|Editor's Note: While this article was written with the 914 specifically in mind, the MSD Ignition System can be installed on any 12V Porsche.|
What Does an MSD Ignition Do For You?
MSD ignition systems were first recommended to me by a fellow who worked for the Colorado emissions testing authority as a way to improve my emissions which also improving performance. I found exactly these results.
The MSD ignition systems combine the concept of capacitive discharge ignition (made popular in the late 60's and early 70's) with multiple spark discharge. On a simple point and coil ignition system, while the points are closed, the coil builds up a magnetic field in its core by allowing current to flow at battery voltage into the coil wires which are wrapped around the ferric core, like an electro-magnet. When the points open, the magnetic field in the core of the coil collapses and rapidly introduces a strong, high voltage current into the output side of the coil, which becomes your plug spark. As RPM goes up, the charge time of the coil between sparks goes down, as a result, the spark energy is lower as RPM increases. Capacitive discharge solves this problem by providing a very quick higher voltage charge to the primary side of the coil which is the same at all RPM levels.
Multiple Spark Discharge helps to provide complete combustion at speeds up to 3000 RPM by issuing several sparks during each combustion stroke. The number of sparks varies, but fills up 20 degrees of crank rotation. Above 3000 RPM, there is not enough time for multiple sparks, so the MSD sy! stems then provide a single high power spark. The result of multiple sparks is easier starting, smoother idling, and smooth, crisp, powerful acceleration. An added bonus of more complete ignition is cleaner emissions.
Which MSD Box to Pick:
MSD produces quite a few multiple spark ignition systems. The "6" Series seems to be most widely used and appropriate for 914s. The models in this series include units with and without "soft touch" rev limiters, which keep you from over reving your engine. The rev limit is set either by a plug in "pill" with a designated rev limit, or an external adjustable control. Some units include shock mounts, which are really not necessary on a 914. Other units are available to meet NASCAR specs, to provide spark retard as turbo boost pressure increases on turbo cars, or to provide mult! i-step retards and rev limits for cars using nitrous oxide systems; not of much interest to 914 enthusiasts. All Series 6 units are "legal to sell, distribute, or install on non-OBD II vehicles in California according to Executive Order E.O. D-40-2 and legal in all 50 states." Here is a simple matrix of feature of the most popular models:
|Rev Limiter||Shock Mounts|
|6A, 6200 (6246*) ||No||No|
|6AL, 6420||Pil! l||Yes|
|6T, 6400 (6446*) ||External Control||Yes|
The long and short of it all is that the 6A, part number 6200 works for most street 914s and the 6AL, offering rev limiting, might be considered for racers.
* One important note. MSD makes units which are designed to prevent cross-fire on odd-fire V6 engines. These units have been known as 4/6 cylinder units (p/n 6246 or 6446). While they will work on our 914s, you are leaving horsepower on the table if you use these units. The multiple spark duration of these odd- fire units is only 10 degrees of crank rotation and they do not provide as strong a spark above 3000 RPM according to the techs at MSD. (I was mistakenly recommended a 6246 an! d used it for many years before I learned this. MSD gladly converted my 6246 to a 6200 and I can really feel the difference).
Other Parts You Need:
Our 914s have VDO tachometers in the instrument panels which do not understand multiple sparks. The good news is that MSD sells a "tach adapter", part number 8910. There is no way around this. Just order it when you order your MSD 6 unit.
If you have decided to get an MSD unit which uses rev limiter modules (a.k.a. "pills"), you will need to order the appropriate pill. The Series 6 units come with pills for 3000, 6000, 7000, and 8000 RPM. The kit of five pills from 5100 to 5900 RPM, in 200 RPM steps, is part number 87451, from 5000 to 5800, in 200 RPM steps, is p/n 8745. Sorry, but they are only sold i! n these kits of five.
This is also the time to upgrade your spark wires. The sparks from an MSD system in addition to being more numerous, are much hotter. Quality 8mm spiral wound wires work well. MSD makes a set of universal "Heli-Core" wires that you cut to fit. The four cylinder set is part number 3104 and costs about $30. Don't buy their custom VW set as those wires will not plug into your Bosch distributor cap. If you call MSD and ask real nicely, they might send you a set of their excellent quality VW boot seals (they call them insulators). These are very solid and fit tightly in the holes in the engine tin. (Tips on how to install these below). While you are shopping, pick up some di-electric silicone grease for the spark wires and some plug wire spacers. Mr. Gasket makes a set of nice looking blue plastic spacers that cost only a few dollars from places like AutoZone. !
New spark wires will most likely require that your spark plugs have the screw-on slip-over connectors which you probably removed and threw away when you installed your plugs, since normal VW type wires slip onto the threaded rods at the top of the plugs. So, either find four of those spark plug top thingees, or buy a new set of plugs. You can consider a plug one step cooler for use with the MSD system.
You may also want to invest in a new coil at this point. The Bosch "blue" coil works quite well with the MSD systems (NOTE: some users have experienced difficulties with the blue coil. Pelican Parts recommends using MSD coils with MSD Ignition Systems - Pelican Staff). MSD also makes a series of "Blaster" coils which, of course, work well with the MSD systems.
While you are at it, you should go ahead and replace your points and condensor (for the last time), cap and rotor.
Finally, you will need two crimp-on ring terminals: 12 gauge wire, 1/4" hole, to attach to the battery connections after you trim them. Also, one or two 1/4" cable clamps are useful to tie down the magnetic pickup wire (which you do not use, but should not cut off) and main harness. All other jumpers, hardware, connectors, etc. you will need are included with the Series 6 kit.
Where to Mount It?
This seems to be a subject of personal taste, but I will submit that having the shortest wires is a sound objective in selecting a mounting location for MSD unit. To this end, mounting on the firewall, under the rear window, above and to the right of the coil, near the battery, keeps all wires nice and short. As an added bonus, when you open the engine lid, people notice your investment in an MSD unit...
The unit is simply mounted with 4 #8x3/4" sheet metal screws provided with the kit. The tach adapter can be mounted directly below the MSD unit with two similar sheet metal screws.
While mounting the unit, secure the two wires coming out to the unit. The short wire harness, used for magnetic triggering and not by you, can be turned under the unit and tied off with a wire clamp sharing the lower left mounting screw. The long wire harness, which goes down to the coil, can similarly be secured at the lower right mounting screw.
NOTE: Disconnect battery ground while installing MSD unit. The heavy red wire should be connected directly to your positive battery terminal connector. I found the best place to connect the heavy black ground wire was the chassis lug! located behind the battery, where the battery ground strap connects. A disconnect on the ground lug of the battery is handy to have. In both cases, dress the wires neatly and cut them to length, replacing the lugs with new crimp-on terminals.
The wiring of the MSD unit is well illustrated in the excellent manual which accompanies the unit, but for the record:
Red wire: Red wire formerly on + side of coil Also connect to one side of 8910 tach adapter (use splicer in kit to attach directly to red wire)
Black wire: - side of coil
Orange wire: + side of coil
White wire: (green) wire from points, wire from tach (black/purple). (You can fashion a one to two wire adapter or use a splice co! nnector here) Also connect other side of 8910 tach adapter (use splicer in kit to attach directly to white wire)
When attaching these wires, I recommend sticking with the connectors already in place and using jumpers to make the female-to-female connections. In the event of an unlikely failure of the MSD unit, it is a trivial matter to drop back to standard spark but reconnecting the red coil wire (+), green point wire (-), and black/purple tach wire (-) back onto the coil and drive off.
Set Plug Gap, Connections, and Points:
Install your new points and go ahead and set the dwell angle with the old ignition system.
As noted in the MSD installation manual, the gap on your spark plugs should be increased well beyond the normal .028" to around ! .050". My spark plug gap tool only goes to .040" and that seems to work, but you should experiment with gaps up to .060" in .005" increments. Install the new plug tops to match your new spark plug wires too before you reinstall the plugs. Do not over-torque your plugs and ruin your day...
Installing New Spark Cables:
If you are installing new spark cables at this time (and you should), follow the cutting an crimping directions in the kit. Using the MSD wires with their VW air seals, you need to know the tricks to getting these in the holes. First apply silicone dielectric grease to the inside of the connectors, center of the air seals, and, with a Q-tip, to the notch on the bottom of the air seals. Now slide the air seal all the way up the spark plug boot. Connect the boot to the plug, then work the air seal back down the ! boot and work it into the tin hole until it seals all the way around.
Spark plug cables should have good separation, not cross, and stay away from all metal. The use of a few wire spacers are helpful here. New wires are pretty firm and stand up on their own with the wire spacers holding them together/apart.
Install MSD Iginition Decal on Tool Box and Go Drive Car...
Tony Wong (Tony_W@swbell.net) adds the following advice:
I have a comment about this article which is my experiences with running a MSD 6A with a Bosch Blue coil. I killed two MSD units before I figured out that I had sparks arcing from the high tension lead to the trigger of the coil. This burned out my MSD units and gave me different symptoms until I saw the spark jump from the high tension tower to the trigger post.
After my first MSD burned out, I bought the second unit with a set of their 8mm heili core wires. I don't know if it was because of the rubber boots leaking or if the insulation material in the Bosch coil cannot stand the intense firing but, this was not enough to prevent damage to my MSD. I will admit that I did not know about or order the rest of the wire hardware but I know that the only way to stop the arcing was to wrap more insulating material around the high tension tower.
Also, beware of a foggy or high humidity day in which you will definitely get sparks arcing from your coil to the nearest ground. In the future, if I can buy another MSD, I want to use another coil recommended by MSD.
Mike Wadkins adds the following:
Here are some lessons learned from my installation of a MSD unit in a Carrera style car:
I found that mounting the MSD unit was a major chore. The 1985 911 did not have a CD unit and therefore the fuse/relay box did not have an aluminum extension to mount the MSD unit. I asked a few other people for their ideas on alternate places to mount the unit and the only other place that was suggested was on the firewall. To me this was unacceptable since there is sound proofing on the firewall and all of the MSD wires would have to be lengthened. As is, the red power lead must be lengthened to connect it to the starter solenoid on the other side of the car. Additionally, on the 3.2L engine it is very difficult to get to the back engine firewall. Therefore, I removed the ignition coil and proceeded to mount the MSD unit in its place. After looking at the various orientations to mount the unit, there was only one way the unit could be mounted in that area. The MSD unit had to be mounted on its end since there wasnt enough room to mount it horizontally. There is just enough room (top to bottom and side to side) for the unit to fit. Another problem which has to be over come is that the fender wall inside the engine compartment is curved, not flat. Unfortunately, I could only use 3 of the 4 rubber mounts due to the wall being curved. The bottom two rubber mountings had to be put in so that the rubber mount was against the wall and the metal stud from the mount went through the MSD unit. Overall the mounting is the hardest thing to do. If you can get past the mounting issue for the MSD unit itself then you must determine where the coil will go. If you mount it on the fan housing like a 77-79 SC then the engine lid will hit it. Also, the distributor wires will be in the way since they are mounted on outside of the fan housing. My solution was to make a bracket that would hold the coil and mount it to the passenger side of the fan housing. Once these two problems were solved the installation was a breeze. I gapped the spark plugs at .055 and everything seems to work just fine. The car started the first time, and the tach worked just fine. P.S. I installed the tach option but didnt connect it to the Motronic unit. I installed it just in case I had to use it, and just for the record the installation time is greater than 4 hours (Way greater since I had to figure out the MSD and coil mounting problems).