EFM
Why should I consider installing a FloScan Fuel Management System when the engines I have just purchased offer an Electronic Fuel Managment System as an option?
Engine manufacturers conduct bench testing of their engines to calculate the amount of fuel that actually passes through the injectors at different rev ranges.This data which does not take into account actual load conditions and variances of up to 20% are not unusual. The FloScan system is an "opto-electronic", turbine-type flow sensor which is mounted on both the feed and return fuel lines. This data collected under actual conditions is used to calculate the fuel consumption.
Primary Filter
I have just installed a FloScan Unit to my boat and my installer has advised upgrading my primary filter to 5 microns. I noticed in your installation manual that you specify a 30 micron primary. Please help!!
Finer secondary filters are always installed on the "Pressure" or "Discharge" side of an engines lift pump. A lift pump has no problem pushing fuel under pressure through a very fine filter. It has a great deal of difficulty, "Lifting" fuel under partial vacuum through a fine filter. Secondary filters are usually between 2 and 9 microns.
Engine manufacturers do not want 2 or 5 micron secondary filters installed on the lift pump's vacuum or inlet line. 2 and 5 micron filters are secondary filters, not primary filters. They never want a secondary filter used as a primary. They want the filter they recommend installed, not what the owner, diesel mechanic or dealer wants. 2 and 5 micron primaries inflict a life of hard labour on the lift pump. Since the article about 2-micron primaries appeared in Passage Maker, I believe that both Volvo and Yanmar have voided warranties on lift pump failures caused by fine filters.
2 and 5 micron primary filters create a high enough partial vacuum that vapours are pulled from the fuel after only a few hours of use. Lighter elements in diesel fuel such as butane, which is present in all No. 2 diesel, forms bubbles when 2 and 5 micron primary filters are used. The bubbles are formed downstream of the primary filter, (between the filter and lift pump). As they travel through the lift pump they collapse and are very destructive. Collapsing bubbles are like mini explosions. They erode and wear away parts in the lift pump. It's like the lift pump is spending its entire working life under an artillery barrage.
As the vapor bubbles pass through our sensors, the sensor reads them as an expanded fuel volume causing high readings. 2-micron filters cause the most problems but 5 micron filters can also cause high readings.
Generally, piston and diaphragm lift pumps require 30 micron primary filters. Vane and gear lift pumps usually require 10 micron protection.