Difference of Differential

Of course, it is unlikely that fuels are going to have equal amounts of various sized contaminants. Some fuels with be relatively clean and may have only smaller-sized particles. Other fuels can be relatively dirty with relatively large particles in addition to smaller sized particles. This variance in fuel quality often makes it difficult to select the optimized filter types for each stage. Fortunately, installing a differential pressure gauge at each stage can indicate which stage of filtering is being taxed the most. The filter showing the highest pressure differential is going to tell the story. If the stage one filter is showing the highest pressure differential, you may need to swap to a more open element (move from a 100-micron to 120-micron filter). This change should decrease the amount of pressure differential by reducing the amount of particles captured in stage one. Instead, stage two would now be responsible for capturing the particles that are between 100 and 120-microns in size. If stage two shows the highest pressure differential, there are two potential ways to correct the issue. Either a more open element can be used in stage two (i.e. moving from a 60-micron to 75-micron element), or a finer element can be used in stage 1 to remove more of the particles before they get to stage two. This same logic can be followed for each successive stage of the filter system.

This XRP filter has been stacked to provide three successive stages of filtration. Best of all, a fourth stage can be added in the future if needed.

These differential pressure gauges can be plumbed in at each stage of the filter system. The gauges will indicate how much pressure loss is being seen across each stage of filtering.

One Body, Multiple Filters

Since we are converting our 1996 Nissan Skyline GT-R to flex fuel operation, we wanted to address the fuel filtering system. Ultimately, we turned to XRP for the solution. Recently, XRP released its lineup of multi-stack in-line fuel filters. These modular filters are designed to allow the benefits of multi-stage fuel filtration within a single body. XRP offers three series of multi-stack filters, the narrow-bodied 70-series, the full-size 71-series, and the clamshell quick-disconnect 72-series. The 71-and 72-series features a 2.47-inch body diameter while the 70-series uses a smaller 1.98-inch diameter body. The larger 71- and 72-series filters offer higher capacity filters (for a given length) and inlet/outlet sizes ranging from -6AN to -20AN. Standard body length is about 9.5-inches while a shorter body is available with a 6.5-inch length. In the 71-series, the inlet/outlet sizes run from -6AN to -12AN while the body size is 6.5-inches.

One advantage to the modular system is the reduction in total length as stages are added. For example, we ended up with a two-stage, 71-series system for our R33 Skyline GT-R. While a single-stage measures out to 6.2-inches from end of fitting to end of fitting, adding a second stage increased the overall length by just 3.875-inches (overall length of 10.0 inches). This was ideal for the limited amount of space that we had available. If we had enough room to add a third stage, the total filter length would be just 13.875- inches.

All for filter element choices, the 70-series can be used with stainless screens of 120-, 100-, 75-, 60-, 45-, 20- or 10-micron filtration levels or cellulose screens of 20- or 10-micron ratings. The larger 71- and 72-series filters offer a selection of low-pressure and high-pressure stainless screens rated at 120-, 100-, 75-, 60- or 45- microns. We selected a 100-micron high-pressure screen for the first stage and a 60-micron high-pressure screen for the second stage.

If there is enough space available, the optional fuel temperature sensor port can provide easy access to fuel temp data.

The Bottom Line

While the expansion of our Hard Media, Inc. facility will likely limit our time on the water this tuna season, our sportfisher’s multi-stage fuel system will help ensure that we return safely. While an inadequate fuel filtering system on your vehicle won’t leave you stranded in the middle of the ocean, it can result in clogged injectors, accelerated fuel pump wear or, at worst, catastrophic damage to your engine. Some careful planning and a minimal investment will allow the implementation of a multi-stage fuel filtration system on your vehicle. Making the multi-stage upgrade will significantly increase the capacity and efficiency of the fuel filtering system. A small investment now can prevent a high-dollar catastrophe in the future.