Ignition System

Spark Plugs

Ignition System

Splitfire Direct Ignition System

[3/10/2005] Reviewed by: emilio

Applicable to: '99 +

Replaces factory coil pack and high tension (sparkplug) wires

Good so far. Just put it on. Instructions in English are easy to follow. Super simple install and easily reversible. Seems to run a tad smoother but that might be my imagination. Idle droop is still there but I suspect my intake manifold is carboned up and causing that. The hardest part was getting at the mounting bolts for the old coild to take it off. It's nice to have that space behind the head opened up to service other items.

Looks very cool. Still easy to pull plugs for inspection. Timing lights that have an inductive pickup won't work since there's no external wire to clip onto. Planning on a JRSC so I'm hoping this will help control detonation and allow me to run a bit more advance. Clears the OE shock tower brace but some very low pro ones might be closer.

Under 30 minutes to remove completely

Spark Plugs

[2/1/2000] Reviewed by Jay Bell - morganmiata@miatadriver.com

Applicable to '90 - '97 1.6 liter

Splitfire Spark Plugs

After installing my 3rd set of these plugs it became very clear that this was an inferior product and that the manufacturers claims were completely bogus garbage. In fact they did anything but increase the performance when three of the four literally fell to bits inside the motor costing me a lot of head work and engine cleaning. A basic rebuild on the motor after all was said and done just to make sure that all of the little metal bits were out of the block.

I would recomend imediate removal if you have them installed and go back with either NGK or BOSCH PLATINUMS.

Under 5 minutes to remove

Reviewed by: John Daeschner - sugarmsc@swbell.net

I have nothing positive to say about this product, I believe that the technical performance claims are eroneous - to use no stronger language. I think the performance of your ignition system has more to do with the electronics than the plugs. I did install Bosch platinum plugs long before the Split Fire's were "worn out" and noticed, to my surprise, that the idle was smoother. I will stick with Bosch as I have had good experience with them in the past. I think the Split Fire's are a gimick and if they were less expensive, NO ONE WOULD BUY THEM!

Sometimes you don't get what you pay for - that old adage will sometimes cost you.

Reviewed by: Jim Creer - ojcreer@groupz.net

These are the plugs with the split tip and increased performance claims.

They did not perform in my 1990 Miata.

After installing new Splitfires and new plug wires I immediately experienced mis-fires at idle, acceleration, and cruise speed. Suspecting the wires, the first step was to replace the old wires. The problem persisted. Next step was replacing the new wires and old plugs. Problem solved. Suspecting that one Splitfire may be bad, I purchased a fifth plug and began a rotation of the Splitfires to include experimenting with a series of gaps from .36 to .46. Tried were conflicting gap settings from the manual, dealer, splitfire book, and went extreme. Nothing eliminated the problem. Some gap settings alleviated, and some gap settings increased the problem. During experimentation, one of the new plug wires broke from excessive handling. Got my money back for 5 Splitfires, and bought 4 NGKs. Problem was cured.

There are many who praise the Splitfires, so they must work well in other Miatas. No intent to discourage their use is intended, and they came with a money back guarantee. My experiences may save others some time, trouble, and $45 for more new spark plug wires.


I had the Splitfires installed by my dealer while having synthetic gear oil put in the tranny and the timing advanced to 14deg. btdc. Unfortunately, a few days later, Miata Magazine informed me of the proper gap for these plugs. The factory gap causes the only problem I've had in about 20K miles: some minor misfires when taking the car out of high gear at high revs. My '95 PEP loves 'em! Gas mileage is up slightly and the engine feels better, although the timing change has something to do with this. Whatever the case, I recommend both the Splitfires and the timing advance. FWIW, my brother raves about Splitfires in his '91 Nissan truck.

As for increased heat under the hood I've heard about, just remove the thin plastic cover in front of the radiator as would be required for installation of CAI units...the increased air flow into the engine compartment helps my Miata; it's especially noticeable in 5th gear on long uphill climbs (less downshifting required). Enough said!

Try 'em, you'll love 'em!

Reviewed by: Evan Spiegel - Spiegel@law3.law.ucla.edu

Spark plugs that increase horsepower w/ aledged performance increase.. They cost aproximately $4-$5 apiece.

BEWARE!!! I installed these items, like many others, as a simple way to find a few extra horses. They may give the horses as stated by the manufacturer, but... As confermed by Mazda Service Advisors and Mechanics, they pose a problem for many Miatas. They can cause a lack of power and rough idle after downshifting and coming to a stop. If you have splitfires and have an elussive problem of stallouts and rough idles when coming to a stop, get rid of the plugs and use factory plugs to cure the problem. I spent months trying to figure out what was causing my Miata's problem. First I did a Bilstien power-hot oil flush, then I had the injectors cleaned, then a tune-up, etc... When I finally took the advice of Kramer (Santa Monica) Mazda Service Advisors and replaced the plugs, the problem was instantly fixed. (P.S. The plugs were all good and properly gapped)

Update from Evan

Since my removal of the Splitfire spark plugs from my Miata last spring, my Miata has been running perfectly and hasn't had a rough idle or stall-out a single time. I have also received about a DOZEN thank you messages from other Miata owners who had Splitfire plugs and rough idle and stall-out problems before removing the Splitfire plugs. I did, however, receive one comment from somone who did not provide a name or reply address. This one annonaymous commentator stated that the dealership that recommended removing the plugs to fit the problem, "didn't have a clue" (among other comments). I wonder if the person has a stake in the plugs. Eitherway, if anyone else out there has Splitfire plugs and has rough idle or stall-out problem, try removing the plugs. It has worked for many Miata owners out there.

Reviewed by: Spencer Chrislu - spencer@pacificnet.net

I installed these plugs shortly after buying my '92 Miata used last year. I left them in my car for approximately 3 months.

I cannot say that I was pleased with these spark plugs. I noticed no change in acceleration or improved gas mileage with these plugs. The only thing they seemed to do was cause an inordinate amount of heat to build up in the engine. Since replacing them with Bosch Platinum plugs, my car runs much cooler, my acceleration seems to have increased slightly and I get much better mileage. My vote is thumbs down on the Splitfires.

Reviewed by: Jim Guidry - jim.guidry@jacobs.com

I've been running Splitfires in my 1992 white "B", K & N filter, Pacesetter exhaust for 32,000 miles. I've been completely happy with the performace of these plugs.

 There has been no almost no wear on the electrodes. (Pulled and checked every 5000 miles.) I removed them at 40k, and replaced them with the original NGK-R's. Very definite reduction in "brightness". Put Splitfires back in, the old sparkle was back. An old friend of mine was finally brought into the fold last month (1996 M Edition). He had used Splitfires previously in his Civi Si. Based on what I'd read in Miata.net,(negative reviews), I told him to reconsider. As usual, he took his own advice and put Splitfires in. His report is nothing but glowing! Better idle, better sound and increased acceleration.

 Caveat: Due to non-fluted ceramic, a little care must be taken in removing wires. Big Deal!

 Four thumbs up!

Back to Product Reviews 10 April, 2005