Injector trims = which cylinder?

[bdearnley]

Quite a basic question but one which I can't find an answer for. I am using a PnP v1.99 in a version 5 Subaru WRX. I am monitoring egts in each exhaust port want to use the injector trims to correct the differences.

Does inj1 refer to cylinder #1, inj2 cylinder #2 and so on? Or does it go in firing order, so inj1 is cyl#1, inj2 is cyl#3 etc?

[Ian]

All PnP boards (both SMD and SM4 variants) have injectors wired in firing order. So the Subaru boards have Inj O/P 1 = Cylinder 1, Inj O/P 2 = Cyl 3, Inj O/P 3 = Cyl 2, Inj O/P 4 = Cyl 4. So the Injector trim 2 is for Cylinder 3, etc.

As a side note, with SM4 ECU's it is possible to wire injector outputs to cylinder numbers and change the injection angles to suit the firing order so that the Injector trim refers directly to the Cylinder number. But even more advanced is that even if the injectors are wired in firing order or the wrong order it is possible to reassign the outputs between the trims so that the trim represents the cylinder number.

[bdearnley]

Ok, thanks Ian. That explains why I couldn't get the EGT results I expected with the trims.

[MRMRacing]

Regarding Ian note of reassigned injector O/P when wired in firing order.


Here is a basic guide:Menu "Injector O/P Events" - "Advanced tab"Here you find :

"Injector O/P&Events" which is the numbers of O/P used.
"Event" Cant be changed but SM4 is firing injectors in "Event" order, first 1 then 2 and more.
"O/P Pattern 1 Inj 8..1" This value corresponds to which physical O/P each Events is bound to. Normally Event 1 uses 00000001 which is injector O/P 1, event 2 uses 00000010 which is injector O/P 2.
"Base angels" which is the degrees each Event should occur at.So if you from beginning will wire them so each fuel trim corresponds to each cyl number: Wire O/P 1 to cyl 1, O/P 2 to cyl 2 and more. Then trim the Base angles to fit your firing order.
Example: a 4-cyl with firing order 1,3,4,2 is wired like above to same cyl number, the we change base angels to , 0, 540, 180, 360. The third cyl fires at 180 degrees and we change event 3 to 180, The fourth cyl fires at 360 degrees so we set event 4 to 360. You can easily check the graphics pattern showed to verify your settings.

But reassigned O/P wired in firing order needs little more effort, by changing the O/P Pattern1 inj8..1 we physically move the event to another O/P pin.
In this example we have wired a 4-cyl engine with firing order 1,3,4,2 like this: inj1 = cyl1, inj2 = cyl 3, inj3 = cyl 4, inj4 = cyl 2.

So we change:
Cyl 1 is OK so we leave that,
Cyl 2 is wired to inj 4, so we change event 2 pattern to 00001000 which is the O/P where cyl 2 is wired.
Cyl 3 is wired at inj 2, we change that to 00000010 which is the physical pin cyl 3 is wired.
Cyl 4 is wired at inj 3, we change that to 00000100 which is the physical pin cyl 4 is wired.
We then trim Base angles to fit the firing order 0(cyl1), 540(cyl2), 180(cyl3), 360(cyl4).

See pic for a reassigned 4-cyl

[Chris]

I have been using a four channel digital thermometer/egt guage lately. I plug egt probes into the guage in firing order. Thus, for a Subaru Channel 1 =CYL1 Channel 2 =CYL3 Channel 3 = CYL2 Channel 4= CYL4.

Cuts down the brain duty cycle a fair bit.

Chris

[bdearnley]

Great info - thanks everyone.

[Enzo]

Good Info....

[p1prodrive]

makes sense