Ignition systems are a bit of a mystery for many people. You can't really see what's going on inside the wires and transistors. Most of which is covered in a black box.
There are several companies out there that are producing self-contained ignition systems. MSD, Jacobs Electronics, D.E.I. and Accel just to name a few. Many of these kits cost well over $200. Many don't even come with everything that's required to take advantage of the unit. (For example most will require performance spark plug cables)
There are two ways that have been used to increase spark. One way is to just amplify the current sent to the spark plugs. Another way is to send a chain of sparks. Also some companies use a combination of both.
There are also two different way's they go about this. Some companies use a seperate stand alone box that replaces the stock ignition while others use a stock coil that has been modified to run 'Hot'. The stand alone kits require a bit more wiring and can be finiky at times. They also take up a bit of room but are usually sealed so mounting them low isn't a problem.
Performance Distributors went with a modified stock set up. Their kits are very complete and inexpensive, too. What you get is a new Distributor cap, Rotor, Modifed Coil, Firepower Spark plug and coil cables and some Billet Aluminum cable retainers. It's nice to see a new rotor and distributor cap come with the kit for once. The coil looks exactly like the stock unit and will uses the existing bracket. The spark plug cables are huge in comparson to the stock cables. Not only do the cables use a silicon jacket but they also have a abrasion shield. Not to mention they are numbered for each cylinder! (They also come in your choice of colors!)
The cables will not fit into the stock retainer so that can be removed. Two studs on the valve cover hold it on. The coil can be a bit of a pain to get to. It sits next to the starter on the passenger side of the engine. (If your engine's dirty, it might be a good time to clean it up some.) Replacing the distributor cap and rotor are a snap. (Beware that there are two different types of rotors for the TJ and the YJ. Make sure you get the right one.) Since the cables are all numbered they are easily routed to the correct cylinders. Just make sure you get the firing order correct (1324). The only thing the PD kit doesn't come with are new spark plugs. For our project PD suppiled us with Autolite Spark Plugs. These were pregapped from PD to .065". (For comparison, the stock gap is .035".) The larger gap will make for a nice big spark if it's able to jump it. Two billet aluminum retainers are a nice touch. They are very easy to install and look nice. There are only two since the coil cable can stands alone and out of the way. Basically, that's all there is to the kit.
ConclusionFirst off, I will say, I had a hand in helped PD develop this kit for the 2.5L. It all started with a simple email asking which spark plug boot had a bend in it. Then it all snowballed from there. When the first parts started rolling in I found that the #1 cable boot was a bit short and wouldn't clip onto the end of the sparkplug without some force. The boot would then rest against the head of the engine which wasn't good. Steve, the president of the company, listened to my recommendation and quickly ordered the new boot from his supplied and sent out a new test cable. This one worked prefectly. The only other problem I had was with the rotor. At first I was sent one that turns out was what the TJ required. (This was all new stuff since no one checks to compare rotors between models) Again Steve knew exactly what was needed and had it sent out.
Previously, the Jeep had a Jacobs Electronic Omni-Pak. One of the originals when they first came out in 1994. The spark plug cables were replaced with MSD 8mm with the silicone jacket. The stock boots at the spark plug end were reused. The spark plugs were Accel U-Groove performance plugs gapped at .055". With this setup the engine ran pretty good. With the PD kit, all that was replaced.
For the test drive, was a 300 mile stretch of I-5 that runs between San Francisco and Los Angeles. This stretch of road has some steep hills, rolling hils and flat lands too. The baseline was set with the Jacobs. The only other differenece between the two trips was that the conical K&N filter was replaced with the stock air box and off the shelf Fram paper air filter. If anything the PD would have it's work cut out for it.
Here are some imediate differences. The engine seemed to have a bit more low end torque and smoothed out at the high end. Running at 3000 rpm at 70 mph the engine had a rythm as each cylinder went through it's cycle. I could count as the cylinders fired off in the Power stroke. It sounded similar to a floor waxer actually. With the PD ignition, all that disappeared as it was a more uniform hum.
The biggest problem with this stretch of road is that the slow lane has a minimum speed of 70 mph while the fast lane is usually around 80-90 mph. In the Jeep, it's either 4th gear @ 3000 rpm or 5th gear at @ 2400 rpm. With those gears, the Jeep would be doing 65-70 mph. With the Jacobs the top speed was around 75 mph in 4th with the engine screaming. Shifting to fifth was no help since the rpm's dropped and the speed would quickly drop to 60-65 mph. With the PD though, the engine smoothed out at 4000 rpm and could be driven fast enough to get 5th near 3000 rpms for crusing. This was impossable with the Jacobs.
