Filter Minders for Dummies

[davidbrady]

Hi Al,

My favorite DD Series-60 tech, Gonefishen over on the dieselenginetrader site, has long recommended changing air filters annually, which is what I do. I don't think we understand yet what the Filter Minder is telling us so I'd simply ignore it, pending more investigation.

Diesel engines are air rich. At cruise just enough fuel is injected to keep things going with air fuel ratios (AFR) going as high as 40:1. The S60 doesn't run a lambda (O2) sensor. It injects fuel based on the throttle position sensor and the boost sensor. For a given load the ECM wants to see a specific boost pressure. Because a diesel can run with a wide range of AFRs, to make power it needs to either inject more fuel or cram in more air. Less restriction means more air, and for the same power or same boost it means less fuel. This means less exhaust heat, less exhaust back pressure, less turbo work, and higher engine efficiency, which translates to better fuel economy.