The best ignition coils for the Mazda RX-8 in New Zealand depend on your performance goals and budget. For maximum reliability and spark strength, the LS (D585) Coil Conversion Kit is the superior choice, offering higher voltage and heat resistance than stock units. However, for unmodified daily drivers, Genuine Mazda “Rev-C” OEM coils remain a viable option if replaced every 30,000 kilometers.
Introduction: The Achilles Heel of the Renesis
If you own a Mazda RX-8 in New Zealand, you are likely intimately familiar with the anxiety of a hot start. The Renesis 13B-MSP rotary engine is a marvel of engineering, but it is plagued by a notoriously weak ignition system. Unlike piston engines, the rotary engine fires three times per output shaft revolution, meaning the ignition coils work significantly harder and hotter than those in a standard vehicle. Combined with the confined heat of the engine bay, this creates a perfect storm for component failure.
For Kiwi enthusiasts looking to preserve their engine’s compression and catalytic converter, choosing the best ignition coils for RX8 NZ is not just a maintenance task—it is an investment in the car’s survival. This guide compares the factory Original Equipment Manufacturer (OEM) setup against the popular LS (General Motors D585) conversion to help you decide where to spend your money.
The Weakness of Stock Mazda Coils
To understand why upgrades are necessary, we must first analyze why the factory components fail. Mazda’s original ignition coils (specifically the early revisions) were insufficient for the demands of the Renesis engine.
Why Do OEM Coils Fail?
The primary issue is heat and dwell time. The stock coils are mounted directly to the engine block on a bracket that acts as a heat sink. Over time, the intense heat cycles cause the internal insulation of the coil to break down. Once this insulation is compromised, the high-voltage electricity looks for the path of least resistance, which often results in it arcing to the mounting bracket rather than traveling to the spark plug.
This failure manifests as the infamous “white spot” found on the bottom of used coils. When a coil fails, it leads to misfires. In a rotary, a misfire dumps unburnt fuel into the exhaust, which destroys the catalytic converter (a very expensive replacement in NZ) and washes the oil film off the rotor housings, leading to rapid compression loss.
The “Rev-C” Update
Mazda eventually released the “Rev-C” coil (part number N3H1-18-100C), which is significantly more durable than the original Rev-A and Rev-B units. While these are an improvement, seasoned rotary mechanics in Auckland and Christchurch still recommend treating them as a consumable item, requiring replacement every 30,000 to 50,000 kilometers to ensure engine safety.
The Solution: LS (D585) Conversion Kits
Enter the LS coil. Originally designed for General Motors V8 trucks (like the Yukon and Silverado), the D585 coil (often referred to as the Yukon coil) has become the gold standard for RX-8 ignition upgrades.
What Makes LS Coils Better?
The D585 coil is a beast compared to the stock Mazda unit. It is physically larger, has a built-in heat sink, and is designed to deliver a much stronger spark. More importantly, it can handle higher dwell times (the time the coil charges before firing) without overheating.
A stronger spark ensures a more complete combustion of the fuel-air mixture within the long, flat combustion chamber of the rotary engine. This results in smoother idling, slightly better fuel economy (a rarity for RX-8s), and a noticeable improvement in top-end power.
Pros and Cons: LS vs. OEM
When searching for the best ignition coils for RX8 NZ, you must weigh the benefits against the drawbacks. Here is a commercial breakdown.
OEM Mazda Coils (Rev-C)
Pros:
- Plug and Play: No modifications required. They fit the stock bracket and plug directly into the factory harness.
- Cost: Generally cheaper upfront than a full conversion kit.
- Simplicity: No need to worry about dwell settings or aftermarket bracket fitment.
Cons:
- Lifespan: Short service life (30k – 50k km).
- Performance: Weaker spark energy compared to LS coils.
- Risk: High failure rate can lead to catastrophic engine damage if not monitored.
LS Coil Conversion (D585)
Pros:
- Durability: These coils are nearly bulletproof and can last the lifetime of the engine.
- Performance: significantly higher voltage output ensures complete combustion.
- Heat Management: Mounted on a custom bracket (usually lifted slightly off the engine) and equipped with external heat sinks.
- Availability: GM coils are widely available globally.
Cons:
- Initial Cost: A high-quality kit (coils, bracket, harness, leads) is expensive.
- Installation: Requires a custom bracket and adapter harness.
- Fake Parts: The market is flooded with cheap, counterfeit D585 coils that perform worse than stock.
BHR vs. Generic Kits: What to Buy in NZ
If you decide to go the LS route, the brand of the kit matters immensely. In the global RX-8 community, Black Halo Racing (BHR) is considered the benchmark. However, sourcing these in New Zealand involves shipping costs and import taxes.
The BHR Standard
Black Halo Racing kits use genuine, globally sourced coils and a proprietary wiring harness that is unmatched in quality. They are plug-and-play and require no dwell tuning. For a Kiwi owner who wants “install and forget” reliability, importing a BHR kit is often worth the premium.
Generic and eBay Kits
A search for “RX8 ignition coils” on TradeMe or eBay will yield dozens of unbranded LS conversion kits for half the price of BHR. Avoid these.
Most generic kits use “fake” D585 coils. These knock-offs often lack the internal circuitry to handle the high RPM signal of the rotary engine, leading to high-RPM breakup (misfires above 6,000 RPM). Furthermore, the wiring harnesses in cheap kits often use thin-gauge wire that cannot handle the current draw, leading to voltage drop and weak spark.
Sourcing in New Zealand
For New Zealanders, the best approach is:
- Import BHR: Pay the duty and get the best.
- Bennetts Motor World or Rotorsport: Check with reputable local rotary specialists. They often stock high-quality conversion kits (like Ryan Rotary Performance or locally fabricated options using Genuine AC Delco coils).
- Build Your Own: If you are handy, you can buy Genuine AC Delco D585 coils from a GM parts supplier, buy a bracket and harness adapter from a reputable performance shop, and assemble it.
Installation Complexity and Tuning
One of the main hesitations for switching to LS coils is the installation process. Fortunately, for the RX-8, this is a relatively straightforward DIY job.
The Physical Install
The LS coils are physically larger than the OEM units, so they cannot fit in the stock location without a specialized bracket. Conversion kits come with a bracket that bolts into the stock location but spaces the coils out appropriately. You will need to remove the air box and intake hose to access the coils. It is a tight squeeze, especially near the firewall, but manageable with standard hand tools.
The Wiring Harness
The LS coils use a different connector than the Mazda harness. A conversion kit includes an adapter harness. One end plugs into the factory Mazda coil connectors, and the other end plugs into the new LS coils. Crucial Tip: Ensure the ground wire on the harness is bolted to a clean, unpainted metal surface on the engine block. Poor grounding is the #1 cause of issues with LS conversions.
Spark Plug Wires
Because the LS coils have a different terminal post, you cannot use stock spark plug wires. You must use the custom wires provided in the kit (usually 10mm wires) which are terminated specifically for the D585 coil on one end and the NGK spark plug on the other.
Dwell Tuning?
A common myth is that you must tune the ECU for LS coils. While the D585 coils can handle higher dwell settings to produce an even stronger spark, they function perfectly fine on the stock Mazda ECU map. They will simply run at a lower duty cycle than their maximum potential, which actually contributes to their longevity. Tuning is optional but recommended for those seeking maximum performance.
Maintenance and Longevity
Once installed, how do the two options compare over the long haul?
OEM Maintenance Schedule
If you stick with OEM Rev-C coils, you must adopt a strict testing regimen. Every 10,000km (or every oil change), you should inspect the bottom of the coils for white spots. You should also use an HEI spark tester to verify the spark remains blue and snaps loudly. Plan to replace them every 30,000km to be safe.
LS Conversion Maintenance
A genuine LS coil setup is virtually maintenance-free regarding the coils themselves. They rarely fail. However, because they deliver such a strong spark, they can accelerate the wear on your spark plugs. You should continue to check your NGK spark plugs (Leading and Trailing) regularly. The spark plug wires should also be inspected for heat damage, as the rotary engine bay gets extremely hot.
Final Verdict for NZ Owners
So, what are the best ignition coils for RX8 NZ?
- Best Overall Value & Performance: The LS (D585) Conversion Kit. While the upfront cost is higher (approx. $600-$900 NZD for a quality kit), the longevity and peace of mind are unmatched. You eliminate the single most common failure point of the Renesis engine.
- Best for Purists/Budget: Genuine Mazda Rev-C Coils. If you cannot afford the upfront cost of a conversion, or if you want to keep the engine bay looking 100% factory, these are acceptable. However, do not buy “OEM style” aftermarket coils from auto parts stores; buy Genuine Mazda only. The generic replacements are often worse than used stock coils.
For the New Zealand market, where protecting the engine is paramount due to the scarcity of rebuild parts, the LS conversion is widely regarded as the smartest insurance policy you can buy for your RX-8.
People Also Ask
How do I know if my RX-8 coils are bad?
Common symptoms include difficulty starting the engine when hot, rough idling, a flashing Check Engine Light (misfire code), and a loss of power at high RPMs. You may also see white burn marks on the bottom of the coils.
Do LS coils add horsepower to an RX-8?
LS coils themselves do not “add” horsepower in the traditional sense, but they restore lost power by ensuring complete combustion. They prevent high-RPM spark blowout, allowing the engine to pull smoothly to the redline, which feels like a power gain.
Can I use cheap eBay coils on my RX-8?
No. Cheap unbranded coils often fail within weeks and can cause engine misfires that destroy your catalytic converter and engine bearings. Always stick to Genuine Mazda or reputable branded conversion kits.
How often should I change spark plugs on an RX-8?
It is recommended to change spark plugs every 15,000 to 20,000 kilometers. Rotary engines consume spark plugs faster than piston engines, and worn plugs can stress your ignition coils.
What is the difference between Rev-B and Rev-C coils?
Rev-C coils (N3H1-18-100C) are the updated version from Mazda with improved internal insulation to prevent arcing. Rev-B coils were prone to premature failure and should be replaced.
Where can I buy BHR coils in New Zealand?
Black Halo Racing (BHR) coils usually need to be imported directly from the USA. However, some specialized rotary workshops in NZ may stock them or high-quality equivalents like Ryan Rotary Performance kits.
