Nov 12, 2010
What effect, if any, would increasing the fuel pressure to 5bar have on the performance of a 1.8tqs?
As a mod on its own, it would make no difference whatsoever.
The car would run rich, reducing performance, however the ECU would soon work that out and pull the fuelling back to compensate, putting you back to where you were when you started.
The other issue is that it would put far more load on the fuel pump, because not only is the pump then running at a baseline of 5bar, but when your then running 1 bar of boost the pressure rises to 6 bar, which is seriously thin ground for a standard fuel pump.
The only time you need to touch the fuel pressure, is when your running out of injector duty cycle. Plus with the B5's already stupid 4 bar base pressure, i'd be looking at swapping back to a 3 bar regulator and fitting bigger injectors if i needed more fuel.
Just makes the car run very rich if you own a narrow band 02 sensor car. It could even make the ECU throw a "rich" code if the amount of fuel the ecu is trying to pull back is beyond its range.
Increasing the fuel pressure ends up decreasing the amount of flow from the fuel pump. Raising the fuel pressure does help if your maxed out at the injectors. It wont help if your maxed out on the fuel pump, actually causes the fuel pressure to drop even sooner.
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