Strange LBZ Issue

[MotorsportsArsenal]

First off, I have to say I didn't write this file. I don't know who did; the customer gave me this file and said "it's really smoky, hang shifts, here's a datalog."

I really would like to better understand these older trucks - I don't know why the truck is only commanding (maybe better said - is only allowing) 40-50ish mm/3 of fuel in first, second, and third gears. When it gets to the end of third it comes to life and starts commanding near 100mm/3 (which is what the tune file seems to call for).

Can anyone shed some light on what may be causing this issue? All of the limiters seem to be set to allow for more than 50mm/3 - and I am not aware of a limiter that is "by gear." Sensor issue? Supply Pressure issue? I'm stumped on this one.

The truck has a single S472, 100% over injectors, and a 12mm stroker pump...pay no attention to the file names...I don't know why it says 60% overs and 10mm pump in the file name (and I didn't bother renaming it).

TIA for any suggestions/help!

[dhoagland]

Your Actual boost channel isn't logging
But look at your MAP flat at 14 for quite a long time after your throttle stab, once it climbs to about 20 PSI then the MM3 jumps from 50-60 to 100

24892

Don't have time to look into tune tonight, but to me its boost related.

[MotorsportsArsenal]

Good call, gonna try and see why boost channel isn't giving us anything here. Thank you for looking at it!

[MotorsportsArsenal]

Since it's an LBZ I don't think there will be a "boost" PID. I don't think it shows Barometric Pressure at all (b/c the baro sensor is part of the ECM)? Correct me if I'm wrong on that front. It's clearly limiting fuel based on air...but I don't know why at this point.

[dhoagland]

Since it's an LBZ I don't think there will be a "boost" PID. I don't think it shows Barometric Pressure at all (b/c the baro sensor is part of the ECM)? Correct me if I'm wrong on that front. It's clearly limiting fuel based on air...but I don't know why at this point.

If you don't have the pids required in the boost pid you are correct it will not work.
I added MAF flow to the graph after the picture and it follows MAP and everything else to a Tee

Be interested to know what you find
I'll try and look over it a little closer today

[dhoagland]

Looks like LBZ platform has Baro pids...

24899

[MotorsportsArsenal]

Here's a cropped version of a DL with both Baro PID's (voltage and pressure) there is a problem with that data as well. It's making me wonder if there isn't an issue with the baro sensor (which is not serviceable, of course, on LBZ as the sensor is part of the ECM - if I'm wrong on that please correct me)?

EDIT: the TCM Baro PID was logged here as well...so there's three baro PID's that all show a flat line. I just don't remember if LBZ's just didn't show baro data in datalogs...been years since I have even looked at one.

[dhoagland]

Not sure, I do see the one pid reads 97

What stood out to me in this last log was fuel pressure never got over 17K, last nights was 26K

[MotorsportsArsenal]

I can't figure it out at this point. I am going to keep searching for an answer on the LBZ baro PID's. I've pulled fuel and pulled fuel from it and it's still ridiculously smoky as well. Even for 100 over injectors it's crazy smoky.

[Cougar281]

Maybe bring this over to DuramaxDiesels.com? Lot of knowledge people over there.

[MotorsportsArsenal]

So we datalogged and tuned another LBZ today and a few things to note. 1) there is no Barometric Pressure PID that I can find that supplies data for the LBZ. 2) the original truck has a spool issue (which I believe is a direct result of too big of an exhaust housing on the S475 on the truck). The LBZ we tuned today with 30% over injectors and a VGT ran awesome after we were done. It did exhibit the same fuel limitation until MAP pressure came up though (just not to the degree that the non-vgt truck in the datalogs above did).

[dhoagland]

Thanks for the follow up.
I was wondering about the S475 but thought maybe this platform could spool it.
Might be able to spool it quicker with timming? But probably not enough for a street driven truck with I imagine stock gearing..