Help with pilot timing

[AdamRRT]

I'm pretty ok with single event timing right now, but want to learn more about pilot timing. It seems so foreign to me since I'm inexperienced with multiple events. I mean, I look at tunes that I have made that run well, and they have 35* of pilot timing at 140mm3 and 2700rpm. Giving them like 45* total timing counting main event. Seems like a LOT of timing. But I know it's not, cause when I knock it down to like 10-20*, I end up with my pilot cutting out and puffing white smoke cause of too little timing. So I know it needs a lot of timing.

Anybody able to explain it for me? I'd like to grasp it a little better in the hopes that I can better use the pilot down the road, once I play around with it after getting a little better understanding.

All help would be appreciated.

[AdamRRT]

Ok let me be a little more specific. I know I left that pretty open. Granted, it's because that's about as vague as my understanding is haha. But to tighten it up a bit:

1 - with the pilot event being so early in the stroke, and being of so little fuel volume, it seems that it wouldn't have much effect upon power output. BUT that said, I seem to have much better throttle response in tunes that I build with a pilot event compared to single event. Any info to help me understand this?

2 - given that the stock tune is so crazy with low timing numbers, are you guys moving your pilot shot a little closer to your main event, even after moving the main event to a more aggressive commanded timing?

3 - I understand that if you spray a large pulse too early it sprays outside of the bowl and we see melted piston crowns. But the pilot event is spraying crazy early in many stock cases. Is the reason that it is of no such negative consequence due to its low volume?

I've just got very little understanding of pilot. I know that as much as I love the efficiency of the single event tune, I love the quieter nature and smoke reduction that I get when including a pilot event. But I am far from having a good grasp of it, and any help would go a long way to helping me understand. I don't want any secrets to tunes. Just some help in my general understanding of the pilot. I've searched but am not finding the specific answers to the questions in my brain. Thanks in advance!

[someguy]

subscribed.

I don't understand why a single shot gets smokey.

Is it because its late if the pilot isn't there, ie if the wasn't there it should be a lot earlier ?

Or is it because the injection rate is too high unless the combustion chamber is really hot and pressurized from a small, early pilot ?

What is this about burning the piston tops if the pilot is too early ? Akin to what you see with predetonation in a gasser, ie cylinder pressure and temps really high from a really early injection event ?

Very interesting, all of this. Thanks for sharing it.

[easymon]

I am sure lot has to do with cam shaft and in cylinder egr will never get it perfict without regringing cam. Thats my opinion.

[icem237]

In my experience with the 90hp nozzels i had installed. My single event tune is very clean compared to the way the stock tips reacted. But I also had new injectors installed too. So could have been that an injector was sticking and dumping fuel. Now with pilot that cuts off after coolant reaches 146F start up is clean in the cold . Runs really well. Wish someone with more knowledge than me could tell me why this could be with larger nozzels?!?!

[killerbee]

Without the pilot pulse, the same main timing schedule is far too retarded. If eliminating PI, then advance the main timing schedule.

Think of PI as a fuse, that ignites the main pulse. Also, you will find information by searching "flame front propogation".

[AdamRRT]

Thanks, Michael. You're always helpful and I really appreciate it.

[AdamRRT]

In my experience with the 90hp nozzels i had installed. My single event tune is very clean compared to the way the stock tips reacted. But I also had new injectors installed too. So could have been that an injector was sticking and dumping fuel. Now with pilot that cuts off after coolant reaches 146F start up is clean in the cold . Runs really well. Wish someone with more knowledge than me could tell me why this could be with larger nozzels?!?!

You may just have it narrowed down a little better, man. Glad to hear all's well.

[jordylee18]

If I cut out all pilot activity above 2400 rpms how do I increase main timing to compensate? Surely a person has to change something!!!!

[olboyowl]

increase main timing from where you cut pilot out at. thats what ive done and it works well