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Project RX-8 - To Improve Performance, Add Reliability - Tech

Black Halo Racing Helps Us Address Several Known Problems On The RX-8.

David Pratte
Dec 2, 2010

Lotus founder Colin Chapman famously said, "To add speed, add lightness." Well, Charles R. Hill of Black Halo Racing may not be quite as famous as Chapman (though in his other career as a rock musician, he has played in front of 15,000 fans), but his company's mantra could easily be, "To improve performance, add reliability." That's because BHR - a small but widely respected Mazda RX-8 specialist based in Phoenix - has focused its attention on fixing a number of the 8's most glaring shortcomings.

Modp_1012_01_o+project_rx 8+front_view Photo 2/15   |   Project RX-8 - To Improve Performance, Add Reliability - Tech

As we showed you with a baseline dyno graph last month, the Renesis in our 8 isn't performing to its full potential, with power dropping off after 7100 rpm when it should continue to build power all the way up to about 8100 rpm and then drop off gradually to the 9000-rpm redline. When I posted this graph on RX8club.com, the more experienced members immediately chimed in that this type of power drop off is typical of tired old ignition coils and spark plugs. One way to fix this is to swap in fresh OEM coils, plugs and wires every 20,000 miles, but a more durable and long-term solution is the product that really put Black Halo Racing on the map, its bulletproof BHR ignition system.

According to Charles at BHR, "Weak ignition coils are a source of frustration for a lot of RX-8 owners, since these lead to loss of power and catalytic converter function, in some cases even leading to destruction of the cat. If you add forced induction, nitrous or any kind of racing to the mix, having an ignition system that's reliable and with higher electrical output becomes even more important."

And that's exactly what BHR's ignition system kit is designed to provide, using stronger GM ignition coils (used in many racing applications and proven reliable in high-heat/high-stress environments), custom-built MSD ignition wires and a patent-pending plug-and-play wiring harness. Installation is a breeze (we removed the intake to ease access to the coils), and with a one-year warranty, you're covered in the unlikely event of a manufacturing defect. Better yet, BHR takes customer service so seriously that if you buy one of its ignition systems second-hand, for $20 they'll completely refresh the wiring harness, rebuild the ignition wires and check the coils for you.

After installing the BHR ignition system, we headed over to SG-Motorsport to dyno test the 8 on U2Ndyno.com's Dynapack, a machine that produces extremely reliable and repeatable numbers even when testing isn't done on the same day (as is the case with this test). As you can see, we've picked up some good horsepower and torque in that critical area between 6500 rpm and 8000 rpm (peak horsepower having improved by 5.1 whp and peak torque by 3 wtq), but we didn't see that third hump in the graph outperform the second hump the way a healthy Renesis graph normally looks, where power normally peaks 10 whp higher and 1000 rpm later.

Normally, a refreshed or upgrade ignition system cures weak high-rpm performance, but since we've installed the best available ignition upgrade and are still seeing poorer than expected power above 7000 rpm, it would appear our Renesis has some other issues that need to be addressed. We suspect a clogged catalytic converter may be the culprit, since RX-8s that see a lot of high-rpm abuse like ours tend to destroy the cat pretty quickly. Since we've got a very special motorsports cat on the shelf waiting to be mated to a Racing Beat resonated mid-pipe, we'll find out soon if this is the source of our Renesis' poor high-rpm output.

Although BHR is best known for its ignition system, the company makes a growing number of products for RX-8 enthusiasts who want to maximize the reliability and performance of their Mazda. The RX-8's OEM fuel pump is a known problem among track day enthusiasts, where fuel starvation during high-speed corners is commonplace (causing a sudden drop in power). We experienced this for the first time in our 8 while doing some track testing with less than a quarter tank of fuel, though apparently this can also happen during extended highway cruising.

Modp_1012_08_o+project_rx 8+parts Photo 9/15   |   Project RX-8 - To Improve Performance, Add Reliability - Tech

Jeff from MazdaManiac came up with a very simple and elegant solution that BHR has subsequently implemented on its drop-in replacement unit, equipping the OEM pump housing with a 255-lph Walbro. This pump just so happens to fit the OEM housing perfectly, has the correct size outlet and uses the same electric connector as the OEM pump. This upgrade, completely assembled by BHR and ready to drop into the fuel tank, not only solves the fuel starvation issue caused by the undersized OE pump (approximately 115 lph) but also ensures adequate fuel pump capacity for up to 450 hp, meaning we've got one less upgrade to make once we add a forced induction kit.

Finally, we also installed one of BHR's welded OEM clutch pedal assemblies, since our transmission has a bad fourth gear grind when shifting at high rpm. After doing some research on possible causes for our fourth gear problem, it came to our attention that the 8's clutch pedal has a lot of flex, which can cause poor clutch engagement/disengagement. That's because the OEM pedal has just three small tack welds holding backplate to the mainframe, and over time these welds can fatigue and even fail.

To solve this, again BHR has taken a very simple but effective approach, welding the clutch pedal mainframe and backplate together more securely with some nice neat TIG welds in the areas where there's the most contact between the two pieces. Although there are also some clutch pedal reinforcement brackets out there that you can use instead, replacing the clutch pedal is such a simple job (literally three nuts to remove and a couple sensors to unplug), there's no reason not to swap in a BHR pedal or remove yours and have it welded up locally. For our 8, a reinforcement bracket isn't a STX Solo 2 legal mod anyway, so a welded pedal was the only way to go.

Although the welded BHR pedal has provided a much more solid feel when shifting and we don't have to worry about it breaking off during heavy use on the street or at the track, unfortunately our fourth grind is still as bad as ever. The ENEOS gear oil BHR provided has made shifting a quieter and smoother experience and should reduce future wear and tear on the gears and synchros, but it hasn't solved the existing fourth gear engagement problem. In other words, it's time to pull the gearbox out and rebuild it. Not a fun job, but it'll make for an interesting tech story in a future issue.

By David Pratte
216 Articles

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