Duramax Diesels Forum Truck of the Week
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Old 11-19-2017, 10:48 AM
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TheBac TheBac is offline
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Default Cold weather tuning changes?

Ive read more threads than I care to where someone is concerned with excess gray/white smoke on cold starts in the winter. I have this same issue along with the engine "chugging" until it gets some heat into it. Its been three years and Im tired of it.

In a recent thread, Dave made mention that some changes could be made, but I have no idea what. I realize my larger injectors (30%-ishs) and lower compression (similar to LBZ) play a role in all of this, but what can I change within my tuning to help somewhat alleviate these ridiculous cold starts??
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Old 11-19-2017, 11:15 AM
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clrussell clrussell is offline
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Sure all of your glow plugs are working?

Started mine this am 30 ish degrees no glow plugs and 45%s.. chugs about 5 sec and clears up smoke in about a minute
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Old 11-19-2017, 12:11 PM
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I've had success with tables {B0915} "Injection Timing ECT (C)" adding 1 or 2 degrees at idle. and {B1002} "Fuel Pressure ECT". I liked fuel pressure at idle to be around 5500 - 6500 PSI seemed to help

{B1004} "Fuel Pressure IAT" & {B0917} "Injection Timing IAT" may also help but I zeroed mine

you can also mess around with the multiplier tables for these ones too for making it use them at what ever temp you like

this was for stock injectors but should help larger ones
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Old 11-19-2017, 02:25 PM
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DAVe3283 DAVe3283 is offline
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Time to tell my secrets, I guess

As a quick baseline, if you start with my No Logic 3.0 tune, you can look at what I did to the Injection Timing ECT tables ({B0911} through {B0915}). You will notice they are NOTHING like the stock tables. For example, {B0915}:

Stock is on the left, the smooth one on the right is mine. I have no idea what GM was smoking with the stock LB7 tune, it is garbage in the cold.

The real trick here is not the values in this table. We don't actually care. What we want is the final injection timing to be reasonable. I made an Excel spreadsheet to add (some fraction of) the ECT modifier on to the base timing, and show what it will be. Better still, the spreadsheet lets you put in the desired final cold timing and your current hot timing, and it will generate this table for you. I have attached that spreadsheet (Misc Tools.zip), you want the "LB7 Compensator" tab. I make no warranties that the rest of the crap in that spreadsheet is any good, I wrote it randomly for who knows what, so use carefully and please don't judge WTF I was trying to do.

So go ahead, grab my tune, use the spreadsheet, and see what the final timing I was going for is. That is a reasonable start for a stock injector LB7.

But wait, there's more! I attached my current built motor tune, which has SAC 75% injectors and a big stupid cam. Do the same thing with that tune and see what I was going for with timing there. Tom, you probably want your timing somewhere between those two values.

The other big table you need to concern yourself with is {B1002} Fuel Pressure ECT. Do the same trick (with the Excel sheet) to see what final values I am targeting on a stock and built motor.

Oh, and if you see the "Modifier Multiplier" in my spreadsheet, that comes from the "<whatever> Multiplier" table that matches the name of the above tables. You can play with that to adjust how strong the cold engine compensation is for any given coolant temperature. See how I played with that too in my tunes.

Finally, there are a few other tables to look at to get it to start and run nice in the cold. Everyone, please adjust {B0731} Cranking Injection Quantity if you have larger injectors. That fart of black smoke when it lights off isn't cool, this isn't a Cummins, let's get things running right, not fart-y. And the last few are your pilot quantity and timing tables, which have ECT references as well. That usually isn't as big of a deal.

From what I found, the various IAT referenced tables don't work, even if you populate them, sadly. Hopefully this helps!
Attached Images
File Type: png {B0915} stock.png (14.2 KB, 135 views)
File Type: png {B0915} NL3.png (12.9 KB, 132 views)
Attached Files
File Type: zip Misc Tools.zip (274.8 KB, 8 views)
File Type: ctz No Logic 5 BETA r20170515.ctz (327.3 KB, 6 views)
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Old 11-19-2017, 03:43 PM
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Dave did it way better them me. I think Simon posted a timing spreadsheet that had ECT on if years ago. I used it to correct my the ECT from current to get them to what they where trying to go stock. Works great for me down to -5*. I would like to play with them more to get away from the crazy shit GM did, but if I driving in temp below 40* I'm on vacation and don't have time.

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Old 11-19-2017, 05:21 PM
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Dave there is some nice spreadsheets in there thanks!
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Old 11-19-2017, 07:51 PM
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I did similar thing at Dave did but not near as fancy.. end results was same...
Watched the tunes/logs plots log enough I know where I'm at 80% time on a given table
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Old 11-19-2017, 11:45 PM
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Also try bumping your idle speed up. I had problems with hazing in the cold when I had my idle set down to 600. Set it back to 680 and it cleared up. Small increases can really add some cylinder heat to clear things up.
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