26 replies to this topic

[mr.x]

I'm looking at fitting a high end audio system in my Mpi. The question is.....can the factory alternator handle it? The amp I'm using is a 700 watt amp calling for a 60 amp fuse using 12.5-14.5 volts RMS. I'll also need to power a new radio head unit.

 

The factory alt is 65 amp, correct? Can it handle it or will the load require an upgrade/rebuild? The car is a Sportspack with all the extra lighting and it has an air con system, so this needs to be factored into the electrical load (however I have no idea how much volts/amps are being used by these items).

 

Lastly, is the car negative or positive earth?

 

 

[Guess-Works.com]

I'll be more surprised if you will cope with 700watt amp with the engine running, I wouldn't want to be anywhere near the car, especially not with the engine running !!!

 

and it's -ve earth...

 

I'd be putting in a separate electrical system for the ICE and a split charge system, so that if the alternator cannot cope, you car keeps going and you loose your tunes.

[sixtyeight]

You'll definitely need an upgrade. Should be able to find a compact modern high output nippon denso unit that fits up easily with minor mods (if any) to get it to line up.

 

700w / 12V = 60amp.

so at full tilt your amp will be maxing out your alternator when nothing else is loading it up.

 

That is all dependent on your amp being 700W RMS, or it if is PMPO also. amp specs?

[mr.x]

You'll definitely need an upgrade. Should be able to find a compact modern high output nippon denso unit that fits up easily with minor mods (if any) to get it to line up.

 

700w / 12V = 60amp.

so at full tilt your amp will be maxing out your alternator when nothing else is loading it up.

 

That is all dependent on your amp being 700W RMS, or it if is PMPO also. amp specs?

Here is a link to one of the units I'm considering with the specs

http://www.jlaudio.c...mplifiers-98606

[sixtyeight]

Your link didn't work, I'll assume you mean the 5 channel 700 WRMS Amp? Their quoted power is based on 2 ohm load. normally you'd have a 4 ohm load per channel (car speakers have a 4 ohm impedance). This brings the power down to 480 WRMS if you have all 5 channels connected.

 

A helpful formula when designing car audio:

Power = voltage / current

 

P = VI

I = P/V

I = 480/12

I = 40 amps

 

So not as bad off as you originally thought. I've run my 500WRMS amp off an 80amp alternator with no issues.. but I had no spot lights or AC.

[mr.x]

Your link didn't work, I'll assume you mean the 5 channel 700 WRMS Amp? Their quoted power is based on 2 ohm load. normally you'd have a 4 ohm load per channel (car speakers have a 4 ohm impedance). This brings the power down to 480 WRMS if you have all 5 channels connected.

 

A helpful formula when designing car audio:

Power = voltage / current

 

P = VI

I = P/V

I = 480/12

I = 40 amps

 

So not as bad off as you originally thought. I've run my 500WRMS amp off an 80amp alternator with no issues.. but I had no spot lights or AC.

Here is another link.

http://www.crutchfie...-XD700-5v2.html

[mr.x]

Performance RMS Power Output (Watts x Channels) 75 x 4
180 x 1 Peak Power Output (Watts x Channels) N/A

Power at 2 Ohms (Watts x Channels) 100 x 4

Bridged Power (Watts x Channels) 200 x 2

Minimum Impedance Bridged 4

Minimum Impedance Unbridged 2

Best Frequency Response 12-22000 Hz

THD at Rated RMS Power 1%

Signal to Noise Ratio 84 dB

Input Voltage 14.4v

Features Amplifier Class D

Low-Pass Crossover Frequency 50-500 Hz

Low-Pass Slope (dB/octave) 12 or 24 dB/octave

High-Pass Crossover Frequency 50-500 Hz

High-Pass Slope (dB/octave) 12 dB/octave

Bass Boost No

Bass Boost Frequency N/A

Fan Cooled No

Fuse Rating 60

Edited by mr.x, 31 October 2014 - 03:32 AM.

[Ruckus]

Sorry late to the party on this one.

My current system which is aimed at SQ not SPL has a combined output of over 1200watts rms.
But this power is use for control not volume.

The stock MPI alt is much better than the older units but still only 65amps at 14.5volts.

I have done three steps to upgrade my power supply. This does not include a split charging system or a second battery.

1: A direct replacement 120amp alt.
2: The big three. This a cable upgrade for, alt to battery, battery to chassis and engine to chassis.
3: An Exide DC900 battery.

The alt is from a newer land rover and as new with a trade in with my original was about £50.

The battery was about £150 via eBay.

And the big three was 0 gauge cable for all.

I have a volt meter in the dash to keep an eye on things.
Pics etc are in my build thread :)

[mr.x]

Is it possible to fit my new system and see if it works as-is?

 

Is it possible to rebuild the existing alternator to produce more power? or should I replace it with another unit?

[Ruckus]

Is it possible to fit my new system and see if it works as-is?
 
Is it possible to rebuild the existing alternator to produce more power? or should I replace it with another unit?

What you do is up to you mate :) if you want to suck it and see then that's your call.

Rebuilds/upgrades are possible but the cost will most likely be more than an upgraded exchange unit, I think mine was £45 from TA Spares in Chatham.

[mr.x]

 

Is it possible to fit my new system and see if it works as-is?
 
Is it possible to rebuild the existing alternator to produce more power? or should I replace it with another unit?

What you do is up to you mate :) if you want to suck it and see then that's your call.

Rebuilds/upgrades are possible but the cost will most likely be more than an upgraded exchange unit, I think mine was £45 from TA Spares in Chatham.

 

Does anyone sell a factory looking uprated alternator?

 

How would I know the current load? Looks like I'm going to add a 40amp load to what is existing.

Edited by mr.x, 11 November 2014 - 12:56 AM.

[Ruckus]

Does anyone sell a factory looking uprated alternator?

 

 

How would I know the current load? Looks like I'm going to add a 40amp load to what is existing.

 

 

The upgrade Landrover one looks pretty stock just bigger...

 

For the extra power you are going to be pulling just look at the fuses the amps use..

[mr.x]

What is the model number of the Land Rover Alternator? Where can they be purchased online?

[Ruckus]

You don't want to purchase outright as they are quite costly, it's best to exchange.

As I said TA Spares in Chatham, give them a call and tell them you have a MPI mini and want a uprated direct fit alt. You won't be the first I've sent there way.

[mr.x]

What is the model number of the unit?