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Rip out 4 AWG and install 1/0?

J

joblo1978

Full Member
Joined
Aug 15, 2011
Messages
95
I wired up my amps with a 4 AWG install kit from RF before purchasing them.  I ended up going with stonger amps in the end.  I currently have a RF T1000 at 1 ohm and t400 2 chan. at 4 ohms. so figure about 1250 watts RMS, maybe a bit more.

I recently upgraded to a 240 amp Mechman because I was getting some voltage drop to the vehicle, probably not pushing the amps that hard either.

Curently there is about a 17 ft. run of 4 AWG into a distro block with shorter runs to amps.

I should remove that 17 ft. run of 4 AWG for 1/0 shouldn't I?

 

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A 4 gauge cable will effectively carry about 140 amps, depending upon its length.
This will equate to about 1000 watts if you are running a class A or B amp(these run at about 50% efficiency)  Or about 1500 watts if you are running a D class amp, typically around 70%  efficiency.

Upgrading to a 2 gauge cable will allow you to carry about 220 amps, equalling 1500 and just shy of 2200 watts for A/B, and D class amps respectively.

Switching to a 1/0 cable will net you a 350 amp capacity, yielding about 2500 watts for an A or B class amp, and upto 3500 watts for a D class amp.

Don't forget that you will need to upgrade all the cables in th charging system to make the larger cables running from your battery to distribution block work effectively, including the grounds from the amp and distribution, battery ground/grounds and alternator-battery charging cable

So to answer your question, yes.  A 2 gauge cable will get you the power you are looking for at your amps, but upgrading to a 1/0 cable will allow you to fully utilize your new alt.
 
Calicak89 said:
A 4 gauge cable will effectively carry about 140 amps, depending upon its length.
This will equate to about 1000 watts if you are running a class A or B amp(these run at about 50% efficiency)  Or about 1500 watts if you are running a D class amp, typically around 70%  efficiency.

Upgrading to a 2 gauge cable will allow you to carry about 220 amps, equalling 1500 and just shy of 2200 watts for A/B, and D class amps respectively.

Switching to a 1/0 cable will net you a 350 amp capacity, yielding about 2500 watts for an A or B class amp, and upto 3500 watts for a D class amp.

Don't forget that you will need to upgrade all the cables in th charging system to make the larger cables running from your battery to distribution block work effectively, including the grounds from the amp and distribution, battery ground/grounds and alternator-battery charging cable

So to answer your question, yes.  A 2 gauge cable will get you the power you are looking for at your amps, but upgrading to a 1/0 cable will allow you to fully utilize your new alt.
Click to expand...

Thanks for the intelligent response!  

Determining what AWG wire to run for a given number of amps and types is difficult.  My sub amp is a clas B/D while the mids and hi's is an A/B.  I have read on some of the charts that you should double your RMS wattage and then divide by 13.8 to find the actual amperage draw.  Obviously this could over or under rate your figured amperage draw depending on amp efficiency and discrepencies.  Using advertised ratings and using this method to count for 50% inefficiency it would appear I'm drawing 181 amps.

Would it just make more sense to add the fuse ratings to calculate your possible amperage?  If that were the case I would be at 250, but since that is only a fuse rating we're talking a worst case scenario which is probably unlikely.

I wish amp manufactures could just include a nominal amperage draw at certain ohms with their ratings to demystify the whole mess.

In either case it would seem my 4AWG is barely enough while probably leaving some on the table, and the 1/0 would be on the side of overkill which I'm fine with.  My terminals and junctions don't fit 2 AWG so 1/0 it will be.  I just really hate pulling out the interior again to rerun about $100 of wire.  Go big or go home I guess.  Should have just ran 1/0 in the first place...lesson learned.

BTW, the Big 3 was done on the stock alternator and grounds quite awhile ago and I have measured drops of voltage down into the 10.9 range periodically at idle at volumes just before clipping is heard.

Would you predict a noticeable change in the stereo after the addition of the alternator and larger cable?
 
joblo1978 said:
Thanks for the intelligent response! 

Would you predict a noticeable change in the stereo after the addition of the alternator and larger cable?
Click to expand...

If you have enough power to your amps, and your gains set properly, you should not be able to get your subs to clip.
Your sub will try to play the frequency sent to it regardless of whether the amp can keep up or not. 

Having a 240 amp alt. and 1/0 supply should provide all the power your amps are looking for.  If you are achieving a voltage drop of more than -2.5 (i.e. your voltage at idle is 14.0 and with the system cranked your are getting readings of less than 11.5)your system is requesting more power than your alt/battery set up can deliver and you need to upgrade.

Once installed, your setup should be fine.  Most modern amps have small stiffening capacitors built in and you should have no more trouble, but once upgraded, if your voltages are stable and you still experience sub fade (when the subs seem like they are not hitting as hard or deep as a song with longer/lower bass lines progresses) you may want to try adding a stiffening capacitor just before the distribution block.  With a long run (over 10ft), depending upon the cable and battery, sometimes the amps can request amperage at higher current rate than the cable can provide. (Think about a pipe that is 10 inches round, if you stick a garden hose in the other end, the water will always flow through and never back up, however, it will never flow rapidly, this is the case we want, 98% of the time, there is way more flow capacity than the amps will ever need)
but sometimes they request power so rapidly that even though we have a huge alt., battery and cable combination producing and supplying a ton of amperage, we just can't get it there fast enough, this is where a stiffening cap comes in. 12V batteries are designed to discharge very slowly and have a hard time responding to high amp draws quickly (think of the headlights dimming when the subs hit). A cap will not increase the capacity of the charging system, but will provide a small reservoir that can discharge quickly if the amps so request.

So to answer your question, yes, you should notice a change, you should be able to set your gains to match up your amps and head unit, enabling you to then crank the system without hearing any distortion, or have to worry about the damages causes by clipping.
 
Calicak89 said:
If you have enough power to your amps, and your gains set properly, you should not be able to get your subs to clip.
Your sub will try to play the frequency sent to it regardless of whether the amp can keep up or not.  

Having a 240 amp alt. and 1/0 supply should provide all the power your amps are looking for.  If you are achieving a voltage drop of more than -2.5 (i.e. your voltage at idle is 14.0 and with the system cranked your are getting readings of less than 11.5)your system is requesting more power than your alt/battery set up can deliver and you need to upgrade.

Once installed, your setup should be fine.  Most modern amps have small stiffening capacitors built in and you should have no more trouble, but once upgraded, if your voltages are stable and you still experience sub fade (when the subs seem like they are not hitting as hard or deep as a song with longer/lower bass lines progresses) you may want to try adding a stiffening capacitor just before the distribution block.  With a long run (over 10ft), depending upon the cable and battery, sometimes the amps can request amperage at higher current rate than the cable can provide. (Think about a pipe that is 10 inches round, if you stick a garden hose in the other end, the water will always flow through and never back up, however, it will never flow rapidly, this is the case we want, 98% of the time, there is way more flow capacity than the amps will ever need)
but sometimes they request power so rapidly that even though we have a huge alt., battery and cable combination producing and supplying a ton of amperage, we just can't get it there fast enough, this is where a stiffening cap comes in. 12V batteries are designed to discharge very slowly and have a hard time responding to high amp draws quickly (think of the headlights dimming when the subs hit). A cap will not increase the capacity of the charging system, but will provide a small reservoir that can discharge quickly if the amps so request.

So to answer your question, yes, you should notice a change, you should be able to set your gains to match up your amps and head unit, enabling you to then crank the system without hearing any distortion, or have to worry about the damages causes by clipping.
Click to expand...

I set my gains with an SMD DD-1 per it's instructions, according to it my deck clips at a volume of 44 (max 50) using their test tones, I can hear distortion in the subwoofers well before that when listening to music.  I generally cannot turn the volume past 32-34 without audible clipping/distortion.  Coincidentally this is also when the voltage drop is most severe and I think I experience what you refer to as "sub fade".  Maybe I should double check the settings on my filters, but I think I have them set to cover the proper ranges.

Unfortunately I'm stuck over here in Afghanistan for a bit longer.  Will definitely be doing the Mechman install and 0 AWG at the same time per your advice.  Should be a fun install.
 
Looking at the specs on your amps, and length of wire I looks like your total current draw is 126 amps.  They are showing using 2awg.  Im learning and trying to get my things together to run the system im building for my 2003 Avalanche.


 
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