If you’re presented with a situation in your racecar where you’re chasing a miss, it’s certainly not out of the question to consider the ignition box, coil and distributor as the big culprits. But it’s been my experience that the first place to look is the spark plugs and the ignition wires. You see, years ago – in the prehistoric racing era – before high power digital ignition and optically triggered distributors became available, we were often faced with the same issues. Except way back then, they’d actually manifest themselves in short order. You’d go straight to the spark plugs and the wires. Today, with big ignition power available, it’s easy to overlook the obvious.
While spark plugs aren’t a big part of the discussion here, it’s still a really good idea to replace them on a regular basis. Ditto with spark plug wires – they’re definitely maintenance items. Today, plug wires that are capable of suppressing electro-magnetic interference are pretty much mandatory on a racecar. The reason is the cars are filled with sensitive electronics (ignition boxes, various controllers, data acquisition and so on). The best wires for this sort of application are those that include a spiral wound core. When you’re shopping for spiral core wires, the amount of resistance is a consideration. But before you jump right in and start testing wires and reading claims about “this wire has the lowest resistance”, keep this in mind: When you check the resistance of a piece of ignition wire on the workbench, that doesn’t mean that piece of wire is perfect in your race car. In the car, wires have to snake around header tubes, in and around chassis pipe and so on.
As Crane notes, “the most important function of spark plug wire is to transfer the maximum amount of energy to the plugs”. Typically, something like the Crane FireWire® shown in the accompanying photos accomplishes this with ease. These wires have a resistance rating of 25 ohms (remember though that the length of the wire has a bearing upon resistance). They’re designed to filter out RFI and EMI “noise” generated by today’s high-output ignition systems. This protects the on-board electronics we mentioned earlier. The wires are manufactured with an 8.5-mm pure silicone double-layer shell that resists the effects of high under hood temperatures and insulation breakdown cause by abrasion. Pure silicone boots are rated to 550 degrees (F).
You can also purchase Crane’s Firewire pre-sleeved. Here, the wires comes protectively encased with a Kevlar®-reinforced braided fiberglass mesh. This provides protection against abrasion and extreme heat in environments up to 1200° (F). The Sleeved FireWire® comes in over and under valve cover sets for both small block and big block universal applications. Pre-terminated custom sets or universal cut-to-fit sets are also available.
So far so good, but something else that seems to be lost today is the need for good engine grounds (more than just an aluminum motor plate or solid motor mounts). The spark plugs in the engine must be grounded in order to complete the electrical circuit. If they aren’t, then the spark from the ignition system will seek the path of less resistance. That’s where the engine ground strap(s) come into play. Keep in mind that a basic ground strap bolted to the engine block may not be sufficient. Things like the head gasket and cylinder head bolt sealant can actually provide a means of insulating the heads from the ground. The solution is to ground the cylinder heads (both of them) directly to the frame.
So far so good, but what about the coil? The coil should be matched to the ignition system. When it comes to the Crane digital ignition boxes we covered in past segments of this series, Crane’s PS92N coil is the right piece. A step up from canister-type coils, the PS92N is based upon a high output E-core configuration that’s well suited for racing or street use. They deliver 70-100% more spark energy than stock or other aftermarket coils. The E-core design incorporates a closed magnetic path that reduces leakage and improves energy transfer. Crane notes the coil features a lightweight aluminum bracket along with an exposed core for cooling and is safe for harsh vibrations and high-energy breakdown. Note too that the mount is designed with finned aluminum on each side. The idea here is to dissipate heat (and yes, coils can get hot in a hurry).
As you can see, there’s a whole bunch more to ignition systems than meets the eye. There are a lot of options out there, more than a wee bit of snake oil and plenty of over-the-top claims. The bottom line here is, when you invest in an ignition system for your racecar, reliable, well proven piece will always get the job done. Enough said.