The fuel setup on the NC can be the bottleneck when running forced induction, It has been known to have a pressure drop on injector 4 due to the feed is between 1 and 2. Really not good as this will effect the fuelling, you may have cylinder 1 @ 10.8 AFR and cylinder 4 @ 12.0 AFR but an average of 11.5 so you’d think all is fine.. Until it’s too late… 😞
The best method to solve this is to run a return style setup, this involves running another fuel line from the tank and having a 1:1 FPR at the rail coupled with welding a extra fitting on the OEM rail or running a aftermarket fuel rail, what this means is the fuelling is control at the rail and any excess pressure is routed back to the tank.
So why a 1:1 Boost Reference Fuel Pressure?
The regulator needs to allow additional fuel pressure to overcome resistance created by boost pressure. For example, let’s say a boosted application runs 45 psi of fuel pressure to the injector when under no boost. Let’s say the engine is then put under 20 psi of boost pressure. That means the intake manifold, where the fuel injectors are mounted and spray into, is pressurised by 20 psi. This pressure then “pushes back” fuel in the injector/fuel rail by 20 psi. That means the fuel pressure in the fuel rail must be increased by 20 psi to compensate. So, the 20 psi of boost reference to the Pressure Reference Port causes the regulator to increase fuel pressure in the fuel rail/delivered to the injector from 45 psi to 65 psi – thereby compensating for the 20 psi of resistance created by boost pressure.
This is the ideal solution but equally not a quick task with running new lines and fitting a FPR plus you will need a re-tune.
What I’ve done is create a duel feed fuel rail setup utilising the Mountune Racing billet fuel rail and created a duel feed setup using -6AN fittings & Teflon lines (E85 Ready). 💪
To my mind this should remove the pressure drop to injector 4 due to the OEM location feeds between 1 and 2 injector, now it feeds from both ends giving all 4 injectors as even fuel pressure as possible. End goal will be a return style setup but for the time being this should be good enough.
I also went ahead and cut the fuel rail further back and fitted a compression -6AN fitting to clean up the fuel line. ⛽
