Reprogram Cruise Control for towing?

[Mateospeed]

Hey folks, I tried searching but didn't get much. I have an '05 V8 AWD, which I use to tow a rather heavy load: a ~7,500lb box trailer with a race car in it, or the AirStream.

Of course, I'm outfitted and rather used to towing heavy things, so no worries. The truck handles the load like a champ, and is actually much more pleasant to tow with than the 3/4 ton Chevy I'm coming from. The FJ cruiser springs on the 4R are likely a big help there.

Anyways, when towing, I have realized that the transmission and cruise control programming are poorly suited to the job. It does great without a load, but with, it jumps gears frequently (and I leave it in 4th gear when towing heavy). It also uses way too much throttle and too low gears to try to climb even slight hills at the speed requested.

I wonder if there's any way to access the programming for the cruise control and/ or the transmission shift profiles? I'd like to do things like limiting maximum throttle output while the cruise is set, and not allow the transmission to shift once the cruise is set. The way I figure, if I need to downshift to 3rd, I shouldn't be using the cruise control anyways. But, cruising down long stretches of gently rolling country shouldn't require me to NEVER use the cruise. "I don't care if I keep going 65mph up this slight hill, truck. Just chill out and slow down to whatever speed makes you happy. Don't use more than 75% throttle."

Something like that. Perhaps I can play with the logic and or programming overall. Has anyone done something like this, or familiar with how to access or modify the programming? Is the cruise control logic performed in a separate module, or does everything happen in the ECU?

Thanks in advance!

-Matt

 

[Sungod]

I don't think it is a question of programming, but one of physics. That extra heavy load will slow you faster than your engine can maintain the speed. The reason it drops a gear and the engine revs is because you effectively doubling the weight you are trying to move. You can balance out the revs, but the only way it would work would be for you to have a way to slow the time it takes to return to the desired speed. On hills that would be nearly impossible. If you want to pull that much weight and you want to use cruise control on hills, you will have to go back to your 3/4 ton. It is all about the torque.

 

[m85476585]

I think what he wants is a cruise control that's a bit more lax about maintaining speed. Sure you will fall below the desired speed going up hills, but if you are in rolling hills you will pick up speed again when it gets flat or you go downhill. Tow/haul mode in some trucks kind of does the same thing since it makes the transmission shift much less frequently, so it's less likely to downshift without more throttle input. The grade logic system (or whatever Toyota calls it. Grade Logic is Honda) in theory will sense when there is more load, like going up a hill or towing a trailer, but it only makes slight adjustments to the shift point. I haven't driven my 4runner in the mountains yet to get a feel for how it works, but in my Honda I could almost completely let off the gas going up long grade on the highway (after the grade logic activates itself) and it would still hold 3rd gear rather than shift to 4 or 5 like normal.

The cruise control on my Honda worked the same way. If I was carrying bikes on the back at 80mph, the slightest hill would cause it to downshift to 3rd and rev to 5500 RPM at full throttle. By the time it was done shifting, I was often at the top of the hill.

With better cruise control logic, if the speed falls too low and doesn't pick back up, you can always take control and accelerate as needed.

I don't think there's any way to program the cruise control or transmission logic. Aftermarket cruise control is available for some cars, but probably not ours (though it would be easy to intercept the throttle pedal position signal and use some inputs from OBD II to sense speed and engine load). I think cruise control is an afterthought for most car manufacturers.

 

[2014 Warthog]

^^^^ I want this even without towing!

Trying to use the cruise control in a hilly area (and every vehicle I've owned has done this) It's like putting a crazy person on the gas pedal.

I wish there was a setting or a knob that you could turn down the aggressiveness of it to your personal liking. It's perfectly fine to drop a few MPH going up a hill before freaking flooring it. I've even had it drop two gears in short order to 4k+ RPM going up a steep hill. I personally have NO need to put the hammer full down and race up the hill at 4500 RPM ever (Ok maybe when passing someone on occasion)

 

[BlackWorksInc]

Short answer is nope.

 

[Mateospeed]

Short answer is nope.

Well, crap. I was afraid of that answer. Is anyone even tuning the engines on these things with something consumer-friendly? I'm working with a chevrolet cruise control unit and computer on a hotrod project, and everything there is nicely programmable through one of the readily-available consumer tuning suites. I'm guessing that type of product isn't available for these vehicles?

 

[navin]

Sorry, don't have any input that will help your problem... but can you post a picture of your car trailer. Interested to see what type of trailer that is.

<- currently tows race car with open trailer, but would love an enclosed.

What other mods do you have to help with towing?

 

[V8Man]

Throttle Lock?

^^^^ I want this even without towing!

Trying to use the cruise control in a hilly area (and every vehicle I've owned has done this) It's like putting a crazy person on the gas pedal.

I wish there was a setting or a knob that you could turn down the aggressiveness of it to your personal liking. It's perfectly fine to drop a few MPH going up a hill before freaking flooring it. I've even had it drop two gears in short order to 4k+ RPM going up a steep hill. I personally have NO need to put the hammer full down and race up the hill at 4500 RPM ever (Ok maybe when passing someone on occasion)

Forgive me if I am hearing you wrong, but what it sounds like is both the OP and you are describing a throttle lock. My father made one for his truck back in 1974. He used a magnetic solenoid and a disk. The disk was attached to the throttle and the solenoid locked it in place. Going up a hill he might be doing 50 and down it he would get going faster. On rolling hills it worked great!

 

[2014 Warthog]

Forgive me if I am hearing you wrong, but what it sounds like is both the OP and you are describing a throttle lock. My father made one for his truck back in 1974. He used a magnetic solenoid and a disk. The disk was attached to the throttle and the solenoid locked it in place. Going up a hill he might be doing 50 and down it he would get going faster. On rolling hills it worked great!

Sort of Though I can see that maybe being a little too much speed change between steep up and down driving. But something more of a compromise between the two It should give it some more gas... to a point. Or down shift when really necessary, but not aggressively.

I.e. it should just drive like I do normally! And I think if there was an "aggressiveness" adjustment, everyone could trim it to something like their normal driving whoever they were. It definitely acts like an angry lead-foot as it is

 

[BlackWorksInc]

Forgive me if I am hearing you wrong, but what it sounds like is both the OP and you are describing a throttle lock. My father made one for his truck back in 1974. He used a magnetic solenoid and a disk. The disk was attached to the throttle and the solenoid locked it in place. Going up a hill he might be doing 50 and down it he would get going faster. On rolling hills it worked great!

It's unfortunately much trickier to do on 4th gens.

 

[V8Man]

Of course it is. 1974 was a carb with a steel rod for the throttle. I was just referencing a throttle lock and wondering if you could do the same thing through the ECM. Maybe a cruise set point then have a plus and minus set point too.