The question routinely comes up on J/L, and I get my share of
personal e-mails also, on whether these things actually serve a
purpose, or are they just there to make the engine look pretty, or
just to make the end of the hose looked finished.
I daresay, I have probably done more actual measurements on these
ferrules, the hose barb connection, and the FI hose itself, than
probably anyone…with perhaps the exception of the original
individual/team that did the original design.
Below a a quick summary of that information.
- They do add a bit of ‘‘color’’ or ‘‘dressiness’’ under the hood.
- They do make the hose ends look finished.
- More importantly…They Do Work.
The inside diameter of the proper FI hose to use is 7.9mm, 5/16’’.
The OD of the FI hose (non-fitted) is appx 14.5mm.
The OD diameter of the outer edge of the injector barb, or rail
barb is appx 10.0mm. The OD diameter of the lower end of the barb
connection is 7.9mm. (where to ferrule fits).
The ID diameter of the ferrule, where the OD of the hose seats is
So the ID of the hose is 7.9mm. The outer edge (the OD) of the barb
is 10.0mm. The appx 2.1mm difference is what makes the seal of the
hose to the barb.
As the hose is shoved onto the barb, the OD of the hose expands
appx 1.5 mm. So the OD of the hose is now appx 16mm. The ID of the
hose has also expanded. You can’t visually see, or measure this,
but you know it had to, to fit over the outer edge of the barb.
Now the important part. When the ferrule is in place, and the FI
hose is fully seated into the ferrule…the ferrule has effectively
squeezed (compressed) the hose back down to its’
original…preinstalled diameters…both ID and OD, forcing the ID
of the hose end back onto the bottom end of straight portion of the
injector barb. In doing so, it has also squeezed the ID of the hose
tighter onto the outermost edge of the lower barb. And the final
seal is thus made.
Perhaps a bit hard to visualize with words. One of these days, I’ll
post my diagrams on the web site.
For now, I hope the above helps.
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