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Author Topic: Lean Burn on ME 7.1 (Lambda > 1 in closed loop) - better MPG when cruising  (Read 48538 times)
prj
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« Reply #30 on: February 29, 2012, 08:22:45 AM »

1. Maybe. That depends if you already have misfires at idle or not. If you do... time to either tune the fueling properly or get better injectors Smiley
Absolutely incorrect. Depending on cam setups, you won't even have misfire free idle leaner than 13 AFR on more exotic setups.
Of course this is extreme, but your assumption that the injectors are bad is just wrong.
FYI my only car with ME7 is a bone stock RS4 and that would probably be fine idling at 15.4, but I don't only tune my own cars.
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2. There is really no knock present on my car until hitting heavy at 20psi. At least I never logged any corrections at load below 180ish and at this point the car is running on open loop for a long while already getting much richer mixture than closed loop calls for.
If you've never logged any corrections below 180 load, then your timing map is not set up right. That is all I will say.
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3. There wouldn't be since all tables are geared towards gradual adjustment. The system doesn't drop from 15.4 to 11 in one step as you'd think. The values are interpolated so it would do it gradually. But that's a very extreme example which will not be representative of real life tuning situation as no table should ever be set up like that.
Please don't tell me what I think. You don't know what I think. You also don't know that I probably have more experience with tuning and ECU's than you, but this is not relevant to this discussion. I just found your statement rude.
With that out of the way, you missed what I told you. You are tricking the ECU to think that Lambda=1 is actually something else. Yet you are not tricking it to think that for example lambda=0.8 is something else, so you will get less gradual adjustment, and not really what is needed in a number of cases.
You will need to recalibrate loads of other stuff to make it operate correctly or update the code a bit.

This with combination of #2 means trouble. If you want to do stuff right.
That's why the *correct* solution would be to have dynamic USR. I would go as far as saying, the USR should depend on LOAD.

And I will write this eventually when I get there, lacking time right now.
« Last Edit: February 29, 2012, 08:25:02 AM by prj » Logged

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elRey
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« Reply #31 on: February 29, 2012, 08:31:01 AM »

elray: i only have LALIUSH, which appears to be behind cat (secondary)... looking for primary now.

look for identical value (search hex). Are your LALIUSH and LALIUSH2 identical? Let's hope there are 4 identical maps. 2 for rear and 2 for front.
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julex
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« Reply #32 on: February 29, 2012, 11:23:28 AM »


We work with what we have and your points are valid... If you read my original opening post and follow ups you'll notice that I point out to possible issues with this approach, namely fueling changes that would have to follow if you want to do it right... or just let the ECU establish long term trims and that's it.

On a target platform for this (ME 7.1 / ME 7.1.1) which uses narrowband, there is no other point of reference but Lambda = 1 = USR switching point when in closed loop and fueling table when in open loop. The only pitfall I see here is when/if  frao and frao2 corrections kick in and it will affect WOT fueling. I guess one would want to massage few other things for this to work, namely fueling adaptation thresholds, PID controller for o2 corrections, etc.

Now, admittedly there also is LALIUS map for rear o2 sensor which appears to be linearizing voltage to Lambda, but it only seems to be used in cat functionality check. At least that's my impression since I experimented with changing all the rear sensors linearization tables with no effect on actual lambda.
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jibberjive
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« Reply #33 on: February 29, 2012, 11:01:19 PM »

Please don't tell me what I think. You don't know what I think. You also don't know that I probably have more experience with tuning and ECU's than you, but this is not relevant to this discussion. I just found your statement rude.
I'm not sure if you're in the US or not, but I just thought I'd make a quick comment that I think you might have misinterpreted what he was saying, regarding that statement being personally about you.  He said, "like you'd think," with 'you'd' being a contraction for 'you would.' In that context, 'you' is an indefinite pronoun, and could be replaced with 'one', being that it is a general statement meaning 'as one might think.'  Anywho, I don't think he was trying to be condescending  Lips sealed
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julex
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I'm not sure if you're in the US or not, but I just thought I'd make a quick comment that I think you might have misinterpreted what he was saying, regarding that statement being personally about you.  He said, "like you'd think," with 'you'd' being a contraction for 'you would.' In that context, 'you' is an indefinite pronoun, and could be replaced with 'one', being that it is a general statement meaning 'as one might think.'  Anywho, I don't think he was trying to be condescending  Lips sealed

Thanks Jibber. I understand that people have bad days and I filed his reply as such. I am still willing to have a meaningful conversation about original topic Smiley
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prj
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I might have overreacted a little, or misinterpreted your post, came over a bit "you don't really know what you are doing" way...

I don't think you will get this just right by calibrations alone.
I think the way to hack it in, is make USR dependent on load, so this hack is only active when really *cruising*. Maybe specify some lockout RPM range as well.
Then make tweaks to KFLF to get the trims to zero in the given area.
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julex
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That would be nice. It is what it is though.

My personal belief is that altering USR is ok for idle and part throttle but not desirable in higher load situation. I believe we share the same point of view here.

This being the case, the ECU already works that way. At higher loads the closed loop is disabled (where lambda < 1), USR is no longer active and fuel trims have no effect on fueling, leaving the car in open loop where it is getting all the fuel it needs.



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DonSupreme
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That would be nice. It is what it is though.

My personal belief is that altering USR is ok for idle and part throttle but not desirable in higher load situation. I believe we share the same point of view here.

This being the case, the ECU already works that way. At higher loads the closed loop is disabled (where lambda < 1), USR is no longer active and fuel trims have no effect on fueling, leaving the car in open loop where it is getting all the fuel it needs.

Geez, so many complainers. Its a hack with pros and cons, which you fully disclosed.

Thanks for making the effort and sharing your findings.
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rajivc666
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I am running 1.1 lambda now, with lamda .95 at 100% throttle using lamfa, Also decreased torque reserve at idle so my idle consumtion has come down from 1.5 to 1.8 l/hr to 0.9/1.2 l/hr. Mileage has gone up from 8km/l to 11km/l on  daily travel. Had got error code o2 sensor post cat out of limits, so instead of coding it out I have filled the post cat o2 sensor laliush map with all stoic values (will that be a problem). Overall very happy with the setup as the car drives well only problem I think is my catcon is dying as I get a burning smell from the exhaust. Max lambda is limited to 0.75.
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julex
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I am running 1.1 lambda now, with lamda .95 at 100% throttle using lamfa, Also decreased torque reserve at idle so my idle consumtion has come down from 1.5 to 1.8 l/hr to 0.9/1.2 l/hr. Mileage has gone up from 8km/l to 11km/l on  daily travel. Had got error code o2 sensor post cat out of limits, so instead of coding it out I have filled the post cat o2 sensor laliush map with all stoic values (will that be a problem). Overall very happy with the setup as the car drives well only problem I think is my catcon is dying as I get a burning smell from the exhaust. Max lambda is limited to 0.75.

Great!

Are you using USR method or redefining RLLRUN/KFLF?
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rajivc666
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Sorry wrong thread , there was a similar thread for wideband ecu's. Grin I have shifted lalius, reduced krkte by 10%, and increased kfzwop 1/2 did some other mods too dont remember offhand on torque reserve .
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ta79pr
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I am running 1.1 lambda now, with lamda .95 at 100% throttle using lamfa, Also decreased torque reserve at idle so my idle consumtion has come down from 1.5 to 1.8 l/hr to 0.9/1.2 l/hr. Mileage has gone up from 8km/l to 11km/l on  daily travel. Had got error code o2 sensor post cat out of limits, so instead of coding it out I have filled the post cat o2 sensor laliush map with all stoic values (will that be a problem). Overall very happy with the setup as the car drives well only problem I think is my catcon is dying as I get a burning smell from the exhaust. Max lambda is limited to 0.75.

would you mind walking us through those changes? did you just mutliply KFMRES by say .80?
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rajivc666
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I dont have the laptop with me now on which I do all the work , will post soon.
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julex
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I dont have the laptop with me now on which I do all the work , will post soon.

I don't think it is possible to save so much fuel. The possible gain is at about 5% level so your values are not accurate, I am afraid. One thing you might have missed and is affecting your perceived economy.  If you're working off your cluster readout for it though and not calculating gas usage with kms/miles drive vs amount of fuel pumped in since last fill up. Once you change KRKTE, you also need to change KVB so that cluster calculates fuel consumption correctly.
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rajivc666
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Yes I have been taking these readings from the cluster, Can you explain why kvb has to be changed if we change krkte.
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