Irratic running - stable VE gives different lambda?!

[se7ensport]

Getting some really odd behavior that is preventing me sorting out the VE table, depending on when I log gives significantly varing results for what look to be the same situations:

log 1, taken on the way to work sat in traffic, engine is ticking over at 1000rpm, ve shows 37%, battery around 12.5-13v and the lambda shows that it running very rich below .65.
https://app.box.com/s/24yn6yqqesl1ot7hkida

log 2, taken on the way home, sat in traffic, engine ticking over at 1000rpm, ve shows 37%, battery around 12.5-13v and the lambda shows .98, pretty much as planned.
https://app.box.com/s/83ez3tnoosi1b04t1sdc

The same has happened on the last few days, it is making tuning impossible.  In addition the engine now seems to be cutting out more frequently when in stop/start traffic, this didn't a couple of days ago with what I believe to be the same settings....

[GintsK]

Seems it is WBO2 sensing problem. It can not be so rich and read so rich.
In addition you have bad spykes in MAT signal. Sometimes also TPS seems strange - spiky. Wiring?

Gints

[se7ensport]

Gints

Does the WB02 sensing look like a damaged sensor or that it needs a clean or calibrating?

I have replaced the MAT sensor in the last 200miles, I'll check through the wiring thoroughly, same for the TPS.

As usual, thank you for the help.

Alex

[Sprocket]

Can I ask why TPS threshold for idle is set at 3?, also,  idle is so close to EGO lower threshold, drop that down to 800rpm. That might be the reason why EGO correction is enabled eratically.

VE table jumps from 36 36 in the bottom rows at 1000rpm to 29 55 at 1300rpm. Thats a 20% dropin fueling and 50% hike in almost the exact same spot. this could be another reason why EGO correction is switching on and off, since Lambda reads silly values, it switches off. EGO is leaning out by the pre configured max of 15% yet the lambda is still miles off where it should be.

[Sprocket]

Another thought. Should the alternator not be putting out more than 12.8v at idle? Saying that, the morning log shows 14v at the same point as the evening log showing 12v. This is another area to consider, the injector voltage compensation. why is there such a voltage swing?

Check all your power and ground connections are good, and have the alternator tested.

[se7ensport]

Sprocket, thanks for the suggestions:

I've dropped ego correct lower threshold to 800rpm. 

What does the TPS value for idle control and what is a sensible value? I have disabled idle ignition control and I don't have a PWM or stepper.

The VE table at 1300 at 0% is lift off/overrun and and 1300 at 1% is accelerating, the figures came from vemstune with a minimum of 200 hits in the cell.  edit: just read your stalling issue posts from a few years ago, I'll look to increase the 0% TPS line of the VE table for the 1300 and 1700 rpms to ensure that there is fuel when it gets to idle as mine is also stalling when coming down the rev range.

The alternator is a little race unit that only gives about 45amp, injector compensation value needs sorting, but I want to get consistency with the settings before changing other factors, the 12 and 14v figures have the correct slope as changing the load (lights, fan) at idle reduces the voltage vet the lambda is stable during testing.

I'll be cleaning and checking all power and earths next.

[fphil]

The log view of v3.3_u004869-2013.11.11-08.35.57.vemslog shows MAP=cte=102kPa

v3.3_u004869-2013.11.11-16.33.15.vemslog gives min MAP=102, Max MAP=103 


My VT is 1.5.44 (2013.10.18). Something certainly weird  somewhere...

[se7ensport]

fphil, I'm running an alpha-n set-up, the reading you are seeing relates to barometric reading I.e. altitude correction.

[fphil]

of course, stupid I am

[fphil]

and even more, since I do not understand why you get 0.65 lambda on the 08.35.57 log.I was thinking that your sensor is not warming well.
Although I was surprised by the high variations of lambda that you get for rather small variations of TPS at 1000rpm on the 16.33.15 log

[Sprocket]

Before suggesting there is a problem with any hardware, i'd still say the the VE table is miles out and causing massives swings in fueling greater than the 10/15% the EGO can correct. The fact that you have a 'reasonable' fueling at idle is deceptive since as I already pointed out, the values in and around that area are massively rich and lean.

Tune the idle area of the map so that you get lambda 1 and the values in the surounding boxes are of a very similar value and then stretch that across the map to get you somewhere near.

From my experience with Alpha N on ITB's the VE values in and around idle were all pretty much the same, but as the rev's picked up towards the higher end, but at low throttle openings, the VE values dropped off, not rise. Engines can be different, but to have that much of a fueling swing, the VE values, in my opinion show that to be the case.

Other things to consider. The ignition advance at the idle region steps up increasing instability. OK so you want the advance to increase with revs. This is the problem with Alpha N, it's not Speed Density. Manifold depression at low throttle does not necessarily rise much in relation to rpm.

You really could do with another column at 1100 rpm if your idle speed is 1000rpm and loose a column higher up the revs. You could loose the colum below 1000rpm if you don't intend going into that region, or you could keep it, but add more advance at 0 and 1 throttle maybe a value of 25 degrees or so to kick the engine back up to speed if it starts to faulter. Adding the extra column at 1100, you know at idle the values between 1000 and 1100 will all be very similar and not an extrapolated value giving a steady idle. Currently your idle sits on an extrapolation between values in both the ignition and VE tables, and with a 50% hike in fueling from 1000 to 1300rpm on the 1% throttle line. on the 1300rpm column, going from 0% to 1% throttle there is a massive 90% increase in fueling (that is to say 55 is 90% greater than 29)is there any wonder the lambda swings about so much?

[Sprocket]

and even more, since I do not understand why you get 0.65 lambda on the 08.35.57 log.I was thinking that your sensor is not warming well.
Although I was surprised by the high variations of lambda that you get for rather small variations of TPS at 1000rpm on the 16.33.15 log

It could suggest there is a possible issue with the sensor, but then VE table is all over the show. Any lambda value under a threshold (0.67?) the ECU prevents EGO from working since to have a value that low if there was indeed a problem with the sensor, leaning off might damage the engine.

Having said that, looking at the other log you can see EGO correction max out but lambda values still dive way below target Lambda, EGO cuts out, which I think is a symptom of the erratic VE map.

One thing though, with fueling that rich, you'd smell it, plugs would be BLACK and the exhaust very sooty. If the plugs still show tan/brown, then i'd be inclined to say that the sensor or wiring might be the issue, but the VE table is, in my opinion, suspect.

Stop start traffic is the worst case since you have short sharp runs of acceleration and deceleration in very small time periods. If your VE fueling and Acceleration enrichments are away from ideal you can see an eccess of fuel build up very quickly. I notice Overrun fuel cut is also dissabled.

[fphil]

'Tune the idle area of the map so that you get lambda 1 and the values in the surounding boxes are of a very similar value'
I was also surprised recently  to idle in 2 different different idle states, same rpm, same PW, same IACDC but lambda 0.93 in one case and lambda 1.05 in the other. MAT was about 12deg
I do not have much experience in tuning combustion engine, anyway my understanding was that  it could be partial combustions which give different lambda values as the volume chamber can be easily expand when there is no torque to exert.
Indeed, as you say, in order to run for sure the same state, one should  flatten the VE area around the idle point. This is also necessary, I believe, to get rid of the rpm oscillation at idle.

[se7ensport]

I have managed to record a log at tick over that appears to show the problems that were identified earlier:


https://app.box.com/s/r414djv8udxxfmpnpa02



I have changed the connector on the MAT sensor and this appeared to resolve the issue, but looking at the section of the log in the image the current is at it lowest of 11.78 just before the MAT drops around 20 degrees causing additional fueling and lambda to show rich.

I'm about to run a new section of the loom for the MAT sensor as I suspect when the current is higher the fault in the wiring isn't shown, only when the current drops does the resistance drop giving a false temp reading.

Is Vems designed to run with less than 12 volts or do I need to consider a smaller alternator pulley to up its output at lower RMPs?

[se7ensport]

Another 4mths on and I'm beginning to give up hope, even cycling everyday in the awful British weather has been more appealing than trying to get to the bottom of this issue.

New 60amp alternator fitted, all earths cleaned and new MAT loom fitted.

Ran another set of logs today:

First run of the day and the engine is running really rich https://app.box.com/s/g6o13i0fuo2j90225mhh , after a couple of minutes I turn if off wait 30seconds and restart, the lambda then stays on target (as well as can be expected for untuned) for the rest of the 20min drive https://app.box.com/s/91ir7ztnqst7o4652mi7

Drive home from work and again it stays around target for 20mins, I stop for about 5mins and then record a new log, this time sitting in slow traffic the car has real difficulty ticking over and requires quite a lot of revs to pull away, it then leans out and stalls on a few occasions.
https://app.box.com/s/k8bxc0pebg7vn82nc9bd

Is there anything obvious that I can try?