Pilot - minimum?

[AdamRRT]

Is there a point that the pilot just stops firing for some reason? I was cutting it back and just to see what it'd do, I put it at 2 mm3 across the main pilot qty table. It just stopped firing pilot totally. I'm not sure why since stock it has pilot at like 1.5mm3 in the lower end of the table.

[GMPX]

There usually is a minimum before it won't 'bother' with the injection event, usually it is something that can be calibrated, but I haven't looked for it yet.

[AdamRRT]

Ok thanks. Ill go back to where I was before the change.

[THEFERMANATOR]

What happens in the DMAX is at a certain point the duration is so short the injector cannot actually open that fast due to injector lag. It takes X amount of time for the injector to open, then Y amount of time to inject the desired fuel quantity. These 2 added together is what how long the ECM will command the injector open to get teh desired MM3 of fuel. If the pulsewidth drops to a point that is to short of a time for teh injector to actually inject the fuel the pilot will not happen.

[AdamRRT]

That makes perfect sense. We still have nobody who can tell us the injector lag on our trucks. But there's a few who I'm sure will test it out for us soon enough.

Any ideas how this is to be estimated?

[AdamRRT]

Ok a few questions.

1 - Which way is the best way to reduce pilot in my efforts to keep just enough pilot to keep it quiet below 1800rpm? Reducing mm3, or shortening the duration in microseconds?
2 - to re-iterate the last post. Any idea how to estimate our injector lag for now?
3 - how can it be measured?

[tinman]

This is question on my mind also. My goal is minimally effective pilot for a quiet, smooth running, efficient engine. I also would like to compensate for my 50hp injectors. Currently I am at a max of just less than 10mm3 and idle is at 1.8mm3. It runs very well. Wondering how low I could go

[AdamRRT]

I've experimented with a few techniques this past few days. I've basically left the mm3 table alone. I evened it out a bit, going for a smoother, more linear commanded pilot volume. But it's generally the same numbers.

Ive decided it's much easier to adjust the pilot duration than to adjust the mm3. Duration allows a much finer adjustment. So first I ran my single event tune as main + pilot, losing pilot at 1200rpm. That worked.

Then I cut the pilot duration in half. That resulted in no pilot at all.

Changed the pilot duration x .75. That worked well. I'll probably try to reduce that duration slightly in the future, but it's pretty short now. May be a waste of time to mess with something so trivial. But either way, I now have it working & I like it. It's now based off the single event tune that greatly improved my city mpg also. Now she starts & idles easily with no white smoke. Plus it's nice and quiet at parking lot speeds. People no longer come from all corners of McD's to look out the window and the rattle trap.

Just a little info to add to the knowledge base regarding the minimum pilot that still gets commanded.

Should I post it in the repositories? Thoughts? It would be with the inherent understanding that it's got all the risks of installing someone else's tune. Heck it'll probably be weak for most as I've attempted to reduce smoke & wasted fuel because of my 70hp nozzles. I'm 100% sure that some knowledgable guys can improve the tune greatly. I'd love to see some of you experienced guys play with this tune for less smoke, better mpg, and more power. I've done almost nothing to improve MPG on this tune, as thats a later goal in my timeline for this tune.

[tinman]

I'd love to see a single event tune just to see what folks are doing. I'm gonna play with that in the future just to see what kinda of mileage I can get. When you drop the pilot, are you combining the duration of the main and pilot at that point or just dropping the pilot with no change to the main.

[AdamRRT]

That's where tuning comes in. If you reduce it to one event, you then can decide where you need the additional duration and where you don't.