Engine Noise with stereo upgrade

[Shaun Ray]

Yes, the pesky engine noise that sometimes comes with installing aftermarket amps in a car is bothering me. The noise is definetly related to rpm of the engine. It is not loud, and with the stereo on at realatively low levels, you can't hear it. However, it is louder than stock stereo engine noise.

So last weekend, I decided to try a ground loop isolator connected to the RCA terminal. I installed the device just before the EQ input which is located in the trunk. Results were HORRIBLE. The engine noise was amplified 10 or 100 times.

The grounding on my amps are very good and wires are large and short. Also have a 16 ga. ground wire for the head unit. My thoughts are:

1. Try another RCA line from the head unit, out the driver's door and enter the trunk just to see if the routing of the RCA line is causing the noise.

2. Spark plug wires are causing noise? Doubt I act on that one.

3. My a/d/s PQ20 is noisy culprit. Might try another amp but doubt it.

4. Lower the gain of the amp. (It's about 50% or less right now and I hate to take away any power)

5. Just leave alone and enjoy the sound. Just hate that with such a good sounding system I have to settle for the engine whine when starting the car or driving around the sound system on low volume.

Any advice?

 

[D'Ecosse]

I assume this is an OEM head unit?

Your head unit ground wire - how/where is it attached? It should be attached to the black wire in the adapter harness and then to a good solid chassis ground point. I would use better than 16 ga personally.

It sounds like you have grounding loop issues between the three components - head, EQ & amp.

Try removing your EQ and see what happens as point of reference; (what brand/model EQ do you have?) Try the GLI again without the EQ in play and see if it makes a difference in that situation.
Recognize that your EQ may have significant gain in its own right - don't assume that you will be losing power just because you turn your amp gains down. I always start with the gains at zero & go from there anyway.

There are no spark plug wires - the individual coils are directly on the plugs. Some brand of plugs will cause additional interference though - be sure to use the OEM recommendation. Ensure that you have the ground strap attached from the top of the engine front bank to the centre of the bukhead.

 

[SilverStone05]

I'd try a better shielded RCA cable routed a different way. Keep it away from all other wires that carry current and keep it short as possible. No shame in spending 50 or 60 bucks on an RCA cable thats gonna shield against engine noise. This should do the trick.

 

[Shaun Ray]

It is the OEM head unit and the ground is attached to the wiring harness and connected to a good ground surface. Just guessing it's 16 ga. from memory. I recall it is pretty thick, maybe 14 ga. Much larger than stock OEM for sure.

Thanks a lot for all the ideas. Working back from the EQ makes sense. Should have thought of that. Also, a high dollar RCA also makes sense. Thought I'd prove out that idea by running an RCA completely outside the car to reduce the need for shielding and if that is the problem, this idea should bring it to light.

No spark plug wires??? Well that shows my ignorance about the car, huh? Guess I learned something today. Good for me!

Thanks again for the advice. I'll do some tinkering.

-s

 

[zetoolman]

Yes, the pesky engine noise...

Hello Shaun,
I managed to get rid of that alternator noise in my sound system for the cost of a short length of wire and a connector. I opened up the console and tested out various grounding configurations, and discovered that by connecting the negative pole of one of the pre-amp outs to the to the chassis of the headunit, all the noise disappeared!

All I did was basically ground the headunit to itself!

This is from Joshs!

Hope it helps!!

Zetoolman

 

[Shaun Ray]

Thanks Hal. Had not thought about running the engine and testing differnent grounds for head unit. I'll give it a try.

Shaun