pcmhacking.net

here is better : http://jbperf.com/quad_ign_inj/index.html
this is the dude who makes the boards.

and then there is this
http://www.gtsparkplugs.com/pdf/SUBDRV.pdf
soas the injector driver from the 808 is merely a pull to ground, and, does all 8 injectors ; only one section of the above would be required (ie: one driver ; using the TIP121/LM1949
would also pull +5v from the 808 instead of providing it, its own albeit regulated supply ...
thoughts?

Sorry Greg my electronic skills are no where near the level they should be so I can't comment on the information you are posting. I'm trying to follow what you are posting but I'm more of a motor mechanic than an automotive technician (I know they are supposed to be the exact same thing).

After my OP my general idea was to see if someone like VL400 was making a driver box like Kalmaker used to. If one was available and I couldn't get injectors that matched (or come close to) the impedance of the OEM petrol injectors I would use it. If not I would pretty much go the piggy back path which would provide the LPG temp and pressure sensors as well. I really do want to stick with the single delco (424 hopefully) but if I have to piggy back I'll do it.

MAGP. Awesome. our skills are probably on par then. I have no electronics skills.
The diagram above is an injector driver board, which, shouldn't be much different to the Kalmaker one. It will drive hi and low z injectors with different jumpers/configs.
It uses its own transistor for this piece of work.
Just need to understand if driving it from the -ve output from the ECU to pull the injector to ground will work, and, as, all injectors are batch fired, whether the singularity of the seperate driver /TIP will work - there are people here way smarted than me who will know

so toyotas i have worked on previously, have, always had an injector resistor for low z injectors.
the drivers in the ND ECUs will run either low or hi z, it seems. obviously with different supporting maps.
it seems the batch firing of the injectors on the 4AG for example is no different to that of the 808

funnily enough i think i still have a couple of these resistors. time to setup a bit of a bench i think ...

FWIW mitsubishi do a similar thing ;

http://www.stealth316.com/2-injectortypes.htm

and diy autotune who i got my megasquirt off also do this as they quote Using the Peak and Hold Injector Driver Board provides faster and more consistent injector opening times than driving low impedance injectors through resistors. It also provides better cold start performance than resistors since the injectors get full battery voltage to open them; when using injector resistors, the injectors may not even open if the battery voltage drops too far.
https://www.diyautotune.com/support/tec ... are/phidb/

MAGP wrote:What injectors did you use vn5000?

I still have them in the shed , here is a pic of injectors and driver
Was easy to wire up , one relay to switch between fuel pump and gas solonoids , and one relay to switch between petrol injectors and gas injectors , on gas the pcm controlled the gas solenoids for priming and safety cut out , same as it does std for fuel pump