Ok. Since 5115 give me green light, I will share another type of product that do not save fuel NOR increase power.
Its the... jejejengg... Voltage stabilizer & Ground Cables. *duck* *duck* (somebody throw shoe at me) Hahaha.
But seriously, this product I know it by the details of the molecules inside it. I just hope after saying this, those VS merchant wont come throw red paint at my house nia.
Here comes the hurtful truth.
VOLTAGE STABILIZER
What it is? - Its just a box with very basic electronics components on it - capacitors. These capacitors have reasonably big values (around 2200uF or above each pieces). What people do not know is, there is already a bigger capacitor in your car. It is so damn big that I think the value is somewhere around 1000 Farads. (not sure really). Where is this big capacitor? - You guessed it - its the Car battery lah!
Now imagine this. You got 1000 Farads of capacitance, then you add 0.002200 Farad more. What you get? yes. 1000.0022 Farad. Wow. That makes a lot of change? LOL!
Secondly, your onboard ECU does not require any additional regulation. Simply because it already have power supply stabilizing circuit inside it.
Someone would be sayingg: "Eh wait, they actually have graphs showing the noise is filtered after put the capacitor wor". That is true. But the high frequency noise that is caused by firing of plugs radiates EVERYWHERE. Not only through the wires. By just sticking the VS at the battery, of course the noise is reduced, but at battery terminals only. But what for? The battery isnt doing anything except supplying current and voltage (ie power). If you have a digital oscilloscope, you can put the VS at battery, and the you measure at the ECU supply pin. You'll be surprise how many noise is coming in. (But no problem since internal of ECU already have a noise suppressor - manufacturer already cater for this).
Some other person would be saying: "Eh wait.. but i really feel got power wor".. There you go, placebo effect again. I have done a test with VS famous brand (***censored***) and there is no difference. To test it, I ask my buddy to choose by himself either one, but don't tell me:
i) Put in the VS
ii) Take out the VS
We do this for 5 times and after he completed he just let me drive the car. All 5 times I have not noticed ANY DIFFERENCE AT ALL.
GROUND CABLES.
(Boy, am I gonna get in trouble for this part! LOL!)
For new cars, don't bother, unless you like the colorful wires appearance in your engine bay.
What is the purpose of ground cables?
Just to ground all the working parts to virtual earth (ie 0V with respect to the battery voltage). All parts at your engine bay area, (like solenoids (for vtec,AT gbox, lamp,aircon compressor,etc)) are given power supply so the return route is the ground cables. If your car is new, then the ground cables should work just fine. But if your car is old, the grounding cables maybe already rusted and its resistance increased. So the power supply given is lesser since the virtual earth is no longer 0V w.r.t. battery -ve terminal. Maybe we have something like 13V when engine is running (since 1V drop in the rusty cable). So the car performance will be diminished by this. Lamp also not bright as new already, and etc.
And since batt voltage is down, so does the sparking timing and voltage - hence engine not properly combusted.
What the cables does is just to RESTORE (not increase) the car's performance. but since the change goes up, you will recognize it as increase power. Which is not. For eg, if new car, the performance is +5. Then after a while, rusty cable causes it to reduce till +4. Chg cable, it restores it to +5. That's all. No increase of power, no reduce in fuel consumption.
Ok, now shoot me. LOL!