AEM 30-71XX Infinity Stand-Alone Programmable Engine Mangement System Full Manual - Manual (Page 342)

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© 2014 AEM Performance Electronics
Infinity User Manual
Noise
Electrical noise can cause the Infinity ECU to see more tooth edges than there are in reality. This
will result in excessive misfires during normal running. Misfire caused by “noise,” (commonly
referred to as radio frequency interference {RFI}, or electro magnetic interference {EMI}), is
usually due to routing the input signal leads in close proximity of the HT leads. Typically, spark
plug wires cause RFI or primary ignition wires arcing to an engine component, which causes a
frequency that interferes with the ECU. Routing two wires that carry high current parallel to each
other cause EMI. The strength of current necessary to incur “noise” is dependent on the
sensitivity of the device the wires are connected to. A common preventative measure for
eliminating “noise” is to twist the wires together to minimize the electromagnetic field near the
wires.
On any EFI system, resistive spark plug leads are REQUIRED to suppress noise!
Common resistive spark plug leads include those with a carbon impregnated fiberglass core or
spiral wound filament around a carbon core wire. Another source of noise that can cause a
misfire is an electrical “leak” in a plug wire or boot. Even a very small pinhole in a spark plug
insulator or boot will allow electricity to arc to the cylinder head and interfere with the ECU signal.