Mod- built a shift-controller for Gen3 auto transmission S-mode using microcontroller

This is a super long post... sorry for that. You might want to use a computer if you attempt to read it…

I traded in my gen2 tacoma, and bought my 3rd gen, (2016 SR5 double cab LB, automatic) in April 2016. Over the past many months, I have tried so hard but I just can not stand the early-shifting, well-below of the power-band for this engine. I now have about 11,000 miles on my truck. I have had TSB-0077-16 rev 0 and rev 1 installed when they came out. While these TSB's both corrected the shift delays/flares with my transmission, they never affected the fundamental shift-mapping for the automatic gear-shifts. For a couple weeks after TSB it felt a bit better, but soon settled into its same old performance.

I believe the shift-mappings have been developed by Toyota for optimized fuel economy. I also do not expect any TSBs to be released which will change them (I hope I'm proven wrong in the future).

Other than the shift patterns, I love the truck. I like the handling, suspension, off-road capability, styling, towing capacity, etc. I do plan to keep it for a long time.

In my opinion, the gears selections need to be made to keep the engine RPM higher; to take advantage of the full torque of the engine. Gears need to be held longer during acceleration. I have reviewed the torque curves for the engine, and max torque is created up into the 4000-5000 range. Not saying the shifts need to be that high, but running the shifts up into the 3000-4000 range should be the norm. Of course, fuel mileage will suffer a bit, but i'd rather have the performance.

I hate when merging onto an interstate, the engine shifts up to 4th gear at like 38 mph, looses all torque, cant accelerate. Then I have to stomp on it, kick it back down to 3rd, accelerate like hell.. Repeat, repeat, etc.. The truck also shifts way too much when cruising (4th to 5th to 6th to 5th to 6th, to 4th, etc, all the time). I have also tried 'ECT all-the-time' method. This does move the shift-mappings up a bit, but they feel sloppy and overly aggressive to me.

I spent most of my life driving manual-transmission vehicles. My tacomas are the first auto-transmission trucks i have owned. For the past many months, I have occasionally driven it with S-mode as if I would be driving a manual. When I do this, I can hold the shifts as needed, downshift when necessary, and I can actually get this truck to perform exactly how I feel it should, and I love it. [the S-selection is simply a limiter on the max gear allowed, but the truck always wants to be in the highest gear, so it basically ends up working just like a manual shift].

Now for the fun part... I have a MS degree in mechanical engr. My research focus is in dynamic system analysis, measurement and control. Anyway, I asked myself... why don't I just build an automatic controller which is smart enough to take over the S-mode and replicate the sport-shifting shifts exactly as I would make them. Upshifts, downshifts, etc.. I purchased an ELM-327 OBD reader and tracked vehicle speed, RPM, throttle position, pedal position, engine temp, for many months during my drives. I did it in automatic (D), and in S mode with my manual shifts. (OBD data is output from tacoma at about 15 samples per second, continuously). Every day I would download the data and lay it into charts/curve fits. After a short period of time, I was able to extract the stock shift mappings for the automatic transmission, and the 'ideal' shift mappings where I think they should be. The shift points (vehicle speed) are strongly correlated to throttle position or 'pedal' position. The plots below show some of the data. (pedal position OBD-output ranges from extremes of idle=15% to floored=48%.). All of the dots are actual shift recordings.



As you can see, the stock automatic shift mappings are exponential-slope curves, and in my opinion, go to way too low of speed at low pedal positions. For example, shifts to 4th gear at 20mpg, and 5th gear at 30mph should never happen. My manual shifts are shown by the blue and gray lines. Notice they are much more linear curve fit, and the shifts were made generally at higher speeds, especially at low pedal position. Dont get me wrong, im not winding out the engine for my shifts.. , not even close. These are gentle shifts while normal accelerating, basically shifts at the speed where it feels like it should be, not horsing on it. There were a few instances where the truck-computer actually shifted at higher speed, after I made the manual + shift, but those were when throttle position was >40%, which is during a hard acceleration.

Now the extra fun part... I built a micro-controller which takes over and controls S-mode for all shifts between 3rd and 6th gear (I'm actually OK with the auto shifts from 1-2 and 2-3 so I left those alone). It has one plug which interfaces to the OBD-data link connector, and one plug which interfaces to the S-mode wire-connector in the shift-console in the cab. A few photos of the device are shown below..



(pardon the solders, im not an EE!)

The device does not mess with the stock tacoma computer/programming at all. It simply 'automatically' controls the S+/- shifts with relays. Kind of like if you programmed a robot to sit beside you and make the S+/- shifts so you dont have to. That said, this should have no impact on warranty, reliability, etc. This device uses an Arduino-microcontroller for the control/software. It uses a freematics OBD plug to interface to the vehicle, and I built a shield to hold my switching relays, voltage sensing, and shift-control sensing. I included a few LED's and a speaker to be used for various visual and audible outputs and warnings.

The software programming uses the shift-curve equations determined from my S-mode manual shift points over 3 months of driving. It continually monitors speed and throttle position at 15 samples per second, and makes the S+ or S- shift when it is programmed to. It also makes downshifts at speeds determined from my research. For example, downshift from 4th to 3rd always occurs at 30mph, 5th to 4th at 52 mph, and 6th to 5th at 68 mph. I actually loaded two sets of shift mappings; one for cold engine temp and one for hot. The cold temp shift points are all indexed down by about 3-5 mph, depending on the gear. Engine temp is continually monitored every 15 seconds and hot is considered as >160F.

I also programmed-in a bunch of safetys. Shifting into or out of S-mode is what turns the controller on or off. It can only be turned on if the vehicle speed is less than 25mph when shifted into S. Also, if at any time the driver shifts S+ or S- manually with the lever, the microcontroller relinquishes control to the S+/- lever as stock and the program control is cancelled. Audible and visual warnings are given any time the automatic software program is cancelled. Also, loss of signal at any time from the OBD port would cancel automatic control and leave it in the current S-gear selection. Audible warning is given, and the control is relinquished to the S+/- lever as stock. (OBD has never lost signal yet so far)

So far, I've been testing it for a few weeks, and after a few minor software tweaks, it works perfectly! I actually enjoy my truck again, and love the well-timed shifts, at always the right speed/rpm! Feels like my gen2! Now it is using the power/torque that is has, and doesn't get bogged down all the time. It also makes about 70% less shifts than the normal automatic (D) does during the same drive. I haven't checked fuel mileage. I imagine it took a hit, but I'm ok with that to get the performance back. If nothing else, it was a fun project and I learned a lot about the truck performance and the OBD communications.

 

Soooo...how do I buy one?

 

@gearcruncher

 

Cost of project?

 

You're going to get a lot of responses on this, here we go.

 

Too good to be true ?

 

April Fools?

 

Wow, that's really impressive. Like...REALLY impressive.

 

From an EE to an ME... I tip my hat to you. Nicely done.

 

This is freaking awesome!
Maybe the beginning of Tacoma arduino mods? That would be cool!
Downloadable "mods", shift maps, locker functions, and so on.

To stay on topic, this is very thought provoking and cool as hell! Thanks for sharing.

 

The OP is a guy with some brains. Pay attention to his posts And learn. @smitty99 check this cat out... I'm impressed

 

Brad , do you think this for real ? Any potential safety problems ?

 

Yeah what this guy said?! Is this something that can be purchased because I am highly interested in something like this!!

 

That is the shiznit!

 

Very impressive! Please let us know if/when these will be available for purchase!

 

Definitely seems legit. The op is basically electrically actuating the Shifter S Mode increments/decrements electronically. I think the safety is in the "Toyota controlled" S Mode control, which the Arduino only makes requests (that are granted) to. The Toyota still gets to protect itself.

As far as any other reliability risks, there is only one thing I don't know, and that is whether or not there could be any intermittent negative effects from the OBDII data monitoring that is being used to feed the Arduino board. Certainly data capture can reliably be done if safeties are in place to protect the CAN communications.

 

Impressive sir. I'd delete it all now, and sell it to Toyota for $10,000,000, lol

Better slap a patent on that bad boy asap

 

Mike Sweers hot line just blinged

 

props to you! I don't have any experience with 3rd gen automatics but at times I feel like my auto 09 2nd gen shifting sucks.

 

I just bought this on Amazon. Where do I start?