MAF Timing LB7

[LB72004]

Ok, i have searched high and low through various sites and forums and can not find an answer to my problem. i am trying to set up my 2004 LB7 duramax to use the MAF for timing. i have rescaled the MAF voltage (B0201) & Map (B0802) so as to work within the max 32 grams/sec limit in the MAF/MAP selection table (B0901-B0904). i have set my three timing tables based on the Excel timing calculator, and done a bunch of logging to see where my air flow grams/sec is at for different RPMs and loads.

i then set up the tables (B0902-B0904) with new numbers 0, 7, 13, and MAP to MAF. went out and logged again it and it seemed that it was not moving to the other timing tables and was stuck on table A (B0908). i then adjusted the B0902-B0904 tables lower and it was still stuck in timing table A. i even set the grams/sec numbers to 0, 0.1, 0.2, so even at idle it should be using table C, but sure enough it was still using table A. i also set the MAF table A (B0902) to 32 grams/sec so it would have to use timing table B or C but it didn't budge from table A

through logging i have confirmed that the ECM is seeing the gram/sec correctly per my rescaling

i have put table (B0901) back to MAP and it will then correctly use timing table C.

i dont know if this is an EFI Live issue and maybe a question for Ross, but i have almost given up trying to use MAF for timing

anyone know what else to do? if i need to i can always attach logs and tun file for you guys to check out

thanks Jason

[hecatti]

HI!
I had same kind of issues, when I was using MAF it never worked correctly, so I was returned using MAP.

[LB72004]

That is why i was thinking that this may be a question for Ross. thinking that it may be a programming issue from GM or EFILive.

Ross has an excellent comment here: http://forum.efilive.com/showthread.php?1491-MAP-or-MAF-for-timing under post #2

i was hopping to be able to take advantage of the MAF timing, better MPGs and faster turbo spool

if anyone ever got this to work or knows how i would like to hear from you.

Thanks Jason

[GMPX]

Wow, it's been 5 years or so since I looked at LB7, I didn't even remember you could switch between MAP and MAF. I find it funny that the gas guys are busting to run off a MAP sensor and ditch the MAF, your quest is the opposite.

[LB72004]

well it seems to me that you could have the best of both worlds when it comes to turbo spooling and MPGs with MAF timing. with timing table A you could set the low fuel MM3 areas to a higher timing value for light cruising, then set the higher MM3 to a lower timing value to spool the turbo when you stomp on the go pedal. when the turbo spools and the air flow goes up the ECM will switch over to the next timing table (B or C depending on how you set it up) and raise the timing again. or with different combinations of these one could make a tune that will work well for light cruising and for heaving towing, etc.

i am just having trouble getting it to switch over to the next timing table

[LB72004]

so i did some testing and more logging yesterday evening, and it appears that when any of the cells B0902, B0903 or B0904 have any value other then "0" the ECM will only use timing table A. if they are all set to "0.00" then the ECM uses timing table C.

more testing...

Jason

[GMC-2002-Dmax]

so i did some testing and more logging yesterday evening, and it appears that when any of the cells B0902, B0903 or B0904 have any value other then "0" the ECM will only use timing table A. if they are all set to "0.00" then the ECM uses timing table C.

more testing...

Jason

The DSP1 timing tables are described as follows and 2-4 also have the same description:

This is the base start of injection (injection timing) table if MAF flow is within the range of {B0904} "Injection Timing (MAF Map C)" or barometric pressure is within the range of {B0907} "Injection Timing (Baro Map C)" and if the user selected EFILive DSP5 program #1 is running.
This table is based on fuel delivery per stroke (mm3) and RPM.

When not running the DSP program the ECM will use {B0910} "Injection Timing Base (C)".

See also:
- {B0901} MAP or MAF Injection Timed
- {B0915} Injection Timing ECT (C)
- {B0917} Injection Timing IAT
- {B0919} Injection Timing Fuel Temp

[LB72004]

The DSP1 timing tables are described as follows and 2-4 also have the same description:

This is the base start of injection (injection timing) table if MAF flow is within the range of {B0904} "Injection Timing (MAF Map C)" or barometric pressure is within the range of {B0907} "Injection Timing (Baro Map C)" and if the user selected EFILive DSP5 program #1 is running.
This table is based on fuel delivery per stroke (mm3) and RPM.

When not running the DSP program the ECM will use {B0910} "Injection Timing Base (C)".

See also:
- {B0901} MAP or MAF Injection Timed
- {B0915} Injection Timing ECT (C)
- {B0917} Injection Timing IAT
- {B0919} Injection Timing Fuel Temp


for my tests i was running with the DSP in the "off" or "0" position. i have been running with the DSP5 for some time now with my own programming. when i have the B0901 set to MAF the ECM will only use timing table "A" if anything other then "0" is put in B0902/3/4, regardless of my DSP5 setting. if i have the cells B0902/3/4 set to all to "0" then it will only use timing table C.

is there a PID or something that will tell me what timing table the ECM is using so i dont have to keep cross checking between the RPMs and MM3s with the timing to see what table it matches with?

[LB72004]

Do any of you super EFI Live gurus have any insight on this? i would have thought, being that it is an LB7 just about everything would have been done, but there seems to be little information on the internet about this.

if all else fails i guess i could always use the DSP output wired to a relay and set up to turn on when it sees xx number of lbs boost. the relay could then be wired into the DSP switch so as to automatically switch between two diffident tuns. this would almost do the same thing but you would only get two timing tables to switch between instead of three. on the plus side i would be able to have other parameters that i could change ie: MM3, fuel MPA, etc that would automatically change when i stomp on it and the boost comes up.

now that i think of it, one could just use more then one pressure switch and several relays/resisters to switch between all of the DSP programs and have five timing tables that automatically switch. but this would be over kill and not likely to ever be needed

please let me know if any of you know how to get the LB7 to work on MAF timing, otherwise i will end up trying the relay option

thanks Jason

[THEFERMANATOR]

I myslef personally do not see any reason as to why you would need to change this. It is pretty easy to set up a timing table to allow for good milage(high timing in the cruise area), and then set it up for fast turbo spool(moderate timing in teh low RPM power areas). I just don't see any advantage to setting it up so as to change timing tables based on MAF flow. I know I have played quite a bit with timing, and found with the LB7's larger injectors they don't take as well to really high timing at lower RPM's like the LLY+ does(I saw a drop in milage at more than about 6.5 degrees of cruise timing whereas the LLY guys will go up to around 8-10 at cruise). And I have found that a little more timing over stock helped my spool up some. Also just because the option is there to change timing, it doesn't mean the rest of teh code in the ECM will fully support the changes. There is alot in the ECM we cannot see, so like you posted above there could very well be some other hidden tables that need to be opened up to get this to work. Then again, if they open the tables who is to say it will be beneficial. I know i for one like teh MAP based timing as I have been up in altitude ab it and found it to work quite nice with the changed timing at altitude.

[LB72004]

I myslef personally do not see any reason as to why you would need to change this. It is pretty easy to set up a timing table to allow for good milage(high timing in the cruise area), and then set it up for fast turbo spool(moderate timing in teh low RPM power areas). I just don't see any advantage to setting it up so as to change timing tables based on MAF flow. I know I have played quite a bit with timing, and found with the LB7's larger injectors they don't take as well to really high timing at lower RPM's like the LLY+ does(I saw a drop in milage at more than about 6.5 degrees of cruise timing whereas the LLY guys will go up to around 8-10 at cruise). And I have found that a little more timing over stock helped my spool up some. Also just because the option is there to change timing, it doesn't mean the rest of teh code in the ECM will fully support the changes. There is alot in the ECM we cannot see, so like you posted above there could very well be some other hidden tables that need to be opened up to get this to work. Then again, if they open the tables who is to say it will be beneficial. I know i for one like teh MAP based timing as I have been up in altitude ab it and found it to work quite nice with the changed timing at altitude.

thanks for the reply. that makes sense. that's pretty much how i have had my timing when on MAP. with no real data other then how it feels, it seems that when i lower the timing i get faster spooling. let say i am cruising down the highway at 2000 RPMs and 20 MM3. now if i wanted to pass someone driving slow then i press on the accelerator. in a second or two the turbo spools up and i get the power to pass. now if i lower the timing in the higher MM3 areas of the 2000+ RPM band it may spool in one second or less creating a more responsive truck (which is more fun to drive). now lets say i am towing and the RPMs are sitting in the 2000+ range and timing is set too low (for quick spool) then the MPGs go out the window and the EGT go through the roof.

now i know there is a line between the two where one can get both to work, i was just hoping that this would produce a better system.


it doesn't mean the rest of teh code in the ECM will fully support the changes.
i was kind if hoping this wasn't the case. if it is, wouldn't one think that this option would not be available? but what do i know? i not a programmer. i guess the EFI live programmers (Ross???) would be the only ones to be able to confirm this

and another question... when the timing is based on the MAP (baro) sensor is it only set on startup or is the ECM constantly monitoring the sensor and adjusting as necessary? example: driving from low altitude to a high altitude, the ECM would start out using timing table C but as one climbed up the mountain would the ECM switch over to the other tables B or A? or would this only happen if the engine was restarted. and what about the reverse? coming down from a high altitude, would the ECM still use table A/B until the engine was shut off?

i know that this may not help get the problem resolved but if(or when) i end up going back to MAP timing then it would be nice to know that the ECM is taking care of the baro timing selection properly

[THEFERMANATOR]

As I understand it, the ecm monitors altitude constantly. Also I believe it will sort of smooth the 3 tables together as it goes up in altitude. I know I started out at around 2K feet of elevation and went up just over 6K, and the transition was smooth and seemless as I went up and down in elevation.

[LB72004]

As I understand it, the ecm monitors altitude constantly. Also I believe it will sort of smooth the 3 tables together as it goes up in altitude. I know I started out at around 2K feet of elevation and went up just over 6K, and the transition was smooth and seemless as I went up and down in elevation.

thats good to know. i thought that i read somewhere that the ECM only checks it at startup, but maybe that was for trouble codes only

[LB72004]

here is a wiled thought. if the programming was never completed for the MAF timing, could one swap the baro and boost sensors and use that. B0905/6/7 go up to just past 148 PSI, just dont know if the sensor will go up high enough. dont think i would ever do it though

[LB72004]

i guess i am eating my own words, ok, so i ran some small vacuum line to a tee that i put on the boost sensor tubing and connected it to the baro sensor. adjusted the B0905/6/7 based on data from the previous logs. well it worked... sort of. the transition from one timing table to the next is so slow that it would be worthless to set up this way. makes sense as GM knows that one doesn't just drive from sea level to 8000 ft in one second. so there is probably a hidden table that determines how quickly it will switch from one table to the next.

at least i know know that the baro sensor will read up to 29.73 PSI, which is plenty for what i was trying to do. oh well, back to conventional timing.

i may still give the boost switch or DSP output wired to the DSP5 wires a try, will let you know if i do.

[LB72004]

i wired in my boost switch to my DSP switch (it is a 6 position so i wired it to #6) when i have it set to position #6 the ECM sees it as DSP#3, when the boost goes up it automatically goes to DSP#4. right now the boost switch is set a bit to high and would like it to come on sooner, but it works. have to play around some with the debounce and PSI setting. i think i want to wire it up to the DSP output so i can change the boost level to which it will change tunes. need to do some logging and tweaking so see how it runs, MPG, Etc.

[LB72004]

i wired in my boost switch to my DSP switch (it is a 6 position so i wired it to #6) when i have it set to position #6 the ECM sees it as DSP#3, when the boost goes up it automatically goes to DSP#4. right now the boost switch is set a bit to high and would like it to come on sooner, but it works. have to play around some with the debounce and PSI setting. i think i want to wire it up to the DSP output so i can change the boost level to which it will change tunes. need to do some logging and tweaking so see how it runs, MPG, Etc.

well it seems that from a stand still and then flooring it my old timing (dsp#0, 1 or 2) was just as fast and responsive. but when it comes to the "passing gear" or driving 30+ MPH and pressing the accelerator hard, the boost-switch-wired-to-my-DSP 3 & 4 was more responsive and picked up more quickly (better).

i think i am going to wire my setup into my DSP output so i can program the boost level that it will switch timing tables. this should be more stable and make it easier to make changes the level at which it changes the tuns.

[LB72004]

update.

i managed to find a good high quality boost switch to use as the DSP output was not working properly. i have it wired so when it is in DSP #3 and the boost increases to about 22 PSI it automatically switches to DSP #4.

from a stand still and pressing the accelerator down pretty hard it would puff a small cloud and then would be spooled and would take off quite quickly. it also seems to work well while cruising and then going WOT. this is better results then what i posted earlier.

the tuning that i have been running would hardly ever smoke but produced good power. now it will puff a little bit when you get on it, but it spools up fast and clears right up.

i have done some logging and when cruising at 50 mph and then suddenly pressing the accelerator to 90% the boost would go from 15lbs (no boost) to 36 lbs (full boost) in 1.8 - 2 sec. this is about 0.2 seconds faster then my previous times.

i dont have any logs yet of of boost times from a dead stop but will test it soon.

so far it feels good. i think i will run this for awhile and see how it performs

Jason