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swingtan
May 12th, 2008, 10:10 PM
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
May 13th, 2008, 01:06 AM
Simon, have you pm'd Paul...?

swingtan
May 13th, 2008, 08:32 AM
I keep forgetting about that...... :doh2: 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
May 13th, 2008, 08:43 AM
That's an amazing find. If you haven't contacted Paul yet, I'll be making him aware of this thread momentarily.

hymey
May 13th, 2008, 02:42 PM
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
May 14th, 2008, 09:29 AM
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
May 14th, 2008, 09:43 AM
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
May 14th, 2008, 10:41 AM
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
May 14th, 2008, 11:25 AM
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
May 14th, 2008, 11:55 AM
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

swingtan
May 14th, 2008, 04:26 PM
Hi Guys,

I have another query on these OL fuel tables after talking with Hymey.

B0145, B0147 and B0148 are all multipliers for various conditions and effect the final commanded fuel. In the descriptions, the figures are all multiplied to the values in the tables B0141 to B0144, which works in EQ. These tables still work OK when using AFR's but the "seem" wrong. For example, multipliers greater than 1 will cause a richer mixture. But when working in AFR, a multiplier greater than 1 would result in a leaner mixture.

Is it possible to have these tables converted on the fly, like the others, when changing between EQ / Lambda and AFR? For example, if working with AFRs, the table values in B0145, B0146 and B0147, should be displayed as 1/(EQ multiplier). Does any of this make sense?

Simon.

Blacky
May 15th, 2008, 10:36 AM
Hi Guys,

I have another query on these OL fuel tables after talking with Hymey.

B0145, B0147 and B0148 are all multipliers for various conditions and effect the final commanded fuel. In the descriptions, the figures are all multiplied to the values in the tables B0141 to B0144, which works in EQ. These tables still work OK when using AFR's but the "seem" wrong. For example, multipliers greater than 1 will cause a richer mixture. But when working in AFR, a multiplier greater than 1 would result in a leaner mixture.

Is it possible to have these tables converted on the fly, like the others, when changing between EQ / Lambda and AFR? For example, if working with AFRs, the table values in B0145, B0146 and B0147, should be displayed as 1/(EQ multiplier). Does any of this make sense?

Simon.

Fuel multipliers can ONLY be expressed in EQ Ratio (or Lambda I guess). They cannot be expressed in AFR. There is an explanation of why in Appendix-B of the Tuning Tool Manual.

Regards
Paul

swingtan
May 15th, 2008, 11:12 AM
OK, I see the problem. I guess I'll just have to start thinking in EQ from now on ;)

joecar
May 15th, 2008, 02:13 PM
... I guess I'll just have to start thinking in EQ from now on ;)+1 :cheers:

hymey
May 15th, 2008, 05:49 PM
I can see where it gets confusing. For instance it says the value of the cell is measured in lambda which is for instance .95x14.63=13.9:1 (it says lambda on the 3D picture) but in the text it explains the final result is in eq. but eq is 1/Lambda same result is 1.05.

The factors in the PE table are seen as lambda aswell. I am unsure why they use EQ in the open loop tables B0146,47, and 48 when it is lambda in B0141 and B0143. Is it possible to reverse it so that we use lambda(or simply multipliers) everywhere, it is much easier to work with.

Cheers

Joel

hymey
May 16th, 2008, 06:38 PM
I have B0148 table working, I am trying to use this for lean cruise adjustment. I can command a richer idle say 14.0:1 but when I try to force it leaner it doesnt change anything. I can put in a very lean setting to see if its working but its not whereas in the same cells I command very rich and it runs rich. The formula for open loop hasn't been covered thoroughly either.

B0143 + (B0144 - B0143 x B0145) x B0146 x B0148. It is a simple formula but if you want to play with these tables you have to have your pen and paper out to get the final result you desire.

If you look at B0148 and B0146 tables it says to multiply to B0143 or B0141 to get final fuelling command but then we are leaving half the formula out. I believe the formula is
[B0143+(B0144-B0143xB0145)]x B0146 x B0148. So now
B0146 and B0148 can be multiplied to the final results of the left side of the formula not added.

redhardsupra
May 17th, 2008, 03:22 AM
hymey, where did you get this formula from?

hymey
May 17th, 2008, 09:23 AM
It states the formula in sections B0141 and B0143.

cheers

Joel