Tuning Notes by WeathermanShawn

[mr.prick]

VEpcm = {SAE.MAF.gps}*({SAE.IAT.C}+273.15)/((displacement()*61.024)*{SAE.RPM}*{SAE.MAP.kPa})*6155274.24

Try replacing displacement() with your displacement in CC
It should still work for stock CI

[WeathermanShawn]

VEpcm = {SAE.MAF.gps}*({SAE.IAT.C}+273.15)/((displacement()*61.024)*{SAE.RPM}*{SAE.MAP.kPa})*6155274.24

Try replacing displacement() with your displacement in CC
It should still work for stock CI

Thanks for the CALC.LTFTBEN PID(s).

It worked!

[acomp917]

WeathermanShawn,

I am new to the LS1, although I know a few things about tuning.

How can you tune AFR with adaptive spark engaged? When the timing changes... the AFR changes. From what I understand, a tuner has to "IRON" out the tune one simple(unaffected) table at a time.

EDIT: I think it is simple to maintain a consistant "HOT" engine temp. No problem here.
Also, how do you tune without taking the ECT into consideration? Or, why wouldn't you apply ECT into the applied corrections? thus negating the need to maintain a consistent ECT.

Wouldn't it be IMMEDIATELY better to separate the IFR/MAP/MAF into separate variables, then balance them as isolated entities? I know this was set forward as "simple" and I am moving into the area of readhardsupra. I'm just trying to stop the "new" talent from taking on TOO many variables at one time.

S

[WeathermanShawn]

Hi Welcome:

It is true the Adaptive Spark will momentarily pull timing down in the event of KR. If you are in closed-loop you will still Trim to 14.63 AFR regardless (non-PE) mode. In PE Mode, your Commanded Fuel will stay the same. It makes no difference in Closed-Loop. If a different spark value allows you to run a certain RPM at a lower MAP, your MAF Frequency will also lower..

Use the Adaptive Spark to prevent knock, and adjust your Timing tables accordingly. Your tune should be free of knock. Everything Trims to the same AFR value regardless of Spark. Its possible if you were constantly activating Knock, perhaps your Trim distribution would be different. My experience so far has been most that Adaptive Spark recovers very quickly..

The ECT component is a very interesting question. Obviously, the VE Table utilizes 'Charge Temperature' in its calculations and blends ECT and IAT. The CALC.VE Pid, uses MAF, RPM, and IAT. Apparently a MAF does not need an ECT to operate. But, fundamentally it poses a challenge in matching dynamic and cylinder air. You could try a calculated pid that would add ECT, but you might have real problems applying it in a MAF-Enabled Closed-Loop tune.

[acomp917]

Shawn,

Obviously, You DO understand tuning of the LSX... I am used to tuning a completely unknown combination. I always liked limiting the MANY problems to the minimum.

I will keep ALL of this in(my minimal) mind when I start my tuning. I am really amazed how well the LSx PCM controls the engine.

You seem to realize as well as I do, that this is not as difficult as others make it. My biggest problem is the departure from basic engine requirements. I'm slowly trying to eliminate variables by splitting the controller logic into isolated variables. I'm almost there, I will then need to develop equations that will apply needed variables to known tables.

S

[joecar]

...
In Closed-Loop, your non-PE AFR is ~14.63. In PE Mode your Commanded Fuel is determined by the richer of B0101 or B5001.
...

...
You seem to realize as well as I do, that this is not as difficult as others make it. My biggest problem is the departure from basic engine requirements. I'm slowly trying to eliminate variables by splitting the controller logic into isolated variables. I'm almost there, I will then need to develop equations that will apply needed variables to known tables.

You have to separate commanded AFR and airmass since they are determined independently of each other...

This is my understanding of how it works:

airmass is determined from either VE B0101 or MAF B5001 (regardless of OL, CL, SOL) as follows:
- above B0120: airmass is calculated from MAF exclusively;
- below B0120: airmass is calculated from VE (transient airflow/throttle) and/or MAF (steady state airflow/throttle);

fuelmass is calculated from airmass and commanded AFR;

commanded AFR is determined as follows:
- in CL: the AFR is stoich from B3601, trimmed to this by applying LTFT after the fuelmass calculation;
- in OL: from the richest of B3605, B3647(COS), B3618 (if PE has enabled), B3603 (if EPM has enabled), B3659 (if PPM has enabled); PE may be further modified by the PE modifier tables;
- in SOL: the AFR is the stoich cells in B3605 (in OL with B4206 enabled), or the stoich cells in B3647 (in OL), trimmed to this by applying STFT after the fuelmass calculation;

(Entering PE, EPM, PPM, COTP would mean exiting CL since the AFR would be significantly far from stoich.)


So you see that in PE mode the commanded AFR is determined by the richest AFR of B3605, B3647, B3618 (whichever of those is active), regardless of VE and MAF...
the measured AFR is influenced by the commanded AFR and VE and/or MAF.


Continuing on...

injector pulse width is calculated from fuelmass and IFR B4001, and is further modified by the other injector tables;

if VE and MAF are correct, regardless of the IFR and other injector tables, the measured AFR will equal the commanded AFR during steady commanded AFR (steady commanded AFR has nothing to do with steady/transient throttle/airflow);

for either VE or MAF, if the IFR and other injector tables are also correct, the measured AFR will also track the commanded AFR during transitions in commanded AFR [altho this is also influenced by the fuel dynamics (port wall wetting) tables];

I hope this helps...... I can see questions coming...

.

[acomp917]

Joe,

Most excellent! I like information like that... to the point. I have been reading for more than 3 weeks about all of this. I am new to EFI live.

If you don't mind, I would like to add your post to the intermediate area of my future wiki.

Thanks,
S

[joecar]

Thanks to both of you for reading that...

I have always gotten lost in long winded texts that waffle on, takes too much time and clouds/obscures the important points...

short/pointy have always been my favourite, as long as sufficient info is included (unlike most powerpoint presentations).

Yes, copy/paste as you require.

[acomp917]

Joe or anyone that can answer,

Could you tell me what these acronyms mean in GM EFI?

EPM, PPM, COTP

I made it over a couple hurdles in the last few hours and thought I'd take the easy path and bother someone else.

S

[ScarabEpic22]

PPM is probably pulses per mile (trans related most likely) and COTP is Catalytic Over-Temp Protection (causes a very rich condition, like 11.7:1 when active).

No idea on EPM though, Electronic Protection Module maybe?