Another amplifier ground wire question

[Jedidentist]

Before I make a big mistake, can someone confirm that it would be okay to ground my JL Audio 900/5 amp to this bolt behind the passenger's side firewall?

http://i3.photobucket.com/albums/y85/jedidentist/EC548306-5696-487B-AAC6-8F3FDF566714.jpg


I'm mounting the amp on the rear wall and the 4 gauge black ground wire I got in my kit was only 3'...so it can't make it to the battery ground. That being said, the 12v 4 gauge power wire I have is 16' long...much more than I need, but it's red and I'd really rather not use two of the same colored wire, plus I'd have to buy another larger ring terminal to fit on the batter ground post. Thanks!

Derek

[Bitsyncmaster]

Using that bolt would probably work with no problems. But it would be best to run to the battery if your amp draws that high of a current that they sent 4 AWG wire.

[Jedidentist]

Yeah, it's 900 watts. However, the wiring kit is a standard one and the instructions for the amp even say to mount it to a ground bolt and not the battery, so I guess I should be ok. Thanks!

[FABombjoy]

I ran my 600W amp straight to that bolt BUT I also ran another 4ga line from that bolt straight to the battery, in order to supplement the sketchy "battery to frame, other-part-of-frame to ground bolt" arrangement.

I also used the positive bolt just around the corner from that one.


The wiring kit is a standard one and the instructions for the amp even say to mount it to a ground bolt and not the battery
That is standard procedure for a normal car but you'd have to drill down to find enough metal to make it workable at 900W :D

[Trstno1]

Before I make a big mistake, can someone confirm that it would be okay to ground my JL Audio 900/5 amp to this bolt behind the passenger's side firewall?

http://i3.photobucket.com/albums/y85/jedidentist/EC548306-5696-487B-AAC6-8F3FDF566714.jpg


I'm mounting the amp on the rear wall and the 4 gauge black ground wire I got in my kit was only 3'...so it can't make it to the battery ground. That being said, the 12v 4 gauge power wire I have is 16' long...much more than I need, but it's red and I'd really rather not use two of the same colored wire, plus I'd have to buy another larger ring terminal to fit on the batter ground post. Thanks!

Derek

That's exactly where I grounded my amp. However, I think it would be good practice to run another length of 4awg to the battery ground as well. Finding good grounds for electrical add-ons in this car is a bit rough.....

[David T]

That's exactly where I grounded my amp. However, I think it would be good practice to run another length of 4awg to the battery ground as well. Finding good grounds for electrical add-ons in this car is a bit rough.....

The proper way to do this if you are going to add an accessory that draws that much power is to install it's own ground bus (V-) and it's own power bus (V+). You should also add power capacitors to handle the large transients that an amp that size will reflect back into the power system of the car. Often a separate battery is also added so if you run the sound system while the motor is off you still have a battery with enough power to start the motor. Talk to the place where you bought that 900 Watt amp. They can help you design your electrical system. Or there are magazines where you can see what others have done. You can probably find a lot of good info on youtube too. You need to size your wiring to handle the loads too. Don't go by how thick the wire looks. Often the fancy wire looks thick but inside the copper is a small gauge. Use good quality connectors and all connections should be soldered (not just crimped) for maximum capacity.

[Bitsyncmaster]

Those capacitors will do nothing if you have good wiring (heavy gauge wired close to the battery posts). They only help with poor wiring.

[David T]

Those capacitors will do nothing if you have good wiring (heavy gauge wired close to the battery posts). They only help with poor wiring.

Large caps will act like dampers to soak up spikes and absorb back EMF so you don't hurt your battery or other parts of your electrical system. They also provide an extra surge of power for a very brief for when the amp peaks. Even with heavy wiring they can help. They are also useful for filtering the power to the amp and remove any interference that may be in the car's electrical system. Depending on how well built the amp is, it may or may not have sufficient internal filtering capacity. Again, talk with whoever you bought the amp from for the best advice. They should have *some* experience with installing it. 900 watts is not your ordinary car radio that you just plug into the car's system.

[Jedidentist]

Thanks guys. Everything is 4 gauge for the power and ground, front and rear speakers are 14 gauge, and I have some 14-4 wire that I'll double braid to run to my sub. This really isn't a huge power setup...100 watts for my front components and rear coaxial a, and 500 for the 8" sub. None of this is going to be run to ear bleeding levels. I was just looking for a small, class D amp that could run all 5 speakers and this fit the bill..and expensive bill, but should be more than adequate. In any case, the nut on my negative terminal on my battery is so short, that I don't think I could even get another ring connector on there if I wanted.

[FABombjoy]

The negative bolt? Just get a longer one :D

A lot of people run a secondary grounding bus due to the car's potential for grounding issues. Per the grounding diagram (http://dmctalk.org/showthread.php?1301-Ground-Location-List) drawn up by Bill R, if you supplement only the bulkhead bolt ground then you'll pick up quite a few branches at once.

At safe volume levels you'll probably be fine even without the supplement but it's cheap insurance. Even with my gains set modestly, 600W is tinnitus inspiring with a 2 channel system (6.5" Hybrid Audio components in front and a 12" sub in spare tire well)