foxtrot

Ok here is another question for you guys. If I run with no cats I know I will flag and error. Now this implies closed loop control. ie the computer is monitoring the mils then adjusting then monitoring the mils again in a loop. Well what is it adjusting? Is it timing? If it is I assume it will mess the predetermined advance curves set up in the map. This means that the engine is no longer in control of the timing and is defalted to some static level the mils are sending out.

All this implies lower performance (MPG and or HP/TQ) or poor emissions (which I could care less about).

Whats the poop?

jishead

When you put MILs on you put them on your downstream O2's. This is to fool the computer into sensing a slower switching signal which emulates the signal that would be passing if you had cats. The upstream O2 sensors are used by the computer to determine fuel computations / lean / rich. You do not mess with the upstream O2 sensors. With healthy cats, your downstream O2's switch slower than your upstream O2's and that is what the computer considers normal by way of a division test under only certain conditions. If you take your cats off and don't use MILs, then both upstream and downstream O2's are switching at nearly the same rate because the catalytic conversion hasn't taken place and the O2 sensor smells the nearly the same gas stream. When the computer decides that it is the correct time to test, you will get a check engine light (CEL). That's all you will get. Nothing more. Now if you put MILs on, which you can make from RadioShack for like $0.79 from a resistor and capacitor (RC circuit) then that will slow down the swithing rate applied to the comptuer via the downstream O2's sensors. The division test will pass as if you have cats. An example (fake numbers for example), we'll pretend that the computer wants a result of 5 or GREATER:

NORMAL cated operations[8D]
upstream switch = 10 times per second
downstream switch = 2 time per second
result = 5

GUTTED CATS and NO MILS[:@]
upstream switch = 10 times per second
downstream switch = 10 times per second
result = 1

GUTTED CATS and GOOD MILS
upstream switch = 10 times per second
downstream switch = 1.7 times per second
result = GREATER THAN 5, computer is happy.

HOPE I said this all correctly. I oversimplified but you get the point. Hope this helps. I've built MILS on 2 of my cars and they worked fine. I posted on it somewhere if you are interested.

foxtrot

Good info, thanks for taking the time to explain. I see its just air/fule ratio modification and not determined by the down stream sensors. Crap what do I call you Jis or Jishead either way sounds messy lol um unless your a cute chick

Ok,so the resistor and capacitor forms an RC time constant to delay the signal. Sounds easy to make with my soldering iron and shrink tube. What the tau (time) needed or the RC values you have used? Is it a series circuit? I would like more detail as I want to use the extra tubes that come with the X to bypass the cats altogether.

Thanks

jishead

Here you go:

ho to make MILS

Now radio shack didn't have what i was looking for. I went to some electronics warehouse that sells wierd, industrial, used crap. This is because I suspected that a garden variety radio shack resistor and capacitor might not like the exhaust heat. I picked ones that lookes like they may not contain liquied electrolytics. Maybe like metal film. Any one would probably work as long as you get the correct ohm and microfarad values. PS: the aluminum wires are hard to weld because they dissapate the heat too rapidly but it can be done. I've done 4 of them. On my contour, I did them while underneath the car cuz I didn't want to take it all off (hi mileage).

98UAGT

The only time your car will retard timing is if it detonates or knocks.