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#15
by
ORCoaster
on 25 Aug, 2011 12:24
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Mark, Do you have any idea the differences in spring resistance that control the advance? The color scheme is known with the green spring being the softest but does it give the most advance?
I may play around with my pump as I have both a red and silver colored spring. I have a gauge on my IP so I can see if they make any difference in initial pressure and total pressure along with speed at which they get from here to there.
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#16
by
R.O.R-2.0
on 25 Aug, 2011 12:25
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no, it was a standard for the yellow dot pumps, im pretty sure..
1.15mm would be right on par with a 180bar injector, for a timing spec..
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#17
by
Mark(The Miser)UK
on 25 Aug, 2011 13:38
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no, it was a standard for the yellow dot pumps, im pretty sure..
1.15mm would be right on par with a 180bar injector, for a timing spec..
If you take a standard TD pump that normally operates at 155 bar for 1mm, I'd totally agree that 1.15 would get you back on a similar advance.
However that negates the point of a yellow dot being different.
My questions include are all 107 A pumps 'yellow dot' ?
The 107A was what Hagar thought was the holy grail, and internal pressures increased faster than 1.6 pumps. So why would a 107A pump need to be advanced more than a usual pump? ... Unless the advance spring was stiffer, which gents here are saying does not seem to be the case.
This means that the higher revving 1.5 engine would advance quicker and soon run out of advance....Alas I'm not a pump expert, but having the pumps available for testing would answer all the questions, especially coupled with a strobe for dynamic advance readings. Unfortunately, Quantums[Dashers] never had the 107A pump.
( Interestingly, going back the other way ie dropping break pressures dramatically, reduces gauge readings dramatically, {to say 0.5 @125bar} which is where I operate, and makes sense, as at lower pressures, the diesel becomes incompressible [1% @100bar I believe])
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#18
by
RabbitJockey
on 25 Aug, 2011 14:13
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( Interestingly, going back the other way ie dropping break pressures dramatically, reduces gauge readings dramatically, {to say 0.5 @125bar} which is where I operate, and makes sense, as at lower pressures, the diesel becomes incompressible [1% @100bar I believe])
can u explain all this more, i wish i had more time tonight to sit and search old threads, but wasn't there one that discussed more what pumps had what spring? but a stronger spring with a faster increasing internal pressure would make sense, how ever what would the real advantage be, and even then what is the purpose of the initial advanced timing.
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#19
by
Mark(The Miser)UK
on 25 Aug, 2011 14:48
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( Interestingly, going back the other way ie dropping break pressures dramatically, reduces gauge readings dramatically, {to say 0.5 @125bar} which is where I operate, and makes sense, as at lower pressures, the diesel becomes incompressible [1% @100bar I believe])
can u explain all this more, i wish i had more time tonight to sit and search old threads, but wasn't there one that discussed more what pumps had what spring? but a stronger spring with a faster increasing internal pressure would make sense, how ever what would the real advantage be, and even then what is the purpose of the initial advanced timing.
If you are referring to the cold start advance, then that is because of the design defect in IDI's where better starting is not achieved at best operating timing. So the temporary 'over advance' is required.
The break pressure thing of the injectors is perhaps clarified by a suggestion that if I made my injectors open at say 90bar, then gauge timing may be as little as 0, or 0.01mm, due to the diesel acting like an incompressible solid, and there being almost no delay to injector opening 
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#20
by
R.O.R-2.0
on 25 Aug, 2011 14:52
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( Interestingly, going back the other way ie dropping break pressures dramatically, reduces gauge readings dramatically, {to say 0.5 @125bar} which is where I operate, and makes sense, as at lower pressures, the diesel becomes incompressible [1% @100bar I believe])
can u explain all this more, i wish i had more time tonight to sit and search old threads, but wasn't there one that discussed more what pumps had what spring? but a stronger spring with a faster increasing internal pressure would make sense, how ever what would the real advantage be, and even then what is the purpose of the initial advanced timing.
If you are referring to the cold start advance, then that is because of the design defect in IDI's where better starting is not achieved at best operating timing. So the temporary 'over advance' is required.
The break pressure thing of the injectors is perhaps clarified by a suggestion that if I made my injectors open at say 90bar, then gauge timing may be as little as 0, or 0.01mm, due to the diesel acting like an incompressible solid, and there being almost no delay to injector opening
atomization would probably really suck @ 90 bar tho..
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#21
by
Mark(The Miser)UK
on 25 Aug, 2011 15:11
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( Interestingly, going back the other way ie dropping break pressures dramatically, reduces gauge readings dramatically, {to say 0.5 @125bar} which is where I operate, and makes sense, as at lower pressures, the diesel becomes incompressible [1% @100bar I believe])
can u explain all this more, i wish i had more time tonight to sit and search old threads, but wasn't there one that discussed more what pumps had what spring? but a stronger spring with a faster increasing internal pressure would make sense, how ever what would the real advantage be, and even then what is the purpose of the initial advanced timing.
If you are referring to the cold start advance, then that is because of the design defect in IDI's where better starting is not achieved at best operating timing. So the temporary 'over advance' is required.
The break pressure thing of the injectors is perhaps clarified by a suggestion that if I made my injectors open at say 90bar, then gauge timing may be as little as 0, or 0.01mm, due to the diesel acting like an incompressible solid, and there being almost no delay to injector opening
atomization would probably really suck @ 90 bar tho..
Maybe, but perhaps new nozzles would help. However it must be noted that the larger droplets would penetrate further into the swirl, and are torn apart by the swirl and the flame front. Ricardo certainly thought so and he specialised in this 'Comet V design that we use today. A slower burn may be beneficial.
I'm not saying that 90bar is sufficient, but my best mileage straight after my rering last year had the injectors down to 125 bar
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#22
by
RabbitJockey
on 25 Aug, 2011 16:33
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ok thats interesting, now is it due to the better burn from the larger droplets, or is it because the engine doesn't have to create as high of a pressure to inject the fuel?
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#23
by
ORCoaster
on 25 Aug, 2011 17:11
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It might be related to the slower burn of the larger swirling drops. Think of burning a piece of paper from the edge a little at a time versus throwing a match on a pile of shredded paper. One consumes faster but the total energy derived is from the same piece of fuel.
When it comes to atomizing in the diesel I think bigger drops burn slower and thus better consumption to power the net effect. You don't get the fast release of energy as the pistion comes to TDC, it doesn't take away from the piston travelling up the stroke but tends to add downward force to the stroke as the burn completes.
I may have this confused with adding propane or some other additive that slows burn down in the form of micro seconds. Correct if I am wrong please.
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#24
by
RabbitJockey
on 25 Aug, 2011 17:30
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the large droplet thing makes sense, not that it has anything to do with a yellow dot pump, but a larger drop would help keep more fuel burned outside of the swirl chamber. the only thing keeping idis from being far superior to a tdi is that there is soooo much heat energy wasted in the swirl chamber and absorbed into the head.
honestly tho i wonder how a modernized idi would compare to a new tdi. like a 2.0 computer controlled 16v idi with a vnt turbo... would it compare haha. its funny cause red rotors was actually working on a project to have a completely electronically controlled idi. which actually would be pretty easy. use a tdi block(for the crank positions sensor) with aaz pistons and rods, aaz head, you would need 1 bmw injector for the injector sensor thats on one of the tdi injectors, and then bolt on the tdi pump, possibly modefied, with all the sensors and crap, and then u'd need a custom burned chip, and woot woot u could compare an aaz to a 96-04 tdi fairly. wonder what ever happened with red rotors project
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#25
by
R.O.R-2.0
on 27 Aug, 2011 12:30
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where does the burn actually happen? the combustion chamber, or swirl chamber?
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#26
by
ORCoaster
on 27 Aug, 2011 20:17
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Let's think this out. The intake valve is open and air is coming in through the valve opening. Once the valve is closed the piston rises in the cylinder until just before it reaches the peak of the cycle and squirt goes the injector. Into the air that was moving in the swirl chamber but how far down into that chamber is the end of the injector? A fair piece don't you think. The fuel is under how many PSI? So I doubt much is fired up in the swirl chamber itself. I go for combustion occurs in the cylinder. With just a peek of it entering the chamber.
Just my 2 cents less a penny.
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#27
by
rabbitman
on 27 Aug, 2011 20:40
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#28
by
Vanagoner
on 28 Aug, 2011 08:02
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Is there a yellow dot painted somewhere on said pump? I'd like to know where to look for it if I run across one.
where does the burn actually happen? the combustion chamber, or swirl chamber?
From the cutaway it looks like all the fuel needs to come through the pre-chamber to get to the cylinder. Maybe the bigger droplets don't get torn apart and fully burn until they swirl thru the orifice and into the cyl, resulting in more combustion in the cyl. itself. Just guessing.
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#29
by
RabbitJockey
on 28 Aug, 2011 11:07
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yellow dot pumps have a bunch of yellow paint all over the advance mechanism cover and also their part number ends in 107a