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In wiring the electrical system in a car the best way is to run separate ground wires from each system to a common ground point. The common ground point should NOT be just a bolt where lugs from each device are stacked in top of each other. The contact patches between the lugs create their own resistance and ground problems. The very best way is to bolt a short piece of copper bar near the battery to the frame. Connect the copper bar to the battery with a heavy duty ground strap. Drill and tap the bar for each ground return. The heaviest current user in a car is the starter. It can take up to 800 Amps of current. So it should have its own ground strap directly to the battery. So should the alternator. Its wires carry the second most current after the starter. Electronic fuel injection and ignition systems have their own caveats though. Ignition systems create very high current pulses for a very short time. This is especially true for Capacitive Discharge Systems. Those need their own ground wire to the common. EFI systems rely on different sensors in the car. Throttle position sensor, Intake and coolant air temp sensors,

Manifold pressure sensors and so on. These sensors typically have 2 or 3 wires. When they have 2 wires, one is typically the signal and the other ground. 3 wire sensors need a 5V supply, signal and ground. DO NOT connect the ground of these sensors to the common ground as described above. The EFI computer, as any electrical device can only see its own ground and references all measurements to that. The EFI computer also switches the injectors on and off. Injectors use relatively high currents, and these currents have to flow back to the battery through the EFI computer's ground wire. This causes a voltage drop on that ground wire. Were the sensors grounded to the common ground as described above, the ECU would see only the sensor voltage minus the voltage drop of its ground. Instead ground the sensors directly at the EFI computer to its ground. Sensors only take a few mA of current anyway, so the additional drop on the EFI ground caused by them is irrelevant. Another issue arises with sensors that create a very small signal, like thermocouples for EGT and cylinder head temperature measurements. In an engine compartment a lot of current pulses from ignition and injection systems flow around. Any electrical current also creates a magnetic field. The two wires from the sensor (signal and ground) create a loop, which acts as antenna to pick up these magnetic fields. To avoid that, either use shielded wire or simply twist the wires together. Each twist creates a smaller loop, which picks up less of that noise, but also adjacent loops pick up a signal that's inverted from the loop before. This way the induced noise voltages in each loop cancel each other. Audio systems in cars also need to beconnected to this 'star' ground. The human ear is the most sensitive organ we have. The difference between the loudest noise (pain threshhold) and the quietest noise we can hear is over 1 million to one.

So any electrical noise from inadequate grounding can be amplified by the audio system to hearing level. Now to the claims of some of the grounding systems regarding 10 times better (less) impedance. We talked about resistance of the wires before. Resistance applies to steady-state current (DC). Steel has about 10 times the specific resistance of copper. So the material must have 10 times the square area of copper to achieve the same resistance. This is not a problem when using the frame as ground.

The material with the lowest resistance known is silver, followed by copper (a few % higher). High frequency currents (and pulses contain high frequencies) make the wire behave differently. High frequency resistance is called impedance and depends on the frequency of the current. Very high frequency currents tend to flow not evenly in the whole cross-section of the wire, but only on the surface. Therefore multi-stranded wire creates more surface area for the high frequency currents to flow, hence lower impedance. But this effect is only important for VERY high frequencies in the upper radio frequency range. If the electrical system in your car produces high currents with frequencies that high, your car would shut down TV and radio reception for miles around. Frequencies that high are just not normally encountered in a car. The advantage of multi-stranded wire in a car is flexibility and vibration resistance.

As to claims of better performance and lower fuel consumption: EFI systems inject fuel according to the amount of air drawn into the engine, measured with its sensors. More performance can only be had if more air/fuel enters the engine. No electrical system can increase the air-flow, so no more fuel flow either. The only effect a better grounding system can have is if the sensor grounding was so bad before that the EFI computer misread the sensors due to ground offsets. This can be inexpensively remedied by following the grounding guidelines above. Some of the better EFI computers utilize 'differential' inputs. They measure both, the signal and the ground of the sensor itself and calculate the difference. This way they become independent of any grounding issues.

As to ignition system grounds, one of the performance parameters in an engine is ignition timing. Timing is derived from sensors on the flywheel or crank. These sensors create reference pulses. A pulse can either be there or not. If not, the car stops. No additional grounding changes that. As to the ignition system itself: as long as there is enough spark energy to light the fire, the engine runs. More ignition energy does NOT increase power, just spark-plug wear. So if the ignition system is adequately grounded no amount of more grounding can do any good.

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