E28 alternator upgrade project pics

[Robert Bondi]

I finished this project back in the spring, but it took a while to organize and upload the pics. The pictures capture several electrical system upgrades: upgrading from 55A 530i alternator to 80A E28 alternator, installation of new 12V cabling from the battery positive terminal, and installation of an adjustable voltage regulator.

http://www.flickr.com/photos/robertbond ... 228456477/

Swapping the alternator itself is a fairly easy job once the aluminum E28 bracket and tensioner HW is in hand. The by-product "hard" part is what to do about your E12 P/S pump. I see about 3 solutions to this:

1. Use your E12 pump and modified E12 P/S brackets. This results in a few residual spacing issues to get the pulley in the expected plane. In the old archives, most people just threw in a bunch of washers for a quick fix. I think some cuts were also made to the E12 brackets.
2. Convert to the E28 P/S pump. I'm sure this is fine, except the interface problem now moves into the P/S hoses and fittings which aren't identical to the E12.
3. Use E28 bracket design with E12 pump. This is the route I took.

Pics show both E12 and E28 bracket systems on a work bench. After studying the E28 design, I decided it was superior. The E28 has a pivot point that the E12 design lacks. The pivot point helps ensure that the pulley plane doesn't change during belt tensioning, while the E12 design leaves it up to the mechanic's prying skill to ensure that the front and back of the pump move equally while the bolts are sliding through those slots. E28 belt tensioning also uses a rack-and-pinion approach that allows you to tension with a ratchet or wrench - NO CAVEMAN PRYING!

The hard part is the front E28 bracket. It could be used directly if the bolt hole pattern matched the E12 pump, but it doesn't. I fabricated my own hybrid E12/E28 front P/S bracket by machining a 3/8" thick piece
of aluminum 6061 on a router table w/ aluminum router bit. I expect the 3/8" thickness is overdesign; I don't race my car, so I'm erroring on the side of strength. I also had my used brackets plated and assembled everything with stainless steel HW.

The solution in the pics has about 4500 miles on it from summer trips to 5erWest and Four Corners, so it appears reliable.

This would make a good FAQ write-up, although FAQ activity seems to have died years ago and the webmaster isn't easy to reach these days.

Robert

[BumbleBeeTuna]

but what is the advantage to the e28 alternator? more voltage or just longerlastering?

[Robert Bondi]

but what is the advantage to the e28 alternator? more voltage or just longerlastering?

More current capacity is the advantage. The e28 unit is 80 amp (90 amp can be done with a few more changes). The e12 unit was 55 amp.

[GripGreg]

And the advantage of 80 amps over 55 amps is,,,,?

[Robert Bondi]

Advantages of a bigger alternator include things like your headlights no longer dimming when the A/C compressor kicks in.

Looks like this is no longer FAQ material, but it was a common thread way back in the day when Peter Florance was a regular:

http://www.firstfives.org/wwwboard/messages/74022.html

Maybe I should be the First Fives historian.

[Mike W.]

Alternator output is not always linear, ie output at idle for an 80A unit is not necessarily 40% more than a 55 or 65 as was stock on 528i's. That said, I've taxed both 65 and 80's on Es 12 and 28 pretty hard in Las Vegas summers and not a problem with either.

[BumbleBeeTuna]

Right, the cars were built well and im sure they took into consideration the draws you could put on a factory system. Im guessing its best if your putting pretty substantially greater loads on your car. Like that that new box with 6 14" alpines in the trunk, right robert? Haha