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Old 03-09-2017, 08:52 PM   #1
highgear81307
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New Amp Install

I recently installed a new amp and speakers in a non-hk 325Ci.

The new amp is a MB Quart 320watt 4 channel. I used the factory 12v, ground and remote turn on.

Anyways, it all works and sounds fine but I'm concerned the new amp is getting the power it should. I've read the factory amp is only around 100watts.

So I'm considering swapping fuse #41 for the next size up. Thoughts on this?
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Old 03-09-2017, 11:46 PM   #2
steveintheburgh
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I'm no electrical guy but that sounds like a horrible idea.

Can you power the amp direct to the battery?
inline fuse close to the batter on the positive ?
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Old 03-09-2017, 11:49 PM   #3
The rock
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U should never swap a fuse for a higher one.. try getting a auto electrician to check it out for u mate.


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Old 03-10-2017, 02:22 AM   #4
randy72877
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Never use the factory amp power and ground connections. Bmw has conveniently located the battery a few feet from your amp. Use 8 gauge wire and a fuse (80a) on the positive side as close to the battery as possible to protect the wiring if a short circuit occurs. Using the factory turn on wire is ok.

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Old 03-10-2017, 05:18 AM   #5
nealfromnz
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Does your MB quart amp run in class D ? Want does the manual say for amp wire gauge.

If not and you change the fuse value to one greater that the amp cable you can end up with a car fire.
Same with Randys post. NEVER use an 80 amp fuse on 8 gauge !

Last edited by nealfromnz; 03-10-2017 at 05:21 AM.
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Old 03-10-2017, 12:19 PM   #6
steveintheburgh
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neal----
"NEVER use an 80 amp fuse on 8 gauge !"

80a was what was provided to me w/ an install kit I used. Trouble?
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Old 03-10-2017, 03:52 PM   #7
nealfromnz
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Quote:
Originally Posted by steveintheburgh View Post
neal----
"NEVER use an 80 amp fuse on 8 gauge !"

80a was what was provided to me w/ an install kit I used. Trouble?
80a fuse to close to the maxuim amperage for 8 gauge. I'd put in a 50 or 60 amp. 8 gauge in theory can flow 100 amps in short lengths like a few feet assuming a perfect cable. It will flow less in longer install runs. The issue is how long the 80 amp fuse takes to blow. It needs more than 80 amps and you could find the 8 gauge cable heats up and burns through it installation and starts a fire.


From experience I had an amp fail after a couple of years connected via 2 meters of 4 gauge (140 amp recommend max). The 80 amp fuse held on for a while and the cable insulation blackened on a couple of radius points. My e36 filled with smoke.

My advice is to use the right cable size as recommended by the amp manual. Use a fuse size that is the lowest value that you can get away with. Do what randy has suggested and get the fuse as close to the battery as possible. Don't reuse the factory amp power and ground cables for replacement unless it meets the requirements of the replacement amp.

Also think about putting extra protection in the cable ***128512;


My power cable install feeding two amps, one classs ab at 4x100rms and d at 600 rms.

Used short length of 0 gauge into 2 x 4 gauge with 60 amp fuses on each. I've deliberately used lower rated fuses.

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Old 03-10-2017, 08:35 PM   #8
steveintheburgh
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I'm surprised they provided an 80 w/ the kit.
At least I did what you did ad placed mine about 3 inches of wire from the positive terminal
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Old 03-11-2017, 12:51 PM   #9
randy72877
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The 80a fuse is for short circuit protection of the wiring only. Amplifier protection is provided by the fuses in the amp. The picture shows the difference between 8 gauge wire and a 80a fuse. Smaller fuses will create more voltage drop. If anyone thinks that 8 gauge wire will burn before an 80a fuse try it yourself. Take a length of 8 gauge wire and connect an 80a fuse and put it across a battery. The fuse will blow instantly and the wire won't even be warm.

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Old 03-11-2017, 07:41 PM   #10
nealfromnz
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8 gauge will flow to roughly 130 amps at 12v when it's that short. Try it again with the total length of your ve+ and ground cable.

Randy, trying to give the original poster and yourself some insight in to experience gained with 30 years of car stereo installs. hope you take the advice rather than dismissing it. Google will come up with answers either way.

Btw, here's good advice when installing DC cable into a harsh environment ( marine) it's not too different to car environments. Touchs lightly on cable theory.


https://www.westmarine.com/WestAdvis...e-And-Ampacity
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Old 03-13-2017, 03:04 AM   #11
nealfromnz
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Quote:
Originally Posted by highgear81307 View Post
I recently installed a new amp and speakers in a non-hk 325Ci.

The new amp is a MB Quart 320watt 4 channel. I used the factory 12v, ground and remote turn on.

Anyways, it all works and sounds fine but I'm concerned the new amp is getting the power it should. I've read the factory amp is only around 100watts.

So I'm considering swapping fuse #41 for the next size up. Thoughts on this?
So your class D amp needs 10 gauge minimum cable size which is roughly 2.5mm2 cable in metric. The factory amp main power and ground cables are 2.5mm2. By fluke you are ok with the factory cable and fuse size.
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