29074 MALLORY | Alldatasheet
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ACTIVE FUEL INJECTION/TACH ADAPTER PART NO. 29074 Before electronic ignitions were common (and even after they were, in some cases), tachometer designs were geared toward the existing point-type ignition systems. This meant that a parallel-connection tachometer (one that was triggered from the coil ‘-‘ terminal) usually required a relatively high voltage (50-100v) to trigger properly. The other type of tach commonly used was the “series” tach, which was triggered by the current pulse in the ignition supply line whenever the points closed. When aftermarket electronic ignitions started becoming more popular, there arose a need for some way to trigger these tachometers, most of which were OEM designs. In addition, more cars were using electronic fuel injection systems, and many of these systems required a HV pulse on the coil ‘-‘ terminal to tell them that the ignition was working before they would trigger the injectors. The first “tach/FI” adapters were just a coil of wire that simulated a weak coil primary. Our version is the 29074. When connected between the points trigger lead and the ignition power wire, they would make a HV pulse on the trigger wire when the ignition was triggered. In addition, they drew a couple of amps through the ignition wire, and this was generally enough to trigger a series tach that was in the circuit. FORM 1139 (REV B) As distributors with magnetic pickups became more popular triggering sources, the 29074 style adapter wouldn’t work, because the point lead was no longer available as a trigger lead. In this case, a more complex adapter was designed (the 29078). This unit gets it’s trigger information from the “Tach” terminal of the ignition box and generates a HV pulse for parallel tachometers or FI systems, and it also pulls a couple of amps on the ignition line to trigger series tachometers. If you are using the points trigger lead (in other words, points, OEM electronic, UniLite, 50-series, etc.) for the ignition, then a 29074 is the appropriate adapter. It should work with both parallel and series tachometers. The basic wiring diagram is located on the reverse side of this sheet. INSTALLATION INSTRUCTIONS www.malloryracing.com 1
www.malloryracing.com 2 MALLORY IS A DIVISION OF THE MR. GASKET PERFORMANCE GROUP 10601 MEMPHIS AVE. #12, CLEVELAND, OH 44144 216.688.8300 FAX 216.688.8306 FORM 1139 (REV B) Made in U.S.A. Printed in U.S.A.