12200411 - A Few General Questions

[ScottP]

I ran into the same issue when I retrofit a 12200411 PCM to my 455 Pontiac. The problem was that the VE table I started with was far
too low for my application. The 411 uses a VE table whose entries are proportional to engine displacement, so if your engine is much
larger in displacement than the stock calibration you started with, you will need to scale the VE table accordingly, just to get in the
ballpark.

In my case, the finished VE table for my 455 was nearly 2x that of the L31 calibration I started with in the idle/low load areas that
you'd be using when transitioning from startup fueling to the VE table. This meant that before I made the correction, as the PCM
transitioned from cranking fueling to run fueling, it would be VERY lean and would stall.

-Scott

[ezobens]

OK.. A little embarrassed here. It appears I 'thought' about disabling VATS but never actually changed the setting.
So even with VATS enabled, the fuel pump runs and the ignition will fire?
I'm learning something every day with this stuff!
Is this the only place this needs to be disabled (System -> Theft -> Parameters)?

ScottP's comment is probably also valid-
I'm running a healthy 409 CID and I have not touched the VE table.

Guess I need to disable VATS and move to the next step.
Thanks everyone! I will keep you posted.
Elm

[ezobens]

I can't believe it's 2017 and I still don't have this car on the road! The good news is that the car starts and I was able to dial in the CMPRET to +-2 degrees. The challenge I'm having is getting the car to start and run consistently. Sometimes it will start right up, other times I have to hold the throttle open to get it to finally start. Once I do get it started it will typically (but not always) idle pretty smoothly around 1000 RPM. I tried to do the CASE re-learn but I can't get the car to run well enough (consistently) to finish the process. The latest behavior is that it now will surge from around 900 to 1700 RPM at idle and I am at a loss to explain why when it hasn't surged before? A little background since it's been a while: Car is a 69' Corvette with a 409 CI Gen I SBC running a FIRST TPI intake and a 2000 Camaro Fuel module with a returnless fuel system (C5 Corvette fuel filter/regulator). I started with a 2002 L31 tune and swapped segments for the transmission (running a manual), MAF (running a 5-Wire LS1 Corvette MAF) but am still running the L31 coil and Vortec Distributor. I've updated the injector table for 40# injectors and updated the engine parameters to the current displacement. It's basically a 409 CI version of a TPI motor (complete with IAC, MAF, MAP and TPS sensors) running a 411 PCM. I am running a mechanical flat tappet cam (233/241 @ .050, .505/.520 Lift, 110 LSA) so the vacuum at idle (1000 RPM) is about 12". I know I've made a fair amount of changes to the various tables to emulate the fuel and spark tables of a LS1 Corvette but I'm somewhat stuck as far as where to go from here with interpreting the datalogs and how to systematically dial in the tune to make the car driveable. The only DTC I'm getting to date is the P1336, which to be expected since I have yet to complete the CASE relearn. I've found several threads with good information but I'm not really sure as to the order to tackle them since everything seems to be interrelated. I do have a wideband O2 sensor but until I can get it running more consistently, I'm not sure there is a need to use it just yet. Any suggestions would be most appreciated. I can also post my EFI Live tune and datalogs if anyone needs a good laugh. Thank you for your time! Elm

[dave w]

Did you change the injector flows for a return-less system? ... See attached pictures. David

[ezobens]

Thanks David- Yes, it appears my table is correct per your 'Returnless' screen shot.

[ezobens]

I ran into the same issue when I retrofit a 12200411 PCM to my 455 Pontiac. The problem was that the VE table I started with was far too low for my application. The 411 uses a VE table whose entries are proportional to engine displacement, so if your engine is much larger in displacement than the stock calibration you started with, you will need to scale the VE table accordingly, just to get in the ballpark. In my case, the finished VE table for my 455 was nearly 2x that of the L31 calibration I started with in the idle/low load areas that you'd be using when transitioning from startup fueling to the VE table. This meant that before I made the correction, as the PCM transitioned from cranking fueling to run fueling, it would be VERY lean and would stall. -Scott

I have not touched the VE tables and am currently using the stock LS1 Corvette table- How do you know where and how much to adjust? Is it more trial and error or is there a methodology? Thanks! Elm

[ScottP]

To start with, you could scale the VE table by the ratio of your engine's displacement (409ci) to the stockLS1 (346ci) whose VE table you used, so in this case, x1.182.Once its running, you'll need to datalog your trims to begin fine tuning the VE table. Both EFILive andHPTuners have excellent logging utilities that bin your trims into the same cell structure as the VE table.

[ezobens]

To start with, you could scale the VE table by the ratio of your engine's displacement (409ci) to the stockLS1 (346ci) whose VE table you used, so in this case, x1.182.Once its running, you'll need to datalog your trims to begin fine tuning the VE table. Both EFILive andHPTuners have excellent logging utilities that bin your trims into the same cell structure as the VE table.

Do I want to modify just the 'Main VE' table or also the 'VE While Cranking' table (EFILive)? Thanks! Elm