MS II injector wiring

For discussing how to choose sensors and create a wiring harness for all Bowling and Grippo versions of the MegaSquirt® EFI controller.
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CHB
MegaSquirt Newbie
Posts: 19
Joined: Sun Dec 04, 2005 11:52 pm
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MS II injector wiring

Post by CHB »

i've just purchased a MSII on Ver 3 board. i'm going to using 450cc low ohm injectors on my turbo Toyota 3TC. do i need to connect an resistor in series with the injector? if i eliminate it, do i need to make certain setting changes in the Megatune?
CHB
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Posts: 19
Joined: Sun Dec 04, 2005 11:52 pm
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Post by CHB »

For low-impedance injectors (less than 3 Ohms), you need to limit the current to avoid overheating the injectors. To do this, there is a period of time that you apply full battery voltage [peak] current, then switch over to a lower current-averaged [hold] current, i.e. peak and hold. Alternatively, you can add resistors in series with the injectors.
If you are running high-impedance injectors (greater than 10 Ohms), then set the:

PWM Time Threshold to 25.4 msec, and the
PWM Current Limit (%) to 100%.
If you have low impedance injectors (less than 4 Ohms), set the:

PWM Time Threshold to 1.0 msec, and
PWM Current Limit to 75% (30% if you have installed the 'Flyback Board' daughter card).
assume that i have a series resistor pack connected with the low ohm injectors, should i follow according to "High Impedence" or "low impedence"?
FiatFreak
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Joined: Thu Sep 09, 2004 2:40 am

Post by FiatFreak »

Measure the resistance of the series pack and an injector. That will tell you which way you need to go.
'81 Fiat Spider - Turbo charged, MSII, EDIS4
'04 SRT4 - Daily driver
CHB
MegaSquirt Newbie
Posts: 19
Joined: Sun Dec 04, 2005 11:52 pm
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Post by CHB »

if the total resistance (injector+resistor) is more than 10 ohms, i'll need to configure it according to the "high impedence" setup?

currently my wiring is 1 resistor (6 ohm) connected to 1 injector (2.9ohm), there are total of 4 injectors on my 3TC. refered to the VER 3 board external diagram, 2 injectors in 1 bank. should i connect 1 resistor to Bank1 and another to Bank2?
or can i just eliminate the resistor and run directly switched +12V to the "low ohm" injectors as in VER3 External diagram?
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