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High or Low Torque..???

B

BushogPapa

Well-known Member

Confusing, how this is referenced ..

Is it referring to the AMOUNT of Torque, or the RPM at which it occurs..??
Seems to be mis-understood widely...

I do know of Diesel truck engines offered in "High Torque" and also "Low Torque" versions..

Ron.
 
Maybe I've missed part of this conversation?

Torque when expressed in engine specs is usually shown at the RPM when the maxiumum amount of torque occurs.

"Torque curve" shows the increase and decline of max torque in regard to RPMs. A "flat torque curve" is referring to an engine that holds a fairy steady torque rating over a stated RPM range.

When something is called "high torque" by a seller, it can mean it has a high max torque figure, and/or it can mean it has a lot of torque at low RPMs.

High torque is often a result of an engine having a ratio of long stroke to smaller bore - in gas or diesel engines. High horsepower is usually the opposite with short stroke and large bore. And some engines are called "square" becaue bore equals stroke.
 
'High Torque' engines... I assume you are refering to something like IH's DT466... they offer with two different torque ratings and the same maximum power. Basically they're using electronics to vary the fuel curve and give increased fuel at lower speeds to increase maximum torque but then reduce or limit delivery at rated speed to limit maximum power... This was not really possible with mechanical engines as power in those engines was a function fo torque and speed alone.

Rod
 
Hello BushogPaPa,
Torque is a twisting force that is developed by the enigne as it runs.
Torque ratings are a measure of twisting and turning force, and the engine capacity to do the work. Most torque specification will state maximum torque at a given R.P.M. That means that unless the engine is a that R.P.M. torque will be less, with higer or loqwer R.P.M.'s
If you know at what R.P.M., and you need all the torque the engine has, you can choose a final gear ratio to give you that R.P.M.
Guido.
 
Actually, Mack, Cummins Diesel, and Detroit Diesel all offered "High Torque" variations of their engines for use in highway trucks.
Remember the Maxidine's? With only a 5 speed transmission, they would accelerate like a car with the high torque built into the governor.
All those engines had mechanical governors with certain springs, weights, and rack settings in the injection pump governor that would allow higher torque output at lower RPM's while limiting maximum horsepower at top rated RPM's.
A person can use the formula to figure out what maximum torque "could be" at a certain horsepower and RPM, but there are other variables that can be dialed into the governor of a Diesel engine.
A gasoline engine with a carburetor is not the same as a Diesel engine in this regard.
MikeS.
 
you should post this on the pulling board i mentioned something about jd's have more torque than other brands mostly because of the long stroke and folks over there talked about torque for 2 weeks nobody ever did get anywhere
 
jdemaris is exactly correct. Advertised specs call for max torque at ANY rpm for that engine. MAX torque is attained when the specific engine reaches it's highest volumetric efficiency. And that IS RPM specific based on all the design parameters built into that specific engine. IT has a certain rpm where all design specs work together to create the best possible cylinder fill (volumetric efficiency). Peak torque will fall off if you go higher or lower. The less it falls off and the slower it falls off is called the torque "curve" or torque "band". As far as how the manufacturer words it's ads...it's nothing but marketing hype and is all "relative". You could ask "compared to what"? to all their claims. They won't have an answer.
 
Hello Dean,
In order to produce torque, rotational force, the engine needs to be running, R.P.M.'s
Maybe you meen to say that R.P.M.'s effect engine torque?
Guido.
 
Horsepower equals torque times rpm. Let's you have two engines, each of which produce the same rated horsepower, but one produces that horsepower at 2000 rpm and the other at 4000 rpm. The slower engine must necessarily be producing twice as much torque to produce the same horsepower. So, in this context, the slower engine is the "high torque" engine. Both engines will do exactly the same amount of work, but the slower engine produces much more torque.

The real question is "why does anyone care?" In practice, "high torque" really means the engine has a relatively flat torque curve. And that flat curve gives it "lugging" ability: It doesn't need to downshift as often as the faster engine.
 
Maxidyne's and Cummins Constant Power and Constant Power Plus engines were indeed high torque engines but it was more a reflection of their cam grind than anything else. They simply make high torque at low speed and run out of breath at the top end which directly limits their power output. Engines like the 466 HT that I'm refering to would be more than capable of making much more than the 300 horse they're rated for... it's simply that they limit the top end electronically.

Rod
 

I believe that the engine producing the max torque at the Lower RPM is called a "LOW Torque Engine"..

Confusing, right..?..!

Ron..
 

I drove an old Road Boss with a 5 sped and a Low Torque Cummins 250 that would work most 350 Cummins hard to keep up..(80,000).
That was one Stubborn engine, when it came to giving up RPM..!!
If it would pull down to 1,100, it would just hang there...!!
Boring to drive..nothing to do..certainly not much shifting going on..!!!

Ron..
 

Seems like (on a Diesel engine), Injection pump, Turbo size and valve timing would make the difference...
 
Nope. "high torque" generally implies the engine produces max torque at a relatively low rpm. Or, to be more precise, produces its rated horsepower at low rpm.

Back when GM sold both small block and big block engines in their light trucks, there was typically very little difference in the rated horsepower of the small block versus big block engines. But the big blocks always had higher torque ratings, because the torque and horsepower were rated at lower rpms in the big blocks.
 
Hello BushhogPapa,
No... Torque is Force(F) X Lenght (L).
TO FIND TORQUE.....

TORQUE = Horse Power x 5252 / R.P.M.
Guido.
 

NO, you are not hearing what I am saying..

The reference to low RPM torque on some truck engines is "Low Torque"..

Ron.
 

That would be expected, longer stroke and more cu in..===More Torque..

Gasoline truck engines were typically cammed for maximum torque at around 1,600 RPM..
Real gasoline automobile engines were cammed for max torque in the 2,200 to 2,500RPM range..higher for high performance car engines..
I have a Crane came here that peaks torque at 4,500 RPM and HP at 7,500
So sweet, sucking thru the Med-high-rise 427 heads with Tunnel-Port valves..!!

Ron..
 
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