800-900w alternator for 3.2 available?

[Jim Garfield]

Anyone know of a source for an 800 or 900 watt alternator that would work with a 3.2 engine? I'm pushing the limit of the stock 600w unit. I've tried Susquehanna Motorsports/rallylights.com without success.

Thanks.

[RSTarga]

Aase used to sell a high output australian alternator. I think Autofarm also has the same one.

[304065]

Jim, a bit of alternator history to frame this discussion

SWB 35A 490W (these ratings all assume 14V nominal output voltage)
LWB 55A 770W or 60A 840W
SC 70A the dreaded Paris-Rhone 980W
Carrera Alternator 90A 1260W (this is what should be in your 3,2)
964, 993 115A 1610W (only fits on the 964)

If you upgrade to the Carrera Alternator you will have to change the fan housing. In fact you have to change the housing with most upgrades.

Jim, what is your precise electrical load? Please list what you have turned on. List the wire gauge and length of wire connecting them, and where they connect. When you say you are pushing the limit, what are the symptoms? Are the lights dim, are the bulbs blowing? 99% of electrical problems happen with the connections. But some more data can help analyze this and figure it out.

[Jim Garfield]

Therein lies the rub........ I'm an electrical neanderthal. Some sort of black magic is involved I'm pretty sure, but as with computers - I would prefer to throw the switch and have it work without knowing all of the gory details. Trying to figure out electrical current makes my head hurt. I need a consultant. I've tried to get a hold of Daniel Stern, but he seems incommunicado since his move west.

What I'm trying to do is get the car ready to do some nighttime TSD rallies in the Northern Kingdom/NH/ME. Because my eyes aren't what they used to be I have 85/100w H4s and 4/100w Oscars to light the path - theoretically. I read somewhere that the output for the 3.2 alternator was 600w, and using info from this page: http://www.rallylights.com/hella/SensibleWiring.aspx
I figured that wasn't going to cut it with lights on, fan blowing, wipers on, etc. If the Carrera alternator in fact is rated 90A and 1260w, that should be enough I think, but then again, in the words of Manuel the waiter in Fawlty Towers - "I KNOW NUTTHING".

Now I need to figure wire gauge and relays to power the Oscars. I do have the factory foglight wiring/switch/ relay that I was thinking of using for two of the Oscars, but I need to make sure the wire gauge and relays are sufficient.

Thanks for the information John, I checked the Bentley manual and online, but couldn't find the output of the alternator. I've moved you up, just below Tesla, on my list of favorite electrical theoreticians.

[304065]

Jim,

So you are going the Mark Morrissey route of carrying enough forward-mounted candlepower to illuminate an evening little league game. Excellent, and I think that the 911 needs a bit of extra weight up front for rally use.

85/100w H4s x 2 = 200W = 16A

4/100w Oscars x 4 = 400W =33A

That is a lotta juice right there, fifty amps (reminds me of the Stones, "if we don't we're gonna blow a fifty amp fuse") going from back to front.

Now Jim is this for your backdate? Reason I ask is it will help define what we're starting with to carry current. The apple doesn't fall very far from the tree at Porsche, they used an old aircraft technique of having the battery up front and using a single cable to carry current to the starter solenoid, and then using the same cable to carry current from the alternator to the battery to charge it. In the SWB (my world) this is primitive, a little 10 gauge wire from the alternator to the electrical console terminal strip and then back over to the starter and forward to the battery from there. In later years they got smart and ran a nice fat cable directly from the B+ terminal on the back of the alternator, through a rubber block in a hole in the engine tin, down to the starter terminal. That provides a nice high-amperage current path to get the juice out of the alt and forward to the battery (and your lights). How is your car configured?

A 3,2 alternator and shroud will be fine, get the fan with the slots in the center to keep it cool. A complete 3,2 Carrera setup would be fine. You have enough current capacity to run a George Foreman grill and a Thetford portable refrigerator off that thing and still be able to charge your iPhone. The challenge is in getting the juice forward in a correct fashion so you don't have an 800 amp arc welder writhing all over the car when you're trying to call pace notes. Vollgas!

[Dezzmo]

Jim,

there's a place in Providence called General Armature at 516 Broad Street (401) 621-0654 that may be able to help you.

I know 2 people who dropped off the alternators from their 911's recently and had fantastic results. Give them a call and see if they can help you out.

[Jim Garfield]

John, the engine, alternator, and wiring harness are all 3.2 Carrera. I was concerned that the alternator wouldn't be able to keep up, but from what you are saying, the output should be more than adequate. I would like to avoid the 800 amp arc welder scenario.....

Tim, thanks. I'll keep them in mind in the future for rewinding the alternator. One of Curt E's rally buddies from the upper peninsula of MI suggested adding more windings to the existing alternator if the output wasn't enough to keep up with the Oscars, but John has eased my mind that I should be ok with my current (no pun intended) setup. How's the car coming?? Give me a call if you need an extra hand with anything.

[304065]

Jim,

OK, so you have the whole 3,2 setup. If it were me, I would do the following:

1) Disconnect battery positive cable and isolate. Death, grevious bodily injury and property damage may result if this step not performed.
2) Remove M6 screws holding alternator to shroud
3) Loosen fan clamp
4) Gently pull alternator forward.

There should be enough slack in the harness that you can pull the fan forward. Using a small wrench, remove the lock nuts that hold the fiberglass air shroud to the back of the alternator. Have a magnetic grabber handy so you can retrieve the little nuts when they spring from your grasp and lodge themselves between the cylinder cooling fins.

With the air shroud removed, you will now have access to the terminals on the back of the alternator. These are D- (ground), B+ (battery positive) and D+/61 (blue warning lamp/charge control circuit).

Jim, does your car have a nice fat copper strap between D- on the alternator and one of the M8 studs on the case parting line? You want a good ground for the alternator. The connections should be corrosion free and tight. If you have any doubt, pull off the strap and clean it or replace it with a good one. You want a bright metal-to-metal connection for minimal voltage drop.

Next, does your car have a large black wire running off to the northeast corner of the engine compartment? It should, this runs directly to the starter lug. This is how the current gets forward. If for whatever reason this has not been installed, install one, being very, very careful not to route the cable in a way that will subject it to chafing or being severed by the motion of the engine/tin against the body sheetmetal. This would be extraordinarily bad.

Make sure all the other connections are clean and corrosion free and tight and button everything back up. Be sure the cable connections on the starter ar also nice and tight, this is a greasy, uncomfortable job, but necessary.

OK, so now we have a path to get current forward to the battery. Are you using one or two? I assume you are using one due to the shorthood provenance, that's OK.

A lot of batteries are not secured to the car in a reliable way. For rally or racing use the battery WILL move around and WILL short its positive terminal against the fuel tank if you let it. See my previous comments on very bad things. So a positive anchor for the battery, along with protection of the positive terminal, is a must.

If you use a battery kill switch, you can wire it in at this point, per the instructions for the six-pole switch. Something like the overpriced Weltmeister mount (a piece of flat steel plate bent at an angle with a hole for the switch and two holes to capture the fender screws) is a good idea, this provides a solid way to mount the kill switch.

Out the other side of the kill switch you need a big fuse. If one of the wires to the switch gets loose this will blow. There are some big 70A fuses used by the stereo punk crowd, something like this would be fine. Out of the fuse, you need to run the current to a Bosch 70A relay to terminal 30. Ground is 85. Headlamp power goes from the ignition switch, through your headlamp switch and to terminal 86. And finally, wire to the lamp positive terminal goes on 87, the normally open terminal of the relay. When power is present on 86, 87 is energized. Don't connect to 87a or it will be on all the time. This is all standard stuff per DIN 72552.

In terms of wire gauge you can follow the Susquehanna instructions-- for carrying 30A you need some pretty big wire, like 14 gauge. The run is sort of complicated-- if you put the fuse and relay on a panel near the battery switch, you have to run up to the cowl and then down the hood to the lamps, about an eight foot run? With 14 gauge the voltage drop should be minimal. Do not forget to use a ground of the same size, brown color.

You get the basic idea.

Jim what are your current consumers in the car? Here is a list of the 3,2 fuse sizes.

[304065]

Power windows, seat heating sunroof NO
Blower, A/C, Seat adjustment NO
Convertible top, headlight washer NO (headlight washer is a full time employee with this setup )
Clock, glove box, interior light YES 5A
Central locks, emergency flasher NO
Fuel Pump YES 25A
Brake Lights YES 8A
Outside mirror, heating control YES 16A
Cig Lighter, Blower, Rear window heat YES 25A
Windshield wipers YES 25A
Back up lights, instruments YES 16A
Rear turn signals left, right 5A each = 10A

Well you get the idea. These circuits don't actually DRAW that many amps, the fuse is there to blow if they short out and they do. So figure 50% of the amperage-- for example I know a bosch electric fuel pump draws about 15 amps max. Using this as a guide to current consumers you can figure out what the approximate load is.

[Dezzmo]

John, the engine, alternator, and wiring harness are all 3.2 Carrera. I was concerned that the alternator wouldn't be able to keep up, but from what you are saying, the output should be more than adequate. I would like to avoid the 800 amp arc welder scenario.....

Tim, thanks. I'll keep them in mind in the future for rewinding the alternator. One of Curt E's rally buddies from the upper peninsula of MI suggested adding more windings to the existing alternator if the output wasn't enough to keep up with the Oscars, but John has eased my mind that I should be ok with my current (no pun intended) setup. How's the car coming?? Give me a call if you need an extra hand with anything.

It looks like John has you covered on this one so your in good hands. With any luck I should have the car painted by Sunday, then I can start putting it all back together again.

But I still have a friend coming over in a few weeks to help me rebuild the transmission, you can always come down and join the fun anytime.