Fuel Rail Assembly Design on Intake Manifold

Fuel Delivery Pipe/Rail is mounted on Intake Manifold - Design Process 

Stack up Analysis of Tolerance is very crucial to design Rail Mounting. As shown in below figure Fuel injector is placed between fuel delivery rail and intake manifold injector sitting groove. Installation height is perpendicular distance between injector mounting surfaces. Installation height with tolerance must be equal to length of injectors with tolerance. To insure surface finish area and depth on intake manifold following to calculation must be done:

1.    Max distance between upper and lower O Rings of injector < Minimum Gap between (O Ring Position in Rail) and (O Ring Position in Intake Manifold)

if point 1 is not satisfied then fuel will leak from contact point of two parts - either from (injector and intake) or from ( Injector and Rail). 

2.    Minimum distance between upper and lower O Rings of injector > Maximum Gap between (O Ring Position in Rail) and (O Ring Position in Intake Manifold)

Injector O Ring will be crushed if this point 2 condition is not met.  

Step 1 was Requirement Study

Step 2 was DFMEA of Intake Manifold

Step 3- Assembly of Fuel Injector on Intake Manifold plus Assembly of Fuel Delivery Rail on Intake Manifold  

Step 4 - Calculate axis of fuel injector , Axis of cup in Intake Mani and Cup in Fuel Rail. - For Next Step Read next article Co-axiality and Concentricity. 

Co-axiality and Concentricity:

Intake Manifold Injector Sitting Hole must be co-axial to Rail Hole; but as rail itself is mounted on intake manifold, geometric tolerances with maximum material condition must be used to define location of rail mounting hole with respect of Injector Hole in Intake Manifold.