Author: Q7-retired
Subject: Pushing The Limits On Tow Vehicles
Posted: 20 Sep 2016 at 5:32pm
Let's not forget the difference between diesel and gasoline engines. Diesels produce their max torque at much lower RPMs than do gasoline engines, and have a much flatter torque curve (their torque is roughly the same at all RPMs, and yes, I know that's a broad statement). Gasoline engines must rev up much higher to produce their max torque, and their torque curve is much more rounded/ peaked.
Subject: Pushing The Limits On Tow Vehicles
Posted: 20 Sep 2016 at 5:32pm
Let's not forget the difference between diesel and gasoline engines. Diesels produce their max torque at much lower RPMs than do gasoline engines, and have a much flatter torque curve (their torque is roughly the same at all RPMs, and yes, I know that's a broad statement). Gasoline engines must rev up much higher to produce their max torque, and their torque curve is much more rounded/ peaked.
Also, diesel engines produce more torque than similarly sized gasoline engines. Power = torque times RPM times some constants, so you can see that a higher torque capability means lower RPM at same power levels. Your 4Runner is spec'd at 245 horsepower @ 5,200 RPM and 283 pound-feet of torque @ 3,400 RPM. The new Dodge Ram or Jeep Grand Cherokee with the 3.0 liter diesel produce 420 lb-ft @ 2,000 RPM and 240 hp @ 3,600 RPM. Note the torque difference and the closer RPMs on the diesel.
It makes sense to me that you must rev up your engine to climb hills. You have to get to the peak torque point on the curve.
Other things to consider might be valve blow-by or ignition issues that keep your engine from producing its max power. After all, it is 13 years old -- how many miles on the engine? Those other folks might be driving TV with diesel engines or have newer engines with less wear. For comparison, I tow my 2015 RP178 at 60mph max. I slow down going up steep grades to limit RPM excursions on the engine.