Sooo, . . . . . Has anybody tried replacing the . . .

[RCCUMMINS89]

Not following exactly what you're saying Jon.

I do, yet don't.

[cubedeficient64]

Have removed my obvious comment. And will do the same for myself and this discussion. Cheers

[RCCUMMINS89]

I know what he's saying................

I'm asking what he's getting at, as it's only a partial statement.

Timing depends on about 100 variables. We could talk about for pages what dictates timing, but that's pointless.

More air (not boost in itself) actually requires less timing per cc of fuel.............HOWEVER, in the real world more boost (air) is created by increased fuel going into the chamber.

The more fuel, the more timing.................even though, yes the amount of air changes the amount of timing needed.

The more rpm..............the more timing OBVIOUSLY


Now for a higher boost creating a faster burn rate..................AIR creates a faster burn rate, however........the way the fuel gets injected has a TREMENDOUS control of how fast the fuel burns. There is only so much you can do when the droplets of are a certain size and the injected fuel becomes more of a stream.

[BC847]

OK, so the point of this thread was to figure out a way to raise case-pressure, for the potential benefit of better H/R fill-rate, in the higher engine rpm.

We've cyphered that the increased case-pressure is gonna alter the stock/OEM dynamic injection timing advance curve. RCCUMMINS89 & crew have come up with a means of basically correcting such alteration (still in development).

That being said, What is an ideal injection event timing? If I understand the P-pump correctly, it doesn't have dynamic timing and as such, they run at one specific mechanical setting.

I realize coming up with an overall ideal number isn't as simple as that. There's all kinds of variables that would, in themselves have a substantial impact. In my head, sorta summing things up, it gets down to the size of the fuel's "window of admittance" (I just made that up ). That being, the time required to admit the given (and variable) quantity of fuel. Certainly the common-rails have eleventy-billion psig to shove the fuel in and keep it in a narrow window, but we don't. This issue contributes, in my mind, to our dilemma.

We're trying to adjust the time of the injection event. Yeah, well injection event what? The start of the event? It seems coupling how big the window of the event is with that really complicates the question. We want to get the fuel in, ideally, all at once to so as to arrive at an ideal combustion pressure relative to the piston/crank.

As a proposal to that situation, would we benefit by going to larger injectors, but run a higher Pop-pressure? I'm thinking our Pop-pressure can be used to widen/narrow the injection event window.

Hmmm . . . . .


I figure all the above assumes one's talking about WOT conditions. Backing off the throttle throws all our math out the window.

Crap.



If the daggum rain will let up, I'm gonna put the light to my heap to see what all the adjustments are doing relative to the dynamic timing curve. So, if I can actually make a plot on paper to my liking, what would be an ideal starting point based on any info available on these here Internets? Anybody seen such?

[RCCUMMINS89]

Thanks for getting us back on track..............I'm the worse when it comes to veering threads.

However, I do have to say...... Dumping in the fuel all at one time (if I'm reading correctly) isn't what we want for power. One of the reasons the newer pumps can make more power is due to a longer injection event.


As far as timing..............there's no perfect timing. As far as the advance curve..........can't go wrong with the stock curve. To keep things as simple as possible, we simply do everytying in our power to keep it as stock and just adjust the static accordingly and simply lose a little low end, mid, or upper....depending on goals.

[BC847]

With alternating Sunshine and thunderstorms , I've removed the cooling fan and associated shroud, pressure-washed things, and applied timing-tape. I'm using the edge of the serpentine belt as a pointer (that shown here is TDC of #1).

[RCCUMMINS89]

[BC847]

I've got the transducer located as close to the #1 injector as I can while staying on unbent piping.





The displays I've got available . . . .





This timing light doesn't work as easily as regular gas lights I've used in the past. You can't just pull the trigger and see where you are relative to the timing-tape. It turns out, I don't need a timing-tape at all.

This set-up apparently only sees one particular degree reading once it's dialed-in.

- To start with, see the little black slide-button, between the two red push-buttons above? Trigger-Point. What they're talking about is where the system recognizes the beginning of the injection event. Selecting LOW has the event beginning seen at about 30% of the pressure rise in the tube as is seen by the transducer. Selecting HIGH has the event beginning seen at about 70% of the pressure rise in the tube. The instruction manual says most manufacturers work with the LOW setting.

To make a reading:
- Connect stuff and start engine.
- Set desired engine RPM.
- With the engine rpm stable for over 5 or so seconds, the degree display will stop blinking.
- Point the light where your pointer is. In my case, it's where the edge of the serpentine belt interfaces with the damper (or 0 degrees as shown by my timing-tape).
- Pulling the light's trigger will start the strobe-light.
- You'll notice right off, that the light shows the 0* mark WAY off to the left of the damper as you see it. Remember those two red push-buttons shown in the image above? While pulling the trigger, work either of those two push-buttons to move, or off-set, the 0 degree mark on the damper, over to the pointer.
NOTE: there are two little red push-buttons on the side of the gun allowing easy working while pointing the light, and pulling the trigger.

Having lined up the 0 degree mark with my pointer, the timing light says . .. . . .



As one looks at the truck as it stands, my injection event timing is at 18.5* BTDC @ 914 engine rpm.



This may take a few . . . . . hundred . . . . minutes to come up with plots.

[BC847]

It appears I've been on the cusp of a run-away issue as when I raise my idle speed to anything above 1200 engine rpm (using the throttle-linkage tie-rod), the blame thing want to rise on up toward 4000 rpm. Relaxing the linkage again has the rpm come back down.

Crap. I gotta rework my throttle indexing/fuel-screw settings.

[RCCUMMINS89]

So.............sitting at 18.5 at idle.

Where are your timing marks, etc.............. skipped 1 tooth now, right?


and, ya...............my truck randomly started hanging yesterday w/normal driving around. Even though I've been driving at the exact same fuel screw setting for over 2 weeks????????????????????????????????????????? WTH?

[BC847]

So.............sitting at 18.5 at idle.

Yes, My name is David, and I don't know what normal timing rattle sounds like.

[BC847]

IIRC, I'm at one tooth skipped, as well as your spacer thingy (which is equivalent to the M&H spacer plus a little?), and 75psig case-pressure at idle (850ish). The "Marks" are about 1/8th inch retarded.

I'm thinking the case-pressure really has things advanced.

I'm gonna run-in the set-screw on your spacer (it's almost all the way out) as soon as things cool off a little (the fan's blowing as hard as it can) and see what it does with that base figure.

[RCCUMMINS89]

Ahhh........................you're sitting at the EXACT timing I am (according to marks). Once I added 3 1mm timing shims to the spacer, it sounds "normal" again on my mess.

[BC847]

I'm thinking I can back-off the fuel-screw a little to get control of the run-away, and adjust the idle as needed for the tests. I'd like to get readings at say: 1200, 1600, 1800 rpm or there abouts so as to plot the curve.

[turboram]

Longer injection events are not beneficial, acualy it is the opposite . Timing needs to be controlled by fuel rate and rpm ....the one benefit to boost controlled is for spool up and cruise . They should be controlled by both idealy.The ideal timing curve would be stock idle and cruise then as boost comes up 8deg for every thousand rpm.