Change MAF curve affecting idle rpm - 2016 Mustang w/ Whipple

[Ruiner46]

I just swapped to a return fuel system with ID1050's and I'm trying to keep using the Whipple OS. As others have seen, entering the correct numbers from ID for the injectors causes large fuel trim corrections with the whipple tune.

I did some logging and adjusted the MAF curve using only LTFT results. On the next drive, my logs looks decent, although the MAF curve still needs a little fine tuning. However, the car is now idling at something like 1800 RPM when warm. Do I need to make speed density adjustments? I see a multiplier for desired airmass at idle in the Airflow-->General tab. Is that related? If anyone can help explain how the idle works, it would be appreciated. I am not a tuner, just a guy tinkering with his own car.

[GHuggins]

Sounds like your on the right track. You sort of answered your own question without realizing it Idle and throttle in general is controlled via desired torque - torque direct calculation of airflow - MAF altered changing the programmed in airflow model. You might need to lower torque and idle airflow tables... At least to have it more OE like...

[Ruiner46]

I'm not sure I'm on the right track yet. I just went down a rabbit hole of researching the torque and inverse tables and now I'm completely lost. You mentioned idle airflow tables, but I'm not seeing anything like that. Under the idle tab, I only see target RPM's based on various conditions and some other general options. Where are tables for idle specific torque and airflow? Under the idle-->torque section I see a min and max torque correction and I was considering trying to increase those, but it seems like it would be better to correct what it is looking for. I looked at the torque table for mapped point 0, should I be lowering the torque around the idle RPM/load range?

Edit: I discovered that the idle airflow tab is missing, so I will put in a ticket. Since everything is suspect with the Whipple tune, is there a recommended order of steps to get the tune back on track after using corrected injector numbers? Should I have adjusted something before trying to calibrate the MAF?

[Ruiner46]

Well I tried changing the mapped point 0 torque table top row and used the torque inverse calculator to populate the inverse. Generally I increased the torque values in that row hoping that would make the idle target a lower load. I'm not sure that my understanding is correct there, but none of these changes seemed to make any effect.

No matter what values are in the top row, the target load always seems to be 0.18. I also did the same to mapped point 1 in case it was getting some weighting, but no effect either.

Here's a short log of a warm startup:
v3p1 idle.hpl

[Grim5.0]

personally, im not a fan of messing with the maft curve unless you know that is for sure the issue (no maf data etc). i am in favor of using the low inj slope to get fueling in range if this was the only change. Fuel pressure is inferred too. I usually start with fuel pressure first before anything, then any tweaks to inj low slope and usually by then things are within 1-3% pretty much across the board (assuming the rest of the model is ok). SD will and can be used to adjust fueling but ive never tried using fuel trims to do so with a maf setup. the impact on pedal feel sucks when you push the SD to far one way or the other from where it should be.

Injector data is not always cookie cutter. Roush has 3 or 4 variations of the same injectors across the years for example. log PWM and fuel trims on both banks (st and lt). add them up and divide by 2. plot that against the pwm and chart it 1,2,3,4,5 ms etc.. youll usually see the low fuel slope under 2 or 3 ms. this slope is used in a very large portion of normal driving, even at high rpms/airflow. id start with the stock maf curve before making other changes. learned baro will need to settle when using fuel trims to adjust from too.

pwm.png

[GHuggins]

personally, im not a fan of messing with the maft curve unless you know that is for sure the issue (no maf data etc). i am in favor of using the low inj slope to get fueling in range if this was the only change. Fuel pressure is inferred too. I usually start with fuel pressure first before anything, then any tweaks to inj low slope and usually by then things are within 1-3% pretty much across the board (assuming the rest of the model is ok). SD will and can be used to adjust fueling but ive never tried using fuel trims to do so with a maf setup. the impact on pedal feel sucks when you push the SD to far one way or the other from where it should be.

Injector data is not always cookie cutter. Roush has 3 or 4 variations of the same injectors across the years for example. log PWM and fuel trims on both banks (st and lt). add them up and divide by 2. plot that against the pwm and chart it 1,2,3,4,5 ms etc.. youll usually see the low fuel slope under 2 or 3 ms. this slope is used in a very large portion of normal driving, even at high rpms/airflow. id start with the stock maf curve before making other changes. learned baro will need to settle when using fuel trims to adjust from too.

pwm.png

Never thought about doing it that way, but it's just like the old way of dodge tuning. Should work without having to remodel a large chunk of the tune.

[Ruiner46]

Wow, thanks Grim5.0. Setting up that table against my first log after changing injectors is pretty revealing:

inj pw.PNG

I had just assumed that the best path was trying to get everything corrected based on known good injector data from ID. Or maybe I have to adjust their data to make it play nice with whatever Whipple did in their tune. Either way, playing with the low slope seems pretty harmless since the few times I have pushed into higher loads and RPM, the trims have looked reasonable

[Ruiner46]

I'm doing some calculations trying to determine how to adjust the low slope. I could guess and check, but I like spreadsheets

Can someone explain the offset vs voltage? I'm assuming the offset is the x intercept on a flow vs pulse width graph. As in, there is zero flow at the offset, and that is the point where the low slope line crosses the x axis. The offset I have been using is 0.836ms

However, in my logs, I see pulse widths lower than the offset, and the offset is nearly 3x the value ID gives for minimum pulse width. For instance, after fuel trims make corrections, my pulse width is 0.5ms with an 800 rpm idle. I want to target that as one of the points to calculate the new slope, but it would be below the offset, and have negative flow numbers on the line.

If my understanding is not correct, then how do you go about plotting the injector curves?

[decipha]

The offset is not included in the logged pw since it is added in the code as a global adder after the pw is calculated.

[Ruiner46]

Ok, that changes some things, thanks. Does that mean I should include the offset when calculating fuel mass from the injector slope?

(pulse width + offset) * slope = fuel mass?

Edit: Thinking about this some more, I think fuel mass = (actual pulse width - offset) * slope. Or another way to put it would be fuel mass = logged pulse width * slope. I don't think the offset should be multiplied times the slope since it is representing the time it takes the injector to open before it can start delivering fuel. Also, this is only valid for low slope.