Tow/haul mode always when towing?

[bigdodge]

We were hoping you could tell us, because you insisted you can manual upshift.

isn't that manual shifting???
i manually shift from one to eight and from eight to one

 

[Rick3478]

No, I got your point. You didn't get mine because you're not thinking things through.
Cruise control is reactive, and it also cannot predict when dropping a few mph is ok or not. I would prefer to have it stay at the exact speed, rather than drop too much speed and then try to catch up.

No prediction required, it's always okay to drop a little speed under load. I just don't need it to be anywhere near as aggressive as it is. How about something like 1/4 throttle at -1MPH, 1/2 throttle at -2MPH, 3/4 throttle at -3MPH, full throttle at -4MPH? That's just an example, it might be better based on a speed or RPM profile, but some kind of gradual proportional response, not balls to the wall to keep a set speed at any cost.

And "try to catch up" is not important to me, I don't care if it never catches up. In fact, I'd prefer it not to, since catching up would probably involve burning more fuel and increased wear and tear on the transmission. I don't see maintaining an exact speed as very useful, but use cruise control to reduce driver fatigue. Why is maintaining an exact speed so important to you?

 

[Darksteel165]

isn't that manual shifting???
i manually shift from one to eight and from eight to one

Show us proof you can shift up manually. You can't.

 

[theblet]

Show us proof you can shift up manually. You can't.

If you lock out a gear the trans won’t shift to it. When pressing the button to unlock it, it will upshift. Manually pressing the buttons to control the trans shifting.

 

[silver billet]

isn't that manual shifting???
i manually shift from one to eight and from eight to one

No it isn't, it's subtly different as I've tried to explain.

If you're accellerating pulling a trailer (for example) and you are in second gear at 3000 RPMS and you have set your gear limiter to second:
- hitting + on the gear limiter won't (necessarily) upshift to third; the computer will still choose a gear between 1 to 3, and may decide to upshift when it hits 4000+ rpms instead of immediately after you bumped the gear limiter up
- in a true manual with paddle shifters, hitting + would immediately force the computer to upshift to 3rd.

As long as you won't damage anything by your actions, a manual always does what you tell it to do, immediately, whereas with a gear limiter the computer decides which gear to pick in the range you've selected and may take 1+ seconds before responding if ever

I don't think I care one way or the other which setup we have in our trucks because the gear limiter works for my needs. But if we're being pedantic, we have gear limiters, not a true manual.

 

[HSKR R/T]

No prediction required, it's always okay to drop a little speed under load. I just don't need it to be anywhere near as aggressive as it is. How about something like 1/4 throttle at -1MPH, 1/2 throttle at -2MPH, 3/4 throttle at -3MPH, full throttle at -4MPH? That's just an example, it might be better based on a speed or RPM profile, but some kind of gradual proportional response, not balls to the wall to keep a set speed at any cost.

And "try to catch up" is not important to me, I don't care if it never catches up. In fact, I'd prefer it not to, since catching up would probably involve burning more fuel and increased wear and tear on the transmission. I don't see maintaining an exact speed as very useful, but use cruise control to reduce driver fatigue. Why is maintaining an exact speed so important to you?

The transmission downshifting is based on engine load, not throttle position or speed. Yes, when cruise is set, it will downshift to maintain speed, but it downshifts to reduce load on the engine because it's actually worse for your drivetrain, wear and tear wise, to stay in higher gear and lug the motor down trying to maintain speed. Also, in a lot of situations, while towing, it's actually more fuel efficient to use gear limiter to lock out higher gears, and just run higher RPMs. The engine doesn't have to work as hard.

 

[Rick3478]

The transmission downshifting is based on engine load, not throttle position or speed. Yes, when cruise is set, it will downshift to maintain speed, but it downshifts to reduce load on the engine because it's actually worse for your drivetrain, wear and tear wise, to stay in higher gear and lug the motor down trying to maintain speed. Also, in a lot of situations, while towing, it's actually more fuel efficient to use gear limiter to lock out higher gears, and just run higher RPMs. The engine doesn't have to work as hard.

Leave the straw man at home, no one here is "lugging" the engine.

Engine load (torque) is a good concept to get a handle on things, but let me point out that some of you are self-inflicting load by using cruise control to maintain a pretty rigid speed target.

Having said that, does anyone have a fuel consumption map for the hemi engines? If so, please post it. I'd love to see it and might adjust some of my driving habits accordingly. Failing that, here's one I found on Wikipedia.
-
-
Engine load (torque) is on the vertical axis, and speed (RPM) is on the the horizontal axis. The dashed red curve at the top represents maximum torque at wide open throttle, and fuel burn rate is shown with blue contours. I'm not sure what their fuel units of measure were, but I'm only concerned with generalities anyway.

So from the map, it appears that this engine has a sweet spot around 2200 RPM with 85% throttle, and not much loss of efficiency over an area ranging from 1800 to 2600 RPM and 2/3 to full throttle.

You heard that right, full throttle is actually a pretty efficient way to run a gasoline engine. Pumping losses are much higher at low throttle openings. So if you're downshifting to avoid heavy throttle, you're probably wasting fuel.

And full throttle is not bad for the engine, even for extended periods of time, over a pretty wide speed range. I don't have any numbers to put on this, but the force exerted on rods and bearings from centrifugal effects and accelerating the piston back and forth becomes much greater at high RPM than the push of expanding combustion gases. And of course friction goes up with speed. So again, if you're downshifting to reduce engine load, you may actually be making things worse.

As far as wear and tear on the drivetrain goes, I think unnecessary shifting puts more wear on the transmission clutches than anything else, and the direct drive 6th gear is as close to zero wear as you will get.

Tow/Haul mode isn't about efficiency, it's about performance. Use it accordingly and accept the losses of efficiency and longevity that come with it.

For efficiency and longevity, I'd lean toward heavier throttle at medium-low to moderate speed.

Routine day-to-day driving, I mostly just let it shift however it wants to.

 

[HSKR R/T]

Leave the straw man at home, no one here is "lugging" the engine.

Engine load (torque) is a good concept to get a handle on things, but let me point out that some of you are self-inflicting load by using cruise control to maintain a pretty rigid speed target.

Having said that, does anyone have a fuel consumption map for the hemi engines? If so, please post it. I'd love to see it and might adjust some of my driving habits accordingly. Failing that, here's one I found on Wikipedia.
-
View attachment 162494 -
Engine load (torque) is on the vertical axis, and speed (RPM) is on the the horizontal axis. The dashed red curve at the top represents maximum torque at wide open throttle, and fuel burn rate is shown with blue contours. I'm not sure what their fuel units of measure were, but I'm only concerned with generalities anyway.

So from the map, it appears that this engine has a sweet spot around 2200 RPM with 85% throttle, and not much loss of efficiency over an area ranging from 1800 to 2600 RPM and 2/3 to full throttle.

You heard that right, full throttle is actually a pretty efficient way to run a gasoline engine. Pumping losses are much higher at low throttle openings. So if you're downshifting to avoid heavy throttle, you're probably wasting fuel.

And full throttle is not bad for the engine, even for extended periods of time, over a pretty wide speed range. I don't have any numbers to put on this, but the force exerted on rods and bearings from centrifugal effects and accelerating the piston back and forth becomes much greater at high RPM than the push of expanding combustion gases. And of course friction goes up with speed. So again, if you're downshifting to reduce engine load, you may actually be making things worse.

As far as wear and tear on the drivetrain goes, I think unnecessary shifting puts more wear on the transmission clutches than anything else, and the direct drive 6th gear is as close to zero wear as you will get.

Tow/Haul mode isn't about efficiency, it's about performance. Use it accordingly and accept the losses of efficiency and longevity that come with it.

For efficiency and longevity, I'd lean toward heavier throttle at medium-low to moderate speed.

Routine day-to-day driving, I mostly just let it shift however it wants to.

No strawman argument from me. Max torque doesn't mean max efficiency. Torque gets you moving, HP keeps you moving. And in anything but the direct drive 6th gear, your chart is invalid.

 

[theblet]

Constant WOT is not good for 4 stroke gas engines. The load on internals, and heat generated will cause premature failure.

 

[theblet]

Do you have any actual data on horsepower-hours versus load?

Negative. I’ve just seen engines tear themselves apart running high rpms. If your internals and top end isn’t made for it, say goodnight.

Even race car engines only last one for one race, and they have the best parts.

Wouldn’t recommend winding the engine out constantly

 

[Bt10]

No prediction required, it's always okay to drop a little speed under load. I just don't need it to be anywhere near as aggressive as it is. How about something like 1/4 throttle at -1MPH, 1/2 throttle at -2MPH, 3/4 throttle at -3MPH, full throttle at -4MPH? That's just an example, it might be better based on a speed or RPM profile, but some kind of gradual proportional response, not balls to the wall to keep a set speed at any cost.

And "try to catch up" is not important to me, I don't care if it never catches up. In fact, I'd prefer it not to, since catching up would probably involve burning more fuel and increased wear and tear on the transmission. I don't see maintaining an exact speed as very useful, but use cruise control to reduce driver fatigue. Why is maintaining an exact speed so important to you?

If we’re close on cruise and you slow down, I’ll pull out to pass on cruise. If you then speed up, I’ll pass with authority on pedal and pull in close in front of you and let off pedal to cruise, whether you are now trying to go faster or not. Yes, you are the problem for the rest of the normal cruise drivers.

 

[theblet]

That's not wide open throttle, that's high speed, different thing. Sure WOT will get you there if there's no load on the engine, but that's sort of the opposite of what was being discussed.

I know, but you said WOT is more efficient and not bad for a gas engine. I was replying to that.

And a lot of times race car engines hang 6k rpm for hours at high speed

 

[HSKR R/T]

But you didn't. You're talking about speed, which is the other side of the equation.
High throttle at reasonable RPM is not a problem. High RPM is a problem regardless of throttle.

Unless you can keep the transmission from downshifting, which you can't, unless you have a TRX or GT, it will downshift well before you get past half throttle. The chart you posted is under ideal conditions with 1/1 drive, probably at sea level. Nothin absolute about it in real world driving.

 

[Darksteel165]

Unless you can keep the transmission from downshifting, which you can't, unless you have a TRX or GT, it will downshift well before you get past half throttle. The chart you posted is under ideal conditions with 1/1 drive, probably at sea level. Nothin absolute about it in real world driving.

I can keep my transmission from downshifting and I don't have a TRX or a GT .

 

[theblet]

But you didn't. You're talking about speed, which is the other side of the equation.
High throttle at reasonable RPM is not a problem. High RPM is a problem regardless of throttle.

I never mentioned speed. High RPM is literally what I said and was literally my point.

 

[HSKR R/T]

I can keep my transmission from downshifting and I don't have a TRX or a GT .

Well your truck is kind of a bastard right now

 

[Darksteel165]

Well your truck is kind of a bastard right now

My truck isn't sure wtf it is right now.

 

[HSKR R/T]

My truck isn't sure wtf it is right now.

Lol, give it some space. It will eventually tell you what it identifies as.

 

[HSKR R/T]

RPM is rotational speed, same thing. WOT is a different thing.

And you aren't going WOT on an automatic transmission, with no way to prevent shifting, without the RPMs climbing.

 

[Rick3478]

Rick3478 said:
That begs the questions: CAN you change the TCM firmware to get a manual shift mode, and if so what does that entail?

@Darksteel165 said:
Yes

Do you have any details on that you can share?
Does it entail loading different firmware?
Or do you just lie to it and tell it it's a GT or TRX?
Is it something you can do with AlfaOBD or other "tuner"?
Does it then work with the dial and steering wheel buttons,
or does it need a GT or TRX shift lever?

I'm interested, and hoping for more information.
What can you tell me?