Alternators, Amps, and the 818

[Rasmus]

http://i162.photobucket.com/albums/t278/RasmusHansen/Factory%20Five%20Racing%20818R/IMG_0343.jpg
I disassembled my OEM '06 alternator to clean it and inspect the bearings and brushes. While it was open got to thinking how heavy this thing is and if there's anyway to lighten the OEM part. By my eyes, there's not.

Rotor: 2855 g
Stator with Rectifier: 1613 g
Case halves, bolts, and larger bearing: 910 g
Pulley, mounting hardware, and brackets: not considered
Total mass: 5.378 kg (11.85 lb)


The copper rotor and stator make up the bulk of the mass in this thing and I don't think there's anyway to lighten them. So that leaves moving to a smaller alternator with a less massive rotor and stator. But that'll put you down on amps. Ideally, I'd guess, you'd want to produce about 1 more amp than your maximum sustained running draw. So for me that looks like:

Water pump for Air-Water intercooler: ? amps
Radiator Fans running at full clip: ?? amps
Fan(s) for brake ducts: ?? amps
Fuel pump: ?? amps
ECU, instrument panel, sensors, and spark-plugs (e.i. the engine) ??? amps

I don't ever plan on running full out at night so headlights/running lights doesn't factor in. I guess it might if it drew more than the radiator fans and brake duct fans. I can look up the most of that stuff but it's the engine draw I don't know. How many amps does "the engine" need to function?

Ultimately my question is: what is the lightest alternator I can get away with running that doesn't cost Formula 1? What's the smallest amp alternator I can run?

[longislandwrx]

OEM being 75 amps, I think 30/50 would be safe running led (if any) lighting no climate control, no wipers, no defroster, and no stereo... Powermaster 8162... 5.68lbs

6.17lb savings for $230 or less used.

[Rasmus]

http://i.imgur.com/ZTpoQTQ.jpg

http://i.imgur.com/KOSk3ss.jpg

Nice unit. And only 2576 grams vs the OEM 5378 grams. 30amps idle with a slow (i.e. racing) ramp up to 50 amps. What's the "one-wire" vs OEM-wiring difference? Is 50 amps enough?

[Bob_n_Cincy]

http://i.imgur.com/ZTpoQTQ.jpg

Nice unit. And only 2576 grams vs the OEM 5378 grams. 30amps idle with a slow (i.e. racing) ramp up to 50 amps. What's the "one-wire" vs OEM-wiring difference? Is 50 amps enough?

Hi Ramus,
The one wire alternator is simple. Just one charge wire going to the battery.
It has internal field power supply and internal voltage sense circuit.
This would work fine.

Three wire Subaru alternator.
The field power supply comes from the light bulb in the cluster.
When the key is turned of the alternator stops charging.
This can be good in the case of a battery disconnect switch. You do not need an extra contact for the alternator power feed.
This field wire also operates the alternator light on the dash. Not so with the one wire alternator.

The third wire on the Subaru alternator is the sense wire. It's sense the charge voltage.
On a one wire alternator under high load the alternator my be a 14 volts but the dash may only be at 13.3 volts.
The sense wire on the 3 wire alternator can boost up the alternator output to maintain 14v at the dash at any load.

Let me know if you have questions.
Bob

[longislandwrx]

True a one wire alternator has a current draw when off... I think its 300ma so you need a disconnect switch or a battery buddy. if it will be off ( as most weekend cars are) for extended periods of time.

The math says its enough, only way to know for sure in the real word is by having someone with a finished 818 measure their draw.

[Scargo]

Mine's 3254 grams (http://www.amazon.com/gp/product/B000ES8MSK/ref=oh_details_o08_s00_i00?ie=UTF8&psc=1). $93 with Amazon Prime. 15576 - 90-91 Suzuki Swift ( and others) Nippondenso, Clockwise 55 Amp Alternator, remanufactured in USA. It looks good. Power out and three pin connector in the back that looks to easily convert to 1/4" push-on connectors. The pulley is only a three-groove but essentially the same diameter. I guess it will need to be swapped out for a four groove, though power steering isn't used (so the alternator is all that's running off the main pulley.
The only thing that looks challenging is the bracket will have to be skinnied down to fit between the alternator's mount/pivot ears. I may make a new bracket since the massive stock one is for mounting the A/C compressor to, as well as the alternator, and weights a hefty 3-1/4 pounds!
http://ecx.images-amazon.com/images/I/71CGs%2BftDCL._SL1500_.jpg
What do you think?

[Rasmus]

I like that the Swift's has three ears to mount it. Plus with the three wire you don't have to remember to turn it off. Price is nice too. What's the diameter of the shaft? Subaru OEM Alternator shaft is 17 mm.

[Scargo]

I'm at a stalemate with the alternator. I don't know the shaft diameter, though I could estimate it. Just looking at it, I'd say it is several mm smaller.
The nut is an odd size. Bigger than 21mm but kinda sloppy on a 7/8" socket. I used my O2 sensor socket, which allowed me to go in the middle and get a deep, six-point, 10mm socket on the shaft. When I tried to remove the nut the 10mm slipped off, buggering the hex a bit on the end of the shaft.
What to do? I did not heat the joint before I tried to loosen it. I feel like they used a high strength anaerobic adhesive on it or something!
I'm looking for advice as how to proceed.

[Rasmus]

I'm looking for advice as how to proceed.

Put a used belt around pulley. Clamp the belt end in a vise so the belt tighten's around the pulley. Apply a little heat then hit it with the impact gun.

If it's still slipping, clean the pulley groove and belt with acetone (or whatever) then go find the wife's hair spray. Spray the pulley lightly, then the belt, now stick them together. Try again with the vise.

[Scargo]

Sounds like I'm pulling cam sprockets! Thanks, good advice! I picked up a 22mm socket. I hope it fits better than the 7/8".

[Scargo]

Thanks, Rasmus... Got it off with impact and hose around pulley in the vise. It's a 15mm shaft. Same 54mm outer diameter (at the peaks) as off my '08 STi.

[Rasmus]

Sure, man. Good times. When you're doing this kind of work on a Subaru it pays to have invested in both a 22mm and 32mm 6-point 1/2" drive deep impact sockets. Because the things held on by nuts those sizes are measured in the 90-150 ft-lb ranges. They're ON THERE. Like jack-handle-on-breaker-bar ON THERE. I have, personally, ripped apart a 4 groove accessory belt trying to get a 22mm bolt loose on an alternator using my above posted belt-in-vise method.

Scargo regarding the diameter mismatch of your alt's shaft and the Subaru pulley, just get a strip of 1mm-thick bronze and make your own adapter bushing.

[Scargo]

I'm putting this first one on my STi... No A/C in the way. Pure track car. It should be good for charging my 11 pound battery. :p
Just put my mock-up motor in the bay and I've got enough room for my NA intake reversed! I'm so excited! Now, I'll figure out how to mount this little sparky puppy and run the three-rib snaky belt on the rear half of the crank pulley and run just the PS off the front half.
Now, on to doing the rotated Borg Warner EFR 8374.

[Ravendas]

According to DW300 specs, current draw is 10-14 amps @ 13.5V.
http://www.deatschwerks.com/resources/fuel-pump-tech/dw300-fuel-pump-tech

According to this page (http://www.robietherobot.com/storm/fuelinjectorguide.htm), injectors are either 2-4 amps peak pull.

[Scargo]

551685516955170
Can't guarantee yet that it works. I hope to start it tomorrow.

[aquillen]

Scargo / anyone else ? Tested a smaller alternator with success?

55 Amp seems reasonable for a basic 818 setup, but wondering about electric connection issues since it connects to an ECM pin and the alt warn light on the combo meter. I'm looking for more room under my home brew H6 motor's carbon fiber intake efforts in process now. Thanks guys!

[Scargo]

I can say that it has worked fine for me on the dyno and that's about all yet. I used the stock pulley that came with the alternator.
This Denso 15576 alternator from Amazon. (https://smile.amazon.com/gp/product/B000ES8MSK/ref=oh_aui_search_detailpage?ie=UTF8&psc=1) This connector. (http://www.ebay.com/itm/REPAIR-PLUG-HARNESS-3-WIRE-PIN-CONNECTOR-Fits-GEO-Prizm-1-6L-L4-1989-1992-/271534858817) REPAIR PLUG HARNESS 3 WIRE PIN CONNECTOR. Fits GEO Prizm 1.6L L4 1989-1992 (and many more import cars) (DENSO # 100211-1050)

I suppose a situation with two fans and headlights on you might approach 55 amps. A second fuel pump isn't generally needed. Dry sump or oil cooling fans might figure in but I doubt it. Running everything at once is questionable. I just plan on doing daytime events and no enduros. I have my radiator fans on a manual switch.
BTW, I bet these cars at the Rolex 24 hours need some good electricals. This was quite the show!

https://youtu.be/VVjx9KI4r_g

[frankc5r]

[QUOTE=Scargo;267334]I can say that it has worked fine for me on the dyno and that's about all yet. I used the stock pulley that came with the alternator.
This Denso 15576 alternator from Amazon. (https://smile.amazon.com/gp/product/B000ES8MSK/ref=oh_aui_search_detailpage?ie=UTF8&psc=1) This connector. (http://www.ebay.com/itm/REPAIR-PLUG-HARNESS-3-WIRE-PIN-CONNECTOR-Fits-GEO-Prizm-1-6L-L4-1989-1992-/271534858817) REPAIR PLUG HARNESS 3 WIRE PIN CONNECTOR. Fits GEO Prizm 1.6L L4 1989-1992 (and many more import cars) (DENSO # 100211-1050)

I suppose a situation with two fans and headlights on you might approach 55 amps. A second fuel pump isn't generally needed. Dry sump or oil cooling fans might figure in but I doubt it. Running everything at once is questionable. I just plan on doing daytime events and no enduros. I have my radiator fans on a manual switch.
BTW, I bet these cars at the Rolex 24 hours need some good electricals. This was quite the show!

https://youtu.be/VVjx9KI4r_g[/QUOte}

At 24 Hours of LeMans with Corvette Racing at night we monitored current flow from all devices drawing current and we saw a total of about 160 amps draw.. Had solder melt they got so hot. Went
to a Formula 1 altn to solve problem..

[Hindsight]

At 24 Hours of LeMans with Corvette Racing at night we monitored current flow from all devices drawing current and we saw a total of about 160 amps draw.. Had solder melt they got so hot. Went
to a Formula 1 altn to solve problem..

I believe you, but how is that even possible? What is drawing that many amps?

[Scargo]

Guess...
63858

[frankc5r]

I believe you, but how is that even possible? What is drawing that many amps?

I know it sounds crazy but we have multiple pumps for fuel system, other pumps, air conditioning, and lights,
more lights, a radar system. It all adds up. It's more like 50-60 during day.

[Scargo]

That dam n radar! Why multiple fuel pumps, if I might ask? You know, you can heat the fuel by too much pump. Are they not staged for demand? E85?
Suggestion: Switch to LED lighting! JK

[iWire]

Yeah, my concern is really around the rad fans and their initial draw when they start spinning. We see them pull 20 each then drop back down to just under 10 so that's a 40amp spike you need to be wary of when making an alternator/fusing decision.

[UnhipPopano]

"rad fans and their initial draw when they start spinning. We see them pull 20 each then drop back down to just under 10 so that's a 40amp spike".

The battery handles the spike, not the alternator.

"6.17lb savings for $230 or less used."

We must be talking about the car set up for racing, as a small weight savings for a street car would not make much of a difference.

[flynntuna]

yes, Rasmus's build is all about making the car as light as possible. Every ounce counted. :cool:

[iWire]

Ah, that makes sense then.

[Sgt.Gator]

I'm re-building my STI as an endurance racer so I've add a lot of electrical load. Oil Cooler Fan, Brake Blowers, Diff pump, Diff cooler fan, 2 way radio, Cool Shirt Pump, Extra lights, additional fuel pump, windshield fog blower....and probably more I'm missing.

Then I added on the OEM radiator fan, and all the other oem stuff. When I added it all up at night I'll be using 110 Amps!

The oem 2005 STI alternator is only 90 amps cold. Consider they lose capacity when hot and you should never run an alternator at more than 90% of cold capacity, this isn't going to work!

Looking at other OEM alternators:
An OEM Imprezza NA alternator is 75 amps.
A 2005 Legacy alternator is 110 amps but uses a different bracket that's incompatible with the dry sump pump solutions. And I want extra capacity.

So I found DC Power and bought this one:

https://www.dcpowerinc.com/media/catalog/product/cache/1/image/530x424/9df78eab33525d08d6e5fb8d27136e95/i/m/img_3317_3.jpg

180 amps of awesome, exact drop in plug and play. If you want to run a monster sound system they have a 250 amp and 270 amp too.

https://www.dcpowerinc.com/high-output-alternators.html?q=%2Fhigh-output-alternators.html&make=Subaru&model=Impreza+WRX+STI&year=2005&engine=2.5L+H4+Turbo

[turbomacncheese]

Sexy