RomRaider

Another one that I stumbled across but I ran out of time to take a look at tonight is mQGLPM2 (Edit: I think it's just for canister purge flow)

I think at this stage, the biggest unknown with fitting significantly bigger injectors is what impact having so many load thresholds changed will have. There are what looks like nearly a hundred "TP" load thresholds for various functions that will be significantly thrown off by rescaling for significantly bigger injectors. Going through them all, getting an understanding for them, defining the important ones and skipping the non-important ones would be an epic task.

After reading the Nistune manual, I think that mMKINJM "Injector magnification reciprocal number" is the newer equivalent of what Nistune refer to as "Total Injection Divisor" for older ECUs. From the Nistune manual:



A bit further down:



What they are saying is that if you rescale for significantly bigger injectors using mKCONST (or either mKCONST or mQUNIT with our newer ECUs), it throws off the TP load threshold for many other undefined features.

Although applying a scalar to the injector duty cycle during the final injector duty cycle calculations is not the "proper" Nissan way to do it, if it is possible, it would as a good option to get TP at least closer to where it needs to be for the purposes of the many load thresholds for many functions of the ECU. Yes it would be strange to have a TP/BFS of say 20 for example, and a final injector duty cycle after mMKINJM of say 12, but at least all of the "TP" load thresholds in the ECU are reached at the loads that they were designed to be reached at. Obviously we'd still be limited by the maximum TP value of 32 but a combination of mMKINJM (If your ROM has this) and the other traditional mKCONST and/or mQUNIT scalar(s) if needed could be a good compromise.

Not everyone will agree but when I turbo mine and upsize from 370cc to 720cc injectors, if my ROM does not have mMKINJM, I may even just trim down all cells in the individual cylinder trim table in order to keep my TP from halving and needing to find and correct many, many TP load thresholds.

Edit: It looks like my ROM has the "Total Injection Divisor" with the no correction 32768 stock value as described in the Nistune manual. It is different to mMKINJM (totally different value) and it is not present in ZB060 but it is copied to RAM and brought in to the TE calculation and cranking injection calculation in the same places as vMKINJ in in ZB060.

So I thought that the mMKINJM A2L conversion must not apply to my ROM (stock value of 32768 raw or 2.0 divisor after conversion) but I looked at an old log and sure enough, my injector duty cycle is around half of my BFS from factory, meaning that it appears that the A2L conversion is actually correct!

Looking back through some other logs, the most injector duty cycle I've ever seen, despite having a BFS of around 25.5, was just 17 when I was testing heavy high coolant temp enrichment.

People say that you max stock TB48 injectors on very low boost. I wonder if in fact these people were simply running into the 32 BFS limit but the 2.0 divider was severely limiting their final injector output.

The stock divider value of 2.0 on the TB48DE, VQ25DET and probably many other vehicles looks like it is quite limiting in terms of using the injectors all the way to 100% duty cycle.

For example the TB48DE:

4800rpm (peak power where max injector duty cycle is generally needed)
25ms per engine cycle

32 BFS (The maximum possible value)
16ms after 2.0 divider
x1.25 for 11.75:1 AFR target
20ms final injector pulse time - Only 80% duty cycle!

This can be overcome using the fuel compensation table but that's not ideal. It would be far better to reduce the divider value by 20%, compensate the change with mKCONST or mQUNIT and get more usable BFS.

Looks like I really do need to investigate all of the TP thresholds so I can lower them after all because the stock mKINJM value of 2.0 is already too high.

mMKINJM tested and it works as expected.

I reduced mMKINJM from 2.0 to 1.5 then multiplied the following by 0.75 to counteract the change:

K Constant
mTP100
Idle BFS limits
mTTST_R1

If it was auto, I’d need to change mTCCLV too but my already has very low mTCCLV values and I don’t think anything actually uses it.

There are around 100 other things that reference BFS/TP but a 0.75 change is probably not enough to matter. VTC and VIAS threshold is 12 TP so I'm still well above that at any decent amount of load. It does appear that stored fuel trims no longer change at idle, so I suspect I may now be idling below a stored fuel trim enablement lower TP threshold. Edit: Maybe mTPKBL threshold of 5.0 BFS

My BFS is now lower for the same injector duty cycle. I now have enough BFS range to run the injectors all the way up to 100% duty cycle at peak power when adding low boost turbo setup. All A/F Alpha values are similar to what they were before after a bit of driving.

Good info, thankyou

Did you ever solve what causes the LTFT trims to not update after your injector changes? I'm running into the same issue where LTFT's stay at 100% and STFT then keeps fluctuating between its correct value and 100 as it periodically gets reset back to 100% due to LTFT values. I can minimize the swaying with fuel compensation maps but ideally I'd like to fix it properly.

MAF voltage is within MAF Idle Voltage limits, I've scaled the mTP100 and mTCCLV and Idle BFS Limits (mTPRVL) to match the new K-value.