The morphing of state-of-the-art electronics into today's performance vehicles keeps getting better all the time. And in case you're confused as to what magazine you're reading, we're not referring to the latest mega-watt amp and 200-CD changer.
Instead, we in the SUPER CHEVY Gearhead department are referring to the new, state-of-the-art, fully programmable digital multi-coil ignition system from MSD. With this distributorless ignition package, you can take advantage of today's engine management technology and retrofit it to those classic engines that we all love to build. But wait, there's more to this system than simply removing the distributor and connecting a single coil pack to each spark plug. For those cases where superchargers, turbos, high-compression pistons, and multi-stage nitrous oxide systems are used, this technology can help shape the power output you need to take your car to the finish line ahead of the competition, or blow the doors off of the car sitting next to you.
Recently we installed one of MSD's Digital CPC systems on the test engine used on the Vrbancic Brothers Racing DTS engine dyno in Ontario, California. While we could literally write an entire book on the capabilities of this MSD system, and likewise spend hours exploring its tuning potential, the focus of this story was to show the installation process and describe some of the unit's tuning highlights.
First, why a distributorless, coil-per-cylinder ignition you ask? Well, one reason is consistency. Eliminating the engine's distributor bypasses the traditional mechanical link of firing the engine's cylinders. You eliminate the harmonics associated with a distributor being linked through the cam to the timing chain, having cam movement cause timing flutter, gear mesh and all the flexing that takes place between the rotating assembly that is ultimately transferred to the distributor shaft, and thus, the rotor.
Accordingly, a Flying Magnet crank trigger system is used in conjunction with the Digital CPC to trigger the spark to the plugs. The crank trigger is race-proven and highly efficient, and you'll find similarly designed systems being used with most of today's OEM multi-coil setups. The MSD unit uses an aluminum wheel, which houses four small magnets that pass by a non-magnetic stationary pickup. This signals the computer to fire each coil and provides the spark to create combustion.
In addition to the crank trigger and eight single coils-one for each cylinder-the CPC system includes a system controller, an ignition control, a sync distributor plug (also known as a dummy shaft, which is needed to drive the oil pump), and all of the wiring harnesses required to link the system together. All parts are top quality and the instructions map out all of the details associated with installing and setting up the system pretty well.
Perhaps the biggest part of the job was mounting the coils. With each application offering a different set of mounting circumstances, MSD leaves the coil mounting up to us. In our case, George Vrbancic came up with a great idea: pieces of threaded rods and a few nuts and washers. Each coil was placed on the rod at a strategic spot and a nut and washer was threaded along both the rods on each side of the coil. This allowed George to position the coil where he wanted it and then tighten the nuts to keep it in place. From there, he added old wire loom brackets to each end of the rods and attached them to the front and back ends of each head. With the coils spaced accordingly, a short MSD 8.5mm plug wire was attached between the coil and the plug. A clean installation, indeed!
Since we were running the setup on a dyno engine, finding a place for the two ignition "brains" was simple. In a real world setting, you'll have to locate space on an inner fender panel or core support to mount the boxes.
As noted, installation of the equipment is rather basic, however, setting up the engine to "dial-in" the system is a little more complicated. First thing is to set the timing. The instructions describe the distributor plug's purpose, which is to provide a cam synch to the computer. This signal must be phased in roughly 22 degrees before the maximum timing setting of the engine. To do this correctly, the CPC system, including the crank trigger, should be in place and wired.
Setting up the crank trigger requires positioning the number one cylinder on the compression stroke, at the desired maximum timing (say 36 degrees). Next you must add an additional 4 degrees to offset the CPC's built-in timing compensation circuit. (Tabulating our example, you'd have 40 degrees of advance at the trigger.) With the crank trigger and pickup aligned and tightened down, at this point you will back up the engine and add another 22 degrees of advance. This is the approximate lead of the cam synch sensor and will put you right in the neighborhood of getting the engine to fire.
On our test engine, we played with this for a little while before the engine fired. We came to find out that we hadn't programmed the engine's firing order into the program on our PC, so despite having set up the mechanical hookups correctly, the engine still popped and backfired as we tried to start it. (I guess we hot rodders still have a way to go before we're fully computer literate.)
With the computer set and all of the components in place, our 468-inch test Rat came to life and idled smoothly. At this stage, we were ready to start pushing buttons on the PC's keyboard.
As pointed out earlier, tuning the MSD CPC has infinite possibilities. Since our test centered mainly around creating a smooth transition from the distributor to CPC systems, we didn't spend a lot of time changing the setups. We did, however, do a baseline dyno test with the conventional timing and then again with the initial CPC timing. Results were an instant increase of 7 ft-lb of torque and 3 hp.
Not stunning numbers, just an indication of the high-output accuracy and programming control possible with the CPC ignition system. Furthermore, it was an indication of just how easy it would be to fully tune as much performance out of a specific engine as possible. With individual cylinder timing matched with a fuel-injected, supercharged engine, it's easy to see how playing with the computer to put in or take out timing where it was needed most would have a positive effect on squeezing out every last pony.
Once again, this was just a scratch on the surface of the capabilities of the MSD digital coil-per-cylinder ignition system. As we studied the software further, it was apparent that the ability for the user to program such things as an electronic timing curve; an advance that correlates to the engine's vacuum (just like conventional vacuum advance); a launch timing curve for use on the dragstrip; a boost timing curve that will (with the optional MAP sensor) control the timing in relationship to the supercharger's boost; a multi-step retard that can be activated by either engine speed or a separate wire; gear rpm and retards, which allow for a different shift point for each gear in addition to a separate retard for each gear change; and a set of three different rev limits in 100-rpm increments.
While this high-end ignition system isn't for the average grocery-getter, it does offer complete engine ignition management for those applications that see more than one type of use. And, for non-normally aspirated situations, the ability to tweak the combination for maximum performance is worth the price of admission.