$EE - LT1 Crank VE Table?

[NorthernCrew454]

Hi All,

I have been working on cold start (0-32*F) tuning. Have a 94 LT1. I scaled the first and second pulse widths based on the change on injector size and that seemed to help, but i still need to "pedal" the throttle just a touch to get it running when cranking. I think it is too rich. Based on my cam size, has anyone had to lower the cranking VE table and/or cranking AFR table to lean it out for a good start with a cam of this size? How do I go about getting the correct VE values?

Thanks!

1994 Camaro Z-28, 383 stroker, Callies DragonSlayer 3.750" forged crank, Callies Compstar 6" H-beams, Mahle forged pistons (4.030"), splayed 4 bolt w/ARP studs, 12:1, LE2 heads (2.00"/1.56"), Comp Ultra Pro Magnum XD 1.6:1 rockers, LE custom cam (242/248 .585/.580 110 LSA, LE ported intake, 58mm TB, Racetronix 37# injectors, Racetronix 255L/hr, Pacesetter LT's, Yank 3600 Stall, SSW Tuned, Performabuilt level 2 4L60E

[MO LS Noobie]

Based on "but i still need to "pedal" the throttle just a touch to get it running when cranking. I think it is too rich" I would I just lower the cranking VE about 20%, and see what it does. Obviously save your old files first. After about 20 seconds I assume it runs right and your fully warmed up engine is running in closed-loop and near zero fuel trims (+ or -10%). I always get the fuel fully warmed up tune set properly, then do my accelerator enrichment, then finally the coldstart.

In answer to your question yes, it is very common to have to lower the VE in the lower map/rpm range, and raise it in the higher map/rpm range. HTH Jeff

[bobcratchet555]

when i do this for LS engines, to start with i knock off about 10% VE down low, then ADD base air flow (usually 50% over stock), then up the idle speed (normally 1000 cold, 800 hot). have never had a cam not start and idle this way.

[kur4o]

Scaling the prime pulse injector constants is kind of art.

There is some write up on older threads, but will need to dig it out. Usually you need to convert the pulse width to grams of fuel, than scale new injectors and convert back to pulse width. There is also some scalar used in conversion in calibration, Other table that affect starting is start up spark advance. No need to touch VE tables, it will get worse.

Just keep playing with the prime pulse.

Usually lt1 starts in a fraction of a second, no matter what cam is in there.

[steveo]

its weird I've never had trouble just adding a ton of cranking fuel. hell you can pour straight gas down an engines throat and itll fire up immediately. colder the engine the more it wants. if you need pedal maybe your initial cranking airflow is too low. how are your iac counts when running

[NorthernCrew454]

IAC counts are in the 30's at full temp, pegged at 160 during cold start. I 99% of the time i get an initial fire and within a few msec it will die, i assume during the change over to the OL table, maybe the MAF needs to be adjusted in this g/sec range?

[kur4o]

You will need some log with eehack during startup, maybe something is out of spec.

Than figure why it dies, lack of fuel or air or extra fuel, When cold fuel evaporates slower, and it may peg down after crank. Check for leaking injectors, vacuum leak or crap spark plugs.

Getting the throttle to 100% will cut fuel at cranking.

Fine tuning the prime pulses will get you spot on. There is a scalar that might need changing too, to allow for more fuel at cold temperatures.