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pop tester
by
vwroadkill
on 22 Jan, 2013 21:42
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I have a question some of you maybe able to help me with.hell any input would be great.
I recently acquired a pop-tester..I have read what Vince Waldon wrote on the subject. but was left with questions
what volume of spray is considered good or bad?
duration of the spray pattern?
I understand 155 bar is a guide as to a good or a bad injector.
I am finding these injectors are similiar to what I use at work on Rolls Royce engines.
but we dont pop test. we just chuckem and get new ones. so I am left with questions.
any info would be great
Dan
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#1
by
libbydiesel
on 22 Jan, 2013 21:56
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The volume of spray is directly related to the duration which will last as long as you keep the fluid pressure above the break pressure of the injector. The pressure specs are in the Bentley. 155 is the TD spec. 135 bar is the non-turbo spec. In either case there is a range given, tho. I care more about having them all have very similar pressures than I do about the specific break pressure.
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#2
by
vwroadkill
on 22 Jan, 2013 22:06
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Thank you. I didnt realize equal spray. as in per cylinder, pattern was more important than the actual break pressure. bentley talks about it. just didnt get it. so If I get four of these to have a near equal spray and duration I should be alright.
I was given a couple of containers of shims to adjust the pressure. and the bentley gives input.
does the break pressure have to be a min. of 135..
or can I increase or decrease this.. do I have to worry about hot spots on the prechamber or piston for that matter.
I am learning.. it been fun so far
again thanks
Dan
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#3
by
745 turbogreasel
on 22 Jan, 2013 22:38
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It will start and run anywhere in the 135-155 range, but as you stray form spec, you will have to adjust timing to compensate. You probably have no way of measuring how much to adjust.
Dripping or poor spray pattern are way more important than the specific number , as is balance.
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#4
by
vwroadkill
on 22 Jan, 2013 22:55
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thank you for the input. I dont yet have a way to measure.
I am looking for a diesel shop locally to help me. but I have yet to find one that is interested in VW equipment.. one owner told me. It was to small to work on..
I got a two sets of injectors with my truck and parts car. I am doing this to possibly improve economy and improve power.
and spend as little as needed to do this
Dan
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#5
by
TylerDurden
on 22 Jan, 2013 23:46
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Pressure balanced across injectors will mean they all will respond similarly with regard to pump timing. An injector with a higher break pressure will inject slightly later. A closely matched set will allow more accurate IP timing adjustment.
The injection duration is based on the quantity of fuel from the IP, which delivers the same amount to each line.
When I was at the local injection shop today, I asked, but didn't get a clear answer on what the static pressure remaining in the injector lines is after the injector closes, but the Bentley docs mention an example of 60 bar. That pressure is held in the lines by the delivery valves, so the line pressure doesn't drop when the IP plunger pressure drops to IP internal pressure level.
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#6
by
RustyCaddy
on 23 Jan, 2013 09:21
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IIRC reading somewhere that having the set within a 5 bar range is close to balanced. Bentley and Haynes list bar pressures down to 120 but that may included the early style injectors and doesn't distinguish between things like yellow dot 107A pumps at the more advanced timing setting spec (which seems contradictory).
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#7
by
vwroadkill
on 23 Jan, 2013 23:03
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lots of info. I got to speak with diesel tech. he said basically the same thing.. the only way to change the duration from his explaination was to change cam plate.. not what I looking for.. I would buy a giles pump for that. he said to get the spray patterns and bar pressure as equal as possible and be happy. much like im looking for. of course I could just buy new injectors and be done with it...
again thanks for the input...
I may just be spinning my wheels, no pun intended
Dan
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#8
by
tyb525
on 23 Jan, 2013 23:23
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Why are you concerned about the duration? As it, what's wrong with the stock duration?
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#9
by
vwroadkill
on 24 Jan, 2013 22:11
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I was curious about the duration. concern?no. just wondering.. the engine runs good. just dont have the economy that I was expecting. so I located a poptester, to see what I had.
I also gained two complete sets of injectors, shims heat sheilds. and a room full of parts from a local gentleman going thru a Divorce. I checked them out as well. one is a turbo set. I have an NA engine. so I became curious and wanted to know more. that is the reason.Heck I even got a complete turbo system .. all for the not so bad sum of $500.
so now I am just seeing what I got. what I can use and how effective I can us it
any input to steer me in the proper direction would be welcomed.
I am not a diesel mechanic, my specialty is aircraft . not out of my realm..just never been around diesels, only gas engines.
Dan
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#10
by
libbydiesel
on 24 Jan, 2013 22:16
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The injector doesn't establish the duration, the injection pump does. The duration of the injection event lasts as long as the line pressure is above the break pressure of the injector.
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#11
by
ORCoaster
on 24 Jan, 2013 22:29
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A 500 dollar bargain.
Balance the set of 4 to get to the same number of bars as close to each other as you can. Use the shims and if need be sand them down like Vince suggests. Figure 8 pattern with oil. If you want to know volume place a cup under them and pop them off 10 times and measure the volume, do the divide and figure thing and see how well they relate.
Like was mentioned pressure and timing are linked on these engines. Some like the lowered 135 Bar injectors to allow more advance. With all the goods you got you can make a couple sets that have a series of pressures and see how they act as a group. Just make sure you don't mix and match. 135 or 145's only or 165 if you like.