Cruise control RPM limiting after changing tire size and 4lo limiter on 2016 Tundra

Hi All,
I have a 2016 Toyota Tundra. I've modified the following settings from the default tune supplied by HP Tune.

1) Tire Size changed for my 295/70/R18 tires
2) Removed 1st gear 4lo throttle govenor
3) Set speed limit governer to 200 MPH (which I'll never get to)

Since these modifications, whenever I drive uphill with Cruise Control enabled in S or D, my transmission will downshift, but the engine will never rev past 3,500 RPMs. When the engine hits that limit, it's as if the throttle is closed and it's not allowed to open any farther. I'm really unsure where to event start looking for these limits, or if this is a side effect of changing the 4lo and speed limit governor. It seems there have also been issues with GM engines and cruise control when changing tire sizes.

https://forum.hptuners.com/showthrea...Cruise-control


I'm going on a road trip in 2 weeks, and I would REALLY prefer to have cruise control that functions correctly.

Attached is my tune file. Any idea where I should look to fix this problem?

Code:

---

[Specific Controller]
Toyota Denso 992K, ${VIN HERE}, 30CM52, (4)


ConnectionMethod: USB
ID: 2076445202
HardwareVersion: 1.4.0
ManufactureDate: 6/11/2020 2:42:32 PM
PartNumber: 6230
FirmwareVersion: 3.0.30
PoweredOnTime: 00:01:25
VehicleConnectedTime: 00:01:24
VehicleDiagnosticConnector: 1

---

Attachment 110962



Thanks in advance!
Todd

Give this a try, if it still doesn't work let me know and I'll give you another file to try.

Thanks @SlowNStock! I tuned with your changes, and it helped, but I still experienced an issue where the truck seems to up-shift too soon. The truck would accelerate, and I'd get past 3,500 RPMs, but then it would immediately shift up instead of using the power in the current gear. I've attached the log file. It did a premature upshift, then downshift 3 times in succession. You can see it at 14:12 in the logs.

Attachment 110969


Would you be able to explain how the changes to the ETC Throttle Angle affect the cruise control?


Thank you for all your help!

The PCM references the Low Load and High Load limiting tables during cruise (and a few other conditions) - essentially, by increasing the values, the PCM can command a greater throttle opening for a given torque request and RPM pair. If the permitted throttle opening is too low, the truck may not be able to accelerate or even maintain the target speed, which is what you experienced with your initial tune.

In some calibrations, you can simply max out both tables without issue. In others it causes a whole host of secondary problems with cruise control if the values are raised too much because the PCM will command the maximum value when there is a positive torque request and then shut the throttle when there is a neutral or negative torque request, which results in cruise acting like an on-off switch. From my experience, all 2018+ Cal IDs need the tables to have reasonable values, along with at least some 2016/17, but I haven't tested nearly enough to map it out - in general they're still useful tables, so I usually recommend they're either left stock or the any changes are tested well.

There isn't any secret sauce behind the values in the file I sent you previously, they were taken directly from an LC200/LX570, and are generally a little better baseline that doesn't cause too many problems with cruise control.



Back to your log, there are a few different things we can do to address what you encountered:

(0) We can simply command a lower gear when this occurs (undesirable)
(1) We can reduce the amount of extra throttle angle permitted
(2a) We can increase the TPS for a downshift RPM -or-
(2b) We can decrease the RPM for a given downshift TPS
(3a) We can decrease the TPS for an upshift RPM -or-
(3b) We can increase the RPM for a given upshift TPS

With (1) we will eventually return to the point where you started from, but some reduction may help in instances where the PCM can simply command too much throttle angle for our preferred shift schedule. I've attached an example where I've used the average of the two tables.

With (2) we are adjusting our shift scheduling preference towards holding the current gear vs downshifting for a given TPS. This works fine if we have significant additional torque on tap and can achieve adequate acceleration without a downshift, but if we are already close to the maximum torque available at that RPM it won't help us. An easy way to eyeball this is by looking at calculated load, which correlates with the maximum available torque for a given RPM (100% calculated load is providing 100% of available torque) - if we're at, say, 80-90% calculated load just cruising on flat ground at that speed, holding the gear may not be the best choice.

With (3) we are adjusting our shift scheduling preference towards holding the current gear vs upshifting for a given TPS. This works well for those cases like the example given in (2), where the torque reserve at a given speed is relatively low and downshifts are inherently more frequent. By holding a gear longer after a downshift, we tend to encounter fewer cases where we downshift, then immediately upshift again. We can't go too extreme, however, or will never get an upshift back into the higher gear.

I've attached very basic examples of 2 & 3 as "Downshift" and "Upshift", respectively, just to give you an idea of how to approach each of those. You can apply the same approaches to TCC lock/unlock to get even more flexibility (if you do, be careful about creating a situation where you spend excessive time with the TCC unlocked in 5th and, especially, 6th).

Ultimately, a mix of all approaches will get you to the best result, you'll simply have to some experimenting. To speed up your testing, you can copy over all your Normal throttle and shift scheduling tables to Tow/Haul, then make a separate set of changes to those. The advantage is you can test two different schedules against one another every time you do a write, which saves quite a bit of time.

You can also dedicate one setting specifically for unloaded cruise. Tow/Haul is a good candidate for this because you generally aren't using S6 when towing, so it's not a great loss to purposely schedule it to hold 6th much longer (and you can do the same with 5th if you're okay with manually dropping to S4 when needed while towing).

Hope that helps!

Thanks for all the info @SlowNStock! I'm a software engineer, and I'm pretty tech savvy. However equating the inputs on the drive train to the corresponding settings tables, and then creating the desired outcomes isn't very clear for a newbie like me. That explanation is very helpful, and I appreciate it!

I ended up testing the minimal changes first, which was your Cruise Edit 02 file. This slight increase in throttle angle seems to generate enough change in RPM that when in cruise, the truck picks the correct gear over searching. It also has improved the experience of driving without cruise control. I'm attaching the log from my test drive. Hopefully, it provides you with some feedback that's useful in your future tune. Thanks again for all the help!

Attachment 111005

I'll be heading on a road trip from Denver to Bozeman in a couple of weeks. I'll take my tuner with me and perform any tweaks once I can get on the open road and see how it performs over long distances.

This is slightly off topic, but to confirm @SlowNStock 's point, maxing out the torque model table on the 1GR-FE Tacoma (6spd manual, 2008) will cause cruise to act as an on/off switch as well.