Pskhaat
2005 Expedition Trophy Champion
Before Uni I wanted to go to GMI because I loved engines and everything about them; I read it all and studied as much as a high-school kid could. Alas, I'm no automotive engineer and I didn't end up at GMI. But I still love the discussions 
You stated the exact problem when you said ``driving on-highway.'' Don't get me wrong, highway driving comprises at the very least 80% of our travels. Low end torque simply does not fit the bill for you nor anyone who wants/needs the highway performance. That's where you need HP, an engine that can rev to get the HP, and a torque curve peaking higher to facilitate the HP factor.
It is important to look not only at the torque number, but the first derivative or slope of that curve. One that slopes upwards too much with increasing RPMs (high t') will perform quite differently at the exact same torque as another engine where t' is near 0.
I will without doubt stand corrected looking at your 2UZ-FE chart below. I havn't seen as much detail of the 2UZ-FE's curve, it is indeed peaky. It really doesn't drive that peaky, rather drives like a much more rounded or flat curve; and would have sworn it's shape to be different. That looks much more straight-6'y than V8'y. Don't know if the LC's slight differences in components might flatten that out?
You're correct that most folks always look for that flat torque curve; magazines love to espouse them as always a good thing. A flat curve allows someone to utilize their gearing more. However, that only applies really to racing and street use.
On full-time off-highway use (not high-speed) it is beneficial to have a long, steep, steady descent from the torque peak. This is called the torque rise. In off-highway or line-haul or tractor use you want to be driving with RPMs above the torque peak. The concept is that when driving in that rise any hill, obstruction, rock, ledge, water that causes your RPMs to drop will actually cause an increase in torque output from the engine allowing it more easily overcome and labor over said obstacle.
In our modern high-rev engines it's pretty tough to drive that high, we can employ some level of gearing to bring that curve down lower not just for the peak itself, but also to allow more driving on the rise. Look at the venerable 2F with a peak at 1800, or the 1HZ at 2200, or the Cummins 5.9/6.7 ISB at somewhere around 1600 (guess).
But that's actually a good thing for off-highway use
Redline said:
You stated the exact problem when you said ``driving on-highway.'' Don't get me wrong, highway driving comprises at the very least 80% of our travels. Low end torque simply does not fit the bill for you nor anyone who wants/needs the highway performance. That's where you need HP, an engine that can rev to get the HP, and a torque curve peaking higher to facilitate the HP factor.
It is important to look not only at the torque number, but the first derivative or slope of that curve. One that slopes upwards too much with increasing RPMs (high t') will perform quite differently at the exact same torque as another engine where t' is near 0.
I will without doubt stand corrected looking at your 2UZ-FE chart below. I havn't seen as much detail of the 2UZ-FE's curve, it is indeed peaky. It really doesn't drive that peaky, rather drives like a much more rounded or flat curve; and would have sworn it's shape to be different. That looks much more straight-6'y than V8'y. Don't know if the LC's slight differences in components might flatten that out?
You're correct that most folks always look for that flat torque curve; magazines love to espouse them as always a good thing. A flat curve allows someone to utilize their gearing more. However, that only applies really to racing and street use.
On full-time off-highway use (not high-speed) it is beneficial to have a long, steep, steady descent from the torque peak. This is called the torque rise. In off-highway or line-haul or tractor use you want to be driving with RPMs above the torque peak. The concept is that when driving in that rise any hill, obstruction, rock, ledge, water that causes your RPMs to drop will actually cause an increase in torque output from the engine allowing it more easily overcome and labor over said obstacle.
In our modern high-rev engines it's pretty tough to drive that high, we can employ some level of gearing to bring that curve down lower not just for the peak itself, but also to allow more driving on the rise. Look at the venerable 2F with a peak at 1800, or the 1HZ at 2200, or the Cummins 5.9/6.7 ISB at somewhere around 1600 (guess).
But that's actually a good thing for off-highway use
