2 squirts vs 6 and injecor sizing (EFI related)

[trond]

how to delete ?

[trond]

I have been playing with MS2extra and trying to with 6 squirts rather than 2, to see what a finer distributed mist in the inlet will do and it appears to be a good thing wrt throttle respones except I never seem to get dead times correct and which is why I believe I have too much pops and bangs at low settings. Also not easy to find advice and so I let it rest for a while.

Today I tried with #15 injectors (Accel 150115) to replace the #30 ones as an experiment. Thoughts are the smaller injectors need longer opening times which should reduce sensitivity to (less than perfectly set) dead times or just very short opening times in low load settings. This is where popping and bangs happen mostly as opening times approach dead times and those settings become crucial

I am happy to report that most (as in only a minor and not embarrassing at all very occasional cackle left) of the popping and farting at low load settings that made 6 squirts an emberassment is not there with the smaller injectors. And car runs beautifully, especially the sub 4000 range is improved is what it feels like

I did not log as I was mapping & tweaking but did not see any overly short opening times, or long ones either. Seem to recall 1.8 ms at idle which is a good number, and less than 6 at higher load setting but would have to log for better data.

Could be a way for others too wanting to test out 6 squirts. Actually even smaller injectors would have been fine too, certainly not larger with this setup

3.0 SC with stock cams and Triumph ITBs. MS2Extra and twin CDI spark. I run 36 psi fuel pressure which is low so no doubt the #15s are enough with 6 squirts

[chrisbalich]

Seems to be a really small injector and low fuel pressure if you wind it up much past 5000rpm.

[trond]

plenty large with 6 squirts. I did mention the fuel pressure to illustrate there is much more to go on... I run wide band and was monitoring opening times on laptop while applying some throttle so can assure you it works

[jpnovak]

The fun of experimenting with EFI settings.

Yes, more injections per cycle will help with fuel fog on non-sequential systems. It helps with transitions and overall driveability in the mid range.

The challenge is if your injectors are large enough that the PW divided into 6 gets so short that you are at or below the injector dead time (lag time). Even with good time constant numbers for lag time this means you will have missed injection events or differences in fuel delivery causing mis-fires, hesitation and other undesireble drive qualities.

Trond, Glad you are still striving for perfection. Just for fun, Let's all go get into the wayback machine.

Austin, TX EFI install/tech session - 11/7/09

[trond]

with 1/2 size injectors dependency of dead time is reduced to half. I was unable to get 6 squirts work without the driveability issues you mention, but with the smaller injectors that problem has been all but eliminated. But will do some logging to further investigate how much headroom the smaller injectors have. Certainly did not notice any issues with fueling, even at higher load settings. Remember that install session at your place in Austin back in 2009 fondly. What hospitality. Big part of me feeling so welcome in the US. And your continued support has been a great help too and made my immersion into MS manageable and fun

[trond]

On todays mapping session I observed a max injector duty cycle of 70%. Which should be fine I believe. No popping, banging, lean conditions or driveabilty issues