LMM Lambda and Boost

[2004LB7]

been playing around with the Fuel Mixture limits in Efi Live for my tune in order to try and optimize spooling without any or little smoke

I dont have Efi Live here with me right now so i may get some of the tables or there names wrong but bare with me. I think the relevant tables are B0793, B0794, B0795 and B079?.

I set the mixture limit ECM control from 6000 down to 600 so the tables become active. upped the max and minimum limits to there +2 and -2 so i can use the Fuel Mixture table to its full potential.

so far everything seems to be running great. faster initial spool from a stop good at speed spooling, little smoke, etc. i am liking what i see.

My big question is... does this override the Boost and Vane tables? do they become irreverent after the ECM is given the ability to adjust boost to try and keep the Lambda as close to the Fuel Mixture limit table as possible?

I am more concerned with Medium & High Altitudes. with the way GM has it set up we have control of the medium & high altitude boost and vane control.

with the ECM now adjusting the boost, will it work properly at high altitude?

it would work fine if the ecm monitors boost then adjusts the mm3 to match the boost as this would allow the boost and vane tables to continue to work. but i suspect that it doesn't work this way as it would limit mm3 when taking off from a light thus slowing spool as there is no boost at that time.

what i think is happening based on the table descriptions, is that the ecm will try and match boost (via vane control) to follow the actual mm3s being injected.

so if one was driving at high altitude and you went to accelerate, would the ecm close the vanes down as much as it can to try and make up for the lack of air by increasing boost but instead it is just chocking off the flow with the vanes closed too much?

sorry if this is a little long. if anyone has played with this or uses it at high altitudes i would like to here what you think

 

[2004LB7]

Also, has anyone made a pid or spreadsheet that shows air per cylinder?

 

[rcr1978]

There is one in the V8 see pic, it's been a while since I messed with the LMM on V7.5 but i'm pretty sure it's there to.

 

[2004LB7]

Hmm, I'll look into that. If it works that would certainly help speed up dialing it in.

 

[2004LB7]

Well, I finally got around to logging that pid. It only shows 0.62 lambda never changing

 

[Chevy1925]

nvrmd, thinking about this wrong

 

[JoshH]

been playing around with the Fuel Mixture limits in Efi Live for my tune in order to try and optimize spooling without any or little smoke

I dont have Efi Live here with me right now so i may get some of the tables or there names wrong but bare with me. I think the relevant tables are B0793, B0794, B0795 and B079?.

I set the mixture limit ECM control from 6000 down to 600 so the tables become active. upped the max and minimum limits to there +2 and -2 so i can use the Fuel Mixture table to its full potential.

so far everything seems to be running great. faster initial spool from a stop good at speed spooling, little smoke, etc. i am liking what i see.

My big question is... does this override the Boost and Vane tables? do they become irreverent after the ECM is given the ability to adjust boost to try and keep the Lambda as close to the Fuel Mixture limit table as possible?

Lambda has no affect on the boost or vane control tables. The ECM uses target vane position tables as a starting point or as full control of the turbo below certain fuel quantities at various engine RPM. They only thing lambda may do to the operation of the turbo is delay the amount of time it takes for the ECM to reach the fuel quantity required to take the vane control away from the target vane tables and give it fully to the ECM.

I am more concerned with Medium & High Altitudes. with the way GM has it set up we have control of the medium & high altitude boost and vane control.

with the ECM now adjusting the boost, will it work properly at high altitude?

it would work fine if the ecm monitors boost then adjusts the mm3 to match the boost as this would allow the boost and vane tables to continue to work. but i suspect that it doesn't work this way as it would limit mm3 when taking off from a light thus slowing spool as there is no boost at that time.

Lambda really has nothing to do with boost and everything to do with air flow. Of course boost ties into it to a certain extent because higher boost generally means more air flow, but lambda is calculated by the ECM by looking at MAF sensor readings, engine RPM, and fuel quantity. Lambda calculations can be skewed by adjusting intake tube size, MAF sensor scaling, fuel injector size, or injector pulse width. The engine uses air flow as a fuel limiter, so it will in no way adjust boost or affect turbo operation.

what i think is happening based on the table descriptions, is that the ecm will try and match boost (via vane control) to follow the actual mm3s being injected.

so if one was driving at high altitude and you went to accelerate, would the ecm close the vanes down as much as it can to try and make up for the lack of air by increasing boost but instead it is just chocking off the flow with the vanes closed too much?

sorry if this is a little long. if anyone has played with this or uses it at high altitudes i would like to here what you think

I've never played with any of that stuff at high altitude, but based on what I've seen from those tables, I don't see how it would be any different than what I have seen at low altitude. Hopefully my answers have answered some of your questions.

 

[2004LB7]

Thanks Josh,

It did but didn't answer my question. I am really just trying to maximize spooling with minimal smoke and thought I would play with these settings to see how different it worked.

I wasn't really after trying to adjust lambda to any specific values, more of just wanting to slowly raise it up to the point of just a haze.

If there was a working paid that showed the "air per cylinder" as the table seems to use then I could see where the engine was operating and thus be able to change the appropriate cells.

Also, I was thinking I could make a vane table from this too once I get it all diled in

 

[rcr1978]

Well, I finally got around to logging that pid. It only shows 0.62 lambda never changing

The pic I was referring to was the air mass per cylinder pid that's probably what you meant and I'm pretty sure it works, what are you using V7 or V8? You may have to try logging a few different pids to get it to work properly maf, rpm, and maybe baro but I can't remember for sure. Also some pids may be generic or enhanced you may just have to mess around a little. I have some LMM work to do this weekend so I will look into it again, who knows I may be wrong and have forgot since I've been stuck dinkn with LML stuff and haven't messed with my LMM much in the last 3-4 years.

 

[2004LB7]

You are right, I mistakenly was looking at the wrong pid even though I checked it several times. That's why I was confused it was showing lambda.

Looks like mine runs from 0.86 at idle to 3.18 at max boost.

So even at idle, there is a lot of the B0795 table that is unused. Maybe more of the lower cells are used at higher elevations.

Just wish the table went higher as I was reading just over 3 and the table maxes out at 2.4

 

[rcr1978]

I noticed the same thing when I worked on mine it's a great table for keeping them clean down low I remember spending quite a bit of time with it.

 

[JoshH]

What do you think the P0795 table does?

 

[2004LB7]

Limits the amount of fuel injected to what the ecm thinks is a particular are/fuel ratio

And/Or

Tells the ecm how much air it need for a given amount of fuel

With this table enabled, the ecm is running what seems to be much higher average boost then with it disabled and it running off of the boost and vane tables. This is what makes me think it is controlling boost to make the air/fuel ratio match the table

 

[JoshH]

It says right in the description it is a fuel limiter. It does nothing to control boost.

 

[rcr1978]

Without changing the rpm setting in B0797 (left it stock) I've found that B0795 is a fuel limiter based off of maf, I use it to clean up low end smoke only and I set it to 0 in the upper airflow areas.

 

[TheBac]

Moved into Tuning/Logging section.

 

[2004LB7]

Hmm, with mine B0795 didn't seem to change anything until it changed B0797 down to 600 rpm. I dropped all the cells I B0795 down to -1 and raised it all the way up to +1 and there was no change. Then I adjusted them to -2 & +2 and didn't see any difference. Only once I lowered B0797 did it start to effect the smoke, boost and throttle response.

I guess I need to try it again. Leave everything the way I have it now and only change B0797 and see what it does

 

[rcr1978]

My current tune its' set to .925 at 1.0 and lower, .920 at 1.20 above that I have them set to zero since there is plenty of air by then fuel limiting is no longer needed for me. Small changes made a huge difference on mine closer to .9 it was pretty smoky, my pedal position to torque tables and torque limiting tables are pretty aggressive if yours are close to stock in the lower rpm it likely won't have enough fuel to make much difference.

 

[2004LB7]

I will give it a try. It is not too bad where I have it now but I would like to reduce the lag even more. It used to be where I could, from a stop, mash the accelerator down to about half way and there would be a second or so of nothing but a slow increase in rpms and crawling forward then bam it would come on hard and rocket forward.

With my tweaks I have reduced it a lot but I know it can be better. And I know it can be done with out bellowing out tons of black smoke.

Also, my tune is far from stock. I have modified just about every table considerably. So I am sure I will need to ultimately find out for myself what numbers to use.

I will update again when I have done more testing

 

[2004LB7]

rcr,

I played around with some numbers including yours. I had a little issue with your numbers. It will idle fine but won't rev up without dying. It will catch itself at idle before dying completely.

I think the problem is with the "0" in your numbers. When the ecm multiplys the fuel quantity by 0 it gets 0. Thus cuts fuel and dies. I put 0.1 in instead and it seems to run pretty good. It still needs some fine tuning but is very drivable as it is.

When driving at moderate speeds and want to pass or accelerate it will smoke too much for my liking. Also, at wot it looks totally clean and I would prefer a light haze.

I have some logs that I made that I will need to review and hopefully it has enough info for me to make the adjustments