Incorrect Axis In OL Fuel Tables

[swingtan]

Hi All,

Well after spending the past few months working on OL fueling in the E38, I've finally worked out why I was having so many problems. While I've only really tested this in B0143, I think it's a pretty good bet that it applies to B0141 to B0144. Additionally, I think it will also apply to B0146 as it has the same axis values.

Now on to the issue.

All these tables have data that is plotted using Inlet Valve Temp on one axis. Over the past few weeks I've been trying to fine tune fueling, but could not get the logged commanded AFR anywhere near the theoretical levels in the tune. While I could easily get the normal running settings of, say, 14.68:1, I simply couldn't richen up the AFR's when the engine was first started. When I ran my logged data back against the tune file, I should have had richer AFR's when the engine was cold. But the commanded AFR's would always go to 14.68 within a few seconds of starting.

So I started testing what I could and soon realised that if I set the whole table ( B0143 in my case ) I could command any ratio I wanted, so the table worked to some degree. Then I started testing the table, by setting different AFR levels at different IVT temps. The results were interesting to say the least.

It looks like the IVT axis has been off set by 40'c and instead of counting up by 8'c, it counts by 4'c. The combination of the offset and the count up in steps of 8 means that the table only starts having an effect at around 8' and continues up to about 176' at least for me with the current weather. If I measure the IVT and re-plot the axis I get a comparison table that looks like this...

Table    Logged
-40	-40
-32	-40
-24	-40
-16	-40
 -8	-40
  0	-40
  8	-36
 16	-32
 24	-28
 32	-24
 40	-20
 48	-16
 56	-12
 64	 -8
 72	 -4
 80	  0
 88	  4
 96	  8
104	 12
112	 16
120	 20
128	 24
136	 28
144	 32
152	 36
160	 40
168	 44
176	 48
184	 52
192	 56
200	 60
208	 64
216	 68

Actually, I only logged table data from 80' to 112' but the results were pretty clear cut. Basically, if you take your intended IVT settings and cross reference them in the table, you will be able to fine tune your fuel requirements.

The next test is to see if B0146 suffers from the same problem. So far I've had little success with the modifier tables, but that was before I found the IVT offset issue. Hopefully we can get these tables updated ASAP so we don't need the lookup table.

Simon.

Oh, and thanks to JezzaB, ntae and Hymey for keeping me sane while working on this.

[joecar]

Simon, have you pm'd Paul...?

[swingtan]

I keep forgetting about that...... Will do though, he should be up by now

Some more info though.

It also now seems that B0141 to B0144 should be called "Idle OL Commanded Fuel". I can alter the mixtures using the the lookup table to richen up the mixtures when the engine is cold, but as soon as I'm off an idle condition, the commanded AFR's go straight back to 14.68:1. then as I come to a stop and idle again, the mixtures richen up.

I have a log of the start and will post it up once I have a chance to trim it a bit.

Simon.

[TAQuickness]

That's an amazing find. If you haven't contacted Paul yet, I'll be making him aware of this thread momentarily.

[hymey]

Nice logs there Simon, I have mine idling slightly rich on cold start and on hot start through the open loop tables. Car is starting well and will be using the tables to force open loop lean highway cruise. So now we can dial the VE table and command what we want.

[GMPX]

I'm not sure what to say, the axis's are correct. The ECM has a specific routine to rescale the values from -40 to 216 DegC. It's hardcoded in the OS and not changable.
What I do need to check is the IVT DegC scaling in the scantool.

Cheers,
Ross

[swingtan]

OK, that's fair enough. All I know is that if I use the lookup table above, all my cold start issues are fixed and I have a much nicer mixture for a cold engine. Re scaling the ScanTool would probably make the IVT settings more "reasonable" as normal operating temps ATM are around 40'c. After rescaling, they would be 160'c which sounds much better.

I tried a few more tweaks yesterday and have found that the motor is now behaving very nicely. No more cold start lean-outs and the first couple of minutes driving are much better. It took a while but now that we've found this issue, it should help every one that wants to try SD on the E38.

Simon.

[hymey]

Hi Ross, I have found a large discrepancy between ECT and IVT aswell.IVT readings are also consistantly lower than IAT. I am not sure why it's like this. I do not believe its an error on efilive's behalf. Scaling it would be good, In all honesty it should read higher than IAT logs. What we need is a COS with ECT enrichment, much like the injector IAT flow modifier.

cheers

Joel

[GMPX]

The scaling was off on that PID. It's now fixed, I'll Email you guys the updated file to see if it lines up now.

Cheers,
Ross

[swingtan]

Hi Ross,

This looks much better. IVT, ECT and IAT are within 2' before the engine starts which is probably an acceptable difference. Normal running temps now show as being in the 150'c to 160'c range which seems more correct than the previous readings of 30'c - 40'c. Running the ScanTool and watching the cells in the tune makes much more sense now. Thanks heaps Ross.

Simon