Adjusting Pilot Timing when Base Timing is changed?

[Wheelz]

Here is what I've been trying. #10 was when I was thinking in CAD units. #12 is using the logic I mentioned in the above post. Also check out this paper. It took me a couple times to read it before I started to grasp the concepts.
http://archcomb.itc.pw.edu.pl/downloads/46_2010.pdf

E35A_0010.ctz
E35A_0012.ctz

[CwF]

Interesting and good work. I'd really like to see a detailed log of varied conditions. I haven't touched pilot so far mainly since I haven't decided on a suitable feedback to help make decisions. I think you're right to think it is maybe not optimized for efficiency but my take it a little different than yours maybe. I don't think it is nearly as important as main timing. From my readings the factory got it right enough.

First, those two tunes register the same in a compare?

I see you upped the quantity in the meat of the operating area. What have you seen to support the change? You do know that the pilot quantity is taken from total calc, so the main at a given calc mm3 will be smaller? So for example, at 40mm3 calc, under a steady cruise a 1.5 pilot gives a 38.5 main, and your 3.0 gives a 37.0 main. A log may see a difference?

Also I see you have greatly lengthened the gap, or PILOT1MT. Again, any log support? I understand the setup the pilot performs is time dependent, and have seen dat to suggest it is long enough, or not, and a few µ or ° (alt 248) extra has little if any effect that main timing adjustment couldn't also achieve. Actually, to far ahead and it is now extra resistance, though miniscule.

Lastly, I think the stair step does make sense. As pretty as your curve is on b1201 is, I think smoothing is irrelevant to the computer. The variation in the factory table is really for recognizing the different states those ranges are effective, transitional you could say. As mm3 changes or rpm, there is no technical reason I know of for any difference in delay. The differences are for different uses of various ranges, accelerating through, decelerating through, steady state, etc. If that makes sense. Remember, the studies fix factors we don't have to fix. If they show a difference it doesn't necessarily translate when the option to change the main is available.

I congratulate you for not turning off the pilot as rpm goes up. Again, no technical reason to do so unless we exceed the capacity of the rail. No reason to do so otherwise, plenty of higher speed (smaller, shorter stroke) diesels maintain pilot up to 5500 rpms. It is always a benefit. The tune is not set to rev past stock however. You do tighten the time as rpm goes past the stock range, why? Actually you have it curved with a peak. I don't get it.

In my logs I see times that don't follow the tune that suggest there are a few tables or parameters we don't have access to with efilive. This is very apparent with post injection. Who know whats up with those P2 and P3 variables. I've never seen them. I did find the extents of Post2 a year or so ago in maybe 10 various tunes, then turned it off. Now, with a few months of 170 mile mountain runs a bell went off and I used that knowledge in a new way, turned it back on with and have great results. With some negative numbers I solved my earlier issue and find it very beneficial. At some point I'd like to take a look with WinOLS or something and see what I can find, if I can find the time for such brain numbing.

Keep up the good work.

[CwF]

Oh, the last 158.4 mile run used 7.30 gallons! With 4 burst past 115mm3 up long hills! One to 4003 RPM!

[CwF]

I'm back at looking at this and it occurs to me now I was on a side thought. The title is asking 'should' you adjust the pilot 'because' you adjust main. I'm thinking a definitive NO. The pilot will follow the main.

Back to what page I was on is more like 'Is there any advantage in adjusting pilot timing?' regardless of main timing. And to rephrase what I was trying to say, I'm sure there is in some cases and I can't figure out how to tell in a meaningful way. Large adjustment may yield some feel, some mileage change, or sound, but smaller changes seem within some magic margin of error. I looked at some other papers and think there are three ranges: Not enough time and you can hear it, a few thousand micro second range where it's long enough, and over that with no indication what so ever. I think optimal is at the border of the first two in order to minimize excessive (though tiny) pressure BTDC without any advantage that can not be had by simply adjusting the main, or pressure, or another factor. So I'm leaving mine alone.

On these tunes you have the pilot out to 47°+ before the main at peak. I say too far. Way to far. Damaging no, beneficial is the debate. Note that in my logs on my tune the pilot seems to close in at higher RPM despite a timing steady table. Closing up to half or a third the delay my stock table says to do beyond 3300 rpm. And again, no technical reason to turn it off and I do tune to stay within rail pressure capabilities - there enough there for me - so far. There is another hidden parameter or table causing this....?

[Wheelz]

While I do agree with most everything you said, referencing pilot timing in terms of degrees advance is useless. It should be discussed in terms of ms advance as you are attempting to control the ignition delay. I'm not denying my pilot could be advanced too far to be useful. I'm experimenting with this quite a bit. Just note that when you do your calculations don't worry what the degree advance is because the only purpose of the pilot injection event is to control the ignition day of the main event to create a smooth burn. And in doing that you want to keep a smooth ms distance between the events.

[CwF]

Agree, that is why the tables are in μs. I just calculated it out and thought holy crap on a cracker... I'm interested to hear the results of what the extra 2000μs or so is giving.

[Wheelz]

Just got thru comparing it with a tune that had a max PI timing advance of 1700 ms. Ran with a lot less rattle at higher rpms. Ill post up that tune in a few days.

[koolky]

Any theory on why rattle was reduced with the PI timing advanced so much at higher rpm? Do you think that with the advanced PI timing that it is having an effect on the fuel pressure drop/recovery time between PI and MI, allowing the MI to atomize better?

I didn’t realize you guys had commented here since I last looked at this thread. I am still working on my tunes and have sort of come back to optimizing PI timing and now starting to look at mm3.

Wheelz, I noticed in posted tune #10 that you dropped the PI timing down below stock values in the low rpm/mm3 range. Did you notice any changes at idle with this? A few months ago I was playing with advancing the timing in that range with the idea that the MI event would have more time to recover fuel pressure possibly leading to better atomization without upping rail pressure. I also lowered the PI mm3 at idle and noticed only the slightest increase in rattle but figure that would also mean that the PI event is shorter and leave me with more time between PI/MI.