Heavy Duty Details - Engine Builder Magazine

Heavy Duty Details

Old Days Are Gone; Now, Reconditioned Con Rods Must Meet Critical Specs

Too much twist and bend will limit oil clearances and can cause engine damage

I can remember in the old days how rods were reconditioned. We had a dry hone with limited mandrels. Rods were ground, assembled, torqued and dry-honed to final specs. Because there was no liquid, it took forever to recondition the big end. Pin bushings were removed then burnished and dry-honed to fit the pin bore and replaced using a vise as the press to install them.

We checked our bend and twist on an antique tester that had a red zone for rods out of alignment and a green zone for good rods that could be reused. The tester used a pointer with a spring-loaded bar on the bottom for straightness and a spring-loaded bar for the twist. Although we never knew what the exact bend or twist was, if the rod was in the green range, it wasn

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Closed-loop control can be programmed to either add or subtract up to a certain percentage of fuel in order for the engine to reach the target air/fuel ratio.

Electronic Fuel Injection (EFI) is all the rage today and rightfully so. EFI has many advantages that allow us to dial in the fuel in a dramatically more precise fashion than was ever possible with a carburetor. One of the tools at our disposal is the closed loop algorithm where the target air/fuel ratio commanded in the ECU is compared to the actual air/fuel ratio read by the O2 sensor. If the two do not match, the ECU makes small changes by either adding or subtracting from the commanded fuel in the fuel table to equalize the two. 

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