Timing

[petestoy]

I looked at the timing map on the LBZ and it is pretty complicated? Not many people seem to play with the timing, is there a reason? I have heard that most LBZ's only use table A but in EFI Live says that Table B is used under most driving conditions. I am fairly new to the Turbo Disel but why wouldn't you increase the timing a couple of degrees? Is it because of the complicated tables or another reason I can't see? I can't see how a couple of degrees could hurt it should clean up the burn a little? Cylinder temps should not increase that much? Can we just highlight the table and say increase by 1 or 2?

Hope some one can help?

[camcojb]

timing is different with diesels vs a gas engine. For example, a gas engine loves to run 40-50 degrees cruising down the road at light load; a diesel is usually happier (for mileage anyway) running single digits, maybe 7-9 degrees max. As far as power, they do respond to more timing, but most tuners limit max timing to 28 degrees or less (although some of the good race tunes run 30-34 degrees).
To answer your question, they respond to timing, but a lot less than a gas engine in the cruising areas. And yes, there are several tables (5 on the LMM and maybe the LBZ) and many modifiers and limiters to the timing tables. Also different conditions use different tables and nobody that I know of has exactly determined when one is used over the other, although B seems to be used the most, at least at low altitude normal ranges.

You can add/subtract/multiply + or - by percentage to the tables in individual cells or highlight areas or complete tables.

Jody

[petestoy]

Thanks Jody, now that brings up some more questions.

If you were to say increase the main injection timing 2 degrees do you also have to increase the pilot?
Would you also increase every table by 2 degrees?
What is Low altitude, Medium and High altitude?

[camcojb]

Thanks Jody, now that brings up some more questions.

If you were to say increase the main injection timing 2 degrees do you also have to increase the pilot?
Would you also increase every table by 2 degrees?
What is Low altitude, Medium and High altitude?


Most leave the pilot alone. It is a very small shot relative to the main shot, and is one of the big reasons our Duramaxes are as quiet as they are. I haven't seen a tune yet that moved the timing on the pilot.

You'll still want negative degrees at idle, makes it much smoother, so I wouldn't play with that area. I added some to the cruise areas of 1600-2000 rpms and 20-35 mm3 where my truck seems to cruise down the freeway. I also have added timing in the wot areas above 2400 rpms, and then blended the map into those changes. In a 1/4 mile run other than the start you'll be above 2400 rpm throughout.

You could blanket add the timing if you wanted, I'd just leave the idle area alone. As far as altitude, I believe that low altitude is seal level up to 3500-4000 feet or so. Medium is from there to 7000-8000 feet (a guess, the words used were "like Mt Everest" which is much higher than 7000-8000 feet!).

[petestoy]

Thanks again Jody, My logic was that the Map Bosch has laid out works so why play with it? But the timing is more then likely retarded in order to keep NoX emmisions down.

I don't mind playing and trial and error, but I prefer to do it with a litle bit of knowledge first! That way I hopefully don't blow anything up!

I think I will start between 1000 and 3300 rpm with a couple of degrees (baby steps) and see what happens? That way I leave idle alone except for high idle but I can turn that off.

I am assuming that the numbers in the table are actual Timing degrees? And that (-) #'s are ATDC and (+) #'s are BTDC.

[camcojb]

Thanks again Jody, My logic was that the Map Bosch has laid out works so why play with it? But the timing is more then likely retarded in order to keep NoX emmisions down.

I don't mind playing and trial and error, but I prefer to do it with a litle bit of knowledge first! That way I hopefully don't blow anything up!

I think I will start between 1000 and 3300 rpm with a couple of degrees (baby steps) and see what happens? That way I leave idle alone except for high idle but I can turn that off.

I am assuming that the numbers in the table are actual Timing degrees? And that (-) #'s are ATDC and (+) #'s are BTDC.

you are correct.

Jody