L-29, 0411 computer and injector timing

[LS1_Dragster]

I have a '98 L-29 454 with a ZZ502 cam and ported heads using the 0411 computer with 01270003 OS, vic jr intake with holley throttle body and I have some questions regarding the B3702 Injection timing.

I've tried off and on the past few months when I get time to tune this in the garage before it's first road trip and I've had a terrible time getting rid of an exhaust backfire when zinging the throttle quickly. Logic told me that it's either rich, bad valve or an ignition problem so I eliminated the last two items and started looking at the way the injectors are firing.

I figure that with the larger cam the exhaust/intake timing event has changed enough that maybe the fuel is being injected while the exhaust port is still open so I messed with the B3702 and added 20% to all the values and the exhaust pop was instantly gone! Also, the WB showed a lot richer at idle so I had to reduce the idle MAP by 3% and also the idle average jumped 150RPM. Why would I have to mess with that? And is adding 20% advancing or retarding the injection event? Is this just band-aid solution to a problem elsewhere?

Lee

[joecar]

The Edelbrock intakes are Aluminium, and the GM intakes are Nylon...

so I would guess they show different behaviour in what the sprayed fuel does when it hits the inside of intake/head port runners and the intake valves (does it wet the port wall, how long does it take to evaporate,...)...

you might be on to something... but also do have a play with DFCO and Dynamics under the Fuel section;

I don't really know.

[LS1_Dragster]

Also, it starts a lot easier too. The big question still is did I advance or retard by increasing the numbers 20%?

[5.7ute]

You would have advanced the injection timing by increasing that table.
The information I am trying to find at the moment is whether this references the start or end of injection. And also which reference pulse is used.(TDC,BDC or one of the other 22 reference pulses.)