Now that you've read the "Ignition Box Comparo" story, you may just have the Itch to Hang one on your ride.
Most of the aftermarket upgrades can be described generically as an ignition installation basically the same way, and can be made to work on pretty much any engine with a distributor. Most of the manufacturers have the ignition installation down to a plug-on proposition by offering specific wiring adapters for all the popular OE ignition types. Beyond that, ignition installation varies depending on the features built into the unit. Here we'll show you some of the features tied into the all-new MSD Digital-6 Plus, a Car Craft scoop on a product that will be introduced in November '98.
Electronic Distributor? Why Digital?
What's the big deal? For today's ignition manufacturers, "digital" is the hot sell-word. In MSD's case, the digital versions include a high-speed RISC (Reduced Instruction Set Code) microcontroller, unlike the analog units like the MSD 6A. The digital components are much smaller, so more features can be packed into a box of the same size, and the circuitry is more accurate and reliable. However, the power side of the MSD is still capacitive discharge. That means electrical energy is stored inside the MSD, then quickly forced into the coil for each spark. The result is a nastier spark. Another bonus is faster cycling and a longer duration spark. The MSD releases a series of sparks per plug firing below about 3,300 rpm-above that engine speed there is only one full-power spark. Also, the Digital-6 has more power than the 6A, with 520-535 volts to the coil and 135 millijoules of spark energy.
It'll speed your ignition installation a ton if you understand what each wire from the electronic distributor ignition box does. While colors change from manufacturer to manufacturer, and options also vary, the function of each wire on the new MSD are pretty similar to those of other ignitions.
A. Power leads: One red and one black 12-gauge wire hook directly to the battery. Because the MSD electronic distributor draws power right from the battery, you don't need to remove OE ballast resistors or resistor wires in the stock wiring harness.
B. Red: Connect this to a wire that's hot when the key is turned to the "ON" position (for example, the wire that was originally on the positive side of the coil). The red wire turns the MSD on and off.
C. Orange and Black: This orange wire is the only wire that will be attached to the positive side of the coil when the installation is done, and the black is the only wire that will be on the negative side.
D. Violet and Green: These wires go to the mag pick-up connector from an electronic distributor-the MSD includes a harness to plug these directly into an MSD distributor, and no other amplifier is needed. Violet is positive, green is negative. When the violet and green wires are connected, do not use the white wire.
E. White: Just as the violet and green wires tell the MSD when to fire based on input from an electronic distributor, the white wire is the trigger wire for use with points or an OE-style electronic ignition amplifier. When the white wire is used, never hook up the violet and green wires.
F. Blue: This activates the two-step rev limiter. When 12 volts are applied to this wire, the low-rpm rev limiter is activated. It's usually hooked to the Line/Loc circuit. When this wire is not triggered, the high-rpm rev limiter is active.
G. Pink: When 12 volts are present at this wire, the single-step timing retard is activated. This is usually triggered by the same power wire that turns on the nitrous solenoids or a Hobbs switch that's tapped into boost pressure.
F. Green loop: The MSD Digital-6 comes prepped for use with GM or MSD crank triggers. If an MSD distributor or Ford distributor is used, this wire needs to be cut and sealed.
Extra Stuff You'll Need
Any schmoe can install a hot ignition on a musclecar-era street machine in about an hour. Add 15 minutes per model year for every year newer than '75. That can add up to a day's worth of hassle on a late-model car, with much of the time spent finding a place to mount the box. Regardless of the car type, have the following on hand to minimize aggravation:
• Normal handtools
• A drill and bit selection; the MSD electronic distributor re-quires an 1/8-inch bit, or 3/16 if you're using the included rubber feet.
• A test light, or preferably a volt/ohm meter to find the hot wires.
• Spare wiring supplies, including nonin-sulated connectors, shrink-wrap tubing, electrical tape, adel clamps, grommets, and wire ties. To lengthen any wire from the ignition box you should usually use wire one size bigger. So if the wire is 12-gauge, use 10-gauge.
• Soldering gun and solder. Opinions differ, but we prefer soldering and heat-shrinking to crimp-connectors any day.
• If your underhood area is short on flat spaces to mount the box, you may need to fabricate a custom mounting bracket with hardware store sheet-metal.
• Aftermarket ignition may require an adapter to make the tachs operate properly on some cars. Read the instructions before you start the installation so you can find out everything you need.
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