power and engine with peak power below RPM will make more torque than it does power.

Horsepower is work done over time, and torque is simply twisting force. Efficiency has many variables. However if comparing fuel efficiency between identical vehicles generally the one able to cruise at lower RPM's will be better. In order to cruise at low RPM's you need a lot of torque or you will be downshifting and back to higher RPM's again.

Some transmissions will have the torque rating right in the model. Eaton Fuller transmissions all have it after the dash.

RTX-15715 would be a Roadranger, Twin Countershaft, overdrive(with driect pattern), rated for 1,500lbs of torque, 7th generation, 15spd

RTLO-22918B would be a Roadranger, Twin countershaft, Low inertia, overdrive, rated for 2,200lbs of torque, 9th generation, 18spd, "B" gear set

Chrysler transmissions now follow a number system as well.

68RFE= 6 Spd, 800ft-lb torque rating, Rear wheel drive, Full Electronic control.

47RH= 4psd, 7000ft-lb, RWD, Hydraulic control.

62TE= 6spd, 200ft-lb, Transverse, Electronic control.

 

[Uncle Jesse]

Ok, I think I'm beginning to understand it a little more.

So, with torque being the twisting power, horsepower being work done over time, a 300hp/508tq engine (@3,100 rpm) will do the same amount of work over the same amount of time as another engine making 300hp/350tq @4,800 rpm (for example) the difference is engine #1 is using the engines greater twisting force (torque) and engine #2 is using it's faster engine speed (rpm). Stroke length along with the rest of the engine design is what determines the hp-tq ratio at a given rpm, however it will always meet at 5,252 rpm.

This is extremely interesting, you've given me a lot of information I didn't know, thank you very much. There seems to be a lot knowledgable people here, very helpful for young guys like me!


Keep 'er 'tween the ditches

 

[02ilduramax]

Subd

 

[chevyburnout1]

Getting back to "Engine 101". I like it!

 

[superswamper003]

Getting back to "Engine 101". I like it!

Haha!! :thumb:

 

[Hot COCOAL]

Some transmissions will have the torque rating right in the model. Eaton Fuller transmissions all have it after the dash.

RTX-15715 would be a Roadranger, Twin Countershaft, overdrive(with driect pattern), rated for 1,500lbs of torque, 7th generation, 15spd

RTLO-22918B would be a Roadranger, Twin countershaft, Low inertia, overdrive, rated for 2,200lbs of torque, 9th generation, 18spd, "B" gear set

Chrysler transmissions now follow a number system as well.

68RFE= 6 Spd, 800ft-lb torque rating, Rear wheel drive, Full Electronic control.

47RH= 4psd, 7000ft-lb, RWD, Hydraulic control.

62TE= 6spd, 200ft-lb, Transverse, Electronic control.

WOW! Thanks for the incredible posts!!! This is great info!
I'm in no way trying to derail this awesome flow of info here...

But does GM's number system for their transmission line up follow any sort of pattern like those depicted above?

For example, is the Allison 1000 rated for 1000ft/lbs tq?
4L80E & 6L80E rated for 800ft/lb tq?
4L70E rated for 700ft/lb tq?

Etc, etc?

 

[countrycorey]

WOW! Thanks for the incredible posts!!! This is great info!
I'm in no way trying to derail this awesome flow of info here...

But does GM's number system for their transmission line up follow any sort of pattern like those depicted above?

For example, is the Allison 1000 rated for 1000ft/lbs tq?
4L80E & 6L80E rated for 800ft/lb tq?
4L70E rated for 700ft/lb tq?

Etc, etc?

The gm transmissions (excluding the Allison) read this way:

4L80E - 4 speed, 80 is the torque rating, E is for electronically controlled. I know someone on here knows the conversion for the torque rating to an actual value.


Corey

 

[JoshH]

Here is how I like to think about HP vs torque. HP is a method of measuring work done over time. Work is a physics term and is calculated by multiplying the force put into an object by the displacement of that object as a result of that force. So in order for work to be done, the object the force is acting on must move. Knowing that, you can see horsepower requires movement. Torque on the other hand is a rotational force applied to an object requiring no movement. So you can put 10,000 ft-lbs of torque into an object without it moving, but you can't put 10,000 HP into it without it moving because if it doesn't move, no work has been done.

 

[durallymax]

WOW! Thanks for the incredible posts!!! This is great info!
I'm in no way trying to derail this awesome flow of info here...

But does GM's number system for their transmission line up follow any sort of pattern like those depicted above?

For example, is the Allison 1000 rated for 1000ft/lbs tq?
4L80E & 6L80E rated for 800ft/lb tq?
4L70E rated for 700ft/lb tq?

Etc, etc?

1000 just means its the 1000 series trans. Allison does have a system but the torque is not part of it.

4 means 4 speed, L means longitudinal mounting, 80 stands are 8,000lb gvwr. The 4l80E is rated for 440ft-lbs.


Good explanation Josh. Can't have horsepower without torque, but torque on its own accomplishes nothing.

 

[Hot COCOAL]

The gm transmissions (excluding the Allison) read this way:

4L80E - 4 speed, 80 is the torque rating, E is for electronically controlled. I know someone on here knows the conversion for the torque rating to an actual value.


Corey

1000 just means its the 1000 series trans. Allison does have a system but the torque is not part of it.

4 means 4 speed, L means longitudinal mounting, 80 stands are 8,000lb gvwr. The 4l80E is rated for 440ft-lbs.


Good explanation Josh. Can't have horsepower without torque, but torque on its own accomplishes nothing.

Thanks guys!
I didn't know the "L" stood for longitudinal mounting, makes sense tho
And woah, that's crazy that the 80E is only rated for 440ft lbs! I would've thought it had a higher capacity, good to know, thanks again!

 

[malibu795]

I can see 87-97 being rated for 440.. 97 and later had a higher tq rating

 

[JoshH]

I was off on the torque rating. Like Vinny said, the 80 is rated at 440 ft-lbs; the 85 is the one that is rated at 460 ft-lbs.

 

[durallymax]

Thanks guys!
I didn't know the "L" stood for longitudinal mounting, makes sense tho
And woah, that's crazy that the 80E is only rated for 440ft lbs! I would've thought it had a higher capacity, good to know, thanks again!

Yep, and "T" would stand for transverse. So a "6T30" would be a transverse mounted 6spd.

The transfer cases in OBS trucks have a code too. Newer ones probably do but I don't know it.

NP263XHD is what you will find in push button Duramax trucks.

NP= New Process (NV= New Venture)
2= Number of speeds
6= Strength (scale is 1-7)
3= Design feature (3 mean electronic shift, 1 means part time 4x4 manual shift)

I assume the XHD means extra heavy duty.



As Josh stated the 4L85E was rated for 460ft-lb which is what they used in the 06-09ish Duramax vans. The Duramax was tuned to produce 460ft-lb peak. The newer vans with the LMM engine went to 525ft-lb peak and switched to the 6L90 which is a 6 speed rated for 525ft-lb.