dlaitini

ive scanned over the threads in the megasquirt section and this is probobly the only one that has come close to what im needing:

https://www.rx7club.com/megasquirt-forum-153/minimum-injector-turn-time-853144/

here is my issue:

I have a 97 mazda miata (oh noes no rotary :P ) but im currently using a set of fuel injectors from a 89-92 RX-7 non-turbo, the Denso part number is: 195500-2010

I am currently running them with an injector opening time of 1.10

Now after seeing the other post im gogin to change to 1.0, and tune again, my question is where did those numbers come from?

is 1.0ms the optimal time for these specific injectors, and what is the benefit/ drawback to setting it to be more or less then what is optimal and why or how is that figured out?

Its currently 10F here in Salt lake city, and im thinking that i might have mine set to long and that might be one of the issues im having to start my car, it was fine at 50 degrees, but has gotten harder as it gets colder

Other mods done in case they might also be effecting something:
DIY autotune MSPNP
Intercooled BEGI-S turbo kit with seperated gas downpipe
cat blankout pipe with resonator
(after cat is still stock exaust)
460cc rx7 fuel injectors

I cannot think of anything else on the car that will directly effect the engine
Tein flex coilovers
flyin miata sway bars
hard dog DD Roll bar
Flying miata "happy meal" light weight flywheel and clutch ( i did not add this to because i dont think the lighter rotational mass will be effecting it when cold, it had no issues starting when it was warmer)

muythaibxr

1.0ms is just the default that the MS uses. If you never see very low pulse-widths in normal operation, you'll never notice any issues with 1.0 or 1.1 as the opening time.

That is almost definitely not the issue. More likely you just need to tune the cranking pulse settings at that temperature.

As far as opening time for those injectors, I found that below about 1.3ms, those injectors do not inject reliably. I am currently using 1.3ms as the opening time on my 1986 rx7 GXL with injectors from a 1989 NA rx7. I found this recently because I switched to 4 squirts from 2, making the pulse-widths at low load go below the 1.3ms limit in normal operation. I started getting surges, and AFR would go to 17:1+ at very low load (less than 40kPa) even though I had not turned off the injectors.

I fixed it by slowly increasing the opening time until that behavior went away, and now everything is happy, and I have no more bad surging behavior.

Ken