The 'sweet spot'....
I've seen several posters indicate that they have found the 'sweet spot' with their engines. How do you know? My thoughts are that the sweet spot is traveling in the highest gear at the lowest s...
Forum Discussion
Crespro wrote:wolfe10 wrote:
Reality is the "best MPG speed" varies with coach, gearing and terrain.
On flat ground, the lowest RPM you can hold high gear is the best "reasonable" speed. That will be right at peak torque RPM for your diesel.
When I say "reasonable" in most coaches peak torque RPM in 5th gear (MUCH less aerodynamic drag at lower speed) will give better MPG, but is excruciatingly slow!
But, that speed (peak torque RPM, 6th gear) in rolling hills will cause a downshift on each hill-- so a little higher speed that will allow you to stay in high gear is better.
Good question -- max torque first, then top gear, then sufficient kinetic energy to top the hills at your chosen minimum speed (I prefer 50 mph). On fairly flat terrain, that is 65 mph for me. If there are major hills, it is 68 to 70 mph.
Most of my driving is at 65 mph. But with 400 HP and 1200 ft-lbs of torque pulling 36,000# (coach with Enclave), I probably have slightly more power to weight ratio than many on this list.
Mr. Mark, your Volvo and Prevost are quite heavy in proportion to both HP and torque. I suspect you may be 2 mph higher than me based upon those parameters.
Crespro, I will be in the coach next week taking it for a chassis lube and a replacement fog light cover (rock hit). I'll make note of my RPM's at 55, 60, 65 and 70 mph.
We weigh 55,500 lbs., 500 hp, 1750 lb. ft. of torque and pull a 3,500 lb. CR-V.
If anyone is familiar with the Chiriaco Pass on I-10 heading east out of Palm Springs, CA, we pull that hill at 52-53 mph.
MM.
