Author Topic: Injector question  (Read 4822 times)

Roark

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Injector question
« on: May 01, 2011, 01:39:53 AM »
Okay... Complete Noob here. You have been warned. :)

The engine is a Vidhata 1-banger water-cooled 1500 RPM.

Question: the injector has a threaded backshell which when removed shows a slotted adjustment locked in place with a lock nut ala a valve adjuster. A cutaway diagram I found on the net shows this screw sets the pressure on a spring which holds the injector pintle against the seat. Tightening this screw inwards causes the exhaust to clean up considerably. Loosening it yields somewhat dirtier deposits inside the stack.

What is this adjustment really doing??? Since fluid isn't compressible, I don't see it changing the timing, but I am willing to be called wrong. Or is this just setting the injector pressure and more pressure means better atomization?

Help?

Roark
What?!? No engine parts at the dinner table?  C'mon, Hon...

Thob

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Re: Injector question
« Reply #1 on: May 01, 2011, 02:05:01 AM »
And an answer from another noob:

Tightening the spring increases the pressure at which the pintle opens and allows fuel to spray into the cylinder.  Too low a pressure, and the fuel doesn't atomize very well, it dribbles and hence doesn't completely burn.  Too high a pressure is hard on the cam, injection pump, piping, etc.  The spring is normally set on an injector test bench, which typically has a hand pump with a pressure gauge on a T on the outlet; the lever operating the pump can be slowly pressed and the pressure noted at the point where the pintle opens.  You can also watch for leaks prior to opening, which checks how well the pintle seals.  Normally, the gauge can be shut off with a valve, then you can quickly operate the pump by hand and watch the spray pattern to see if it's a fine mist or a dribble.

I've been thinking of building a test setup using a standard injection pump, a lever, a fuel pipe, and a place to hold the injector.  A little cutting, drilling, and welding should make it work.  Project #3,572B, yet to be done.
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dieselgman

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Re: Injector question
« Reply #2 on: May 01, 2011, 04:33:33 AM »
Roark, The adjustment you are referring to actually changes the opening pressure of the injector nozzle. A dirty stack is an indication of incomplete combustion and as Thob suggested, the injector should be set to spec with a tester and proper pressure guage. Also, a close inspection of the spray pattern for proper atomization can be done on a test bench. You may have issues with both the opening pressure and/or the nozzle performance itself.

Your injection timing can be affected slightly by large changes in pressure settings as it will take the pump slightly longer to build the higher pressure vs. lower pressure at the different settings. I do not know if that aspect makes any significant difference though, along side the drastic difference that opening pressure and nozzle performance itself has on proper atomization and spray pattern.

dieselgman
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Roark

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Re: Injector question
« Reply #3 on: May 01, 2011, 02:06:08 PM »
Gentlemen, THANK YOU! Now it makes perfect sense.

I recorded where the factory setting was, and at 3/4ths of a turn tighter, the stack got noticeably cleaner. I will run it in a bit more as a test, and then out to see where things get smokish. It certainly seems smoother at the present setting, but I want to play a bit.

I am learning that the Diesel Bug is a journey and not a destination. If you have a crescent wrench and a screwdriver, even us lowly Noobs can play along.  :)

Roark
What?!? No engine parts at the dinner table?  C'mon, Hon...

billswan

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Re: Injector question
« Reply #4 on: May 02, 2011, 12:44:11 PM »
Well be careful, IF the injector was set correctly from the factory 3/4 turn probably about doubled +some the cracking pressure. At least it would have on my 10/1 and I did break my camshaft although the quality of the part was in question......

Billswan
16/1 Metro  in the harness choking on WMO ash!!

10/1 OMEGA failed that nasty WMO ash ate it

By the way what is your cylinder index?

Roark

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Re: Injector question
« Reply #5 on: May 03, 2011, 05:34:25 PM »
Sorta sounds like a line from the old Ghostbusters movie:

Akroyd: Don't cross beams.
Murray: Why not?
Akroyd: It would be bad. Very bad. Imagine every atom in your body exploding in a different direction
Murray: Ok. Hot safety tip from Eagon. Don't cross the beams...

Seriously however, I didn't notice any improvement with additional input on the injector screw. So I backed it down to where it just started to smoke and then added a smidge more. At some point I need to get the injector on a tester and set it to the spec pressure (whatever it may be) but for my goofings now, I think it will be close enough.  Your input regarding camshaft stresses is well considered however and I sincerely appreciate the heads-up!

Roark
Roark

What?!? No engine parts at the dinner table?  C'mon, Hon...

dieselgman

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Re: Injector question
« Reply #6 on: May 04, 2011, 02:15:26 PM »
Original camshafts are of exceptional quality and we have never seen one broken. The Indian clones unfortunately are not of the same materials and are not hardened to anywhere near the original specs. Our biggest problem with Lister cams is only encountered once they have been left outside in the weather and pitted from water corrosion.

dieselgman
ALL Things Lister/Petter - Americas
Lyons Kansas warehousing and rebuild operations