LTG E85 PE table

[ATrim]

I have added a flex fuel sensor to my Cadillac ATS 2.0T and have been tuning with E85 (70% ethanol)and am not sure how the PE table works for the alcohol PE EQ ratio. When it is on gas it takes the stoich A/F and divide it by the PE gas eq ratio and that gets me the commanded A/F ratio. When i switch over to E85 and take the stoich A/F and divide it by the alcohol PE Eq ratio this does not give me the commanded A/F. My alcohol PE is at 1.029 from the factory, but commanded A/F will go from 10.75 at cruise to 9.32 at wot. Is it possible for alcohol it uses the IVT gain plus PE eq ratio to determine the commanded A/F?

[cobaltssoverbooster]

iirc these have a variable stoich value that changes with percentage of ethanol....did you use the new commanded stoich value when calculating wot pe? it should be the same process.

[ATrim]

Yes it changes stoich depending on ethanol content, at around 70% ethanol it is close to 10.7 stoich. 10.7/1.029 = 10.39 but it will command 9.32 under boost so it must be using another table to calculate PE. Either way i think 9.32 is a bit lean. I will go back and log some more to see what i can figure out.

[ATrim]

Just looked at it again, converted my wideband output to read e85 so i can see the a/f ratio error comparison to what the ecu is commanding. Now on gas i had maf calibration within 0-2% difference on a/f error, now on E85 i'm at about 30-35% on a/f error. I wouldn't think re calibrating the maf again on e85 would be necessary? I have left closed loop off to see where i am at, but now i'm not sure why it is so far off.

[ATrim]

I think part of my issue is the difference between reading on wideband and commanded a/f. Being that my stoich value table reads from 0-100% ethanol , and when using gas my wideband was converting to gas output with stoich at 14.7, but when it starts to see ethanol would i use e85 or 100% ethanol reading for my wideband? I tried to convert it all to lambda and then figure out the a/f error but i dont think i made the pid correct.

[cobaltssoverbooster]

The computer is automatically converting off the gas scale 8)

[cobaltssoverbooster]

I'll open up a file and get more specific later tonight

[ATrim]

So i have been reading up and trying out different pid's. Converted my gas scale innovate wide band output to read lambda on the scanner, logging commanded eq ratio which appears to be lambda as when i hit pe it drops below 1.00. I then made a lambda error pid and just logging against maf calibration but it seems so far off from how it was on 93 octane. Is it normal for the maf calibration to be way off from changing fuel? Also seems the comanded a/f hi res does not match the commanded eq ratio. Thanks for the help cobaltss

[cobaltssoverbooster]

this has a lot going on.
First did you set the flex fuel sensor to active? and switch it to sensor mode? Re-enable its dtc codes? the ecu is set to virtual calculation from factory with everything disabled for this control interface so im just making sure.
if you wired in the sensor then it should be set to "enable" flex fuel sensor master and then set the flex fuel sensor to read "sensor" instead of "virtual".
If thats not done then your ecu is guessing the alcohol composition and this could be giving you weird numbers. If you did that but left the codes disabled then the circuit is ignored completely and the ecu defaults to virtual mode.

If you look at all the axis labels for the IVT correction data you will notice the axis are short and not covering a wide range of data. This is because these tables are referenced in non-wot conditions.
PE functions are designed to be active under the parameters listed in the PE enable section. Once those programmed conditions are met fuel is strictly control via base afr multiplied by the pe mode afr multipliers only. the only outside controls allowed to modify fuel enrichment along side of wot would be afr correction by time in wot (this function can be technically classified as "hot engine" as temps will rise with duration in wot), knock enrichment(factory disabled), cat overtemp correction, and piston protection.

Out of all of that im finding a lot of interesting information just from deciphering the factory repository file. Stock the pe mode is basically disabled; pe delay rpm is set so high you wont enable it until you are at 8000 rpm which is essentially untouchable in stock form. Secondly, as mentioned, the alcohol content sensor is disabled to virtual in stock form which can cause errors as a guess is never as accurate as hard input data.

if i combine everything im finding then i get two hypothesis on what could be happening to you. As you mentioned you cruise at 10.75 afr which means to me you are most likely in virtual sensor mode on the composition sensor. now your wot drops to 9.32 so 10.75/9.32=1.153 this would be the modifier value you are looking to achieve when you look backwards into the ecu data. so you know what multiplier you should be looking for and by adding all the modifiers up you can see how the system is controlled.

the first way would include you having gone back and activated pe by removing the rpm delay limit and lowering it to an achievable rpm threshold such as 2500 rpm. in this case since the sensor seems to be stuck on virtual mode, the alcohol eq table is never used and guess what table has a modifier equal to 1.153? Power Enrichment "EQ Ratio (GAS)" has a 1.154 multiplier value at 3500 rpm in the iat temperature zones you would be running in(68* and 104*f). in this case your fuel composition sensor being deactivated is causing you to command both standard pump and alcohol blends off of the same pe eq ratio table which cannot be done without modifying the eq table with every fuel style change(ie: 91-e85 or e85-91). The error in this mode would be .009 of an afr. This is what i truely believe is going on and if you posted a file with pe corrections then it would basically verify this is what is happening.
The funniest part of this is if you activated the sensor and used the alcohol pe eq(in stock coding) then at 81% alcohol composition your new value at 3500 rpm would be 10.1 afr at wot which is much leaner than you are getting now! Crazy right?

the second way would have pe still disabled. I can note before looking at tables that the ecu is not dropping out of closed loop because when something fails the ecu goes into safety mode, which would be open loop, and open loop is generally set richer than closed loop to keep parts cool and prevent detonations and other harmful events from occurring during part failure. Now with that in mind we look at both open and closed loop IVT modifier tables and prove closed loop ivt is controlling pe afr when pe is inactive.
From your recorded data before your sensor is stuck in virtual mode at 10.75 afr which still means you composition remains at 68% alcohol. Under open loop gains- IVT Gain table you can see at which alcohol percentage the ecu shifts to use a different EQ table value under open loop controls. Since 68% isnt 75% or higher the EQ table being used will be for Zone C. When we compare open loop to closed loop you will open "IVT Gain C" table and "IVT Gain CLO Gas". remember the ecu can interpolate cells so the cells that add up to the multiplying factor closest to the 1.153 multiplier we found before will be the answer to how the ecu is controlling the fuel. in closed loop control the multiplier at full load would most likely be 1.149 and at 10.75 stoich you get 9.355 which is off of your actual by .03 afr. (im guessing on IV actual temp as there is no sensor) In open loop your eq would be around 104-140* valve temp by 110 or 120 which puts you at 1.5256 or 1.35 which would be an afr of 7.04 or 7.96 which is off your target at worst by more than 2 whole afr units and at best 1.36 afr. Therefore the system is programmed to remain in closed loop during wot conditions unless part failure occurs in which case you would dump your afr most likely into the more desired afr range you were looking for with true e85 or e99.

without any logs or tune files posted i strongly believe your Composition Sensor is disabled and set to virtual control which make it hard to control alcohol fuels as you have to use all the gas tables to control your output.
the virtual mode will control the stoich pe but it will not activate an alcohol table as the ecu cannot verify it is truly being fed alcohol. If you did activate it properly and the sensor is truly reading correct composition then something is hanging you up and causing the pe gas tables to still be used in wot.

Since i did a lot of lnf work i like to compare these new di motors to that and use the lnf as the bare minimum of control systems. to make things easier on me i would do a few things during my testing phases to guarantee i have control of my commanded outputs.
1) verify my composition sensor was active and causing a table switch by commanding two drastic pe afr changes. lean on gas and pig rich on the alcohol table. by doing that if i went really rich in pe mode then i knew the ecu recognized it had alcohol fuels and switched its control tables over.
2) i would reactivate the pe control to a reasonable enable range such as 2500 rpm, and 70% throttle (to Start)
3) i would disable all IVT corrections so the composition sensor would be strictly commanding its base afr off the stoich afr table. if your not in pe you technically want stoich afr and by having IVT active it causes rich events making you think pe is active when it isnt. IVT is a mode designed to control the transient fuel by adding a modifier to correct the puddling effect and evaporation rate of the gas by contacting a hot valve. That is why when the valve is cold the eq dumps more fuel in( because it doesnt evaporate as well and requires more spray time to achieve proper charge mix ratio in a gaseous state). Without expensive testing equipment to monitor the physical temperature of the valve head, you wont really be able to tune these tables properly anyways. so since i cant calibrate it correctly in the first place and the gain is minimal i would leave this mode deactivated permanently.
4) cat testing disable
5) and last remove all spark modifiers so i could monitor base ignition values with exception to leaving knock control active for protection backup.


I dont know if my last part would help you much but based off of a factory file and your reporting i would say something is snagging the switching function for alcohol use and a lot of testing will have to be performed to figure out exactly what is causing it. Remember you need to try 1 change at a time or else you wont know which changed fixed the problem. That is why testing is going to take a little while. I hope my short novel has enough insight in it to help you find the true cause of your afr irregularities. Really wish i had one of these to do testing on.
-Booster-

[ATrim]

I have flex sensor active and set to sensor, but just checked and the dtc are set to no report. I attached the file as this is not a stock file. I have no cat on the car currently so I think I disabled most of that. I have been tinkering for awhile with this and did some ve tuning but ended up going back to a stock vve table. I will enable all the flex sensor dtc I can find and try that.

[ATrim]

One more thing, when i was logging the values i posted about up top, i had fuel trims disabled so car would be in open loop so i could see how far off the tune was on e85. Tune i posted i believe they are turned back on.

[cobaltssoverbooster]

i think by having its codes deactivated it is being half ignored.
i hope that gets your tables switching again.

once the tables switch the maf sensor should be calibrated to the fuel that is going to be used most often. since it is adjusted for airflow measurement only, having two pe enrichment maps should allow it to track fairly close to commanded without major adjustments. the airflow is the same, the alcohol composition sensor switches it to the correct stoich, and the two afr eq pe tables set the enrichment percentage.

[ATrim]

i think by having its codes deactivated it is being half ignored.
i hope that gets your tables switching again.

once the tables switch the maf sensor should be calibrated to the fuel that is going to be used most often. since it is adjusted for airflow measurement only, having two pe enrichment maps should allow it to track fairly close to commanded without major adjustments. the airflow is the same, the alcohol composition sensor switches it to the correct stoich, and the two afr eq pe tables set the enrichment percentage.

Next day or two i will reflash and see how close it is to commanded a/f. I will also log to see what other tables its using to calculate a/f on alcohol because i know the 1.029 in PE is not only what it is adding for wot. Appreciate all your help, hope i can add some good info to this thread also.

[ATrim]

I attached a log and config if you want to look. I checked the flex fuel dtc codes, didnt seem to change much. It does read and change stoich depending on alcohol content so I believe that is working fine. Looks like went from 10.85 to 9.16 under wot, almost seems like ivt table and open loop eq ratio table adds up to 1.18. a/f error seems to be moving quite a bit, seems like I need to recalibrate the maf to bring it back to where it was on gas. I will mess with it more when I get time. I think I will change numbers in one table at a time to see what tables are calculating for wot on alcohol.

[cobaltssoverbooster]

As a test you could disable the IVT by setting it's eq ratios to 1. This would test it's effect on pe, verifying if it remains active along side power eq enrichment.
Is there a status bit or scanner pid that can detect alcohol pe switching? A solid verify would eliminate verifying switching function and drive me to figure out which table is adding extra fuel over pe.
keep moving forward, you are offering good information on the ats.

I'll look at the files but idk when it will happen. I'm helping a shop install a new dyno jet and making sure their software is running smooth, so I'm gonna be tied up for a while. I read posts on breaks to keep track and stay up to date between posts.
Booster

[ATrim]

I set IVT gains to 1.00, didnt seem to change wot commanded a/f. If i disable closed loop my trims are way off even though it is reading the ethanol content correctly. Is it normal to have to recalibrate the maf or is something else causing this issue?

[cobaltssoverbooster]

so im looking at everything and matching up numbers from every table and scenario i can think of and im finding numbers that get close but nothing that adds up to the correct values run and received.
i have a feeling there is some interpolation going on in some of the tables, a few may be stacking on top of others acting as safety modifiers, and all this while pe enrichment makes a final change.

if this was me tuning this is what i would be feeling and thinking:
for trying the shortest tuning route (which you are doing) and not seeing any proper gains or differences in commanded outputs i would be getting extremely frustrated; much like i would assume you are.
my first action after not being successful would be to start fresh by turning every useless table off. why? because every table that makes a correction makes it harder to see how the ecu uses each table to control the engines output.
(analogy: its like assembling a puzzle. we have a commanded value and we have recorded output data. it makes a picture once you figure out the garbage in the middle. so with modifiers active it would be like trying to assembly a 1000 piece puzzle in 5 minutes; pretty hard. Well if we turn all the modifiers off and run just the necessary base parameters then the picture turns into well say a 5 piece puzzle which can be very easily assembled in a 5 minute window.) to do this in this ecu i would probably disable cat protection, piston protection, knock fuel modifiers, IVT modifiers (both open and closed loop), open loop EQ Ratio (EQR) compensation, and turbo overtemp protection. Every one of these controls a small portion of the fuel system and i cant have them adding pieces to my puzzle.

As a result of action 1 i would have made a bunch of changes that would require a quick series of drives to verify im not getting to out of hand on fueling.
So to correct said issues i would perform action 2a (a wot safety change):
go to pe EQR and set my afr ratio in the gas and alcohol EQR tables to match each other with a common ethanol value. this defaults pe enrichment to a safe value in both fuel conditions so no matter what table the ecu picks, i get what i command.

Follow that step with action 2b (quick calibration):
use the series of short drives to tune my maf sensor and account for the changes that have been made prior to.
(note: in the file you posted, your maf sensor is set to secondary prediction source. the high rpm disable is set to 7200 rpm which leaves the maf input as the secondary source of airflow predictions. Until 7200 rpm is hit the ecu is using pressure sensors, rpm, intake air temp, and few other data sources to calculate official airmass. It would probably benefit you to enable it a lower rpm as the true VE tables in this ecu have not been officially discovered or verified.)

Well say that i tuned the maf and was successful in getting the fuel trims to behave... i would begin single table effect testing by first commanding one PE EQR table to stoich value 1.0 and verifying the my commands to the output data which would be recorded in the scanner. I would probably start with the gas table in hopes the alcohol composition sensor was switching the tables properly. if that was the case i wouldn't see a pe afr change in the log. if i did see a change towards stoich then i would know the ecu is still using the gas EQR table for pe and not switching based on sensor data. Going back to no pe afr change on the gas table test then i would reset gas pe eqr and then set alcohol pe eqr to 1.0 and test it. this verifies i am controlling pe 100% on the correct table the ecu is using. once i know which one is being controlled under alcohol use i would tune that pe table for power and make the other match in-case it flops back and forth.

Last, with a tuned maf and pe set to match commanded, i would re-initiate modifiers as desired to smooth out imperfections. by enabling one of the prior mentioned modifier tables, i would make a change with a simple value that is easy to calculate such as 2, 5 or 10% changes and verify the tables effects through data scans. By controlling one table at a time i can see how they react to simple changes which help me understand their true effects on engine performance.

Once finished with modifier controls the tune would basically be done as far as fueling goes.
As of right now, you are trying to work the puzzle the difficult way. Start from the bare minimum of data required to control the motor and then add in extra features slowly. the best ecu tunes always follow that extremely generic tuning process. Read greg banishes book, although its not the most in depth series it will show you that you always start by verifying the base data before adding in the extra features. When you dont follow the general rule you get tune problems that lead to a jack stand queen and we all dont want that to happen.

To answer one prior question, when you switch fuels you may have to modify the maf sensor to correct the fuel errors that arise. If you set the base fueling up correctly, using the general calibration method, then switching fuels should NOT have a major effect on fuel trims. The composition sensor would change your stoich command and with pe eq ratio set properly for straight pump gas and alcohol pe set for straight e85, then the ecu would blend by and switch tables automatically keeping your data within a few percent on fuel trim control. Note normally 5% trim shift would be grounds for a calibration change, but when the ecu switches and blends tables automatically as a function, then that same 5 % can be overlooked as accurate enough due to lack of control in the middle ground between the controllable extremes. if it were to exceed 10 or 12 % then i would go back and give that a look and possibly make a calibration adjustment to prevent it from happening again.

I think my initial hint to start from a fresh control did not get through. I should have started my posts with this one and saved some time which has been lost in translation. For that i apologize. I hope my posts are helping.
-Booster

[ATrim]

Appreciate all this help, i will go disable all the tables you mentioned to try to pinpoint what tables are being used in fueling on alcohol and let you know what i find out.

[ATrim]

OK, here is where i am at. I disabled all modifiers i thought that could add to PE. used 1.25 in both gas and alcohol PE, logged a brake torque and checked commanded at idle compared to full throttle and it comes back to exactly 1.25. I then changed gas PE to 1.00 and left alcohol at 1.25 and my eq ratio comes back at 1.195. I then swapped gas to 1.25 and alcohol PE to 1.00 and logged, EQ ratio comes back to 1.054. So it is using both tables from what i can tell but i cant figure out how it is obtaining this percentage, alcohol content is between 68-70% right now. As of right now i'm trying to get a good understanding of what tables are being used before i go any further trying to re tune or calibrate maf.

[cobaltssoverbooster]

its interpolating alcohol content between the composition cells. if you calculate the stoich value for the content you are currently running you can set it as the new stoich in the cells being hit by the ecu. it is using the alcohol table right now so that's awesome a simple sensor activation goes through without any issues. your findings will be worth their weight in gold in the future.