V2Rocket

Anybody know how much power (amps/watts) is required to run a 944 motor? I am looking at different alternators that are considerably smaller than the stock unit for mounting in a different location than stock - they are rated in the 45-60A range peak, 30-45 at idle. I don't have a fancy stereo, just the 4 4x6 speakers and sometimes 2 additional 6x9 - no subwoofers or anything big.

I do have the turbo front end and am adding the driving light option, but I have the harness to power the lights directly off the alternator rather than off the battery. Currently lights are all 55w but the headlights/driving lights may be bumped up to 100w in the future.

Stereo might be 200W (peak, I don't put it very high though), lights (incl. driving lights, at 55w each) would be 330W. 530W/12V = 44A...bigger lights would add another 180W or 15A to the load...so just sitting with the lights on and music is about 60A?

I want to keep air conditioning if possible, dunno how much power that draws but the compressor has a pretty small wire. The blower fan though probably draws some amps.

I know 924 guys put a smaller 65A alternator on their cars for some weight savings and they have the same power requirements as my car, minus fog/driving lights.

How much alternator should I get? Obviously the most A I can find in the smallest package, but what's the minimum?

odurandina

maybe about 4 and a half amps at 14 volts ? just a guess.

Tedro951

I'm sure the loads could be calculated, but I sure wouldn't go too much under the stock output. I just assume the factory engineers used an alternator that is enough output, with some left over.

Hot night, stereo playing while sitting in traffic, both fans on, blower on high, etc...

StoogeMoe

What are you going to save? Like 1 pound? You don't race do you? So why do you care? You could empty your pockets of loose change and save more than the alternator swap.

Techno Duck

Realistically i think you would need atleast 50 amps for a dedicated race car.. for a street car i think you need to look at something around 75-80 amps when you consider the blower for the HVAC, headlights / tail lights / side markers / brake lights, fuel pump, cooling fans..etc. You need to look at all the high load stuff on your car and consider how much current its going to pull in the event everything turns on at the same time..electrical motors can pull 3-5x the current they normally use when running on startup. The HVAC blower and cooling fans alone will be a very high draw when they turn on.

Bosch actually makes a lightweight 'race' alternator that puts out about 55amps and weighs about 7lbs. Honestly i think the weight is easier saved elsewhere, get a lightweight battery if you dont already have one. The Odyssey PC680 if i remember right cut nearly 20lbs off from a stock sized battery, if you want something with more CCA the larger one (PC925 i think?) will save around 12lbs. Or just do the Nissan Quest alternator which is marginally smaller / lighter and also puts out similar amperage.

V2Rocket

depending which one I could go with, maybe 7 or 8lbs.
This is not so much about weight though (though that is a nice side effect - my car weighs right about 2600lb dry). I am finishing up my supercharger project (building bracket to mount it up now) and would like to keep AC. However due to the size of the blower, I can only mount one accessory (AC or alternator) in the factory location. I figure I could mount the AC in its regular place on a modified AC delete bracket, and put an alternator over where the PS pump used to be. There is a fair amount of room over there but not enough for the stock alternator, MAYBE the quest would fit, and many alternators use a v-pulley like the PS pump. I could probably put a 90 or 100A unit that I have on hand down in that location but I would need to get creative with mounting.

If I can't get it to work there then I'll remove the AC again, which will suck here in southern California right as summer arrives.

ZR8ED

Don't lose the a/c. I made that mistake on one of my cars, and made it into such a beast it was no longer fun to drive regularly...I sold it and bought a Porsche that DOES have working a/c, and now I drive it much more often, and I get no more complaints from the wife, which means I'm much more likely able to keep it.

doabarrelroll

I wonder if you could use the early model Nissan Quest alternator? Those are lighter and require a slight modification and seeing as how you are going the custom route anyway...

https://rennlist.com/forums/944-turb...eted-pics.html

Butters944

I've heard the AC takes 25A and the cooling fans take another 25, headlights another like 20 or something. I'm worried about once I fix my ac playing my sound system at night with ac on might overload the alternator

catamax944

I think 60A is fine but to be sure you should also upgrade to a befier battery that could take the strain without relying as much on the alternator. Don't remove the a/c ,try the alternator first and if for some reason it doesn't work go from there.

catamax944

See if this fits and you are set http://www.ebay.com/itm/New-100-amp-...5cdea5&vxp=mtr

V2Rocket

Thanks for that link - I had seen those but not seen how big they are. If he's right about a 4.25" diameter that is a little one for sure.

catamax944

According to the service manual it's not quite 4.25" but close ,it's 121mm .http://www.alternatorparts.com/cs130_sbpage1.htm
It's mounting point looks nice too,with a bit of luck and some triming it might fit the ps pump bracket.

PS:Take a look here http://www.powermasterperformance.co...hp?item_id=376

StoogeMoe

You must be talking about the later alternator. There's no way you're saving 7 or 8 lbs for the early one. It only weighs about 10 lb to begin with.

V2Rocket

You're right, I had forgotten how much smaller the early is than the late. Like I said though, not for weight savings necessarily (especially when adding a ~30lb supercharger) I intend to mount an alternator on the passenger side of the engine where the power steering pump came originally - for that location, the stock unit is simply too big.