MicroSquirt.com read only forum (Jan.15,2018)

Hi guys, I'm finishing up my jumpering table on a DIYPNP unit, there's just one thing I'm not too sure on (well, several, but let's just focus on this one).

I have 4 low impedance injectors, however the PCB can apparently only handle 2, so from what I understand I have 3 options:

1. Current limiting resistors. This seems like an easy solution, infact I already hastily ordered some appropriate resistors, but from reading on here they are not recommended due to a delayed response in injector opening time.

2. Pulse width modulation. I'm really not sure if this is even supported. I've heard microsquirt needs an add-on board, but is this part of the DIYPNP board? I can't see anything to suggest it is.

3. Sequential injection add-on. Probably the most solid solution. Also the most expensive. Installing this will give 4 available injection outputs, each capable of 1 low impedance injector (correct?). Sequential injection is also bound to impress the ladies.

Recommendations, info, experience, all appreciated!

PS. If anyone here has megasquirted an SW20 and would be tolerant of some stupid questions, drop me a line!

These are my opinions on the 3 options:

1. Current limiting resistors will work but depending on your injectors they may be affected by it with a slower response as you mention. And depending on your injector size that may or may not be an issue.

2. PWM is not possible on the Microsquirt module (on which the DIYPNP is based). You could use an external peak&hold driver box or it may be possible to use an internal one attached to the case. Since I don't have access to a DIYPNP I wouldn't be able to say if that would fit or not. By the way, this would be more expensive than option 3 but would drive the injectors in the "correct" peak&hold fashion and would lower the current through the injectors.

3. This option will work and not only give you 2 additional injector drivers identical to those on the Microsquirt board but will allow you to run sequential injection. Sequential injection may impress the ladies (or not) but there is real benefit in idle quality and transient behaviour. (By the way, sequential injection is also possible with the peak&hold drivers and would be the way to go if you use them).

So the best solution that is certain to work would be 3. The best potential solution would be 2 (peak&hold drivers) but you'll have to see how to fit that. And 1 will work but not optimally (and won't allow sequential injection).

Jean

Cool, I've gone ahead and ordered the sequential injection add-on. The peak&hold driver does sound interesting but I don't fancy trying to fit a PCB in the enclosure that wasn't designed to be.

Excellent info, thanks!