Best Fuel Rail For LSA SC Fbody
Thread Starter
Teching In
Joined: Oct 2021
Posts: 36
Likes: 3
Best Fuel Rail For LSA SC Fbody I plan on putting an LSA supercharger in my 2000 Trans Am. Is there any real difference in performance between aftermarket fuel rails and the OEM Zl1 version fuel rails?
TECH Resident
Joined: Jun 2011
Posts: 936
Likes: 472
No. the only time it makes sense is if there's no way to adapt whatever injectors you plan to use or you want a return system (although you can always plumb a regulator inline with it's own return port to the tank prior to the inlet).
TECH Resident
Joined: Jun 2011
Posts: 936
Likes: 472
If it's vacuum biased and you're running boost the effective pressure increases in the rail, providing more fuel through the injectors. Essentially injectors flow more as boost increases. However, the opposite is happening at the pump, so you need a larger pump capacity to supply fuel at the higher pressures.
It is also less prone to fuel line hammer, since the regulator is right at the rail. When an injector opens, there's an instantaneous pressure drop, with the regulator in the tank the time for it to respond is longer, which can result in overcompensation. Essentially you'll get larger pressure spikes which won't be noticeable without lab grade measurement tools, but can have an impact on the fuel delivery. For that reason, factory rails either have an external damper, internal, or self-damping by design. Many aftermarket rails are extruded tubing with no damping (the factory LSA rail is internally damped returnless, so works very well). If the regulator is right on at the rail, the mechanical response is quick enough to avoid these spikes, eliminating the need for a damper anyway.
The reason returnless was popular with OEMs is eliminated one source of evap and shed emissions (no hot fuel return to tank, and fewer connection points to seal). And even considering need of a damper, it was less expensive since only one line is required from end to end of the vehicle.
It is also less prone to fuel line hammer, since the regulator is right at the rail. When an injector opens, there's an instantaneous pressure drop, with the regulator in the tank the time for it to respond is longer, which can result in overcompensation. Essentially you'll get larger pressure spikes which won't be noticeable without lab grade measurement tools, but can have an impact on the fuel delivery. For that reason, factory rails either have an external damper, internal, or self-damping by design. Many aftermarket rails are extruded tubing with no damping (the factory LSA rail is internally damped returnless, so works very well). If the regulator is right on at the rail, the mechanical response is quick enough to avoid these spikes, eliminating the need for a damper anyway.
The reason returnless was popular with OEMs is eliminated one source of evap and shed emissions (no hot fuel return to tank, and fewer connection points to seal). And even considering need of a damper, it was less expensive since only one line is required from end to end of the vehicle.
