boosting injector trigger wire amps/volts?

[Dan_J]

so i'm currently running big lpg injectors in a stagea, my problem is that these injectors ain't running due to the higher capacity lpg injectors as they need more power( amps) to work.
so i've wired up a switched relay from positive battery to the injector positive grounds with a one way diode so the ecu doesn't have power when the ignition is switched off.

so now i have to boost the negative signal wires for the injectors, nissan ecu's always run lower amps than others on the injectors so i'm just wondering if matt or others have any idea on how to boost the injector trigger wire that comes out the ecu, maybe taking direct power from the battery and grounding into the ecu ground ?

or say something like a fast solid state relay set up that is made off the shelf( obviously the relay/ processor will need to operate at speed of less than 0.5 second)?
thanks

[Matt]

What is the current rating of the injectors?

The feed for the injectors normally comes from the ECCS relay if you check the R34/Stagea wiring diagram for the vehicle, so that relay would not be necessary

The output from the ECU would need to be done with transistors which are capable of switching the current of those injectors

Are you running LPG on this engine, or just using those injectors?

[Dan_J]

hey matt,
thanks for the quick reply

yes the stagea is running on dedicated LPG and the rating for the injectors isnt in cc's as lpg injectors mostly go off l/min flow capacity so i guess its quite irrelevant however they are the biggest lpg injectors you can get for a car.

The feed for the injectors normally comes from the ECCS relay if you check the R34/Stagea wiring diagram for the vehicle, so that relay would not be necessary

i'm confused, which relay wont be needed? if you mean the relay i added to the positive side of the injectors, well the old smaller lpg injectors wouldn't run with out them. or do you mean the eccs relay powers the positive side of the injectors ?

an injector will work for a test if i manually connect up a ground source ( 10-15 amp wire grounded to intake manifold) to the trigger wire so i figure the ecu trigger wire takes less than 10-15 amps.
would you have any Transistors to recommend that i can get from my local Jaycar?

thanks

[Matt]

When I say current rating, I mean electrical amps (or you can measure the resistance of the injector to work it partly). Normally you just need to add a resistor to drop the load to the injector driver

However if the injector uses more (power) wattage to function you need to find out the amps (current draw) or watts (power consumed) to adequatly match the power lines and driver chips

Driver transistors you need to find a datasheet which matches the current draw required

Yes it was the ECCS relay running the injector I was referring to. I'm not sure on the current capacity of the lines (relay itself probably 10 amps) but obviously they werent holding the current

Have a look at a LPG system and see what those are rated to

[Dan_J]

so with a multimeter set to amps, one probe on the negative battery terminal i tested in circuit some old 10w resistors i have laying around and its seems that didnt work too well as the injector only worked with out any resistors at 40amps, even tried a resistor which showed 30amps when connected with no luck.

if you can just direct me to the right type of transistors off jaycar that i should be using, then i'll just pick up a 15 amp transistor from that range suggested and work my way up if it doesnt work.
http://www.jaycar.com.au/search?q=trans ... Arelevance

i have spoken to a couple auto electricians and they had no clue how to boost the signal wire, seems your my only hope matt

thanks again

[Matt]

Response from PL:

I reckon I’d probably try using a FET to switch those LPG injectors. They have lower on resistance, so are capable of switching higher currents without generating excessive heat. You’d need to use a P-channel FET in “high side driver” configuration to avoid the complication of needing a driver transistor in between. P-channel FETs are not quite as common as N-channel but Jaycar have a couple that’d be worth a go. And they’re in the easy-to-use TO220 package for $5.95. IRF9540N

I found a handy circuit that describes the idea quite nicely. See attached. R2 and Q2 exist in the ECU as the injector driver. At present R1 is your injector. So this will need to be replaced by a resistor. Their 2.2k is probably OK. This is your “pull-up” resistor that causes the gate of the FET to be pulled high when Q2 is off. This is a “high side driver” so you will need to rewire your injectors (shown as a motor “M1” in that diagram) so one side is GND instead of 12V. Then hook up your mighty FET with Source pin to 12V and Drain pin to you injector. Google “high side fet driver” for more ideas.

Hope that makes sense. That’s the simplest solution I could come up with.

[Matt]

TTL_MotorPowerSwitchMOSFET_high_side01.png

(14.71 KiB) Downloaded 4583 times

[Dan_J]

great just what i was after

now considering the resistor was the only other component mentioned , it was the only one i added to my simple diagram which is just about all i could make sense of .
so i'm wondering if my diagram is correct ? also not too sure on how the p channel FETS runs with out a positive connection, which most likely is wrong anyway ?

[Matt]

Not sure on this. Best to email PL directly from here

[Dan_J]

hey matt, so i sent PL a pm 2 weeks ago, no response yet. wondering if you have his email ?

[Matt]

pl[at]plmsdevelopments.com