The Vortec swap nightmare saga continues.................

[pmkls1]

Just a quick note on the current setup.. The exhaust manifolds were intended to be a very short term solution as I ran into financial problems right in the middle of the swap and just needed to make the car driveable. The intake setup as it is currently configured was not intended to be used much longer either. I've since had major financial problems that have limited me to barely being able to keep up with maintenance so I have long passed the amount of time I had planned on using this configuration. I am now in the position to be able to swap to a sensibly priced exhaust and induction setup that will compliment the L31 longblock. So, the bottom line is that I am fully aware that I have had so many issues with this setup due to it being a sad combination of thrown-together mis-matched parts that are fairly aged as well.

[1project2many]

Since the true VE tables will be drastically different from the typical TBI BINs due to the fuel pressure.

With a specific induction system, changing fuel pressure should not require major changes inthe VE table. Volumetric efficiency represents the engine's ability to move air and is not based on the type of injector or the amount of fuel it delivers.* Injector specific values should be correct such as AE pulses, DE reduction, minimum PW, voltage correction, minimum asynch pulse, quasi asynch enable values. These values are designed to account for a specific injector's behavior. I recognize that getting these values correct can take a long time and that often the corrections find their way into the VE table instead but it is important to remember how the VE is intended to be used and to treat it accordingly.

* Wet flow manifolds will tend to have reduced VE compared to dry flow systems especially at low rpm as expanding fuel in the manifold displaces available oxygen.

[pmkls1]

With a specific induction system, changing fuel pressure should not require major changes inthe VE table. Volumetric efficiency represents the engine's ability to move air and is not based on the type of injector or the amount of fuel it delivers.* Injector specific values should be correct such as AE pulses, DE reduction, minimum PW, voltage correction, minimum asynch pulse, quasi asynch enable values. These values are designed to account for a specific injector's behavior. I recognize that getting these values correct can take a long time and that often the corrections find their way into the VE table instead but it is important to remember how the VE is intended to be used and to treat it accordingly.

* Wet flow manifolds will tend to have reduced VE compared to dry flow systems especially at low rpm as expanding fuel in the manifold displaces available oxygen.

That makes sense and I had not thought of any of that. I had convinced myself that the VE tables would be so different due to the limitations of the '746 ecm and the alterations I had to make to account for fuel pressure and also when tuning for E85 as the majority of my tuning experience has been tuning for E85 fuel as it does "behave" differently than gas. Gotta run for now.

[dave w]

I think I'd try setting the '427 PCM for Open Loop and tune / correct the VE Tables using a WBO2 sensor. Once I got somewhere close with the Open Loop tuning, I'd enable Closed Loop but I'd disable the BLM Update and continue tuning / correcting the VE Tables using a WBO2. Then I'd enable the BLM Update and keep a close eye on the BLM averages. I've seen where BLM averages and WBO2 data do not match, so in that case disable BLM Update.

dave w

[EagleMark]

I'd enable Closed Loop but I'd disable the BLM Update and continue tuning
dave w

D'oh!
Like disconnecting the battery? Man that has saved me so much time...

[1project2many]

I agree with Dave. Although there is more than one way to skin this cat, the goal is to tune steady state first then transients. Disabling closed loop, EGR, DFCO, and other functions mentioned by Mark above is a way to prevent transient corrections from affecting your steady state tables, which are the basis for the entire tune.

At times I've favored disconnecting the battery but there are plenty of times when I don't bother. I think there's a correlation between ecm family or ecm number and whether or not this is really helpful. I am firmly convinced C3 tuning can be finished quicker if the battery is disconnected. P4, not so much. And I have nowhere near enough experience with the 7427 and cousins to tell.

[RobertISaar]

with C3, it's almost a necessity if you don't lock the BLM min/max to 128.

with P4, either send a mode 4 command to clear out the learned BLMs or set the BLM min and max to 128.