Cold Weather F$#%ery

[adamuise]

SO.....ever since we got this 03 ive noticed in the cooler months the rail pressure goes down. It did it with the smarty tuning, and it is doing it with the tune i have in it now.
I suspect heavily it has alot to do with IAT. I logged it with about 21 degrees(C) IAT and all is good. Logged it with about 12 degrees(C) IAT and the RP is aprox 5000psi from commanded under very similar driving conditions. I've been trying to wrap my head around the correction and multipliers associated with rail psi but am hitting a wall
Is there a equation that someone can explain to me on how they control/modify the desired rail pressure table? Both my transient and low air density maps are the same for the DRP.
Attached are the logs i am using to track this down.

Thanks

[Jim P]

With very small changes just bump up the correction tables in the appropriate ranges till your rail pressure is back where it should be for those ranges.

[adamuise]

IATrailCorr.PNG
This is where i get confused. Adding higher values to the "2964" area would make it remove more PSI wouldn't it?

[Jim P]

Not sure with that table, I?ve only used the Rail pressure ECT adjust table to fix my issues with rail pressure I?ve had, high ECT and IMT during the middle of summer in the AZ desert causing a run away condition with rail pressure, lowering values in the upper temp ranges kept it in check. That was on my previous 05, the 05 I have now has 6.7 injectors in it and had to lower the rail pressure air density and rail pressure ECT adjust tables to get it running smoother on startup and in general once the engine was warm, would start hazing and rail pressure was going above commanded. Through those two tables I was able to get rail pressure to stay with commanded through temp ranges.

[adamuise]

ive ruled out the engine coolant being the cause. Reason i say that is the coolant temp is pretty much the same in both the logs i took (they were pretty much back to back). The IAT on the other hand is what changes.

When the truck has been sitting and the IAT is reading a bit higher, the RP will operate where it is supposed to. Once the truck gets on the highway (where it is used 90% of the time) the IAT drops and so does the rail pressure. So i am 99% sure its in the IAT tables, but what confuses me is how they work in correlation with the main table.

[Jim P]

so far I have not found that table within Cummins stuff, not a clue what that table is

[Moparmatty]

That's a normal problem on 2003 & 2004 trucks. I've never had a 2004.5+ truck have the issue.

The IAT and ECT are what is controlling that. Easy to fix with the tables that are there.

It also doesn't help that some of the tables are still not labelled/valued correctly.

[Jim P]

Yea I don?t believe the table in the above picture is correct, if I find a matching table within Cummins stuff I?ll post up what Cummins says about the table above.

Otherwise, I would use like I said above and what moparmatty said, the ECT correction table. Match up the ECT row with where you are getting less than desired rail pressure and match up the IMT column with the IMT where you start getting less than desired rail pressure and give small bumps up till it maintains desired rail pressure.

[Moparmatty]

Yea I don?t believe the table in the above picture is correct, if I find a matching table within Cummins stuff I?ll post up what Cummins says about the table above.

Otherwise, I would use like I said above and what moparmatty said, the ECT correction table. Match up the ECT row with where you are getting less than desired rail pressure and match up the IMT column with the IMT where you start getting less than desired rail pressure and give small bumps up till it maintains desired rail pressure.

The table is correct. It's how it's showing the info is wrong.

[adamuise]

Yep its for sure in those tables. I'm just trying to wrap my head around how they work so that i can adjust them to get what i want. Very confusing

When the truck is back (and I have time) ill start messing with the IAT correction table (in the pic i posted) and see what happens. Ideally i want to try and find a way to tune the IAT rail pressure reduction out so that it is inactive. For what and where the truck operates, i dont see the need for it.

Update: ECTvsIAT.PNGCorrection, we'll see if this fixes it. If it does then i'll probably re do that entire table so that it isn't pulling a huge amount of rail out when its cold. In my head, thats not helping anything.

[Jim P]

The map in the first picture is way way off. It?s for rail setpoint ambient pressure pre-correction. They shouldn?t have IAT on that map and the values in the table are nowhere near correct.

[Moparmatty]

The map in the first picture is way way off. It?s for rail setpoint ambient pressure pre-correction. They shouldn?t have IAT on that map and the values in the table are nowhere near correct.

There is nothing wrong with the map, numbers in it or the axis labels. It works perfectly fine.

It's what the cell values are labelled as is wrong.

[Jim P]

Well I guess Cummins is wrong on their engineering

[Moparmatty]

Well I guess Cummins is wrong on their engineering

HP Tuners is wrong the the label they have for the cell values. It was one of things I asked them to fix when I was at the PRI Show last year but it never got done.

[Jim P]

Yes the cell aren?t anywhere near where they should be, the axis values are fine. Cummins has zero reference to IAT on that map though as well, just ambient pressure

[Moparmatty]

Yes the cell aren?t anywhere near where they should be, the axis values are fine. Cummins has zero reference to IAT on that map though as well, just ambient pressure

Considering that it seems to follow that table properly following both IAT and ECT I don't see why that part is wrong. The values in the cells aren't wrong. Do some simple math and you'll see what the values actually represent Jim.

[Jim P]

So what exactly in that table is wrong by HP Tuners that you see?

[Moparmatty]

So what exactly in that table is wrong by HP Tuners that you see?

I've said like three or four times. The values in the table cells are correct. What HPT has them labelled as is wrong.

[Jim P]

Fuel quantity and rpm? Or the values in the axis?

[Moparmatty]

Fuel quantity and rpm? Or the values in the axis?

The IAT and ECT axis are perfectly fine.

Look at the unit of measure of the actual table cell values. The values are correct.