The injector pop-off spec is within 10% of 2000 PSI. Figure spikes and peaks and such, and 2500 would be a reasonable guess.goglio704 wrote:I thought a VE pump injects at about 5,000 PSI, but I don't know for sure.
However, reading the Bosch VE-style IP book (the "Yellow Book"), it's clear that the fluid dynamics involved preclude anything like a union in the IP line, so scratch that. It will run, but not as Bosch designed. Like two-stroke exhaust expansion chamber design, there are reflected waves back toward the IP when the injector closes; the delivery valves are designed with that in mine. Change the shape of the interior of the injector line, and that throws it all off.
And, as time goes by and I work on more and more VE IPs, I have begun to strongly suspect that pretty much all of our IPs are worn out, in the sense that the hydraulic timing system is probably not functioning anywhere near spec. That is a guess, but a pretty well-educated one at this point. The advance mechanism cannot be tested for proper hydraulic advance functioning via the Tach-N-Time, because there is a Torque Control mechanism that retards the timing under light load/high RPM even if the hydraulic advancer would normally advance the timing based solely on RPM.
I do not make this up, only a German could come up with the mechanism. It is explained in the "Yellow Book".
My own '82 shows 8° BTDC at idle, and pretty much 8-10° BTDC at 4000 RPM. Is this correct? Or does it prove my "non-functional advancer" theory? Who knows?
Add'l variable: the newly-rebuild VE-style IP I installed on Tom Sigmond's Toyota diesel PU showed this data: IP set mechanically per Toyota spec got about 3.6° BTDC at idle; at 2800 RPM and above, I saw ~12° BTDC.
That's only a single data point, but it does reinforce my "LD28 IP non-functional-advancers" theory. Obviously, we need more data (or more-educated forum members).
All this is prelude to me stating: one car's "EGT @ some degree base advance" may not translate at all to the same result on another vehicle, due to differences in the internal advancer's performance.
Bear in mind that the advancer piston is only the part being acted upon; the true wear item is likely to be the vane lift pump, is my guess.
Many repair manuals warn specifically against bending injector lines, and you will note that all diesel injector lines are always of the same length, even when this means making extraneous loops for the injectors that are close to the IP.
If the goal was power & economy, one could do a good job of adjusting the timing using a variety of feedback metrics (dyno, EGT, consumption equipment). But that's not the whole goal, at least it isn't for me. And there is a limit to the number of hours I am willing to spend trying to optimize better than Bosch's engineering staffI have had similar thoughts about using EGT as an indication of timing. Until it produces high EGT, advance is a good thing isn't it? There is also an emissions issue related to advanced injection timing. High levels of something. NOx or some such.
That is where I think we should concentrate timing efforts. I am ashamed to say that I have not gotten around to this, but in my own world, where for much of the time I do not drive my Maxima, it just doesn't get to the top of my To-Do list. Here's hoping someone else will take up the challenge. Every time I start to try to mechanically time mine, I bounce off the project and end up doing something else. Turns out, buying the equipment and tools was the easy part.I think the goal of static timing has always been that it would be a good baseline reference. If two or three cars could be static timed and then shot with a timing light, we'd have reference points. Once the data was collected, no more need for static timing.
, might not even have to remove the injector lines.