Heads/Cam- Need new injectors?

[jonny985]

As of right now, my engine is disassembled in my garage.

I am installing the GT cam from ZZP and ported/polished heads, intake, and TB(with 99+ MAF)

I'm running a full 3" exhaust and a SLP intake. I also have a MAFT

Do I need new injectors? Will I hurt my engine if I run the stock injectors at WOT? How will I know if my engine isn't getting enough fuel. I was thinking GM 24#s or 26#s. I plan to rev all the way to 6000 rpm.

[awesomeame]

autotap is your friend. see what your pulse widths are on #1 injector, (after getting proper o2 voltages) then decide if you need bigger injectors or not.

--matt

[jonny985]

Thanks, I'll log some numbers after the install. What kind of pulse widths should I be looking for?

[awesomeame]

http://engine.firebirdv6.com/pulsewidth.html

imho, i don't think that chart is 100% accurate, but it's close. i'm hitting 22-22.5 ms, at 5800rpm, which according to the chart is approx 107% duty cycle. i just don't understand how one gets more then 100% duty cycle....if someone knows, speak up [img]smile.gif[/img]

--matt

[ October 15, 2003: Message edited by: awesomeame ]</p>

[John_D.]

It's just a measurement of how long the pcm would like to hold the injector open, compared to the firing cycle time.

When the engine is turning at 6000 rpms, that's 100 revolutions every second. Since a cylinder fires every other revolution, it's firing 50 times a second.

1/50th of a second is .020, or 20 milliseconds.

Theoretically, the pcm could hold the injector open longer than 20 milliseconds, and just let fuel pile up in the intake, to be drawn in on the next intake cycle.

But I think the pcm stops at the 100% point. My autotap logs always show me starting to drift lean if the duty cycle goes over 100%.

The formula, after it is simplified down from the various conversion factors, is
Pulse Width x RPMS / 1200.

20ms x 6000 rpms / 1200 = 100 (percent)

[awesomeame]

gotcha. thanks for explaining that [img]graemlins/burnout.gif[/img]

--matt