Auto Unlock Ignition Off

Hi, I have been trying to get my doors to auto unlock and found this diagram, but I can't understand it. Could someone please explain what the capacitor and resistor do, I thought I had an idea, but it didn't work.
I only also seem to have a 100uF capacitor, can I change anything to make this work still?

Also, the protection diode on the relay has me confused, I don't know what this is supposed to protect, terminal 85 or 86? Should this diode be a small signal or a rectifier, can't the current just pass through the two terminals inside the relay anyway?

Any help on these would be much appreciated,
Chris.

Here's the diagram:

Ok, so I will try and answer my own questions.

I went and got a 1K uf capacitor and wired this circuit exactly as shown.
When it is hooked up like the diagram, the relay never clicks. When I take the ignition wire adn put it on the other side of the diode next to the capacitor and resistor, then it works to click and unlock when you turn your car off, but also when you turn your car on.
This is not good. I am not sure why this won't work with the diode in place, any help would be great!

I also put the diode across terminals 85 and 86, but nothing resulted or changed. I still don't understand what this does, I have managed to find something about when the relay closes, it handles a current spike, but I'm not sure what you're supposed to be protecting and which way it is supposed to protect.

I still need help with these if you could be kind enough to help me out some!
Thanks in advance!
Chris.

if you wire it is should work... the diode only lets current flow in one direction either positive or negative..
so the diode on the bottom only lets the ground come through when the ignition is off.. that turns the rellay on when you turn off your ignition.. when you turn off the ignition the cap charges and lets enough current go to flip the lever but when it drains it stops the rellay so the you don't have the unlock signal on all the time...