As an ex-installer, I offer a few words on engine noise elimination. This certainly is not an all-inclusive troubleshooting section, but does cover the most common causes of noise and offers some solutions. Note, that keeping these in mind when installing the system will almost guarantee noise-free operation when it is completed. If your system is already installed, you can still correct these, you will just need to dismantle parts of your system and/or car to reach the necessary items (wires, RCAs, connections, etc.)

Happy hunting!

Inducted Noise:  This occurs from RCA cables picking up the current in power wires and mixing it in with the audio signal.

What to do about it:  Route RCA cables away from ANY power source.  This includes any wire harnesses, computers (ECU, ABS, etc.), the fuse box, and especially the main power/ground wires for the amps.  If it becomes necessary to run RCAs across power wires (or wires that you are unsure are +12V), make the intersection at a 90° angle as this will give the least area for noise induction.  At the very least, a 45° angle is desirable.  The greater the contact (or the less the distance apart) the increased the chances for noise being induced into the system.  I personally use triple-shielded RCAs, however, for all intents and purposes, double-shielded RCAs work fine, but I would not recommend using anything less than that.

Ground Loop:  Probably the single most common cause of engine noise. This problem occurs when several components are grounded in different points to the vehicles chassis.  This results in voltage differences in the various regions of the auto.

What to do: Ground all powered components to the same location. Distribution blocks work wonders for this!  This also includes the head unit (remember, it is a "powered component")  I have successfully eliminated noise by grounding the head unit to the distribution block with the rest of the components.

The next question would logically be where to ground the distribution block.  This is a highly debatable topic among installers.  Some say to make the ground wire as short as possible and others say to ground at the source (battery).  I have had noise-free systems using both techniques. Each individual system (and automobile) has different characteristics so the best thing to do is test it out!  Make a ground and listen for noise.  If there IS noise move the ground to another location and try again. (remember that there maybe other reasons for the noise other than the ground, however!)

NOTE: when making a ground to a body panel, scrape/sand the paint off until there is shiny metal AND use a "star" washer to ensure a good connection.

Other possible causes:  One other common problem is the use of different sized (AWG) wires for power and ground duties.  Since DC power flows in one direction (for the most part), the SAME current that flows through the power wire MUST (physics) also flow back to the source (battery) through the ground wire.  I have seen people using 4 AWG power wire and then 10 AWG ground. For the non-technical folks, that would be like putting a straw in the end of a garden hose and then trying to force water through it.  A lot of back-pressure, right?  Voltage drop occurs due to this, which in turn induces noise.

What to do:  ALWAYS use the same gauge wiring for the power and ground of the same components.  For example, the main power/ground wires may need to be 4 AWG from the battery to the distribution blocks....make sure that they are BOTH 4 AWG. If the amplifier's current draw only requires 10 AWG, make sure that BOTH the amp's power/ground leads are 10 AWG then.

Another common problem is batteries.  Old or weak batteries can cause sufficient voltage drop to allow noise to be introduced into the system.  Batteries also act as filters and remove any "ripple" (AC current over the DC current) that has been introduced in the wire. Batteries that are not in good condition will not filter this out and it may cause noise in your system. This personally happened to me once. After trying MANY trouble-shooting techniques, I ended up at the battery. Even with full cells and a good charge, due to previous drainings, the battery was not 100%.   I replaced the battery, which in turn eliminated the remainder of the noise.

What to do:  The easiest way to check for this is to run the main power and ground cables for the stereo to another car with a good, preferably new, battery (parked next to your car).  IF there is no noise while connected to the other car's battery, the problem is either 1) your car's battery or 2) your car's alternator (usually a bad rectifier will cause noise). Simply, repair/replace as necessary.

If the noise is still present while connected to another car, chances are that the problem is one of the components itself. Locating the offending unit will require some amount of work. If this is the case, you may wish to take it to an experienced (preferably MECP certified) car audio installer.

As you may guess, there are even MORE possible causes of noise. I could fill an entire site with just noise elimination/trouble-shooting techniques!! However, since my space here is limited, this is as far as I will go for now.

A few words on noise filters/suppressors: DON'T USE THEM! These are simply band-aids that cover up the real problem and will, in all likeliness, have adverse effects on your system's sound reproduction. Chances are that if your noise problem is severe, these will not completely remove it anyway. Spend the time necessary to locate the problem and correct it as I have outlined above. You will be glad that you did!

Again, this does NOT cover all possible scenarios. If you have noise, it could be from any one of these causes, any combination of these, or for other reasons not even listed here. Once noise is in your system, only time spent eliminating each possible cause, one-by-one, will identify the culprit.

If you have any questions about this at all, don't hesitate to e-mail me.

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