Curious if someone can help me. I am looking at building a set of high impedance injector drivers as close as possible to a Holley or GM ECU. As far as i have descerned the ground signal sent to the injector is from a MOSFET capable of around 3 amps, but does GM, Holley or Haltech use a Diode between the MOSFET and the injector? Also, if anyone has any information on the actual hardware used inside a Holley ECU, i would really like to know what MOSFET they use, What diode etc. also what they use for a MCU.... infact. if you have pictures of the inside of a Holley or GM ECU id love to see em. Thanks!

 

ive posted the inside of a terminator x here before.
the questions youre asking lead me to believe that you have a long way to go before being able to do what youre attemping.

the diode goes between the drain and gate on the fet to absorb flyback, it sounds like you are expecting it to go inline between the fet and the injector.
id start with studying the megasquirt schematics and documentation. they have some pretty good explanations of the methods of controlling injectors. for instance, GM ecus and the terminator x can only use high-z injectors so using those as reference will be interesting to study but unlikely to be directly useful. the higher end ecus like nexus, dominator, fueltech, etc typically will use a 'peak and hold' method which is also described well by megasquirt.

 

Hi, I use an IRLR 2905 and a 39 Volt Ziener.
I like to open/close the injector fast.

 

Lol, definitely a very long way. I am trying to absorb as much as i can but without an electronics background its a incredibly daunting experience. Definitely going to look into microsquirts data if its publically available, I am trying to build a piggyback box that takes the injector signal from the holleys injector driver, and relays it to a MCU which controls 16 injector drivers (two sets of injectors) so i can run dual fuel injectors/alternate fuels. I think i would need to run two sets of identicle injectors, to avoid issues with injector dead times/commanded duty cycle. but i feel like with some cleaver math, maybe i can account for different sized injectors/deadtimes. I know the dominator offers dual injectors, but i already bought a terminator, plus, learning all this stuff is really interesting. Appreciate you brother.

 

A 36 amp MOSFET? i think holley uses 1.3 Amp MOSFETs... you running low impedance injectors? or are you somehow using that single MOSFET for every injector? also why 39 volts? the largest draw "high impedance" injector i could find was 9.1 ohms. Sorry if this is really basic, i am just trying to learn.

 

youre going to be way better off just buying a dominator or nexus that natively drives 16 injectors unless you really want to do this for the novelty.
theres more to selecting fets than just their amp rating. heres a really good primer on fets: https://github.com/SpenceKonde/Produ...SFETs/Guide.md
all the megasquirt stuff is open source so schematics, firmware, etc. https://www.msextra.com/manuals/schematics/

 

HI, I most do run LOW Impedance Fuel Injectors. My Customers had that Choice, Low/High.
I have tested " dead" fuel injectors and @ 2 ms PW, that LR-2905 would LIVE. They can also stand a direct short at higher PW often.
WHEN you choose a driver, look at the RDS ON TIME?.
The Ignition Coil INSIDE the injector has a "kick back" Voltage when released.
MAYBE to driver you have specified has that Ziener built in ?
DO NOT BELIEVE the manufacturer.
Lance

 

diodes are a bad solution, they slow the fet/injector down. there are better solutions (like the zener mentioned) but imo the best one is to get a fet/igtb that can withstand the flyback spike (v d/s = 300 volts should do).

it will depend on your signal if a dedicated driver for these is needed.

 

Hi Grumpy, try this test, RAISE the Fuel Rail Pressure.
This method can LOWER the fuel delivery at a LOW PW with a large fuel injector.
When you "scope" the injector, you can see the spike when it opens.
Lance