Cheesy IAT Mod

This is a 10K-ohm potentiometer (a rather classy one) I had lying around from an old light meter project a few years back. I soldered two 22-gauge solid copper wires to it, and put lots of heat-shrink tubing (actually three layers, to protect the wires since it gets hot in the engine bay).

My idea is to fix the sometimes-rough idling of the car by putting this thing in series with the IAT (Intake Air Temperature) sensor on the air box.

According to the trusty Haynes manual, the IAT is around 50K-ohms at ambient temperature, dropping to 7 ohms at 60 degrees Celsius. The engine computer needs to know the temperature of the air so that it can calculate how much air is getting into the engine. Cold air is denser than warm air, so for a given volume, you get more air per second into the engine if the temperature is low (see Ideal Gas Law).

To maintain stoichiometric ratio, if the air is cold, the ECU has to squirt more gas. So all that this variable resistor does, when in series with the IAT, is lie about the air temperature and force the ECU to squirt more gas. A bit more gas will hopefully smooth out the idle.

If the fuel consumption goes through the roof, I can always turn the trimmer to minimum (equals zero ohms) and it's as if it's not there.

Institutionalized D-I-Y

I went to Cruven last August 14 to have my shock absorbers "refilled." For the un-initiated, this is a pretty popular proposition here in the Philippines: instead of replacing your shock absorbers when they're worn out, you take them to a shop which welds/brazes a valve to them, then fills them with nitrogen from a big welding tank.

Apparently the refilled shocks are good for another year or so. Then you go back and have them fill them up again. Rinse and repeat until your shock seals finally give out.

Damage? well a new KYB or Tokico shock absorber is about 3,500 pesos or so ($70 a pop). The cost of a "refill," inclusive of removing the shocks and putting them back in, is about $20 a pop. Not too shabby, considering that my new-as-of-2003 shocks only lasted 25,000 kilometers or so. If these "refills" last a year, that's almost half the lifetime of new shocks.

Now my problem is that the front suspension is now rattle-y. Probably stabilizer links or ball joints.

R = Ripoff

This fellow on the Tsikot.COM forum famously said that the "R" in RS Components stands for "ripoff."

Well an Allegro Micro Hall sensor that goes for 80-odd pesos on the RS Philippines web site actually costs 18 pesos at Alexan. And just yesterday, I paid another visit to Megamall and discovered that the STMicro TDA2005 audio power amplifier (which goes for 270+ pesos at RS) actually costs 53 pesos.

So with something less than 500 pesos worth of parts, one can actually construct a 4-channel car audio amplifier.