Technical > Spud Miller's Cave

Nozzle body hole

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tony1966:
Hi Guys:

I was replacing some injector nozzles that split, and i noticed that the old ones have a small hole on one of the flats, and the new ones don't.  What's the hole for, and do i need it?

Thx!

Tony

Spud Miller:

 That's an air bleed hole. If your nozzles are in a hat (above a blower) or naturally aspirated, you'll need the holes. If they are port nozzles in a blown application (below the blower), you DON'T want the holes. The holes would make for a boost/fuel leak if they existed below the blower.

 The engine sucks air through those holes at idle and it helps to break up the fuel stream. Naturally aspirated applications generally utilize two holes per nozzle body.

 If you need bodies with the hole, it's perfectly ok to drill holes in what you have there vs. send them back.

 Spud
 

tony1966:
Thanks Spud!  Holes driiled. Is there any magic to calculate the size of the hole?  Mine were 0.076 with 0.038 nozzles. I made them the same.

Tony

dreracecar:
All air bleed holes are the same dia, they dont vary do to nozzle size.   the other thing about the air bleed holes as they are a reference to the direction of the fuel spray, Having the hole on the top flat would mean that fuel direction is down

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