e38 ECU information

[snax]

Hi guys once again.

Ive been reading lot and messing with the tune on this C6 z06 but my lack of basic knowledge on this ECU is causing me a lot of frustration. Lets talk about how the ECU functions in stock form.

Does this car run purely off of the MAF or purely off of the coefficients? Or is it a little bit of both? From what I understand the ECU switches between the 2 modes based on RPM, or am I wrong.

Ive followed Swingtan's VVE tutorial and it pretty clear for the most part. The car has a pretty aggressive cam and will not run with the yellow MAF wire unplugged and disabled in the tune. So at this point do I start to modify the VVE table until I can keep the car running or do I adjust the idle tables? What are the key idle tables? What VVE table should I be using, B8101?

I know this car is not fitted with the IMTV so what coefficient table does the stock tune use?

If I have the MAF plugged in and functioning would I then be able to make changes to B8151 and apply that to the coefficients table?

For a richer than commanded mixture do you add or subtract from the VVE table?

So once the car is running good and fuel mixtures are good I then want to plug in the yellow wire, enable the MAF and then tune the MAF table if needed? What MAF table, B1097 and B1098?

I know alot of this is very basic information but for someone like me who is tuning an e38 ecu as their first GM tune this will be very helpful.

Thanks again
Bryan

[joecar]

I don't know the answers to all your questions (I'm an LS1B guy, not an E38/E67 guy)...

But...

it runs from MAF during steady state airflow (most of the time), and reverts to VE during transient airflow when below some threshold rpm.

I don't know which of the 4 VVE 1-bar tables you use (when you don't have IMTV and/or AFM).

Increasing VE means more airmass, and therefore to meet the commanded mixture, more fuel.

VE/VVE does not control commanded mixture... to change commanded mixture go to the commanded mixture tables.

If wideband lambda/AFR shows leaner than commanded lambda/AFR, then you have to do this:
- isolate VE (to exclude MAF and CL influences), take logs and adjust;
- isolate MAF (to exclude VE and CL influences), take logs and adjust.

There are quick methods, like assuming MAF is dominant, and using LTFT's to trim MAF, but this doesn't work for WOT (trims are not updated at WOT).


More info: E38-VVE-Setup-Guide (http://forum.efilive.com/showthread.php?8961-E38-VVE-Setup-Guide)

[gmh308]

Maybe I can add to Joe's coaching...

If you are running O2 sensors and they are going into closed loop, then the engine is running from the O2 sensors for mixture control.

When it is open loop (O2 sensors/closed loop disabled or in power enrich mode or startup prior to going into closed loop) then it is running from the MAF, which is filtered/referenced against the VVE table (which Speed Density MAF value is calc'd from) to come up with a smooth MAF signal - above say 4000rpm it is in high speed mode, the MAF signal gets less "noisy" and it runs MAF only.

If you are open loop and unplugging the MAF (MAF fail) and the engine wont run then it may mean that your VVE is too lean or too rich. Increasing it as Joe mentions will add fuel whereas decreasing it will remove fuel. Generally with a cam airflow is higher so the table needs to be increased. Try 10% at a time.

And yes the IMTV open table is the one that is used. B8101.

[snax]

Ok...here we go again.

Ive got the car currently running on the MAF. Looking at the following log what maps and changes should I be looking at making. fuel trims are very high but any changes I make seem to make the trims even worse.


8854

[swingtan]

You have fuel trims enabled ( running closed loop ) and have a WB O2 sensor. Just remember that when adjusting the fueling, you want to disable CL fueling.
There are no STFT's in the log, only the LTFT's. They don't help a lot without the STFT's to show what's going on.
DO NOT make changes to the fueling while in CL mode unless you are certain of what you are doing.
You can see that once in to PE mode ( which disables CL mode ) you are running rich. However as the LTFT's are so high, any changes to fueling will be masked by those trims unless you drive for a long time.


In your case, I'd do the following....


Warm the car up to normal temps.
Disable CL mode as per the VVE guide. This is achieved with the tables under [Engine operation] - [Fuel] - [O2 Trims]
flash in the tune and watch the WB data closely while logging. Best option would be logg from the passenger seat and have someone else drive, unl;ess you have a dedicated WB gauge that's easy to see.
take the car out for a gentle drive, still watching the WB. do a bit of cruising as well as a few gentle runs up to high RPM's in lower gears. If the WB indicates a lean out stop!
Work on getting light load areas corrected before trying any WOT work. Doing it this way will give you an idea of what the corrections are going to be for high load areas. It's unlikely that the MAF tables will want to be lower at high load than load load.
Once light to medium loads are running correctly, move on to WOT and high loads, again keeping an eye on the WB data.


Better yet, I'd dial in the VVE first, then once it is good, move on to dialing in the MAF.

If you get some logs with the O2's disabled and post them here with the current tune, we should be able to help.

Simon

[joecar]

Your BEN pid would be BEN1_E38.

[joecar]

Your sample rate is still low... about 5 S/s.

[swingtan]

Adding to Joe's comments....

Drop the following PIDs..

GM.AFR : ( covered by E38.AFRATIO_DMA )
GM.IBPW1 and GM.IBPW2 : Not helpful if the PC is logging slowly
CALC.INJDC1 and CALC.INJDC2 : Not useful if removing the above PIDs
SAE.LONGFT1 and SAE.LONGFT2 : O2 trims should be disabled for fueling adjustments with a WB O2 sensor.
GM.HO2S11 and GM.HO2S21 : as above.


Add the following...

GM.MAFFREQ2 : ( if wanting to dial in the MAF )
E38.APCYL_DMA : For dialing in the VVE


Simon

[snax]

You have fuel trims enabled ( running closed loop ) and have a WB O2 sensor. Just remember that when adjusting the fueling, you want to disable CL fueling.
There are no STFT's in the log, only the LTFT's. They don't help a lot without the STFT's to show what's going on.
DO NOT make changes to the fueling while in CL mode unless you are certain of what you are doing.
You can see that once in to PE mode ( which disables CL mode ) you are running rich. However as the LTFT's are so high, any changes to fueling will be masked by those trims unless you drive for a long time.


In your case, I'd do the following....


Warm the car up to normal temps.
Disable CL mode as per the VVE guide. This is achieved with the tables under [Engine operation] - [Fuel] - [O2 Trims]
flash in the tune and watch the WB data closely while logging. Best option would be logg from the passenger seat and have someone else drive, unl;ess you have a dedicated WB gauge that's easy to see.
take the car out for a gentle drive, still watching the WB. do a bit of cruising as well as a few gentle runs up to high RPM's in lower gears. If the WB indicates a lean out stop!
Work on getting light load areas corrected before trying any WOT work. Doing it this way will give you an idea of what the corrections are going to be for high load areas. It's unlikely that the MAF tables will want to be lower at high load than load load.
Once light to medium loads are running correctly, move on to WOT and high loads, again keeping an eye on the WB data.


Better yet, I'd dial in the VVE first, then once it is good, move on to dialing in the MAF.

If you get some logs with the O2's disabled and post them here with the current tune, we should be able to help.

Simon

With the car running in OL with the MAF disabled...well it wont stay running. Its too lean, Would I increase or decrease the numbers in the VVE table to start to correct that?

If I can keep it running I will get a good datalog and post it up along with the tune tonight.

Thanks,
Bryan

[swingtan]

You can leave the MAF enabled, only disable the O2's.....

However, the VVE tells the ECM how much air is entering the motor, so if you are way too lean, you want to increase the numbers to richen it up. It does work on a direct relationship to the WB reading, so if you are 10% lean, increase the values by 10%.

Simon.

[joecar]

Simon, is there an E38 pid to show the equivalent airflow calculated from VE...?

[ e.g. in LS1 the DYNAIR pid in most cases it tracks the MAF pid ]

[swingtan]

E38.APCYL_DMA gives gm/Cyl

AIRPERSEC gives gm/Sec ( not that I've logged it though )

I set up a CALC PID a long time ago and normally use that to show gm/Sec from the E38.APCYL_DMA and RPM

[gmh308]

In Scan & Tune for BBL it is called MAFSD. MAF Airflow - Speed Density. GM calls it SD MAF. :)

[swingtan]

that as well..... :p

[joecar]

In Scan & Tune for BBL it is called MAFSD. MAF Airflow - Speed Density. GM calls it SD MAF. :)lol, interesting.

[snax]

Finally some good progress

Disabled fuel trims, left MAF plugged in and enabled. logged a few drives and WOT pulls. made adjustments to the VVE table 8101 with good results. Im going to attach the last datalog and tune file for you guys to review. Its rich in some areas and WOT is still rich but im working on it. Anything else you can see in the log that I need to work on

8867
8868

Thanks again swingtan and joecar...Finally getting the hang of this

[swingtan]

If the MAF is enabled, then there will be no point in adjusting the VVE at WOT and little use while cruising. The E38 will use the MAF signal only over 4000 RPM and will cross compare the VVE at any RPM under 4000, so changes will make little real effect. You can adjust the MAF tables though and they should have a much greater effect on the final fueling.

BTW, try disabling spark smoothing ( B0301 ) , it may help with the timing being pulled while cruising.

Simon

[snax]

If the MAF is enabled, then there will be no point in adjusting the VVE at WOT and little use while cruising. The E38 will use the MAF signal only over 4000 RPM and will cross compare the VVE at any RPM under 4000, so changes will make little real effect. You can adjust the MAF tables though and they should have a much greater effect on the final fueling.

BTW, try disabling spark smoothing ( B0301 ) , it may help with the timing being pulled while cruising.

Simon


Does the MAF table adjust the same as the VVE tables. If the mixture is rich then I should Lower the MAF values?

[swingtan]

Yes. You will need to cross reference MAFFREQ2 and the WB BEN to get an accurate adjustment, though with the log you have, you could just add / remove 5% in areas to flatten the WB reading off a bit.

Simon

[snax]

Todays lesson is...returning engine to idle!!!

The car wants to die when you shift into neutral coming up to a stop light. You can see it best in the following datalog at around frame 455. Alot of the time the revs will hang around 1600-1700rpm for an excessive amount of time before it returns to idle speed, ~850ish. You can see the revs hanging up at around frame 420.

What tables should I be looking at for the idle issues?

8876

Thanks,
Bryan

[swingtan]

Post the tune.....

[snax]

8877

Here you go

[RAZRS EDGE]

Todays lesson is...returning engine to idle!!!

The car wants to die when you shift into neutral coming up to a stop light. You can see it best in the following datalog at around frame 455. Alot of the time the revs will hang around 1600-1700rpm for an excessive amount of time before it returns to idle speed, ~850ish. You can see the revs hanging up at around frame 420.

What tables should I be looking at for the idle issues?

8876

Thanks,
Bryan


Post the tune.....


8877

Here you go

Any thoughts? Thank you for everyones help!

[joecar]

Hi RAZRS EDGE welcome to the forum :cheers:

What vehicle/year/model do you have...?

[swingtan]

OK....


Idle fuel mixture is very rich, way richer than commanded. You need to adjust the MAF to fix this up. Running very rich at idle will make it more difficult to control the idle.
Min idle air flow is very high, much higher that what the car seems to want. In the tune, you have around 12gm/S to 13gm/S but the engine is only using around 7 to 8. Looking at the log from frame 1092, you can see the ECM is slowly pulling air out to get the engine to idle at the required RPM. When you command too much idle air, the ECM needs to pull progressively more air and timing to drop the RPM to the commanded level. This then moves the ECM further into the "Idle Proportional Step Size" table, causing even more air to be pulled. The results tend to be massive over shoot of the idle control.


So this is what I'd do...


Reduce the MAF table in the 1600hz to 2000hz range by 6% to 8% and then blend it back in. This should help with the fueling.
Drop the "Min Idle Air" to around 8gm/S to allow the ECM to use less of the idle correction tables.
Raise the idle spark table to 20' to help with idles control.
Clean up the idle over / under speed control spark tables to help with idle control.
Raise the minimum values in the idle and deceleration spark tables to stop the commanded spark from dropping below 10'. This will also reduce the amount of exhaust backfire ( crackle and pop ) when slowing down.


There is probably a bit more but this should be a start. Here's a tune that I've played with a bit.....

8891

I can't say if it'llmake things better or worse though..... :angel_innocent:

[RAZRS EDGE]

Hi RAZRS EDGE welcome to the forum :cheers:

What vehicle/year/model do you have...?

Thank you for the welcome and help!

My personal car is a 2006 Corvette Z06.

[joecar]

Did swingtan's comments/edits help...?

[RAZRS EDGE]

Did swingtan's comments/edits help...?

Absolutely!

[joecar]

Cool :cheers:

[BowlingSS]

How it is running now?

Bill