Forum Discussion
- Of course all the discussion about needing more gears only pertains to those folks that operate at wide open throttle a significant amount of time.
wnjj wrote:
philh wrote:
wilber1 wrote:
philh wrote:
Stupid question, but do more gears really make a difference on typical superduty diesel?
Yup. How much I don't know but having the perfect gear for every situation is definite plus.
I'm having a tough time understanding how it will help given the relatively flat torque curves on a diesel engine.
Because counter to Ford’s advertising a few years ago, torque is not power. Producing the same engine torque at a higher RPM means it’s producing more power.
Another way to think of it is this. If you can downshift and raise the engine RPM, you can now send this same (flat curve) torque through a lower gear and produce even more torque at the wheel than before the downshift. Lower gears multiply engine torque.
With less gears, a downshift may not be possible because it could push the engine up past its torque producing RPM.
Yes, thank you. So many people only look at the horsepower and torque numbers and think they have an idea of how well this machine will tow. But they ignore the transmission. If you have a transmission that keeps the engine in its best power range, it can easily out perform a more powerful engine with less gears or bad shift points.
This is also why an electric or hybrid pickup would easily smoke any of the diesel trucks. The Rivian, for example, has over 10,000 pound feet of torque at the wheels and it has a very flat torque curve. So, it puts 10,000 lb-ft to the wheels up to around 60mph, then it will start t decrease. A diesel with 1,000 lb-ft of torque will put out torque to the wheels of 16,000 lb-ft in first gear, 9,900 in second gear, 6,400 in third gear, 4,900 in fourth gear, 3,700 in fifth gear, and 2,900 in sixth gear. So, the Rivian has more torque to the wheels at all times except when the diesel is in first gear.
I don't understand why people are still getting excited about these relics. If the consumers would demand better trucks, we would have diesel-electric hybrids that could easily tow 30,000+ pounds at 65mph up the Ike- A flat torque curve means as the engine slows down as a truck is pulling up a hill the torque remains the same at the rear wheels... you feel the same push from the seat throughout the entire rpm range that the torque is flat. It also means the the power at the rear wheels is dropping off as the engine slows down. As the engine rpm drops a downshift would keep the axle turning the same speed but cause an increase in torque and therefore put more power to the rear wheels. More gears allows the engine to run slower when less power is needed and higher when more power is needed. The ten speed should help obtain a little better fuel economy as well as a greater pulling capacity. On the other hand the new diesels, especially the Cummins have a fairly flat power curve, ie the torque builds as the engine slows down. This means more gears is of less value as far as pulling goes. My Peterbilt has an 18 speed transmission and a completely flat horsepower curve. At any one speed I can select one of 3 different gears to run in. Running in any of the 3 gears will put exactly the same power to the rear wheels.
- I'll take more gears anytime.
philh wrote:
wilber1 wrote:
philh wrote:
Stupid question, but do more gears really make a difference on typical superduty diesel?
Yup. How much I don't know but having the perfect gear for every situation is definite plus.
I'm having a tough time understanding how it will help given the relatively flat torque curves on a diesel engine.
Because counter to Ford’s advertising a few years ago, torque is not power. Producing the same engine torque at a higher RPM means it’s producing more power.
Another way to think of it is this. If you can downshift and raise the engine RPM, you can now send this same (flat curve) torque through a lower gear and produce even more torque at the wheel than before the downshift. Lower gears multiply engine torque.
With less gears, a downshift may not be possible because it could push the engine up past its torque producing RPM.wilber1 wrote:
philh wrote:
Stupid question, but do more gears really make a difference on typical superduty diesel?
Yup. How much I don't know but having the perfect gear for every situation is definite plus.
I'm having a tough time understanding how it will help given the relatively flat torque curves on a diesel engine.philh wrote:
Stupid question, but do more gears really make a difference on typical superduty diesel?
Yup. How much I don't know but having the perfect gear for every situation is definite plus.- I don’t think you will notice. ;)
One of your numbers are inverted. I’m betting 137# difference. rhagfo wrote:
What will be the weight cost for the 10 speed? How much heavier is it than the current 6 speed?
Russ
Ford's 10 speed transmission will weigh only 3.5 lbs more than the 6 speed it replaces.- Stupid question, but do more gears really make a difference on typical superduty diesel?
