Total duration looks long

[AdamRRT]

Just for discussion's sake. I'd like some of you guys who understand the multiple events to help me a little. I'm trying to get a grasp on these multiple events so that I know that I'm not giving too much duration. Sure main might fall into a safe range, but with pilot and time between them, I've gotta be careful with that too, right?

The Min and Max timing limits that most are setting at 25* and 45* BTDC (5* & 25* if considering bias) seem to be good, but what total do you guys like overall, from start of pilot to end of post, to make sure we're safe?

For the sake of learning, I added the total duration (in degrees) from start of pilot to end of post (including time between) and at like 2000rpm and 45mm3, I'm looking at like 47* of total duration. Seems a little high to me, even at such low RPMs. And yes, it was acceptable uS durations past the minimum time limiters. Thoughts?

[FUBAR]

I'm also curious...

[AdamRRT]

So I know that guys I've seen looking at this thread have been posting about tuning trucks. Can you help us out?
Or is my question not making sense?

You guys who are tuning trucks as a business even... what are you doing with pilot in the daily driving ranges when you change the main timing duration (and by correlation timing)?
Basically, are you guys calculating the TOTAL injection duration from start of pilot to end of post (where applicable)? My mind tells me to do that, but some guys I've talked to just ignore everything except for the main, and let pilot and post do what they're doing as if nothing had changed in the middle. To me that doesn't make sense, cause I may be initiating pilot injection at 45* BTDC. That's horribly early IMHO.

Thanks for any help.

[2006Cummins]

I have been wondering about this also. There has got to be a maximum "window" before and after TDC when the injector will still be spraying in the piston bowl. I think this is why some are going to a single injection event when a lot of duration is needed, so that the pre and post events don't get in the way. I would also like to hear from those who have spent some time playing with this.

Mike

[olboyowl]

i have post takin out completely and pilot is completely 0'd from 2600rpm on. i also smoothed it out where it still takes effect in daily driving. i have my main timing pick up from around 2400 rpm and rise gradually up to 3500rpms where i hit 45* (25 with the bias) in my tables. hope this helps some

[AdamRRT]

I have been wondering about this also. There has got to be a maximum "window" before and after TDC when the injector will still be spraying in the piston bowl. I think this is why some are going to a single injection event when a lot of duration is needed, so that the pre and post events don't get in the way. I would also like to hear from those who have spent some time playing with this.

Mike

Yup you're exactly where I am, Mike. There IS a window of where you'll be spraying out of the bowl. And yes, I know it's RPM-dependent. But I don't know what the duration limit is at what RPM. I've heard to never run more than 30* timing on these trucks, but looking at the pilot event we're way past that almost all the time.

I have bigger than stock nozzles. So I'd like to cut down my duration (just like a 10-20% reduction if that on main, and about 75% less on pilot) at daily driving areas of the maps. But I need some of these guys who are actually reporting these complete comprehensive tune jobs on these trucks to help us out a little bit. Their knowledge far exceeds mine, obviously, since they're tuning and I'm not.

I'm sure we'll get help soon, Mike. I know with the little bit of gasser tuning I've done the info is freely shared and everyone is helpful. Right now it's very strange in that guys act like their tunes aren't to be shared, but give it time. With vehicles that have been around a while, there are entire tune repositories that people upload their tunes to so that people can see what helped them on their tune, or what strategy helped them fix an issue. You want a tune for a 2001 C5 Corvette with stock heads, FAST intake, and a Trex cam? It's available. Of course you won't USE it on your car. But you can get an idea of what to do. It doesn't replace knowledge and tuning skill at all, so it's not a worry. It's not like someone wants to get a custom editor like EFI Live just to run a tune that is dialed in to someone else's truck and not their own. And if they want to, pfft! I say let them. It's their loss. (Sometimes I think some guys are to tuning what Metallica was to MP3's, the way they act like people would want to steal their tunes) So give it time for more people to get involved and I'm sure it'll get to normal tuning like we're all used to, and this information vacuum will be gone hopefully. Until then we'll just keep asking questions and begging for the assistance we need from the guys who have been doing this ahead of us. We have good members here, and I'm sure it'll be no problem to get help from them. I know most of the guys who I thought would respond have already been in this thread looking, so maybe they're gathering the info to help us before they start posting randomly.

[AdamRRT]

i have post takin out completely and pilot is completely 0'd from 2600rpm on. i also smoothed it out where it still takes effect in daily driving. i have my main timing pick up from around 2400 rpm and rise gradually up to 3500rpms where i hit 45* (25 with the bias) in my tables. hope this helps some

No that really doesn't tell us anything about how you calculated the change in timing and incorporated it into the tune. Care to share that part? The actual theory of operation so that we can start with a tune that's close. You can actually make a "good enough" tune just going by theory, and then perfect it on the dyno. But without knowing how a change in duration changes the timing and the ignition point of the fuel, it's pointless.

Example: say you add enough main duration to equal a 2* increase in overall duration. Do you then want to add 1* timing to keep it centered at the same point across TDC?
Or are you not adding timing accordingly, just allowing the main to push further ATDC?
If you do add timing to make up for the added duration, are you then removing the same amount of timing from the pilot event, putting the injection event back to the same initial degree at which injection begins?

[olboyowl]

i left the pilot timing alone (other then smoothing all the spikes out of it). just adjusted the timing in the main injection event.

[AdamRRT]

Anybody who is able to describe the thought process and answer the questions in detail?

[Dmaxink]

This is a nice subject...many will not chime in due to this is what separates opinions... Different strokes for different folks and different results for different setups. I will say this, i eliminate post injection...Pilot+main does have to be calculated together... it is typically not a surprise to see a tune set up with 100% btdc in the cruising range...however, this is not a preferred method of many. One rule of thump is whatever you advance the main to, try among the pilot to keep in in stock form, yet smooth... To get a x=y rule of thumb answer wont happen on this topic sadly. I do recommend wiki for diesel combustion, pilot injection, ect ect to get a full understanding of what is going on in the chamber, however.

Hope this helps a little.

Rule of thumb #2 If it rattles, take it back a couple of degrees and i have pilot off past 2600 rpms 60mm3.