FIREWALLIT
New member
I see the term TORQUE RISE used in many brochures regarding engine performance on utility tractors. I would appreciate any help in explaining/defining this term. Thanks.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
TORQUE RISE
- Thread starter FIREWALLIT
- Start date
- Views: 22331
MikePA
Super Moderator
Google search produced 2,460 hits. Here's one one of the results /forums/images/graemlins/cool.gif
What’s So Important About Torque Rise?
Torque rise, or torque reserve, is a measure of lugging ability (low-end power) when the going gets tough and the engine revs down. If your engine came from the United Kingdom, specifications may refer to “torque rise” as “backup.”
General rule of thumb – The more torque rise, the better! The engine may sound like it’s about to bog down and stall, but then it just keeps on churning, like the Energizer bunny.
You can feel, hear and mathematically see torque reserve. Your A.R.A.-affiliated rental expert can look up “peak torque” and “torque at rated horsepower” on the engine spec sheet. Then, to determine torque rise:
Divide peak torque by torque at rated horsepower
Carry it out to two decimals
The answer will be “1” followed by a two-digit number that represents torque rise, expressed by a percentage.
Example:
1.27 = 27 percent torque rise
A rating of 30 percent would be better yet
High torque rise is especially important in such machines as articulated wheel loaders, for instance, which lug down as they burrow into a pile of dirt or begin to dig.
On machines like excavators and backhoes, you can hear them respond to the increasing load as the crowd cylinder forces the dipperstick through the pass and the bucket curls into the dirt. If they stall out, they may not have the torque reserve to handle the load as it builds up.
What’s So Important About Torque Rise?
Torque rise, or torque reserve, is a measure of lugging ability (low-end power) when the going gets tough and the engine revs down. If your engine came from the United Kingdom, specifications may refer to “torque rise” as “backup.”
General rule of thumb – The more torque rise, the better! The engine may sound like it’s about to bog down and stall, but then it just keeps on churning, like the Energizer bunny.
You can feel, hear and mathematically see torque reserve. Your A.R.A.-affiliated rental expert can look up “peak torque” and “torque at rated horsepower” on the engine spec sheet. Then, to determine torque rise:
Divide peak torque by torque at rated horsepower
Carry it out to two decimals
The answer will be “1” followed by a two-digit number that represents torque rise, expressed by a percentage.
Example:
1.27 = 27 percent torque rise
A rating of 30 percent would be better yet
High torque rise is especially important in such machines as articulated wheel loaders, for instance, which lug down as they burrow into a pile of dirt or begin to dig.
On machines like excavators and backhoes, you can hear them respond to the increasing load as the crowd cylinder forces the dipperstick through the pass and the bucket curls into the dirt. If they stall out, they may not have the torque reserve to handle the load as it builds up.
AndyMA
Elite Member
- Joined
- Oct 11, 2000
- Messages
- 3,713
- Location
- Windham County, Conn
- Tractor
- Ford 2120 , Kubota MX5200 , Deere X748SE. 1956 Economy Tractor
In the New Holland TN series, the torque rise in % gets higher for the higher HP models. It is 36% for the TN75 turbo models and I sure can feel it kick in when pushing or pulling a tough load.
Andy
Andy
OP
FIREWALLIT
New member
Thanks Mike and Andy. I have my NH3930 sold and am seriously considering a TNA75D. I am concerned about torque because the 3930 has a shorter stroke than its bore, which greatly reduces low end torque. Both my dad and brother have Massey Ferguson utility tractors with 5 in. stroke Perkins engines and there lugging power blows my tractor away. I just don't want to make the same mistake twice.
To20Chris
Platinum Member
Here's an interesting thing: A short stroke engine of equal displacement produces a higher peak torque during the crank revolution than a long stroke engine! The long stroker has more leverage due to the longer crank arm, but the short stroker has bigger piston area. Think of it as a pnuematic piston. Right after it fires, given equal cylinder pressures, the bigger piston has more force on it. However, I think that the torqure falls off faster with the short stroke as the piston moves away. Once the crank are moves away form TDC, I think the mechanical leverage of the long stroke engine wins out.
timb
Veteran Member
- Joined
- Jun 14, 2002
- Messages
- 1,058
- Location
- Southwest PA
- Tractor
- Deere 4710/reverser, JD 318 (still needs TLC), JD LT160
Ok - really arcane question - It's obvious that more torque rise % would be better than less - but (regardless of HOW the numbers happen i.e. bore vs. stroke, valvetrain design, etc., ) how does the rpm where peak torque occurs play into the real world nature of the motor?
Example -
Engine "A" can produce 100 lb ft. @ 2500 rpm (48 hp peak), and has peak torque of 125 lb ft. @ 1700 rpm (equal to 40 hp at that point). So... a 25% rise.
Engine "B", has the same exact peak hp output at the exact same 2500 rpms, and the same peak torque output and therefore 25% torque rise - but that torque peak occurs at just 1300 rpm (equal to 31 hp).
One way of looking at it says that engine "B" has a "broader power band" which sounds good for variable speed use (like in a car). However looking at it the other way - while engine "A" has the same torque rise % - the torque peak occurs closer to the hp peak rpm - which if graphed would show a steeper 'slope'. That sounds like it would make the engine 'stiffer'. That is - with both engines running at 2500 rpm - and both see the same increase in load simultaneously - would engine "A" sag fewer rpm in overcoming the load than engine "B"?
Would that make an engine with type "A" characteristics better for nominally 'constant' rpm use (like a tractor at PTO speed) and type "B" better in variable speed applications?
Tim
Example -
Engine "A" can produce 100 lb ft. @ 2500 rpm (48 hp peak), and has peak torque of 125 lb ft. @ 1700 rpm (equal to 40 hp at that point). So... a 25% rise.
Engine "B", has the same exact peak hp output at the exact same 2500 rpms, and the same peak torque output and therefore 25% torque rise - but that torque peak occurs at just 1300 rpm (equal to 31 hp).
One way of looking at it says that engine "B" has a "broader power band" which sounds good for variable speed use (like in a car). However looking at it the other way - while engine "A" has the same torque rise % - the torque peak occurs closer to the hp peak rpm - which if graphed would show a steeper 'slope'. That sounds like it would make the engine 'stiffer'. That is - with both engines running at 2500 rpm - and both see the same increase in load simultaneously - would engine "A" sag fewer rpm in overcoming the load than engine "B"?
Would that make an engine with type "A" characteristics better for nominally 'constant' rpm use (like a tractor at PTO speed) and type "B" better in variable speed applications?
Tim
tough451
Silver Member
Now Im confused Massey advertises this as a Long 5" stroke what are the strokes of the Deere's and Kubota. And Ive been telling my wife all along that 5 was ooops sorry. /forums/images/graemlins/ooo.gif
To20Chris
Platinum Member
Actually, a broad flat curve makes the engine "stiffer", to use your term. In general, the closer the torque and hp peaks are, the more the engine is "peaky". Think of it this way: If you are running along near the hp peak, and you load it suddenly, there will be a RPM drop (there always is some). In a peaky engine, you may well drop below the torque peak, RPMs drop more, it has less power, and it can't pull it back up. With a big spread between the peaks, if you drop back down a little, you're just heading toward the torque peak, so it can pull it back.
Did I make any sense?
Did I make any sense?
To20Chris
Platinum Member
In the case of the engine, 5" is a long stroke. I'm not even goin' near the other!
timb
Veteran Member
- Joined
- Jun 14, 2002
- Messages
- 1,058
- Location
- Southwest PA
- Tractor
- Deere 4710/reverser, JD 318 (still needs TLC), JD LT160
Chris - I know what you're saying - and certainly if you get on the wrong side of the torque peak going down you're in trouble. I'm just wondering if there is a 'happy medium' - especially as relates to nominally constant-speed applications.
What got me wondering is what the in-use behavior differences may be between the large-frame JD 4000 Ten and 4000 Twenty motors. The new ones have a 10% larger motor with about the same peak hp as before - but the peak hp occurs at 2400 rpm instead of 2600 - and not only is the peak torque slightly higher overall - it occurs much lower - at 1440 rpm instead of 1700. In say a truck or Jeep type use with a lot of regular acceleration from low idle on up needed --- I'm pretty sure the newer, slower motor would be the better all around puller, but I wasn't as sure about a constant rpm use as in a tractor where you'd be running long periods at PTO rpm - nearly at the hp peak.
Tim
Tim
What got me wondering is what the in-use behavior differences may be between the large-frame JD 4000 Ten and 4000 Twenty motors. The new ones have a 10% larger motor with about the same peak hp as before - but the peak hp occurs at 2400 rpm instead of 2600 - and not only is the peak torque slightly higher overall - it occurs much lower - at 1440 rpm instead of 1700. In say a truck or Jeep type use with a lot of regular acceleration from low idle on up needed --- I'm pretty sure the newer, slower motor would be the better all around puller, but I wasn't as sure about a constant rpm use as in a tractor where you'd be running long periods at PTO rpm - nearly at the hp peak.
Tim
Tim