Automatically actuated grill block - Mk3

[gone-ot]

What are the UNITS of the Y-scale (20-0.1)? Obviously i's logarithmic.

[Daox]

The Y axis units are kOhms.

Here is another image from a Toyota service manual. It seems most coolant temp sensors are nearly identical.

[LittleBlackDuck]

Few hints for the coding:

Make sure you program in hysteresis so it does not try to open and close rapidly.
Most sensors for the ECU are 0-5V - use a multimeter on the coolant sensor wire.
You could use a relay from the fan circuit to switch the arduino input pin to the arduino 5V rail.
For ambient temperature use a Dallas 1 wire sensor.

Feel free to shoot me a message if you need a hand with the code. I have been doing this for far too many years.

Simon

[LittleBlackDuck]

Originally Posted by Daox

The Y axis units are kOhms.

Here is another image from a Toyota service manual. It seems most coolant temp sensors are nearly identical.

Yep, just a cheap thermistor in a hunk of brass. I have used the Dallaqs 1 wire sensors inserted into the casing of an old sensor that did not work. This eliminates the possibility of interfering with the ECU but needs a spare hole thermostat housing (or a drill...)

Simon

[Daox]

We're getting a bit beyond the initial open/close, but might as well plan ahead. Do you really thing an ambient temperature sensor is necessary? I would think a loop that monitors coolant temp and adjusts the position would suffice.

[MetroMPG]

If it were me, I would set up a quick 'n' dirty test:

1) duct tape cardboard over the grille opening,
2) cut a hole in it
3) duct tape the original, imperfect actuated prototype in the hole,
4) hack together some code that sort of works
5) get some data of it working

... then forget about making the "good" version of any of the above and move on to my next distraction!

[Natalya]

What are the dimensions for a G1 Insight grill block area?

[LittleBlackDuck]

Originally Posted by Daox

We're getting a bit beyond the initial open/close, but might as well plan ahead. Do you really thing an ambient temperature sensor is necessary? I would think a loop that monitors coolant temp and adjusts the position would suffice.

I tend to plan in all of the variables at the start. The ambient temp will affect the rate of fall of coolant temp, and I would try and reach equilibrium rather than flap open and closed. I would look at the delta-T (difference between coolant and inlet air) and then calculate an opening angle.

I would use the radiator fan turning on as the trigger, and back it up with an upper coolant temperature. That would open an amount based on the ambient temp. You could even set an opening rate of x degrees per second and then start the closing when the fans cycle off.

Lots of different ways that will work.

Simon

[Daox]

Originally Posted by Natalya

What are the dimensions for a G1 Insight grill block area?

I'm not exactly sure. I plan on putting this actuated block in the lower grill opening. When I measured things, I measured about 3" of vertical clearance in the grill at the smallest point which is farther back into the bumper cover. Toward the front it flares out more.

[Daox]

As you may or may not know, I've been working on an automatically actuated grill block for the Insight. I'm getting to the point where I need to start evaluating the electronic side of the mod. My current stumbling block is... where is the ECU located on this car? I need to tap into the coolant temp sensor.