Installing Amp ?? - best ground

cij911 · Jun 21, 2009, 08:51 AM

I am installing a 5 channel amp in the trunk of my Evo. I am running power down the passenger side (complete) and RCAs and speaker wire probably in the middle (along the tunnel). Where should I ground the amp (is there a common spot / bolt that people use without having issues)? Thanks in advance!

cij911 · Jun 21, 2009, 12:52 PM

bump for the guys/gals that have done this already....all sorts of pretty pictures, but nothing that shows / tells how folks are grounding....

biggie5252 · Jun 21, 2009, 08:52 PM

Factory bolts usually aren't good grounds. That being said, I've used shock mounting bolts before with no issue. That's the only stock point I'd use. You can drill your own hole and run a nut and bolt through it. Either way make sure you remove any paint down to bare metal. You can check the quality of your ground by measuring resistance from your ground point to the negative battery post.

The most ideal ground is run a ground cable (same size as power) up from the trunk back to the battery itself.

cij911 · Jun 21, 2009, 10:15 PM

Thanks! I remember doing cars when I was a lot younger and we would sometimes run a 0awg back to the battery....I am hoping to not do that....I think I'll try your shock mounting bolt idea -- 4 awg...

303WIN · Jun 21, 2009, 10:58 PM

I mounted mine on the shock bolt also and it's working well for now. I'm looking to relocate that soon for a cleaner look.

LancerEVA06 · Jun 21, 2009, 11:02 PM

There's 2 bolts on either side underneath the bottom cushion that hold in the back cushion. Scrape the paint away from that and you got a pretty good body ground. Measured 0.00001 ohms to both alternator case and battery.

cij911 · Jun 22, 2009, 06:45 AM

Quote:

Originally Posted by LancerEVA06

There's 2 bolts on either side underneath the bottom cushion that hold in the back cushion. Scrape the paint away from that and you got a pretty good body ground. Measured 0.00001 ohms to both alternator case and battery.

So the resistance from the grounding bolt to the alternator case or the battery should be 0.00001 Ohms (or basically no resistance) ? I guess this is exactly what I was looking for -- a way to determine if you have a 'good' ground. So basically what you are saying is the closer to zero ohms (from grounding point to battery) the better. Thanks!!

Psquared · Jun 22, 2009, 06:51 AM

The shorter the ground the better too. I would not run a ground wire back up to the battery unless yours is in the trunk.

matt55 · Jun 22, 2009, 07:00 AM

Quote:

Originally Posted by Psquared

The shorter the ground the better too. I would not run a ground wire back up to the battery unless yours is in the trunk.

4ga wire = less restance than a uin-body

Best bet is run the biggest + & - from Batt , to atl , to Batt and from Batt to motor .

LancerEVA06 · Jun 22, 2009, 01:35 PM

Quote:

Originally Posted by cij911

So the resistance from the grounding bolt to the alternator case or the battery should be 0.00001 Ohms (or basically no resistance) ? I guess this is exactly what I was looking for -- a way to determine if you have a 'good' ground. So basically what you are saying is the closer to zero ohms (from grounding point to battery) the better. Thanks!!

Yes, your assumption is correct. Have you upgraded your "BIG 3"? If not you may want to do it. Definately helps, and as an added benefit it smooths out the entire car's electrical system as well.

cij911 · Jun 22, 2009, 03:14 PM

Quote:

Originally Posted by LancerEVA06

Yes, your assumption is correct. Have you upgraded your "BIG 3"? If not you may want to do it. Definately helps, and as an added benefit it smooths out the entire car's electrical system as well.

LancerEVA06 -- Thanks for the guidance....What is the "Big 3" you are referring to ?

I found the resistance from the negative battery terminal to the alternator case to be 0.2 ohms, so I trying for that or better...I have been trying a spot to work (where the cushion frame is bolted to chasis) and cannot seem to get better than 1 ohm with the 4awg cable (cable itself is 0.6 ohms) -- will this cause a problem ?

Also, where would you guys recommend buying an inline fuse? The one that came with the wiring kit looks more like a distribution box (non weather proof) and I'd like to place the fuse close to the battery (needs to be weather proof).

Thanks for your help!

LancerEVA06 · Jun 22, 2009, 08:11 PM

4awg should have approx. 0.00025 per foot. If you're getting 0.6 ohms from your ~15' wire you have a problem with either the wire or ohm meter.

I just went outside and checked resistance from battery (-) to alternator body. 0.0003 ohms which is with the "BIG 3" upgraded.

The big 3 is upgrading the following wires with the biggest you can possibly use; 1) alternator positive to battery positive, 2) battery negative to chassis, and 3) engine ground to chassis. Some people replace the factory wiring; others add additional cables to the factory wiring.

cij911 · Jun 22, 2009, 10:16 PM

Quote:

Originally Posted by LancerEVA06

4awg should have approx. 0.00025 per foot. If you're getting 0.6 ohms from your ~15' wire you have a problem with either the wire or ohm meter.

I just went outside and checked resistance from battery (-) to alternator body. 0.0003 ohms which is with the "BIG 3" upgraded.

The big 3 is upgrading the following wires with the biggest you can possibly use; 1) alternator positive to battery positive, 2) battery negative to chassis, and 3) engine ground to chassis. Some people replace the factory wiring; others add additional cables to the factory wiring.

Interesting on the ohm meter -- I am guessing based on other readings I took around the car, that my meter is not uber accurate and/or needs a new battery.

Thanks on the Big 3 definition. I may use some leftover wire to further ground the chasis. Thanks again for your help...I sure hope the system sounds good...

Here is what I have going in:

Memphis Audio 5 channel Amp
Memphis Audio 6.5 comps up front
Memphis Audio 6.5 comps on back shelf
Memphis Audio 12" sub (may change to an 8" )
edead80 sound deadening

biggie5252 · Jun 23, 2009, 12:08 AM

When you're doing resistance checks that you short the meter leads together first to check the resistance of the meter leads. Subtract whatever you get from your readings around the car.

cij911 · Jun 23, 2009, 08:11 AM

Quote:

Originally Posted by biggie5252

When you're doing resistance checks that you short the meter leads together first to check the resistance of the meter leads. Subtract whatever you get from your readings around the car.

Ughhhh....I owe you a

.. .I assumed the cables that came with the ohm meter were calibrated with the device....Apparently not -- touching the two together yields 0.6 ohms, so I guess my ground location is pretty good 0.2 - 0.4 ohms....

Thanks guys....