wh944

" If you increase the opening time you will get more fuel "
I thought the opening time is the time the injector needs to start spraying after receiving the signal, not the time the injector stays open?

Speedtoys

And dialing around the injector size is not the way to go about it, it screws up the whole map.

If you believe they are 42s, then setting the ST to 42, should start and idle at any temp with stock fuel maps...if off some, maybe tickle the injector dead time.

With that right it should idle warm at 14.7ish with little +/- correction required

Ge3t inj sie and dead time good, and go from there.

FredR

The opening time is what the name implies- it is a finite element of time needed for the injector to open before it starts to spray fuel- it is a bit like taking a pee- you think about it, the brain sends a message to open, the elements involved react and all being well you get a flow stream- I just wish my system could open in 0.5 milliseconds- it is more like 5 seconds these days!

So, if you have an originally specified opening time set of say 0.5 msec and you then reset it to 1.1 msec, and at idle [700 rpm] the actual pulse width specified injects fuel for say 0.6 msec, the total event time will increase from 1.1 msec to 1.7 msec and that is why more fuel will be injected at that operating point and more to the point, the percentage change you are actually injecting fuel can thus vary wildly. Thus messing around blindly with the opening time can have a dramatic effect on the fuelling at idle/low rpms. At full throttle the impact of such change is much less percentage wise for a given tune.

In my case I knew what the injector part number was but could not find the opening time for it so I set it the same as the stock 19lb injectors. This was not a problem for me as I was doing a complete custom tune but as you can see, if tomorrow I decided to fit say 24lb injectors I could not retain my current tune in ST2 by simply changing the injector size unless of course I "lucked out" and got the opening time correct by chance.