Help! SOS, I need a tow!

[DMAXchris]

Could be something like that. The motor stays at a constant rpm on cruise. I know with stock tcm tuning, that rpm is under or just at 2k at 75 with a 6speed.
The little bit of knowlegde I have, thanks to Fingers' research, leads me to believe that harmonics play a major role in breaking things with the cruise on.

 

[DAVe3283]

If you don't edit the cruise tables, most of the tunes I've seen end up over fuelling compared to the normal throttle tables. I know on my LB7 I have my cruise fuel limit set at about 70mm3 to get it to drive normal.

And sadly, many of the variables we need to edit to make cruise run like stock are either hard coded or not exposed by EFILive. Even with all the tweaks I've done, my cruise is really only good for level ground or rolling hills. Anything more than that and the truck loses its mind. The price we pay for power, I suppose.

Sent from my FlashScan V2

 

[Hot COCOAL]

Could be something like that. The motor stays at a constant rpm on cruise. I know with stock tcm tuning, that rpm is under or just at 2k at 75 with a 6speed.
The little bit of knowlegde I have, thanks to Fingers' research, leads me to believe that harmonics play a major role in breaking things with the cruise on.

yeah, I've been under and right at 2000 rpm both times, with the cruise set

there is specific talk about the engine harmonics that occur with the cruise set?

If you don't edit the cruise tables, most of the tunes I've seen end up over fuelling compared to the normal throttle tables. I know on my LB7 I have my cruise fuel limit set at about 70mm3 to get it to drive normal.


And sadly, many of the variables we need to edit to make cruise run like stock are either hard coded or not exposed by EFILive. Even with all the tweaks I've done, my cruise is really only good for level ground or rolling hills. Anything more than that and the truck loses its mind. The price we pay for power, I suppose.

Sent from my FlashScan V2

interesting...
good info, good stuff to know and think about when I get the urge to be lazy and push that little button...

thanks guys!

 

[LBZ]

If you don't edit the cruise tables, most of the tunes I've seen end up over fuelling compared to the normal throttle tables. I know on my LB7 I have my cruise fuel limit set at about 70mm3 to get it to drive normal.

And sadly, many of the variables we need to edit to make cruise run like stock are either hard coded or not exposed by EFILive. Even with all the tweaks I've done, my cruise is really only good for level ground or rolling hills. Anything more than that and the truck loses its mind. The price we pay for power, I suppose.

Sent from my FlashScan V2

I wasn't aware there were cruise tables. Just an lb7 thing as far as efilive goes? Not sure how slightly overfueling would cause an issue though. I never noticed an egt difference between cruise on/off or change in engine noise to indicate any significant difference in how it runs.

Speed limit cruise around these parts and most of the country are 60-70mph which in my one lml stock tire size 3500 SRW work truck is about 1750 rpm. Give or take 100.
In my LBZ with 35's at 75-80 mph which is where I normally roll on the fwy that nets me about 1700 - 1800 rpm. My experiences seem to fall in the middle of the bad harmonics range. I believe I would have had a failure with or without cruise.

 

[DAVe3283]

I wasn't aware there were cruise tables. Just an lb7 thing as far as efilive goes? Not sure how slightly overfueling would cause an issue though. I never noticed an egt difference between cruise on/off or change in engine noise to indicate any significant difference in how it runs.

There is at least the one table for the LB7 that limits how much fueling is allowed on cruise. I've found if I leave that stock, it lugs 5th gear and smokes, even when it wouldn't using the throttle. I just tweak that table down until it down shifts like I expect.

The other difference I've noticed on cruise is the fueling can oscillate, especially on hills. It will be cruising at 30mm3 (or whatever), start up a hill, and start slowing down. Instead of adding more fuel quickly to avoid slowing down, it ramps in fuel slowly, then tries to "catch up" to the set MPH. Inevitably, it over shoots the speed, and ramps the fuel down too much, and repeats the process.

The closer your power level is to stock, the less it does this. If we had access to the source code, I suspect we could tweak the algorithm and make it work even with big power.

But you are right in that I've never seen it run differently on cruise (timing, pilot, etc. are all identical). It just gets stupid on hills, and wants to lug the motor to the point of smoking. I just turn cruise off and drive by foot on hills.


Sent from my FlashScan V2

 

[malibu795]

If you don't edit the cruise tables, most of the tunes I've seen end up over fuelling compared to the normal throttle tables. I know on my LB7 I have my cruise fuel limit set at about 70mm3 to get it to drive normal.

And sadly, many of the variables we need to edit to make cruise run like stock are either hard coded or not exposed by EFILive. Even with all the tweaks I've done, my cruise is really only good for level ground or rolling hills. Anything more than that and the truck loses its mind. The price we pay for power, I suppose.

Sent from my FlashScan V2

I have been able to manipulate mine.. Via throttle tables And some anothers I can't remember off the top of my head...
Also playing with down shit tables in the TCM..

Example say I need 1000uS pulse to maintain speed..
Running BBX in live scanning I've got the pulse fluctuation to less then 25uS +/- swing. With non VVT turbo.. With VVT I would see up to 400uS swing.. Couple times a second

 

[Dozerboy]

You guys are grasping if you think the cruse control has anything to do with it. Thats not to say the harmonics at a cruising RPM aint a part of the problem, but I just dont see being one of the main causes. Think of how many guys would be breaking cranks. I have made several trips driving a straight 24hrs. where my cruise only came off to get fuel.

I've never see a difference in fueling while using the cruise. Only thing I can think of would be for acceleration rate to achieve the set RPM. I know a guy that did a rolling burnout up a very steep bridge in his 1000hp truck while towing his gooseneck with the cruise on.

This is an easy enough fix though for the 6 speed guys put it in 4th and cruise at 2400RPM. Get 10 MPG and blow you $$$ on fuel instead of fixing your crank.

 

[LBZ]

I believe cruise would do this because it's operating on reaction conditions not anticipating ones. It doesn't know the grade or length of the hill, only that it's losing speed. To keep it from being too aggressive for short inclines or wind gusts, they likely designed it to operate that way. On a long steep climb I have as likely everyone else had it drop up to 10mph before it kicks down gears, and in some cases cruise kick right out as it could no longer stay within its programmed range if that makes any sense. Or also overshoot at the top as by the time it realizes it's going flat or downhill again after trying hard to get up to or maintain speed, it's too late.

When you run the throttle, that is if you have throttle control and not a constant on/off person, you apply and release the throttle earlier and more smoothly as you can anticipate the upcoming grades/turns in the road.

Again, I don't believe cruise itself as the issue but more rpm range and time/duty cycle.

Sent from my D5803 using Tapatalk

 

[Dozerboy]

The other difference I've noticed on cruise is the fueling can oscillate, especially on hills. It will be cruising at 30mm3 (or whatever), start up a hill, and start slowing down. Instead of adding more fuel quickly to avoid slowing down, it ramps in fuel slowly, then tries to "catch up" to the set MPH. Inevitably, it over shoots the speed, and ramps the fuel down too much, and repeats the process.

The closer your power level is to stock, the less it does this. If we had access to the source code, I suspect we could tweak the algorithm and make it work even with big power.
Sent from my FlashScan V2

Hell my truck did this 10x worse stock. I had to take the cruise off in rolling hills the truck was almost dangerous in the way it drove. Not that I make big power to most on here, but my truck drives way better since I tuned it in this aspect. It might be the extra power to pull the hill or the fact I lowered how fast the boost ramps up, but I still have the VVT.

 

[LBZ]

I feel TCM tuning is key for any truck. Especially if you lift it or change gears/tire size.

Just changing shift points makes things night and day better when cruising or towing. I hate lugging, and I hate braking. I would rather let the engine and trans do the work for me. But cruising rpm or harmonics wasn't even a thought when I broke my crank. Fingers testing has definitely made me think about how I will do things a bit differently. Part of the reason I went with the AF cam. It makes sense to me.

Sent from my D5803 using Tapatalk

 

[Hot COCOAL]

I believe cruise would do this because it's operating on reaction conditions not anticipating ones. It doesn't know the grade or length of the hill, only that it's losing speed. To keep it from being too aggressive for short inclines or wind gusts, they likely designed it to operate that way. On a long steep climb I have as likely everyone else had it drop up to 10mph before it kicks down gears, and in some cases cruise kick right out as it could no longer stay within its programmed range if that makes any sense. Or also overshoot at the top as by the time it realizes it's going flat or downhill again after trying hard to get up to or maintain speed, it's too late.

When you run the throttle, that is if you have throttle control and not a constant on/off person, you apply and release the throttle earlier and more smoothly as you can anticipate the upcoming grades/turns in the road.

Again, I don't believe cruise itself as the issue but more rpm range and time/duty cycle.

Sent from my D5803 using Tapatalk

Yes, that is what I was saying.
I don't think the cruise function has anything to do with it, rather how that cruise function manipulates the fueling tables and such..

Sure, it may be grasping, some call it brainstorming, but how often is that when you find an answer? how many times is it when your at your wits end, you've used up your rational ideas and you've exhausted all your resources and you are "grasping" at something, when you find that "something" to hold onto:angel:

 

[LBZ]

I don't feel how it operates to be the issue.
I'm going with extended duration in a fixed rpm range as the prime cause.

 

[Dozerboy]

Well I was probably taking you guys a little to literally then. Still look how many guys sit at cruising speeds/RPMs for long times. Thats every truck that that actually is driven not just a grocery getter. Adam is the only one really does this a ton and has failures and well we all know his luck.... Im all for AF cam ETC I just think its more of a QC issue that harmonics exploits. I just feel we would see rampant failures if it was all about RPMs and duration. Ive seen several Dmax fleet trucks that are driven to a inch of their lifes that put on 50-60k a year mostly at cruising speeds and I have never seen a broken crank.

 

[Hot COCOAL]

it's a conundrum, fer sure, and when it happens you start having all these "fringe ideas" cuz hey,myou want answers so it doesn't happen again! am I right?

on another note, walked out the front door this morning and I got my EBC 3GD brake kit....but something didn't seem quite right...

its a front and rear, rotor and pad "kit"
yet one box is half the size and weight and had two 5 lug rotors in it
:doh:


really.....

they say karma is a bitch N all, but I'd really like to know what the heck I'm doing so I can stop doing it!!!!

 

[malibu795]

Well I was probably taking you guys a little to literally then. Still look how many guys sit at cruising speeds/RPMs for long times. Thats every truck that that actually is driven not just a grocery getter. Adam is the only one really does this a ton and has failures and well we all know his luck.... Im all for AF cam ETC I just think its more of a QC issue that harmonics exploits. I just feel we would see rampant failures if it was all about RPMs and duration. Ive seen several Dmax fleet trucks that are driven to a inch of their lifes that put on 50-60k a year mostly at cruising speeds and I have never seen a broken crank.

I'm not ready to jump on the harmonics is the defacto problem wagon yet...

Russ posted up a picture of a burnt main from a spun bearing.... Seams noone but me acknowledged that..
Post #76

I lost my first dmax engine that way back in 07. Spun #2 main end up riping main webs 2, 3, and 4 and cracking the crankshaft.. All because injectors fails on a lb7..

I lost my LMM crank due to reluctor wheel doing its own thing... Throwing timing off..

So unit there are more cranks broken with everything else right... I'm not jump on that wagon yet

 

[RitzBlitz]

I'd have to agree. Correlation does not equal causation. I'd venture to guess a lot of these trucks see the majority of driving with their cruise on. So of course more often than not many issues that arise will be during the time cruise is on.

In fact, I've made that same drive about 15 times over the past year (WA to Central Cal, even interviewed in Los Banos). Always in one shot. I would think that if something were to do my 200k+ mile motor in (with a large majority of those miles being with cruise on), that would do it if cruise caused it.

Unless injection events are significantly different under cruise, I can't see it being the main contributor to these failures.

 

[LBZ]

I'm not ready to jump on the harmonics is the defacto problem wagon yet...

Russ posted up a picture of a burnt main from a spun bearing.... Seams noone but me acknowledged that..
Post #76

I lost my first dmax engine that way back in 07. Spun #2 main end up riping main webs 2, 3, and 4 and cracking the crankshaft.. All because injectors fails on a lb7..

I lost my LMM crank due to reluctor wheel doing its own thing... Throwing timing off..

So unit there are more cranks broken with everything else right... I'm not jump on that wagon yet

I know of over a hundred crank failures. And I'm sure there is more. My buddy at a gm dealer gets a couple every month and that's a small dealership.

I believe the main spin in this particular one was an after the fact. He never mentioned an oil pressure issue before the failure which tells me it didn't cause the break.

 

[malibu795]

I know of over a hundred crank failures. And I'm sure there is more. My buddy at a gm dealer gets a couple every month and that's a small dealership.

I believe the main spin in this particular one was an after the fact. He never mentioned an oil pressure issue before the failure which tells me it didn't cause the break.

He probably wouldn't have seen much oil psi drop. #1 is last to go get oil...
Idk how often Jason checks his gauges while driving..
I know for me when I lost my LB7 I have no clue how long it ran with a case full of fuel and it still did 35-40psi. Even after injector swap and fresh oil it was still "low" buy not below spec
Since then I have made it a habit to check gauges at least once every 60 seconds or so..

 

[LBZ]

Wouldn't matter if it's one or two or five Adam. Loss of pressure in the system due to an increase in bearing clearance, broken squirter or broken hose yields the same result. It's all a common system with one gauge, one pump, one relief valve.

Sent from my D5803 using Tapatalk

 

[Harbin_22]

My oil pressure dropped enough to set the dummy message when my crank broke.