Cloud Car Performance Ignition

The below list represents a collection of commonly asked questions concerning the ignition system. While meant specifically for enthusiasts who drive the Chrysler Sebring Convertible, Chrysler Cirrus, Dodge Stratus, and/or Plymouth Breeze, the concepts presented here can be applied to any vehicle. If you have any further questions about the ignition system, please feel free to e-mail me, and I'll answer, and maybe even put the question into this list.

What does the ignition system do?

The ignition system does two things.

1. The ignition system ignites the fuel/air mixture inside each cylinder inside the engine.
2. The ignition system performs the above at precisely the correct spot at each piston's compression ratio in order to optimize performance and/or economy.

These are pretty basic functions. As you can see, the ignition system is pretty important to an engine's working correctly. On the same note, though, the ignition system is not a hidden resource to tap tons and tons of HP that the factory neglected to enable. Changing out the spark plugs, wires, and distributor components will give approximately 1 HP gain, and modifying the ignition to use a CDI ignition (described below) will get you about another 2 HP on a stock engine. Timing adjustment will release the most power, but even then, you'll see maybe 15 HP gained over a stock engine.

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What the heck is timing, anyway?

Timing refers to firing off the spark plugs while the piston is at a certain point in its compression stroke, measured in degrees before top dead center (BTDC), or more commonly referred to as degrees advance. Timing is necessary, because combustion of the fuel/air mixture is not instantaneous, but depends instead on how much fuel/air mix was drawn into the cylinder during the intake cycle of that piston. Timing is critical to an engine's performance, because it is timing which determines whether an engine will run at all, let alone whether that engine will produce any usable power.

Timing isn't constant, but changes due to engine speed and how much fuel/air mixture has been drawn into each cylinder. Optimally, the timing curve should be set so most of the fuel/air mix will have burned by the time the piston is 12 to 14 degrees after top dead center (ATDC); this will allow the most amount of useful work to be applied to the crankshaft, hence to the wheels. Timing that pushes this point past 14 degrees ATDC lowers power output due to the engine's not being able to utilize all of the available work output, while timing that pushes this point before 12 degrees ATDC wastes some of the available energy by making the piston compress the rising pressure due to combustion.

The stock timing for our clouds is controlled by the powertrain control module (PCM), and is developed off both the crankshaft position sensor output and the camshaft position sensor output. The stock timine curve is optimized to allow our clouds to give adequate performance, good gas mileage, and reasonable durability using the 87 octane gasoline sold at any gas station. The stock curve, unfortunately, doesn't lend itself very well to performance. In fact, the stock curve can be optimized (with a little work) to give at least 10 HP above the engine's normal rating.

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How do I optimize the timing on my ride's engine?

There are two currently known methods of optimizing the timing curve, and both require fine-tuning the timing curve. Fortunately, by the time you see either of these methods applied to your ride, they should already be fine-tuned. Either method should raise the engine's power output to rise by at least 10 HP, and raise torque by about 12 ft-lbf. Both methods require the use of a higher octane gasoline (at least 89 or 91 octane) in order to prevent engine-destroying detonation that would otherwise occur.

The first method involves re-programming the powertrain control module (PCM), the brains behind the engine. This is a costly and risky venture, and does not allow the owner to switch back to the stock curve in order to use the cheaper 87 octane gasoline.

The second method involves using a small microcontroller to intercept the stock ignition pulse coming out of the PCM, and modifying the timing at that point. This method is costly as well, but does not involve risk to the PCM. In addition, this method allows the owner to switch back to 87 octane if desired, simply by bypassing the microcontroller.

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What's this "performance chip" I keep hearing about?

A "performance chip" refers to an aftermarket ignition module that intercepts the stock timing pulse coming out of the powertrain control module (PCM). This module either anticipates the pulse, or delays it, in order to modify the timing curve and performance. Such a module does not store a timing curve as such, but stores timing curve adjustments instead. Typically, the module installs easily enough (if you know how to install a car stereo), and only has 4 wires to hook up. Also, some modules come with either a dial-in or programmable way of changing the timing curve adjustment, so that you may tweak the timing curve to your liking.

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What's this business about RF interference?

Whenever you pass a large current through a wire, you will generate a large magnetic field. Whenever the current changes, such as when ignition current starts to flow or dies off, the magnetic field will also change. Since ignition current only lasts for about 2 milliseconds or so, the magnetic field changes fairly rapidly. This rapid magnetic field change causes radio-frequency interference, or RFI.

RFI is bad for our clouds' powertrain control modules (PCMs), which control the running of our clouds' engines. RFI is known to cause engine mis-fire, and can even cause the PCM to destroy the engine and/or itself. RFI also causes undesirable noise in any vehicle's sound system. FM radio reception may be broken up by a series of pops corresponding to engine RPM, and radio operation in general may be adversely affected due to RFI effects to the tiny computers that control today's radios.

RFI is typically controlled in our clouds by usage of spark plugs and spark plug wires that limit RFI. These components have built-in RFI suppressors which limit the RF noise generated by ignition current. There currently exist two methods of limiting RFI.

Lower quality spark plugs and wires use a purely resistive method of limiting RFI by limiting the ignition current itself. Spark plugs of this nature generally have a large internal resistor, while wires of this type are composed of some carbon-impregnated string. Remember, a strong current generates a strong magnetic field. Therefore, if you weaken the current, you will weaken the magnetic field. This resistive method is excellent for limiting RFI; however, this method also wastes some of the energy of the ignition current, and such components may fail earlier then components with the other RF limiting method described in the next paragraph.

A better method of limiting RFI is to allow the RFI to cancel itself out, while minimizing the suppression of the ignition current itself. This is how higher-quality spark plugs and plug wires handle RFI. Spark plugs using this method utilize an internal wire-wound coil before the electrode, while plug wires of this type are composed of a central wire conductor with another finely wound smaller wire surrounding the center wire. While the ignition current is also affected by this method of RFI suppression, the current is affected to a much smaller degree than with the purely resistive method described above. Also, more of the energy of the ignition current is allowed to go to the combustion chamber than with the resistive method; therefore, there's less chance of such wires and plugs failing prematurely.

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What kinds of spark plug wires are out there?

There are three different types of spark plug wires available for use. There are wires composed of some type of carbon-impregnated string, there are wires that have a fine wire wrapped around a central core, and there are wires that have a solid metal core. All types of wires are generally insulated with some sort of high-temperature silicone rubber, and come with the proper boot connectors on either end.

The solid metal core wire is not recommended for our engines. While these wires will transmit almost all available spark energy from the ignition coil to the engine, these wires will radiate an excessive amount of RFI during use, and will cause the engine's powertrain control module (PCM) to malfunction. This, in turn, will cause erratic engine behavior, and may even destroy either the engine, the PCM, or both.

The carbon-impregnated string core wire is what is found on vehicles that have come straight from the factory. The big benefit of this type of wire is that it's cheap to produce. This type of wire will reduce RFI, but it will also reduce the amount of spark energy available to the engine.

The wire-wound core wire is a better performance wire than the carbon wire described above. Since it uses no carbon, this wire can transmit more spark energy to the engine than the carbon wire can; some name brand wires actually approach the solid core wire in this respect. Also, since the wire-wound core uses a small finely wound core, it is able to provide excellent RFI suppression, and will not cause the PCM to malfunction.

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How important are spark plug wires?

Spark plug wires seem to be the most ignored item in a tune-up, but they are vitally important to an engine's ability to run correctly and give performance. If worn out or internally damaged, plug wires can cause misfire or engine damage, and yet still appear to be visibly undamaged. It is possible for enough RFI to be generated from the firing spark plug wire to actually induce a current in a neighboring spark plug wire, and induce another unintended spark. If the cylinder associated with that unintended spark were to be early in its compression cycle, the fuel/air mix could ignite prematurely, leading to engine wear and damage.

It's also possible for a spark plug wire to develop pinholes, and leak the ignition current to the engine block even before it gets to the spark plug. This will cause misfiring, excessive fuel consumption, a loss of power, and will eventually damage your catalytic converter. This condition is easy enough to diagnose. If you have your ride running at night (or in a darkened garage) and you notice that your spark plug wires appear to glow or spark, you need to replace your spark plug wires.

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I'm going to use replacement stock wires because my mechanic friend says so, okay?

Go right on ahead and use a factory replacement wire set if you want to. It's a free country, right?

After all, for the price of a good aftermarket spark plug wire set that will last a long time and a good spark plug set and a distributor cap and rotor, you can buy just the stock wire set that will: 1. Fall apart in your hands after about 5000 miles of service, and 2. Cause your ride's performance to suffer after about the same mileage has elapsed.

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What do spark plugs do?

Spark plugs are the ignition part that actually generates the spark needed to fire off the fuel/air mixture inside a cylinder. They typically have a carefully measured gap between the center electrode and one or more outer electrodes, which allows the formation of what's known as a spark kernel to form. The spark kernel forms as a result of a large voltage potential difference being formed between the center and outer electrodes. This potential quickly causes the fuel/air mix immediately between the center and outer electrodes to ionize, and allows the ignition current to flow. It is this process that actually ignites the fuel/air mix.

Spark kernel size and strength are directly related to how efficiently the fuel/air mix burns. If the kernel is too small or is too weak (due to shoddy plug wires or ignition components), the fuel/air mix will not burn as completely as it could. This can lead to reduced performance, as well.

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What are the different types of plugs out there?

There are many types of spark plugs available, generally categorized by the center electrode construction. There are also plugs available that have modified outer electrodes, or may have more than one outer electrode. The center electrode can be composed of a number of different metals or alloys.

Traditional spark plugs had center electrodes composed of copper. While copper is an excellent conductor of both heat and electricity, copper is also fairly soft, and tends to erode fairly easily in the combustion chamber of a typical engine. This is the reason why copper plugs generally get replaced every year, or about 10,000 miles.

Initial research into making plugs last longer led to the development of center electrodes composed of a harder copper-nickel-chrome alloy. This alloy resisted erosion of the center electrode better than pure copper, and allowed changing plugs containing such electrodes every 20,000 miles, or two years.

As manufacturing methods improved, platinum center conductors were made possible. Platinum is superior to copper or any copper alloy in resisting erosion, and led to spark plugs that could be changed every 100,000 miles. Platinum's ability to resist electrode erosion also led to the use of smaller center electrodes, which are better at keeping a uniform spark over the life of the spark plug. However, the manufacturing process involved with platinum center electrodes led to spark plugs that cost anywhere from two to six times what a more traditional copper plug would cost.

Lately, plugs containing center electrodes composed of an iridium alloy have been introduced. The iridium alloy resists erosion better than platinum, and allows plugs using the iridium alloy to be changed out every 200,000 miles or so. However, these plugs cost up to 15 times what a traditional copper plug would cost, and up to three times the cost of a platinum plug.

The outer electrode of a spark plug can either be a standard steel alloy, or can have a small platinum disc welded onto the end to better resist erosion. Some plug manufacturers modify the outer electrode shape, or add more than one outer electrode, in order to present a larger spark.

On another note, spark plugs typically have an internal RFI suppression device in line with the center electrode, to limit the generated RFI that can cause engine computers to go nuts. Such devices can either be composed of carbon resistors, or can be made out of tightly coiled wire.

Finally, spark plugs are grouped by what's known as a heat index, which is a measure of the spark plug's ability to shed the heat of combustion off its center electrode. "Hotter" spark plugs generally heat up faster than normal plugs, and are used in older engines where spark plug fouling by oil or gasoline additives are a concern. "Colder" spark plugs heat up more slowly, and are used in engines that are turbo/supercharged, or have some form of nitrous oxide delivery. "Colder" plugs are used in these engines to prevent preignition and detonation, which can otherwise quickly destroy an engine. However, the use of a plug that is "too cold" is discouraged, because use of that plug will lead to that plug's not being able to become hot enough to clean itself of deposits, and will lead to mis-firing and reduced power.

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What about the spark plug heat range or index?

The spark plug heat range, or heat index, refers to the ability of the spark plug to cool itself off while inside a running engine. It is important to have a spark plug set with the correct heat index, because this allows the spark plug to become hot enough to clean itself of combustion deposits, while remaining cool enough to prevent preignition of the fuel/air mixture entering the combustion chamber.

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Do I need to change my engine's spark plug heat index if I modify my engine?

It depends on what you did to your engine. Generally speaking, engines that have not had their compression ratios changed (as a result of piston/head work, turbo/supercharging, or nitrous oxide injection) should not need have a switch to a plug with a colder heat index, nor should the plugs on that engine need to be gapped smaller than stock. Typical mods that don't require spark plug heat index changes include installation of headers, a cat-back system or free-flowing muffler, head porting, and intake induction improvements.

Mods that require switching to a colder heat index include super/turbocharging, nitrous oxide injection, piston changes, or head work that raises the compression ratio. Generally speaking, for every 75 HP gain, you should go one heat index colder. Hotter spark plugs are not recommended unless you're experiencing severe spark plug oil or fuel fouling.

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I've heard that copper is better than platinum. Is this true?

No. The myth that "copper is better than platinum" probably came about after somebody noticed that a platinum conductor has about 10 times the resistance of an equivalent copper conductor, and used this to justify not spending the extra money to purchase platinum spark plugs. Worse yet, at least one spark plug manufacturer seems to be deliberately trying to perpetrate this idiotic myth in an effort to maintain cash flow by selling more copper alloy plugs than platinum plugs. This plug manufacturer artificially raises the resistance of its platinum plug by using a larger RFI suppressor than what this plug maker uses in its copper alloy plug. Think about it: If this certain plug manufacturer champions this sales strategy by selling its platinum plugs (which are changed every 100,000) miles at $2.99 apiece, and selling its copper alloy plugs (changed every 20,000 miles) at $1.19 apiece, that plug maker can sell 5 copper plugs at $5.95, over selling 1 platinum plug at $2.99, over the same mileage interval of 100,000 miles. Since it cost pennies for that manufacture to actually make these plugs, the profit margin become pretty large when you multiply that example by a few million cars.

The truth is, while a platinum conductor has about 10 times the resistance of an equivalent copper conductor, this is irrelevant where spark plugs are concerned. If you were able to measure the resistance of the center conductor by itself, without the RFI suppressor, you would find that the copper alloy electrode would measure about 0.00008 ohms, and the platinum electrode would measure about 0.0004 ohms. Compare these resistances with the resistance of a carbon resistor RFI suppressor (50,000 ohms) or a wire-wound RFI suppressor (3700 ohms), and you'll quickly see how irrelevant electrode resistance is. Below is a table comparing spark plugs made by two popular aftermarket companies. See if you can determine which company uses a wire-wound or carbon resistor RFI suppressor.

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I've heard that iridium plugs are the absolute best plug out there. Is this true?

Again, not really. Iridium plugs are advertised as having about half the resistance of platinum, while lasting about twice as long. Such plugs also are advertised as having overall better performance, while requiring less voltage to fire off. This may very well be a good thing, but not at three or more times the cost of otherwise similar platinum plugs. The performance and voltage benefits can be realized using a better set of spark plug wires, than what came stock from the factory.

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Can I upgrade the rest of the ignition system?

Sure, it's possible. However, unless you're planning on turbo- or supercharging your ride, or if you plan on using a nitrous oxide system, it's really not necessary. One exception, of course, is if your distributor breaks electrically. Odds are, the camshaft position sensor internal to the distributor is still functional, but the integral ignition coil and transistor switch that fires that coil may have gone bye-bye. In this case, you may want to upgrade at least the ignition coil and switch for about $120 in parts, compared to the $700 replacement cost for a new distributor.

Since our rides have a distributor with an internal coil, upgrading the ignition system can seem to be a formidable challenge. However, it's quite easy if you're mechanically competent, and you have a little bit of knowledge on how to solder electronic parts together.

A popular addition to upgrading the coil is to also upgrade the method of ignition current formation. Our rides use what is called an inductive discharge ignition, which is so called because the ignition voltage potential needed to fire the spark plugs is formed as a result of taking away the battery voltage from the stock ignition coil. Capacitive discharge ignitions (CDIs) use a large capacitor, rapidly charged to about 400-500 volts, which is then quickly discharged to the ignition coil. While this quickens spark formation, some CDIs generate a fairly weak spark.

A variation on this idea is to have the CDI fire the spark plug multiple times per timing pulse. CDI systems of this nature have up to six capacitors which discharge in sequence to the ignition coil. This allows for more complete and reliable spark formation, and will ignite the fuel/air mix for a heavily turbo/super/nitrous charged ride.

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I want to have the ignition system parts you have. Where do I get them?

I got the replacement distributor cap and rotor from my dealer; however, you should be able to get the same cap and rotor from any major auto parts store by now. I got the hardware to modify the distributor cap to accept an external coil, as well as the external coil and CDI ignition from Autotronic Controls Corporation. I used the Blaster 3 coil, and the MSD 6AL ignition module. Any reputable local speed shop should carry these parts. You can also go to Summit Auto Racing to get these items.

I made the transistor switch by myself. Most of the parts can be bought at RadioShack; however, the actual transistor was purchased at a local TV/VCR repair shop, since the RadioShack transistor proved to be incapable of lasting more than one week.

Instructions for making both the modified distributor cap and the transistor switch may be found at this link. Alternately, you can contact me and I will sell you completely assembled modified distributor caps and transistor switches (also referred to as ignition amplifiers).

I made the CCPM, my current ignition module, from a microcontroller kit found on the Internet, and wrote the code to make it work. I eventually plan on selling CCPMs, but I'm currently working out the rough parts. I got my old performance ignition module, the SuperChips ICON, from Performance Ford, from this section. The ICON normally sells for $395 plus shipping, but Performance Ford will sell the same item for $355 plus shipping, instead. If you do decide to order this part, and you have a 2000 model year cloud, ensure you place the order to a 1999 model year or earlier cloud instead. It'll save you about a month and a half wait for the ICON. Keep in mind also that SuperChips has discontinued the production of the ICON, so they'll be harder and harder to find.

Any local AutoZone should carry both the Bosch Platinum +4 spark plugs and the Bosch Premium Spark Plug Wire Set (P/N: 09827).

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