Quote:
Originally Posted by sjf911
Now I know what I want on my next build, beautiful!
Why the rising rate fuel pressure regulator?
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Differential pressure is the critical yardstick when discussing injectors in forced induction applications. As boost pressure increases inside the inlet manifold where the injectors are situated, the fuel rail pressure must also increase proportionally in order to maintain a constant pressure difference across the injector orifice. This is called a constant differential pressure fuel system. Less sophisticated fuel systems may not employ a constant differential pressure fuel supply - instead they maintain a constant fuel rail pressure that does not increase with increasing boost pressure. These are called constant fuel pressure systems and were only ever designed for naturally aspirated applications.
With a constant fuel pressure system, the pressure difference across the injector orifice drops as the boost pressure increases - and consequently the volume of fuel supplied by the injector drops as well. This can lead to engine damage through lean mixtures at moderate to high boost pressure levels.
The manifold referenced rising rate @ 1:1 addresses this issue and is a true constant differential pressure fuel system that maintains a constant pressure difference across the injector orifice. For every pound of boost the engine creates, you get an equal increase in fuel pressure. Hence the 1:1 ratio as it was referred to.
In conjunction with a single Bosch 044 fuel pump in the car, and a clean prefilter in the tank, I have found the data from Motec with the engine in the car replicates exactly what we see on the dyno, lambda numbers wise, which incorporates a high volume system using the 044 pump. Anything less than the above pump in the car is trouble for this particular engine. Data logs confirm... lean to very lean, and that was using the stock OEM twin pump system. Installed the 044, and results were the same lambda that was shown on the dyno. So installing this engine in the car and assuming the OEM fuel system would suffice would have meant trouble in some form down the road.
In order to ensure precise fuel pressure delivery at high horsepower levels, one 4.0 Bar fuel pressure regulator is used, and we have a center mounted Rothsport designed billet regulator housing to incorporate this regulator. In addition the fuel pressure regulator is vacuum/pressure referenced to the engine's intake manifold. In this way, fuel pressure across each injector orifice is maintained at a constant level regardless of the turbocharger boost pressure level - a configuration as found in the world's best turbocharged high performance production engines.
Shown below on another engine on the dyno is the regulator housing. The gold anodized part. It is also our pivot point for the Rothsport designed throttle linkage to work in conjunction with our individual throttle bodies. The regulator is towards the fan end of that piece.
