Wargasm

Heya... just thinking out loud here. I don't know if this will end up helping anyone but I figured I'd put it here for future searching newbies

Sorry if this is long.

AS ALWAYS, MAKE SURE YOU KNOW WHAT YOU'RE DOING AND TAKE EXTREME CARE WHEN CHANGING PARAMETERS IN YOUR POWERFC

If you have put in larger secondary injectors and you have stuttering or bucking that occurs when they transition this may help you.

Short Version:
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Try changing Sec Transition (ms) using your Datalogit from 1.500 (stock) to around 0.800 or 0.900

Long Version:
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Start up FC EDIT and the Map Watch Utility. Now create a "watch" on Advanced FrInjSc. Hit F1 on your Map Watch and start driving. As you drive, have a passenger keep an eye on your Advanced FrInjSc watch. When you see it go from 0 to greater than 0... it tells you that your secondary injectors just tried to kick in. Was there a bad stutter just at that moment? If so, you might benefit from this info....

According to the manual that comes with FC EDIT:

"Sec transition; initial Secondary injector “on time”. Primary injector “on time” will reduce so the total fuel injected remains correct"

To me, this says that at the moment the computer decides to phase in the secondaries, it says, ok let's fire them for X amount of time to start. And to compensate, I will reduce the primaries. X = whatever you have sec transition time set to.

On a stock car with 550 and 850 injectors with a 1.500 ms transition time... when the secondaries kick in (for 1.500 ms), it will cut back the primaries an equal amount (FUEL WISE, not TIME WISE). So your 850s come online for 1.500 ms, which means it must cut back the 550 secondaries for about 2.3 ms.

Now let's say you've upgraded to some nice and big 1680s for secondaries and kept the stock 550 primaries. Now when the computer fires off those 1680s for 1.500 ms, it must reduce the primaries by 4.6 ms. If that 4.6 ms is a large percentage of the time that they're already on, the car is basically trying to quickly turn on some big *** injectors, and cut way back on some small and accurate ones... and you end up with a stumble.

By changing the transition time to a value of say 0.800, the calculation works out a bit differently and now the car will only try to cut back on the primaries by 2.4 ms which is close to the factory reduction.

Makes sense I think.... I hope this info can help some people that might be having trouble.

Brian

Zyon13B

Interesting, but what if I have 1600's and 850 's?

sub-zero

"Also try adjusting SECONDARY TRANSITION.

Recalculate it as: (1.500ms) * (850/ new secondary size)

As with any unsure change, do one at a time and test drive it"

Quoted from cewrx7r1