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300ohm resistor effect on indicated flowl Posted by Kevin K [Email]  (#374) [Profile/Gallery]
(more from Kevin K) on Thu, 3 Jun 2004 11:58:57
In Reply to: LH2.4 / 30# injectors / 300ohm resistor experiment. Qs?, Taylor, Thu, 3 Jun 2004 06:31:20 Members do not see ads below this line. - Help Keep This Site Online - Signup |
the 300 ohm R will make a constant % drop for the amm output voltage. but, because the relation between volts and flow is very non-linear at the amm, the change in % flow info sent to the ecu is higher at mid to upper loads.
assume 2.5 bar, and 30 lb accel inj'rs (3 bar rating). the fuel supply increase is 30/23 = 1.30, so 1/1.3 = .77 is the reduced flow signal input to ecu desired, with the big inj's.
I used a similar ford 55mm amm curve as an example. using 'some' resistor to drop output volts to 91% of original values gives the desired 77% of measured flow signal near max amm output of 5V. But the resistor has less effect at the bottom end, so tendency with this mod is richer at low end of range of amm rated flow.
in my example, using 91% of the amm output volts to ecu, the fraction of original flow signal to ecu, vs raw, unreduced amm output volts is:
V -- %flow
1 -- 87
2 -- 83
3 -- 80
4 -- 78
5 -- 77
(5.5 -- 77)
so a hobbs vacuum switch to short out an additional series resistor at any + boost would likely help with over rich idle.
but, amm has a limited functional flow rating (mabe 225 hp limit) so you could then swing lean at higher hp levels.
best to chip ecu like jak said, to also account for load issues. might be possible to use an AIC driver to kick in and control firing 34lb inj's at high hp levels, avoiding 2.4 fuel cut.
posted by 52.128.3...
, Thu, 3 Jun 2004 11:58:57 <-- Viewing This Message
, Thu, 3 Jun 2004 07:38:04
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