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kellcats521 kellcats521 is offline
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Join Date: Feb 2005
Location: Atlanta Metro
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Originally posted by beepbeep
72lbs/hr = 700cc/min.

I believe 700cc shouldn't be the problem idle-wise as long as cams aren't wild and you use fuly-sequential peak-and-hold ECU with good PWD-resolution.

Batch/fully sequential injection usually doesn't matter power-wise but when it comes to fiddling with final idling characteristics it can matter a lot. To put it this way:

You have two engines. Both have same 92lb injectors but one is equipped with Megasquirt I for 200$ and other with kitted-out Autronic/motoronic/DTA/whatever. Both can be mapped for same top-end power, but MS will suffer when it's batch-fired injectors try to quirt small amounts of fuel at idle (and try to do it with low resolution).

If you still get rolling idle with sequential injection you can try to vary the injection phase. If that doesn't it's time to go to staged injectors (a twin set where second set is activated on demand).

But frankly, I don't believe you'll have problems as long as other things are taken care of. I saw four-bangers idling with 1600cc injectors.

Good luck!
Just remember that a 1600cc injector is low impedance, and there is no comparison WRT short PW operation between low and high impedance (700 cc Siemens). At 700cc you are on the ragged edge of high impedance use, and low PW operation will suffer. Low impedance injectors by nature will perform better at short PW, so it's not out of the realm to have better idle characteristics in a 2.0L 4cyl with 1600cc injectors than in a 3.3L 6cyl with 700cc injectors.
Old 06-15-2007, 08:07 AM
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