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Old 04-21-2010, 08:45 PM   #1
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Default injector settings...

If im going from a 230cc (stock) to a 750cc (high impedance) what should my injector opening time (ms) be set at if im at 1.0ms now? I tried to do the math but gave up after a few min.....

Also where do i find the accel enrichment pw, and what does that get changed to?

Lastly should i use 12.7 or 14.7 for a/f in the required fuel calculator?

I copied this from the megamanual to save you guys the hassle of looking. Any help would be awesome, i suck dick at mega squirt but im trying to learn...

"There are a few settings which do not adjust when you change REQ_FUEL as they are static pulsewidth (PW) settings, so you will need to adjust these by hand. The acceleration enrichment settings will probably need to be retuned for the new injectors. Also, larger injectors require shorter cranking pulse widths. If you double your injector size, you will need approximately half the cranking pulse width. As a general rule, it’s easier to fine tune the cranking pulse widths by setting them to a lower value than expected, and then increase this in 0.1-0.2 millisecond increments until the engine starts. This will make it less likely that you flood the engine.

For both the cranking PW and Accel Enrichment PW you can do much of the adjustments using math—then do the rest via fine tuning.

For example—you need to first subtract the injector opening time from your current numbers. Injector opening time by default is set to 1.0ms. So if your Cranking PW at 100degF is 4ms, subtract 1.0ms from that and you have 3ms. Now, that that 3ms and divide it by the percentage of the size difference of the new injectors compared to the old. If you had 20lb stock injectors, and you’re going to 42lb injectors, you’ll need about ½ the cranking PW minus the opening time. So in this case, ½ that 3.0ms is 1.5ms. Add that 1.0ms injector opening time back and you’ve got 2.5ms. Your old cranking PW at 100degF was 4ms, your new time at the same temp is 2.5ms. This should be pretty close to what’s needed. Do this for all cells in your cranking PW and Accel Enrichments and you’ll be close with only fine tuning remaining.

After swapping in new injectors and making these adjustments, it’s a good idea to make sure your air-fuel ratios are still where they should be. Sometimes the VE table will need a bit of fine tuning due to differences in the way injectors behave, and it’s also a math check for the changes you just made. Make sure the air-fuel ratios are good before pushing the engine hard after an injector swap."
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Old 04-21-2010, 08:50 PM   #2
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you use 14.7 in your req fuel... you can use a calculator posted up in the super important megasquirt threads to calculate your new PW based on your injector change. Its easy... really easy.
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