MoTeC Global Forum

Hi I had a question about a couple of parameters in M1 Tune. The Idle Activate Throttle Pedal Threshold and the Idle Activate Throttle Pedal Hysteresis. We have a drive by wire system and it says to use values of 0 for Threshold and .1 for Hysteresis. One of our old tune files from a different engine for a previous FSAE year had these values set at 2% for each. This previous year used the same drive by wire system and Electronic Throttle Body. We are struggling to get our engine to come back down from pedal mode into idle control and I was wondering if these values would help pull the engine down into idle control if the engine struggles to do so with retarding timing.

That will not make a difference with a hanging RPM. You need to lower the torque at the engine operating condition, so try reducing the ignition timing where the throttle is hanging. Alternately you can give the idle control system more range to operate in. I will look up the parameter names (you got it - Idle Aim Ramp Down Limit) and update this thread.

What having an Idle Activate Throttle Pedal Threshold too high will do is sometimes make it difficult to exit Idle mode smoothly. The driver will apply more pedal, but the idle control system holds the engine back, and when the throttle does go above the threshold, suddenly it's too much throttle and the engine revs quicker than the driver wanted. So set the value so it enters and exits idle mode when you want -- which is usually at a very small pedal position.

We manually retarded timing in the cells all around the hanging RPM window area and it would only reduce engine RPM 50 to 100 RPM. We would retard timing all the way down to 5 degrees to test our theory. So it seemed as though it was a air parameter rather than a timing parameter which was allowing the engine to sustain that hanging RPM. Are you suggesting we increase the Idle Aim Ramp Down Limit in order to extend the operating range of idle control?

Yes, change the Idle Aim Ramp Down Limit. Double check your airbox for leaks.

Consider enabling Engine Overrun Mode to cut fuel at 0% throttle until the RPM is within the Idle Aim Ramp Down value.

Make sure the throttle position 0% (throttle body), is set with a fully closed throttle (not the partially open limp position). I know the FSAE setups with extra large manifolds are a challenge, but if the throttle is fully closed (0%), then engine speed should not be able to continue higher than idle unless you have an air leak, or seriously advanced timing.

BTW why did you stop the timing at 5deg -- you could go as far as -10deg if you need to.

Capture a log (or at least a screen shot of the Engine Systems->Idle Aim (or Idle Ignition) screen, showing the problem.

Our throttle body does not have an air bypass circuit around the butterfly, so it currently defaults to a rest position of 3% when the servo enters power save mode. We have not found a way to get the servo position or aim to go any lower than this 3% value, it almost seems as though it is a pre-configured setting that comes with the throttle body we are using when we selected it from the pre-configured drop-down options list for throttle bodies in M1 Tune (ours is a Bosch 0 280 750 101 1.0)

That being said, when we q key to set the "rest" position when configuring the pedal, I would guess that we are actually setting the rest position at 3%, not a true 0% butterfly position. Is there a setting somewhere that can be changed to allow the servo to achieve a true 0% fully closed position?

If my understanding is correct, wouldn't there have to be a rest position above 0% though in order for the engine to stay running when pedal % is at 0 ( a decel situation). With no air bypass circuit around the butterfly, achieving true 0% with the butterfly would theoretically allow no air into the engine and cause it to die on decel.. or is my fundamental understanding of this wrong?

Any help is greatly appreciated!

When calibrating the "Throttle Servo Bank x Position Sensor Main Offset", you need to physically push the throttle plate to the closed position (either disconnect the motor, or be sure the Diagnostic is "Power Save".

Even with a running engine, you should be able to set the "Throttle Test Aim" to 0%, and set "Throttle Test" to Static Test, and close the throttle.

Hi,

Another workaround for this is to have an extra column in the Idle Mass Flow Feed Forward Main table that has an Engine Speed just above your Idle Entry Engine Speed that has low numbers in it, this will drag the throttle closed when it goes through this region and assist in the M1 Idle Control capturing the Engine Speed.

Setting the Throttle Servo 0% requires that the Throttle Plate is pressed firmly against the throttle closed stop, zeroing the position at the throttle rest position will result in the M1 not being able to correctly control the throttle closing. The Open position is set by holding the plate to approximately 90 degrees to the airflow, not against the opening stop.

The M1 will control the throttle position on overrun using the Idle Mass Flow Feed Forward Main table and the Idle Aim Engine Speed, so having the Throttle Servo correctly configured is required.

The throttle position aim during idle is controlled by the "Idle Actuator Throttle Aim Maximum" adjusted by the "Idle Mass Flow" (which you basically set with "Idle Mass Flow Feed Forward Main"

Thank you guys so much for the help. We are taking this information one step at a time starting with ensuring our servo/pedal calibrations are done correctly. David, we took our intake off and were able to manually press the butterfly to it's true 0% position as you said.

However you said we must have this depressed when we go to Q-key the rest position for "Throttle Servo Bank x Position Sensor Main Offset."

I currently cannot seem to locate a parameter in M1 Tune with a name like this which offers Q-key functionality to calibrate. The only throttle-related parameters I'm seeing with Q-key functionality for calibration are under the Throttle Pedal Worksheet, and titled, "Throttle Pedal Sensor Main Offset," Throttle Pedal Sensor Main Scale," and Throttle Pedal Sensor Tracking Scale."

Is the "Throttle Pedal Sensor Main Offset" value the one we need to Q-key while manually pushing the servo butterfly to its true 0% position, and if not, where do we find the correct parameter in M1 Tune?

Thanks

Ok I was now able to find that exact parameter as you mentioned David--it was hidden from us because we were using a pre-configured calibration for a Bosch 0 280 750 101 1.0 as an available drop-down option in M1 Tune. Do you think we are better off setting the configuration to "manual" so that we can manually set all of these values?

Thanks