when adjusting timing what should i be looking for. I am looking for more cruising adjustments which would be from 2000 RPM to 2500 RPM. I have the boost right now at 25 PSI at max and i see around 15 cruising i think it is.

should i go positive or negitive to help fuel economy or should i just try it and see what happens

I can tell you my thoughts, as this is a project I wanted to do. Advance the timing 5-10 degrees (negative) then observe DIC before/after. DIC should be reliable for determining changes as long as you are not messing with pulse width or quantity.

There is some eveidence that some of the fuel additives for cetane are helping with the diesel cycle torque stroke. If I understand effect of increased Cetane, it will "slow" the explosion over time. Intuitively, this tells me that advancing timing would be a good thing. Interested in what you find out Brian.

If possible, monitor you egt for changes as well. It may be significantly lower. If it is obviously higher, stop what you are doing. FWIW

Unless this works differently from every other engine out there, to advance timing you increase the number of degrees before top dead center. In other words advancing is POSITIVE (or adds to total timing) and retarding is NEGATIVE (or take away from total timing).

What he said Brian :)

i am going to give that a shot....right now my DIC is off by 2 mpg. if it reads 13 i am really getting 15.

so you are saying move it just 1 degree towards TDC. so if it was 5 i should make it 4

No, if you are wanting to advance the timing ( and I think you do) if it is currently 5, advancing it 1 degree would bring to 6 dgrees. If it is -5, it would be -4.

degrees BEFORE top dead center. advancing is earlier, retarding is later.

Hope that helps!

Usually you will get better mileage by advancing the timing. So instead of 5 go 6.

gotcha...i changed it between 1200 and 2600 RPM

You could datalog (pid) your runs as well, say 60 mph. That way you could have verification of the timing change.

what exactly will changing the timing do exactly

one other thing which table should i be modding

Brian, suggested reading (http://mb-soft.com/public2/engine.html), an article I like

one other thing which table should i be modding

What is your elevation?

ummm.....no more then 1000' any time....

B0910

Somebody check me on that.

that is the one i am using and seems to work. changing the timing seems to make it run alittle smoother. i changed the vanes by lowering them from what i had them and they increased the timing 1 degree more at cruising speed. i am going to up load it tomorrow and see what it does. It did not change power really.

there is a max timing table it appears to keep you "safe"

You should be able to play with 5 degrees with no real danger, even 10. But I like the caution, always a good thing. Like doing your first heart surgery :)

Here is some nice bed time reading -

http://www.tytlabs.co.jp/english/review/rev373epdf/e373_009hotta.pdf

Cheers,
Ross

i am doing a little at a time. with fuel prices the way they are i can not just go out and drive to test what i have done. i can just see when i do normal things i have too.

Ross, are the MAF fuel tables disabled when MAP is selected?

Nice article BTW

You referring to the MAF Fuel limiter tables?, they are still active even if the timing is MAP based.
What has me a little confused though, it appears the MAF expected airflow tests are not run (enable temp is set to max), so there might be a chance the MAF is reading wrong numbers, the ECM would never know, yet you might get fuel limited values based on crazy MAF readings :confuzeld , but sorry, this is timing talk.

Cheers,
Ross

Disregard, my question was invalid.

well it seems what i have done is increasing my fuel economy. i will not know till this tank is done. but the DIC is .7 higher then it was the last tank.

So after reading the article to which Ross provided the link, it states that one of the keys to lower fuel consumption at light loads (cruising?)is a small close-coupled pilot injection event timed closely, but just (5 to 10 deg) before, the main injection. In addition, the full load condition apparently benefitted the most by an advanced 4.5mm^3 pilot event timed at approximately 50 deg BTDC. Can both of these strategies be incorporated into the timing maps of the Duramax?

Interestingly enough, the extreme advance in the pilot event under full load is reminiscent of the "fumigation" strategies that I have read about previously in other diesel text books. Of course, fumigation doesn't necessarily have to be just diesel fuel.

The other thing that I noticed is that even though the 4.5mm^3 pilot event at approximately 50 deg BTDC was "best" for full load power, their other experiments show that any fuel quantity above 2mm^3 would start to adhere to the cylinder walls in these conditions.

NOTE: I don't have a DMax anymore. I now own an older PSD, however I do find all of this fascinating...:ro)

Regards,

Here is some nice bed time reading -

http://www.tytlabs.co.jp/english/review/rev373epdf/e373_009hotta.pdf

Cheers,
Ross
just wanted to say that was good reading:ro)