MoTeC Global Forum

Hi All,

I'm using an Aux table on my M800 for dgital switching and I want a little insight to how it behaves (without experimenting).

Let's say I've got it set up to turn a fan on with engine temperature. Now, the Aux table will switch the fan on with a Z-value of >=50 when using a range of 0-100.

Now, if I've got the cells set to zero at 80 degrees, and then set to 100 at 90 degrees, how does the output behave between 80 and 90 degrees?

I've got two scenarios below, which one is true?


1. At 85 degrees, the Z-value jumps from 0 to 100 as the cell swaps from the 80-degree site to the 90-degree site.
2. At 85 degrees, the Z-value is 50 as a 50% linear interpolation between the 80-degree site value of zero and the 90-degree site value of 100.

I'm assuming the more intelligent way (scenario 2) is what actually happens, as this would be more accurate.

The reason I'm asking is that I want to know whether I can use the Z-value to control accurately at which point the output is switched on. To use the above example, I've got my temperature axis set up with ten degree increments. If I want the fan to trigger at 88 degrees, I could set the 80-degree cell to be 0 and the 90-degree cell value to be 63 because a linear interpolation between the two gives a value of 50.4 at 88 degrees. Is this the way it works?

Thanks,

George.

Scenario 2 is correct.
I have tested and used this method myself.
Are you driving the aux table as PWM ?
I have had great success running the DHB to power my water pump and thermo fan with PWM in a 'closed loop' speed control environment. Love it

Thanks for that

This isn't a PWM output, simply a digital switched output.

I'm actually using the M800 to control my gearbox oil cooler pump. I've got gearbox temperature on one axis and throttle position on the other. Basically it's set to pump when the gearbox temperature is above 80 degrees regardless of throttle position. Between 30 and 80 degrees it's set to pump when the throttle position is 95% or above. This is because the oil cooler return line sits above the 5th/6th gear cluster which is notorious for inadequate splash lubrication under heavy load. This way the cooler pump will serve as a lubrication pump at normal running temperatures under high gearbox load, and then will switch to being a cooler pump when the oil gets hot. It also avoids overcooling the oil by becoming inactive at lower temps regardless of throttle position.

To switch accurately we usually would have an axis site at say 84 and one at 85. The 84 site is zero % and the 85 site is 100%. Or if you want to be super accurate, the 84 site is 49% and the 85 is 51%.