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What is the consequence of using a fuel filter with a higher-spec'd bypass valve opening pressure ?

Currently have a UFI ‎31.833.00 / 6Q0201051C on my 2008 City Golf - rated at 4.0 bar.
Considering a HENGST H155WK02 as replacement, but it is rated at 6.4 bar.

Would this higher pressure rating cause fuel delivery issues, if the valve doesn't open until higher pressures ?
Would it just cause lessened fuel economy ?

Or is the rating just a max-permitted before the component blows-out, and have no adverse effect at all ?

robut
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2 Answers2

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Seeing as my other answer was not correct in this case, I would propose that the reason there is a bypass valve is to ease the load on the pick up fuel pump while there is low demand for fuel by the high pressure pump that is further down the line.

The majority of the time, the pick-up fuel pump will be able to provide more fuel than is required by the engine. Without the bypass valve, the pump will be working harder than necessary, raise the fuel pressure higher than necessary and also use more electricity than necessary. The bypass valve will allow this excess fuel to be sent back to the tank and the ease the load on the pump.

HandyHowie
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Under normal operation the bypass valve should be closed at all times, your engine will be getting protected from dirty fuel by the filter.

Without a bypass valve, if the filter becomes clogged with dirt, the fuel pressure to the engine will drop and the engine will become starved of fuel and possibly run lean. This could cause damage to a petrol (gas) engine.

The bypass valve is there to open in the event of a clogged filter. The contaminated fuel will bypass the filter, but the engine will be getting a normal supply of fuel. This is good for keeping the engine supplied, but bad that dirt is getting to the engine.

If you put a filter on that opens this valve too late due to having a higher pressure specification, you could cause the engine to be starved of fuel in the event of a clogged filter. This could be bad for the engine.

HandyHowie
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