Does the BLM vary with engine temp?

[LZeppelin513]

I have a 3500 running on 7730 with nast1 code. I have been tuning in closed loop lately an find it difficult because the BLMs will vary by 7 or so points based on engine temp AFTER it has warmed up.

I let the engine warm up to around 185 before I start tuning. If I am driving it at higher speeds the temp sticks around 185 but if I am slow stop and go it will climb to around 110 to 120. The BLM will change by increase by about 4 points above 128 as temp increases (120F), but will be a few below during cooler running temps (185F). Is that normal? Thanks

[robertisaar]

so BLMs rise with higher temps and drop with lower?

[LZeppelin513]

Yes that is correct.

[robertisaar]

odd.... i would have expected it to be backwards, wanting more fuel when colder.

BLM above 128 = more fuel added
BLM below 128 = less fuel added

does your spark advance vs coolant temp table (F2) change much in the ranges you mentioned?

actually, let me do a quick look...

do you have "intake runner temp" in your datastream? and are you emulating or burning PROMs? it sounds like your F31(or the tables used to calculate intake runner temp) table might need tweaking since you're using a considerably different intake/head than the LH0 that the calibration was originally intended for.

may want to make sure that the F8CLTBLA and F10CLTBL tables aren't commanding different values near the area you're having trouble with as well.

[LZeppelin513]

When it first starts up and is cold it does want more fuel like you expect, it runs pretty lean until its around something like 130 ish F. According to the wideband it starts off ~16 when ~14.2 is target, but this could just be wideband error. I'm not sure how to make it richer here but not too rich after its warm.

I haven't messed with it yet but here is my f2 table around the warmed up operating temps:
.......30....40.....50.....60....70.....80.....90. ....100
176__0.00 -2.12 -1.06 -1.06 0.00 0.00 0.00 0.00
197__0.00 -4.24 -5.29 -5.29 -5.29 -4.24 -2.12 0.00
219__0.00 -4.24 -5.29 -5.29 -5.29 -2.12 -2.12 -2.12

Yes i have "intake runner temp" in my datastream. Right before i turned it off today coolant was 209 and intake runner temp was 234.
I am emulating.

My F8CLTBLA and F10CLTBL tables are identical.

Thanks for helping

[robertisaar]

are F8CLTBLA and F10CLTBL trying to force the O2 target value up or down in the ranges you're playing with? basically, anything other than a 0 in those temp cells.

if you know how, change the equation for the F31 table to just "X", then when logging/emulating, wait for the coolant temp to hit your problem areas, then watch intake runner temp and once it gets close to one of the breakpoints, adjust the table value up or down in increments of one to see if you're getting closer to having the BLM back to it's normal value.

^ that table works as a multiplier, so higher numbers SHOULD increase fuel delivered.

[LZeppelin513]

F8CLTBLA and F10CLTBL are -35 at 176 and then zero at 197 and 219.

So change the equation from the ADX editor > Values > intake runner temp? I can do that. Curious, why change it to X?

[robertisaar]

not in the ADX editor, the XDF editor.

select the table, hit F2 and it's fairly simple from there.

and it's due to GM's odd way of describing the effect temperature has on the mass of air in the cylinder.

[LZeppelin513]

OK thanks,

one more question, I am not quite sure what you mean by this:
"then watch intake runner temp and once it gets close to one of the breakpoints"
what do you mean by breakpoints?

[robertisaar]

i think it's a 17 value table? wait until it gets near one of the 17 values listed, then change it. changing it while it's between two values, or otherwise not very close to any one value, can cause trouble.

[LZeppelin513]

Thanks for the help, needed to add just a touch of fuel on the hot and cold, but not warm, sides of the base pulse inverse term table and it is keeping a steadier blm.

[LZeppelin513]

Is it possible to add "intake runner temp" to $A1? Does it use the same byte that it does in nast1?

[robertisaar]

if you want to replace an item in the stream with another, it's pretty simple. from GM, it was not transmitted in the datastream.

got something in the stream you think is pointless? i know there are a few i never bother to look at.

[LZeppelin513]

corrosive sensor is pointless for me

[robertisaar]

oddly enough, that's actually the coolant level sensor, which GM used the instrument panel to control after roughly 1990.

that's byte 44 of the datastream, so if you have the nAst1 XDF, you can open the Mode 1 Address Transmit Table and go down to byte 44 and change it from 01D1 to 00F3.

transmit portion is finished, now the ADX just needs changed to reflect the change.

go into the ADX editor, scroll down in the values section to the corrosivity sensor, give it a new title, change the Range Low and Range High values(optional, but if you watch the value via the Monitors, do it -40 and 305.6 are highest and lowest possible values), click to the conversion tab and change the equation to

X * 1.35 - 40

save and now the ADX is finished as well. go do a log and it should show up now.