Reviving A Dead Optima Red Top Battery

I stupidly left the key on in my 323 for over a month. I don’t know how quickly the battery drained but it wasn’t completely done – the trunk light was still dimly lit but nothing else. 

This was a brand-new Optima Red Top and I wasn’t about to spend $150+ on a replacement. Unfortunately, neither of my chargers was having any success. Fortunately, the Optima website is very consumer-friendly and not only did it explain why my chargers didn’t work, it had fantastic instructions for reviving a spent battery.

My off-the-shelf, generic chargers have their own logic that will abandon the charging process if it detects battery voltage to be below a certain threshold. My dead Red Top was down to 1.5v according to my multimeter. The charger will give it a hearty try but call it a lost cause if the voltage can’t be maintained above X.Xv. 

The Optima website gave three options:

  1. buy the correct charger for an AGM battery that will not give up
  2. use the Optima as a slave to a good battery as the master (and keep the master charged)
  3. bring it to a professional shop who will do either 1 or 2

I opted for #2 because I can’t turn down an opportunity to learn a new skill. I bought a set of jumper cables (always good to have those anyway) and connected my Honda battery to the Optima. Right away I had 10.2v at the Optima. 

Then I connected my strongest charger to the Honda battery. I checked voltage every 15 minutes and in under an hour I had 13.4v on the Optima!

I then disconnected the jumper cables and put the trickle charger back on the Red Top and let it do its thing. After two hours it was still going! I had infused enough electrons into the Red Top that the charger’s fuzzy logic accepted. I let the charger work overnight and it continued to put out over 13.5v the next morning. I drove the 323 to work that day with no issues and the voltage gauge reading over 13v the whole time (between 12-14 and closer to 14).

I guess you can say “I’m charged up!”

E21 Winter 2016 List

List of things to do this Winter:

Finish garage wall! Can’t do much when I have one of the walls under construction. And I need to plan the layout to allow me to work in the Winter. The original M20B23 engine is on an engine stand and more in the way than I expected. COMPLETE!

Complete the wiring for the M20 swap. It’s all there and connected and everything works. I just have to run the sheath over it and plug the metal connectors into the right places on the fuse box plug and C101 plug. I’m only using 7 pins but there are 20+ connections so I have to get it right the first time. I have a few spare connectors but it still makes me nervous. Then I have to mount the C101 connector on the firewall. COMPLETE!

I also need to connect the VDO oil pressure and oil temp sender. Edit: this is not going to be as simple as screwing it on and plugging in some wires. The owner’s original wiring is incomplete. I’ll have to re-do that too, all the way back to the gauges.

Then install the cowl cover and the engine swap should be 99.9% complete. COMPLETE!

I should set the idle speed to a more normal 750-800 RPM. It’s still up over 1,000 to keep it from stalling, but the O2 sensor seemed to take care of it. I might have to wait for warmer weather to do this though.

The temp gauge only gets to 1/4 on the gauge. I’m running the standard E30 80* thermostat and E21 fan. With a cold temp the DME richens the fuel mixture. I can adjust the fuel map but probably better to have the temp in the right place before I start tuning. First I’ll try removing the fan (done.). If that doesn’t work I’ll install a 88* thermostat. 

Other work on the engine should be: check the bottom end and make sure the rod bolts are tight and there are no spun bearings, and check for any leaks. COMPLETE! Bearings look great. A few small leaks from loose bolts and hose clamps. 

While I am around the subframe I need to replace the tie rod boots because they are ripped (COMPLETE! What a job to get the inner tie rod off!). And finish rust-proofing and painting the frame rails.

On the inside, I have a full Euro non-A/C center console to install. That will mean removing the radio (maybe a new one?) and reinstalling it in the normal horizontal position (COMPLETE! Center console is installed and looks great!). I need to fix or replace the radio antenna. I need to fix a few pieces of the center console before installing it. And I don’t have any hardware for it (COMPLETE! Hardware was sourced from Lowe’s and it looks great). At the same time I need to fix the heater controls because the temp and the vent knobs don’t move. I’m hoping I don’t break anything. And I want to check the hazard light switch because they are a known to be problematic (I bought a backup to have).   

how I want my interior to look

I don’t have the ECU mounted. It’s just dangling on the floor (COMPLETE! Mounted to the firewall. The glovebox closes too. Need to tidy up some other interior pieces and I’ll be ready). I want to try the Ostrich emulator so I can make tuning changes on the fly. And I have to recalibrate the wideband O2 sensor in the Spring (COMPLETE).

Lastly, I need to modify my battery hold-down tray so the Optima battery fits in it. It was supposed to fit but Optima must have changed the case and the battery tray manufacturer didn’t come out with a new one. 


I also installed new hood and trunk BMW emblems (roundels) and new wheel emblems.

Wow that seems like a lot! I’ll probably go down this list in order rather than pick and choose. But it all needs to be done before I can really start driving the car in 2016.

The Infamous E21 Shimmy

The E21 suffers from a front-end shimmy between 50-60mph. This plagued the E21’s reputation and led BMW to introduce a brand new front suspension design for the E30.

I’ll tell you about my car first and then get into the usual causes. My car had a shimmy from around 40mph and then it went away. It didn’t have the usual 55mph shimmy. I wasn’t too concerned about it since all of my focus has been on the engine swap. 

Then on one of my test drives I realized the shimmy was completely gone! No shimmy at 40, 50, or 55. I completely expected there to be something because there were loose control arm bolts, ripped tie rod boots, and I don’t think there are any of the usual shims or stiffer bushing fixes commonly used (see below). The previous owner said he liked the handling “lively”. My guess is that the tires were slightly squared from sitting for a few months. 

The shimmy has quite a few potential causes: 

  • the shimmy is inherent to the design because there is no locating link [solution: none other than full tubular A-arms]
  • worn ‘outer’ control arm bushings where the sway bar connects to the control arm [solution: replace with Genuine BMW rubber or urethane]
  • loose or worn wheel bearings [the wheel bearings should be re-tightened every 20k miles]
  • bent wheel(s) [straighten or replace them]
  • flat-spotted tires [drive on them for a while and they should re-shape themselves]
  • worn sway bar bushings on the frame rails [replace bushings with rubber or urethane]
  • wheels torqued to the wrong spec [loosen and then re-torque]
  • the wrong wheels (the wrong center bore or bolt pattern) [confirm wheel specs. If these are the wrong wheels, replace them right away]
  • bad strut or strut mount [replace strut inserts and mounts]
  • worn steering rack bushings [replace with urethane]

E21 323i Exhaust Layout

One of the first things people notice is that the 323i has a dual exhaust. It’s the only modern BMW with one until the 1998 M Roadster arrived. The single tips on both sides give the car some added muscularity and I love them.

The rest of my car’s exhaust is also interesting. It is a true dual exhaust; each exhaust outlet is traced back to one of the manifolds on the engine. Even though this is an inline 6 engine, we still refer to groups of cylinders as “banks”, just like in a V layout. Bank 1 is cylinders 1-3. Bank 2 is cylinders 4-6.

There is no X or H pipe in the exhaust stream. This would probably improve performance but BMW didn’t see the need. There is a center resonator and a muffler on each side. There is no catalytic converter which I have seen on other grey market cars. 

The sound is fantastic. There’s a bit of rasp throughout the RPM range. Because I’m still breaking in the new engine I haven’t revved it past 5,000 RPM but I bet the sound is glorious. Can’t wait to get the car on some backroads in warmer weather and open the sunroof and windows. Video to be added when that happens.

Update: Supersprint just told me that they are re-introducing their headers and all-stainless sport exhaust. That will bring some more power and improve the sound even more. They’re going with 2 round tips on each side (4 total) though. I’ll have to see how that turns out.

Update 2: the Supersprint system has been ordered! I went for the whole system – headers, center section, and mufflers. Supersprint will have two muffler types available: Performance with 4 60mm tips and Race with 2 60mm tips. I opted for the Race mufflers because I want an aggressive and “ripping” sound. If my past experience with Supersprint holds up I think I’ll be pleased. 

Some of my favorite 323i M20 exhaust sounds –

E21 Wheel Info

The original E21 320i and 323i wheels were 13×5.5″ with an 18mm offset (ET). There was also a 13×6.0″ ET13 Motorsport wheel available. These sizes  are slightly larger than what was used on the 2002 models. It’s interesting that BMW did not give the 323i a wider wheel.

If you want to maintain the the OEM appearance from the factory wheels you can use wheel spacers. A 15mm or 20mm spacer would work nicely.

Tuners at the time jumped all the way to 15″ wheels for their upgrades. Here are three examples –
Alpina Kopi – 15×6.5 ET20
Melber – 15×7.0 ET12
Ronal LS – 15×7.5 ET25

Of those, the Melber wheels are the most aggressive, putting the wheel 25mm further out towards the fender. We can use this as our benchmark as a “maximum aggressive” fitment. Meaning, if they were any further out they would probably be rubbing on the fender. But they look impressive!


The Ronal are the second most-aggressive, adding 18mm to the track on each wheel. The Ronal is an E30 fitment so there are few resources to go by.

The Alpina Kopi (replica) wheels are the more conservative but still give 11mm of extra poke from the stock fitment.

E30 325i wheels are not a direct fit. They are a good size but a higher offset –
BBS Style 5, “Basketweave” – 14×6.5 ET30
BBS Style 5, “Basketweave” – 15×7.0 ET24

The higher offset means the wheel sits closer to the inside of the car (towards the strut). To use the E30 wheels you will need to use wheel spacers, probably a 15mm for the 14″ and a 5-8mm for the 15″ wheels.

Here are 14″ E30 wheels on 12mm spacers –

Of course, the one variable I left out of this is the tire size. Running tires with a taller sidewall would lead to rubbing. I left tires out on purpose because of all of the variables in sizes.

Have something to contribute? Let me know in the comments section below.

M20 Engine Specs

Here are the specs of my initial M20B28 engine build.

I started with a standard M20 2.5 that was mostly complete but partially disassembled. A 2.7 crankshaft, connecting rods, and flat-top pistons came with it. The 2.7 rods and pistons are commonly used in turbo builds.

I used the 325i rods and custom Wiseco pistons. I could not use the stock i pistons because they are too tall with the long stroke of the 2.7 crank.

Here are the final specs:

Type: M20B28, SOHC, 12-valve, inline-6, 325i iron block (bored) and 325i aluminum head, port fuel injection
Displacement: 2,758cc / 168cu in.
Bore: 85mm
Stroke: 81mm
Camshaft: stock 325i
Compression ratio: 9.5:1
Fuel injectors: 18.25psi @ 3.0 bar
Intake: stock 325i AFM and intake manifold, K&N cone filter
Exhaust: stock 325i exhaust manifolds, stock E21 323i non-cat exhaust
ECU: Bosch 0261200173, custom chip tuning
Power: 190hp (est.)
Torque: 190ft-lbs (est.)

M20 Conversion Basics

Could there be an easier engine swap than an E30 325i M20 into a E21 323i? Actually, yes: an S52 into an E36 is pretty plug and play. But this almost as easy. There are a few really good guides online, including the ones covering 320i swaps. They didn’t always apply to my project so here’s what I learned along the way.

First, here are the best resources I found:

Todor’s: thread:

The swap is easy enough that you don’t need a lot of how-to. This is what you will need:

Complete M20 engine with wiring and ECU (get it as complete as you can)

E30 air flow meter

E30 cone filter intake (the E30 air box might fit but I didn’t try)

E30 throttle cable

New rubber fuel lines from the frame rail to the E30 fuel rail.

E21 fuse box plug and pins

E21 fuse box plug

E30 C101 connector. The top should be on the engine wiring but get the body-side for a factory look.

If you have a 1988+ M20 you will need the 1987 cooling system parts (water pump and hoses). Some of the hoses can come from the E21 system.

An extra E30 front exhaust manifold. The E30 exhaust layout has the manifold outlets next to each other. The E21 has them spread apart. This might vary from car to car, however. I could have used the E21 manifolds but they looked too rusted on the studs. On my car I could not use the E30 rear manifold and had to source a front one. Everything bolted up from that point.

E30 oxygen sensor and bung. And realize that the bung cannot be welded to a rusty exhaust pipe.

You will probably want to relocate the battery to the trunk. That required a battery tray, battery cable, junction box for the engine bay, and wiring from the junction to the starter and alternator. And you will need to cut several holes in the interior sheet metal.

You also need to cut a hole in the firewall for the engine ECU so it can mount under the dash, a la E30.

The E21 flywheel and clutch will bolt on to the E30 M20. Some of the parts are actually the same anyway.

Make sure the engine is complete and running. If you buy a non-running engine upfront you will be chasing those issues later instead of driving it. I chased a no-start issue for weeks because the engine I bought needed basic maintenance. Here is what tripped me up once the engine was in the car:

  • fuel pump relay
  • short in the fuel rail
  • alternator voltage regulator
  • alternator ground
  • TPS adjustment
  • throttle stop screw

They’re not expensive so make sure this stuff is taken care of.

You will need the motor mount arms from the E21 (which you won’t get until the engine is out of the car).

As for the actual swap itself, I did it in my driveway with a Harbor Freight engine hoist. You have to pull the hood off and the latch mechanism and rods need two people to safely remove.

I pulled the engine with the transmission attached but it was SCARY. I won’t be doing that again. It came out pretty well but the two pieces together made it a struggle to reinstall.

Here is the wiring that needs to be done:

oil pressure light in instrument cluster
fuel pump power
alternator charge light in cluster
ignition coil power
ECU power
power to starter
coolant housing temp to cluster
RPM signal to tachometer. This was the only connection that did not work. I ended up running a dedicated wire from the coil to the C101 plug (bypassing the E30 ECU).

Here is my wiring inventory:

I was very pleased with the results and how straight-forward this was. It was a great learning experience and I’m enjoying the fruits of my labor.

in it’s new home

Here are the links to my engine build and pics from the swap:

My Purchase

Here’s how I came about owning this 1980 323i. In 2014, I sold my 1994 E36 325is track car project for no good reason. 

I didn’t have enough to keep my mind occupied so I decided to rebuild an engine. I’ve done almost everything else on a car but have never done a solo rebuild on an engine.

I decided on a BMW M20 inline-6 from an E30 because it’s a simple design, easy parts availability, and plenty of tech support. The rebuild went extremely well and by January 2015 I could think about what it was going into. The M20 came in only a few models – E21 323, E28 528e, E30, and E34 525i. The easy choice was the E30 because I had previously owned two, as well as built a Spec E30 racecar for my boss, Will Turner. The E21 323i was never sold here so that was unlikely. A E28 528i would be interesting but it was hard to find a pristine one with a manual transmission. I don’t have any interest in the E34 unless it’s an S52 swap. I focused my searches on E21 and E30.

I used several sites for E21 engine swap research, including where the E21 section has some decent activity. And that’s where I stumbled on a guy from down South who was having engine trouble with his 323i. It was blowing smoke, drinking oil, and would barely idle. I didn’t think he would actually sell the car but I pursued him and was caught off-guard when he agreed to sell. I think he was trapped by his words and couldn’t say no. I’ll keep the price a secret for now but I believe I made out better than he did. The car also came with half a dozen boxes of parts, 4-sp transmission with driveshaft, and the factory “blue book” service manuals.

The 323 arrived at my house on April 5 and I could finally, officially call myself an E21 owner (and make the requisite Facebook post).