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I had an aftermarket tachometer on my engine test stand that would often read twice the actual rpm. The engine stand was set up so that the power to each of the four ignition coils could be controlled independently. The spark plug wires were Mazda OEM. The behavior of the tach would sometimes be affected by the combination of ignition coils that were active. In the course of troubleshooting, it was found that the tach would consistently read twice the actual RPM when its input wire was completely disconnected at the tach. It was concluded that the tach was responding to signals emitted by the spark plug wires and the doubled rpm indication was due to triggering by the ignition signals from both rotors. Replacing the Mazda spark plug wires with Magnecore wires from the installation in my plane cured the tach errors. Now, however, checking the ignition timing with an inductive timing light pickup on these wires was difficult whereas it was not a problem with the original wires.

It should be noted that the EC2 on the engine stand never gave any indication of having problems when either set of spark plug wires was installed in spite of being physically located closer to the coils and spark plug wires relative to the tach.

Steve Boese

RV6A, 1986 13B NA, RD1A, EC2

From: Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of Dale_R [dale.rog@gmail.com]
Sent: Saturday, January 12, 2013 8:04 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Hiccup

Dunno how many people here remember when spark wire was just that: wire. But it was electrically noisy. So it got replaced by carbon impregnated fabric, which has rather high resistance (a cheap way to damp the "noise").

Another way to suppress the "noise" is to wrap the wire (many turns, closely spaced) around an insulating core, which creates an inductive impedance, which accomplishes the same goal but readily passes spark current. AFAIK, "MAGNECORE" was the first to explore this method, but several companies offer a similar product now. According to some sources, the core material can make a large difference in the inductive effectiveness. Therefore, I'd recommend
MAGNECORE.

-- 
Best Regards,
Dale_R (who has no financial interest in Magnecore)
Cozy MKIV #497

On 1/12/2013 7:21 AM, Bill Bradburry wrote:

Anybody have a recommendation for ignition wires for the Renesis? I have the original Mazda wires. I checked them out yesterday and they seemed fine, but I am still considering replacing them to see if it helps.

Bill B