The three major fuel supply mechanical components for the Slowtra's engine are the fuel injectors, the fuel pump and the fuel pressure regulator. The fuel pressure regulator or FPR's job is to maintain the fuel pressure in the engine's fuel rail. The fuel pressure regulator "regulates" the fuel pressure in the fuel rail by returning excess fuel back to the fuel tank. Some of the newer engines such as the Honda K20 run a returnless fuel system which dispenses with the need of having a fuel pressure regulator. The ECU takes over the role of the fuel pressure regulator by altering the injector pulse width to give a precise fuel delivery.
Picture below of the stock fuel pressure regulator
Once the engine's fueling demand is significantly increased the stock FPR becomes a redundant paperweight as it is unable to cope with the increased fuel pressure from higher flow fuel pumps and larger capacity injectors. The stock FPR is also not adjustable hence one cannot adjust it to increase or decrease the fuel pressure. The fuel pressure at idling for all QG engines as stated in the service manual are as follows:
Vacuum Hose Connected
Approximately 235 kPa / 2.35 bar / 2.4kg/cm2 / 34psi
Vacuum Hose Disconnected
Approximately 294 kPa /2.94 bar/ 3.0kg/cm2 / 43psi
This is where the installation of an aftermarket FPR becomes critical as the fuel pressure can be adjusted to suit the engine's fuelling modifications. I was initially going for the Sard FPR but decided on the Tomei instead as the Sard is becoming too common. Having a Bro using the same FPR help convince me too! You know who you are :) Also while the Sard is initially cheaper than the Tomei it only comes with one type of end fittings (the push fit type) and one will need to purchase AN fittings separately if one decides to go the AN route or purchase the SARD FPR which comes with AN fittings standard at additional cost. Pictures below of the Tomei's Type S FPR's box
The contents of the box sans manual. Lovely looking decal. Wonder where I should stick it? :)
The excellent manual is in both Japanese and English.
The mounting bracket. Tomei separately sells nicely customized fuel rail adapters for specific performance engines. Obviously QG engines are not in the list but I'm not planning to use the stock fuel rail anyway so not a problem here. If you're looking to purchase the Tomei Type S or L please ensure you are getting from reliable sources as there are already fakes around. Details of the fake Tomei FPR can be found here. The problem is even more prevalent with the Sard. The first guiding principle when dealing with such problem is please don't be a cheapskate. If you're being offered a Tomei or Sard FPR at prices to good to be true then it probably is a fake. The regular Sard FPR with push fit end fittings retails in Bolehland for RM3XX while the Tomei is slightly more.
More details to follow post installation. Please be patient as this may take a while :) Next will be my upgraded injectors and fuel pump. Stay tuned.