I need to lie to my ECM

[eboggs_jkvl]

My last effort for the dieseling is to change out my 52# injectors and install a 65# set. Since that is over the injector limit for my E38, I was told to double the A/F and load the injector flow rate at half the value. So, I did that as shown in the 2 attachments. My question is: Is the a specific spot in the tuning where the Commanded A/F is entered to show 14.7? If so where so that I can make the value 29.4


Thanks,


Elmer

[joecar]

Hi Elmer,

My understanding is you multiply by 2 the whole curve (your second pic).

[eboggs_jkvl]

So I double the commanded fuel table as I did in the B3671 table. It seems to me that doubling one should require the halving of the other? Heck, what do I know...

So, there isn't an entry somewhere in the tune that says a value of 14.7 for the A/F that I need to change? I looked everywhere for the entry to state the commanded fuel.

[swingtan]

I think you may have it all wrong.....

When going to bigger injectors, ones that exceed the max limits in {B4001}, you would do th following....

• Work out the "real" flow rate of the injectors at each row point in {B4001}
• Depending on the injector, then "halve" the real flow rate so that the same curve shape can be loaded into {B4001}. This gives a somewhat "referenced" base line for fueling. If you wanted to make the smallest impact on the ECM, you'd reduce all the "real" values by a factor that allows the curve to just fit into {B4001}.
• Adjust the airflow calculation tables (MAF or VVE, depending on tune) by the same factor amount. The injectors will flow, say, 2x what the ECM thinks, so you want to make the ECM think there is only half the amount of air entering the motor, so it gets the final air-fuel ratio correct.
• You should not adjust the stoichiometric ratio as the fuel being used is the same. If you run closed loop, the O2 sensors will still work on the real fuel stoich point anyway.

Just remember, that the IFR fudge can upset auto shifting as the ECM will think the engine is producing much less power than it really is.

BTW, what's the dieseling issue you had?

Simon.

[eboggs_jkvl]

Well, that is certainly more complicated than I thought.

So, put the B3671 table back to stock.
I then use the IFR spreadsheets to get the numbers for B4001 and then reduce those numbers by a "factor" that gets the whole slope into the table and doesn't flat line anything at the 62 limit.
Take what ever "factor" was used to fit the slope into B4001 and reduce the air flow through the MAF by that same amount.

Did I paraphrase that correctly?

My dieseling is due to an installation of an E-Force supercharger over a year ago. The car runs great! It just doesn't like to stop. Normal shutdown for our cars takes approximately 1 second. The RPMs drop on a straight slope to 0 but my RPMs make a surge in that slope and cause the motor to turn or diesel. I take 2 seconds to shut down and there is a definite "diesel" action made by the motor.

It had no issues before the SC addition.
I've replaced the injectors with another set of 52s.
I've removed the BAP.
I've installed a higher volume fuel pump in the tank.
I've had 4 different tuners working on the tune for the car including Edelbrock and their "proportional" tune (Makes the DIC read incorrectly for Instant average MPG and Miles left in the tank.
I've replace the SC on top of the engine.

The latest thing I am going to try is a different set of injectors that sprays a different pattern into the cylinders. I've had reports that the LS9 injectors that the SC kit uses have a special spray pattern and it has been proven to cause the dieseling condition. This is probably my last stab at this as I've been chasing the dieseling for over a year.


This link shows the dieseling when I shut down the car. Go to post #55 http://www.ls2.com/forums/showthread.php?t=841927

I don't think I have the correct IFR spreadsheet. The base in my tune is 18.6 - 92.8 my spreadsheet is 0 - 80.


Elmer

[eboggs_jkvl]

Ok, here we go. I took the 65 slope and multiplied it by 0.953846 and got the slope to just fit in the 63.5 maximum allowed in the B4001 table.
B3671 is back to 14.68 as it was.
I then multiplied B1097 & B1098 by 0.953846 (Low and High flow MAF tables). I will need to adjust these further if the LTFTs need to be tweaked into limits near 0


Does that sound close to what you were posting?


Elmer

[eboggs_jkvl]

Well, I'm obviously going to screw this all up so I'll leave it to my tuner to flog the tune into submission. The injectors get installed on Monday (that's Tuesday to you progressive guys in Oz.)

Elmer

[swingtan]

I think you have it correct now. Lie to the ECM about the IFR, then correct that by making the ECM think there is less air entering the engine ( so it commands less fuel ) and it all balances out.

On the dieseling, the ECM shuts down the injectors on key off. So there should be no additional fuel being injected after key off. If there is dieseling, then the fuel is coming from somewhere else. Boost referenced regulators have been to blame for this before, when the boost diaphragm ruptures and allows fuel to leak into the manifold. Another cause would be leaking injectors. If it's the later, the new ones should fix it. I'm not sure how a spray pattern can cause dieseling if the injector is turned off, unless it's resulting in excessive fuel puddling in the manifold.

Simon.

[wait4me]

Also if you had any extra fans or something with a brush motor on it that is hooked up to the ignition will cause that. What you need to do is, CHECK VOLTAGE on the ignition wire on the injector while shutting down the car. It should instantly quit showing voltage. If it does not then you have something backfeeding like a fan onto the ignition line.. As the fan comes to a stop, so does the voltage it creates..

[wait4me]

Also check for sticking relays as well.