Want one map for the track and one for the street? Want to change the characteristics of your rev limiter as you are driving? How about being able to choose from as many as 12 different target boost levels? All this and more is possible with the Haltech rotary trim module!
Let’s say we want to have a few different boost curves programmed into the ECU for different scenarios. For example a softer curve for a wet track, a more aggressive curve for good track conditions and something in between for day to day driving.
We then want to be able to switch between these curves without having to plug a laptop in. To do this we need to have a way to tell the ECU which boost level we want at any given time, and that’s where the rotary position trim module comes in.
The rotary trim module has 3 wires; power, ground and signal. When you change the position of the knob the module sends a voltage down the signal wire to the ECU.
Different positions on the knob send different voltages to the ECU and the ECU uses this voltage information to change how it behaves.
With the module wired in we can now program the ECU to target say 15 PSI of boost on position 1, and 22psi on position 2, and so on.
Setting it all up
Using ESP software for Elite Series ECUs go into the Setup menu, Main Setup, Functions, and select “Rotary Trim Module 1”. Currently, you can have up to 3 modules controlling any number of different functions at once.
Hit the Edit Connection link and select an available input to wire the signal wire to. There is also a calibration tab that has been preconfigured to match up with the voltage output of the Haltech 12 position trim modules.
With the input setup sorted let’s head into the tuning maps. Starting with boost, we navigate to the Boost Control and within the Boost Control Map we select Setup, Table Setup or simply press the F3 shortcut key.
We are now in the Axis Setup for Boost Control. Originally this was set up for RPM but now we want to add another axis to that map. Select the Axis to be “Rotary Trim Position Knob 1”. Let’s add a few positions in here and press OK.
Now when we go to the Target Boost Map, we have 5 different target boost levels based on the position of the trim knob. We can now change the numbers to go from full send boost all the way down to grocery getter at the twist of a knob.
But wait, there’s more!
The trim module is not restricted to just boost control. You can use the same knob to also control any other function in the ECU.
Along with a 10psi target boost level at position 2, you might also want to drop the rev limit down to a measly 4500 RPM. This is a common setting for a “valet mode” or for those times when you hand over the keys to your significant other.
You can also adjust the ignition timing or lean the fuel out a little for that extra economy – the process is the same. Go to the map you want to make changes on the fly with, add the trim knob to an axis of that map and make your changes based on the position of the knob.
NOTE: if it’s fuel that you want to trim out or add in, the place to do this is in the Target Air Fuel Ratio map and not the main VE map. This way, when you add your new map axis to one of the target AFR maps the ECU will “learn” toward the updated target. If you make corrections to the main VE map, however, the ECU will just learn its way back to whatever is in the target AFR map.
You can get as creative as you like with these rotary trim modules they really do put all the ECU functions at your fingertips, so don’t be afraid to experiment.