Author Topic: Nozzle holder air bleed holes  (Read 339 times)

Offline hemidakota

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Nozzle holder air bleed holes
« on: September 07, 2018, 07:53:18 PM »
I have a question about nozzle holders and the air bleed holes in them. This is not a typical system. I have been messing around with Waterman/Mitchell injectorator systems for a while. The waterman nozzle holders have two 1/8" holes in each nozzle. Last time we ordered a nozzle holder it had no holes in it, Waterman told me they are not necessary. We ended up drilling the holes to match the rest. Well for many years we fought high idle rpm due to how much air they pull in. It is a throttle body deal with accelerator pumps so you can run the idle lean and have no stumble. Well a few years ago I taped them off for an idle only test. Low and behold we could adjust throttle body and make idle speed below 2k rpm. Well my father has the same system on his engine and I talked him into plugging the holes. Now the idle circuit is much easier to tune in my mind. It was tough to not be very lean on the idle circuit before, now is much more adjustable. The question I have is now I have been told in a N/A engine the holes are there to atomize the fuel delivery better. Is it really that important or can we just run the system as it is? At one point we had a mix of nitro that was told to be 10% but the crackle it had made me think it was more, the problem I had was I could not give the motor enough fuel at idle to keep the lean chirping to go away. Nitro guys will understand. I have not put the same mix back in the motor but I think it would be much happier with the plugged nozzles. So do we need the holes or can they stay plugged? The nitro deal was just fun but maybe try it again someday when the tune up is figured out. Sorry for the long post but I would like everyone's opinion of what is right and wrong. Thank you Greg S.
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Offline wideopen231

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Re: Nozzle holder air bleed holes
« Reply #1 on: September 08, 2018, 02:01:09 PM »
While I have always ran enderle stuff. I have never ran the one with holes on NA motor.I have used them in hat on blower motors. Since one 1/8 np pipe hole is worth about 250 rpm its easy to see where 8 of these smaller holes and I think you said yours had 2 each meanig 16 would make adjusting idle difficult. I have issue with my injector a D-ported birdcatcher being too much are and difficult to adjust and adding extra air bleed would be nightmare.  I do use pipe plug holes to add idle if need to avoid change BV position.
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Offline Spud Miller

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Re: Nozzle holder air bleed holes
« Reply #2 on: September 08, 2018, 05:12:47 PM »

 Besides helping to break up the stream for better idle and allowing idle air in, the holes also serve as a vacuum break. With the vacuum pulling on the fuel without a hole there, it can suck a BUNCH more fuel into the engine. Things generally change drastically in regard to idle leakdown if you tape the holes off. Big adjustments needed.

They aren't critical in a supercharged engine...when a guy has way too big of a hat on a tiny engine, you pretty much HAVE to get rid of those holes to make it work or you'll never get the idle down.

 In a naturally aspirated engine where the nozzles are in the runner, it really helps to have them - even if they're smaller than the standard 1/8" hole.

 Related story: I tried getting rid of them on my car last summer to see what would happen...I was hoping for better idle control. We start and warm the car up on a bottle. Usually we get 2 minutes or so on a small bottle of methanol WITH the nozzle body holes. I put bodies in without the holes and it was literally out of fuel in about 12 SUCKED the fuel out of the bottle instead of letting it gravity feed. I could have made the nozzles much smaller and probably made it work, but I put the bodies with holes back in and got our 2 minutes back. Also it idles much smoother and more even idle temps across the board with the holes when on the bottle.

 Bottom line is, I do think they are optional but even when properly adjusted to suit either way, you might find idle quality and temps are better with them. But of course that's only at idle. At race speed, they are irrelevant for sure.


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