Originally Posted by ATC Crazy

The point in downshifting before the grade is so the hill doesn't pull your speed down enough to downshift. You downshift at the bottom as to maintain a constant speed from the bottom to the top.
I'm with "rvpuller" on this one. It works great for me!

Originally Posted by ATC Crazy

The point in downshifting before the grade is so the hill doesn't pull your speed down enough to downshift. You downshift at the bottom as to maintain a constant speed from the bottom to the top.
I'm with "rvpuller" on this one. It works great for me!

Originally Posted by ATC Crazy

The point in downshifting before the grade is so the hill doesn't pull your speed down enough to downshift. You downshift at the bottom as to maintain a constant speed from the bottom to the top.
I'm with "rvpuller" on this one. It works great for me!

Originally Posted by dnewton3

Yup; me also.
It's about maintaining the desired speed without loss; keeping a gas engine below peak HP and above peak TQ gives the greatest opportunity for making it uphill.


To expand on the details of these situations ...
Let's assume we're driving through MO and all the hills on I-70 pulling our 10,000 lb RV; there are LOTS of grade changes from level to 4%, and everything in between.

Option 1; you leave it in Drive and let the system self-maintain speed of 60mph:
As you begin to proceed up a hill, the grade begins to increase from 0%, then 1%, then 2%, etc. And so the vehicle will drop to 59mph, then 58mph, then it will downshift from 6th to 5th. It will lose another 2mph and then downshift again to 4th. It will loose another 2mph and then downshift to 3rd. It does this because it cannot anticipate the change in grade; it can only react to a loss of speed, and then try "make up" the speed by overcompensating after the fact. To create the needed force to climb the grade, the system is always searching for the right gear to maintain that desire speed. But it always reacts and each reaction loses a few mph. Suddenly you're not going 60mph; you're running uphill at 54mph and now it's screaming at 4800 rpm trying to make up that 6mph delta; it's trying to get back to 60mph. And in fact, it may not have the ability to make it, because the load and grade may present a force requirement such that once you've lost the momentum, it cannot be regained until you crest the grade. This happens all because your engine is not above peak TQ rpm, and so as the rpm falls, so does the available torque.

Option 2; you manage the shifts prior to grade change.
As you approach the hill, you judge (by experience) when to shift down into 5th, or even 4th, ahead of time. That puts the engine ABOVE the peak TQ rpm, so that as the grade increases the force requirement to overcome, the engine actually "falls" closer and closer to it's peak TQ value as it drops from peak HP to peak TQ. You manage to maintain the desired 60mph because you are keeping the engine in the power-band, as close as practical to peak TQ. Admittedly, it takes some practice to learn. And there is always a grade that will make you have to downshift. But anticipating those grades, pre-planning those shifts, means you'll not loose the 60mph, or at least stay as close to it as possible given the total load value based upon grade.

The choice can make a BIG difference in how you successfully drive the undulation of repetitive hills. It can be the difference between keeping up with traffic, or becoming that PITB person who slows other vehicles down. It can multiply to a significant difference in both time and distance when you consider that it can happen literally hundreds of times when traveling a hilly route. And, it really does not waste fuel to any degree that's going to make a tangible difference in your wallet. It might cost one or two tenths of MPG at the most. And yet it gives much better confidence to the driver, and it is also more courteous to other drivers, by not being that "slow" RV rig going uphill.

And the same goes for going downhill. The grade-braking feature in today's trucks is great, but it also is "reactive" and not "proactive". If you want to maintain a safe downhill speed, set your CC to the speed, engage TH, and manually shift the gears to keep the rpms up where engine braking is prevalent. Don't wait for the PCM to realize it's going too fast, and then it panic shifts down three gears and you've gained 5mph over your desired speed. Shift ahead of the grade change; get the rpms up and gears down PRIOR to the need.

I recently returned from a trip out to CO and back with my brother. Drove his 2019 F250 CCLB 4x4 with 4.30 gears. Pulled his 10k lb toy hauler and our bikes. On the way out, he drove and did the driving the way he wanted to; used "D" and let the CC just self-manage. He soon realized he was often compromised into velocity loss and got "sandwiched" in-between big-rigs because he was not keeping up with traffic on the uphill sections. To me, it was frustrating because he really had not spent a lot of time driving an RV load. He was not unsafe at all, but he didn't anticipate nearly far enough ahead. He was not looking up-road 30 seconds ahead; not planning for passing opportunities and not planning for challenges. Then it came my turn to drive. I showed him how to start looking well ahead of your position; don't look at the car in front of you, rather look 5 cars in front of you. See the big-rigs as obstacles to maneuver around. See the hills prior to getting there. Shift BEFORE you loose speed. Shift to maintain position in the line of vehicles, and pass slower rigs. Then when we swapped back to him driving, he had the "a-ha!" moment and finally understood that driving a large load is supposed to be an interactive thing. I do appreciate that vehicles today are so very capable in terms of capacity and amenities. But they are also capable of lulling us to sleep mentally; they make us lazy.

Until they make a CC system that anticipates traffic and grade changes, it will always be more efficient to shift for yourself. (even shifting an automatic via manual mode).

Originally Posted by 7.3F350

Anyone else disappointed that the 7.3 has same stroke, but a bigger bore than the 6.2?

Looks like the 7.3, like the 6.2, will be more "hot rod" and less "low rpm torquer" than I had hoped.

Originally Posted by rvpuller

Gas motors make more power at high rpms and the new motors are designed for higher rpms. Diesels make power at low rpms but gas motors make it at high rpms.

Denny

Originally Posted by 7.3F350

What is "power"? If it is horsepower, then diesel motors also make more power at high(er) rpm since rpm is a factor in the hp formula.

I'll grant that I'm an outsider on this, but I don't want a high rpm motor, gas or diesel. I'm more concerned about low rpm torque than high rpm horsepower.

I thought that this new motor would be more 460 and less 6.2.

I'm looking forward to 7.3 hitting streets so we can see how it performs. Fuel mileage is generally a function of rpm. A big block that needs to be run at high rpm doesn't sound like a recipe for decent mileage...

Originally Posted by gsxr1300

Just because peak torque of 475 is at 4k rpm doesn't mean it doesn't have low rpm torque, it may have 470 at 1500 rpm and peak out at 4k.

Originally Posted by rvpuller

... unless heavenly modifided a compression motor will not run at high rpms but a gas motor will and likes it up there.

Originally Posted by rvpuller

I always say power because I don't want to get into the hp verses versus torque thing.

Originally Posted by dnewton3

Yup; me also.
It's about maintaining the desired speed without loss; keeping a gas engine below peak HP and above peak TQ gives the greatest opportunity for making it uphill.
Now this statement makes no sense. How are you keeping it below peak HP by downshifting first ?

To expand on the details of these situations ...
Let's assume we're driving through MO and all the hills on I-70 pulling our 10,000 lb RV; there are LOTS of grade changes from level to 4%, and everything in between.

Option 1; you leave it in Drive and let the system self-maintain speed of 60mph:
As you begin to proceed up a hill, the grade begins to increase from 0%, then 1%, then 2%, etc. And so the vehicle will drop to 59mph, then 58mph, then it will downshift from 6th to 5th. It will lose another 2mph and then downshift again to 4th. It will loose another 2mph and then downshift to 3rd. It does this because it cannot anticipate the change in grade; it can only react to a loss of speed, and then try "make up" the speed by overcompensating after the fact. To create the needed force to climb the grade, the system is always searching for the right gear to maintain that desire speed. But it always reacts and each reaction loses a few mph. Suddenly you're not going 60mph; you're running uphill at 54mph and now it's screaming at 4800 rpm trying to make up that 6mph delta; it's trying to get back to 60mph. And in fact, it may not have the ability to make it, because the load and grade may present a force requirement such that once you've lost the momentum, it cannot be regained until you crest the grade. This happens all because your engine is not above peak TQ rpm, and so as the rpm falls, so does the available torque.
Keeping it in drive ? You're talking about keeping it in drive and cruise control here. Not what I was talking about.
Option 2; you manage the shifts prior to grade change.
As you approach the hill, you judge (by experience) when to shift down into 5th, or even 4th, ahead of time. That puts the engine ABOVE the peak TQ rpm, so that as the grade increases the force requirement to overcome, the engine actually "falls" closer and closer to it's peak TQ value as it drops from peak HP to peak TQ. You manage to maintain the desired 60mph because you are keeping the engine in the power-band, as close as practical to peak TQ. Admittedly, it takes some practice to learn. And there is always a grade that will make you have to downshift. But anticipating those grades, pre-planning those shifts, means you'll not loose the 60mph, or at least stay as close to it as possible given the total load value based upon grade.
And here, you're essentially doing exactly what I recommended.
The choice can make a BIG difference in how you successfully drive the undulation of repetitive hills. It can be the difference between keeping up with traffic, or becoming that PITB person who slows other vehicles down. It can multiply to a significant difference in both time and distance when you consider that it can happen literally hundreds of times when traveling a hilly route. And, it really does not waste fuel to any degree that's going to make a tangible difference in your wallet. It might cost one or two tenths of MPG at the most. And yet it gives much better confidence to the driver, and it is also more courteous to other drivers, by not being that "slow" RV rig going uphill.

And the same goes for going downhill. The grade-braking feature in today's trucks is great, but it also is "reactive" and not "proactive". If you want to maintain a safe downhill speed, set your CC to the speed, engage TH, and manually shift the gears to keep the rpms up where engine braking is prevalent. Don't wait for the PCM to realize it's going too fast, and then it panic shifts down three gears and you've gained 5mph over your desired speed. Shift ahead of the grade change; get the rpms up and gears down PRIOR to the need.

I recently returned from a trip out to CO and back with my brother. Drove his 2019 F250 CCLB 4x4 with 4.30 gears. Pulled his 10k lb toy hauler and our bikes. On the way out, he drove and did the driving the way he wanted to; used "D" and let the CC just self-manage. He soon realized he was often compromised into velocity loss and got "sandwiched" in-between big-rigs because he was not keeping up with traffic on the uphill sections. To me, it was frustrating because he really had not spent a lot of time driving an RV load. He was not unsafe at all, but he didn't anticipate nearly far enough ahead. He was not looking up-road 30 seconds ahead; not planning for passing opportunities and not planning for challenges. Then it came my turn to drive. I showed him how to start looking well ahead of your position; don't look at the car in front of you, rather look 5 cars in front of you. See the big-rigs as obstacles to maneuver around. See the hills prior to getting there. Shift BEFORE you loose speed. Shift to maintain position in the line of vehicles, and pass slower rigs. Then when we swapped back to him driving, he had the "a-ha!" moment and finally understood that driving a large load is supposed to be an interactive thing. I do appreciate that vehicles today are so very capable in terms of capacity and amenities. But they are also capable of lulling us to sleep mentally; they make us lazy.

Until they make a CC system that anticipates traffic and grade changes, it will always be more efficient to shift for yourself. (even shifting an automatic via manual mode).

Originally Posted by dnewton3

I cannot tell from the pictures, but it appears go also have 2 plugs per cylinder, not unlike the 6.2L. With a bore that large, it may make sense for proper flame propagation. Not sure it's true; just looks that way in the photos. Looks like the COP is on the valve cover, and clearly there are leads going down to the plug between the header legs.

Originally Posted by baddad457

I never recommended using cruise control on hills. What I recommended was increasing speed in Drive before the hill, then downshifting as needed manually.

Originally Posted by 7.3F350

I would love to have a heavenly modified compression motor.