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[B][COLOR=Red]DISCLAIMER: I have used the method outlined below successfully to tune my car. I am an amateur and not a professional. If you use this method then you accept full responsibility for whatever damage you do to your car. If you are concerned about voided warranty and damage to your car, you are better off leaving your car without any modifications to the ECU[/COLOR][/B].
On average, your crusing injector pulsewidths will be double your idle injector pulsewidths. So, any changes that you make in the injector deadtime will affect idle twice as much as it will affect cruising. But, yes, it will affect both if they are both in the same Volt range that you are adjusting for.
Basically, as follows:
1. Choose a global setting (ECUFlash injector scaling number)
2. Log trims at idle and cruise
3. If trims are roughly the same, but positive, then you need to increase your global fueling, or in terms of ECUFlash, you need to lower your injector scaling number.
4. If both trims are roughly the same, but negative, then you need to descrease your global fueling, or in terms of ECUFlash, you need to raise your injector scaling number.
5. If idle trim is more positive than cruise trim, then you need to increase the dead time, or in terms of ECUFlash, you need to increase the latency value.
6. If the idle trim is less positive than the cruise trim, you need to decrease the deadtime, or in terms of ECUFlash, you need to decrease the latency value.
NOTE: After #5 or #6, you may need to readjust #1 accordingly.
NOTE 2: Basically, let's say that the IPW is 1ms at idle and 2ms at cruise. If you adjust the deadtime to add 100us (.1 ms), then you are affecting the idle fueling 10% and the cruise fueling 5%.
EXAMPLE:
Let me give a quick example using your numbers and show you how you would have to change the resulting scaling:
Idle trim: +3%
Cruise trim: -6%
Assuming that your idle pulsewidths are half of your cruising pulsewidths and idle is about 1ms (just using round numbers for the example...you would have to log to find out for sure), then let's see what adding 100us (.1 ms in ECUFlash) would do to the trims:
The 100us would add 10% fuel to idle, so it would subtract 10% from the idle trim, now making it -7%.
The 100us would add 5% fuel to cruise, so it would subtract 5% from the trims, now making it -11%.
So, now you have:
idle: -7%
cruise: -11%
So, now if you scaled your injectors to be 7% larger, then your trims would be:
idle: 0%
cruise: -4%
EDIT: Therefore it will look something like this for LTFT CRUISE/MID.
If you are using a scaling value of 731 (for example) and now you need to add 7% of scaling. Do the math: 731 x 0.07 = 51.17 = New scaling is 782.17.
So now, options in ECUFLASH are either to use 770 or 790 scaling. Using the 770 will make the injectors inject more fuel, but make the fuel slightly negative, since the computer has to take away from fuel. Now making it 790 will make the injectors inject less fuel, thus forcing the computer to compensate and add more fuel making the trim towards the positive. Now you have to work on getting the idle closer to 0.
I usually shoot for LTFT Cruise +/- 3% and LTFT Idle +/- 3-5%. These are averages. So if you are using EVOSCAN. Open up your log. Select the column with LTFT Cruise & Idle. Open the log in EXCEL or SPREADSHEET.
Select the correct column look at the first number you want to average. Lets say it is Column A ||| Row 02. The last log entry in the log for that column is Row 999. Therefore in that column select Row 1000. Then enter this equation "=AVERAGE(A02:A999)" this will average all your LTFT. Now you will able to adjust the scaling properly.
Of course, if you make any changes to your injector scaling, you will have to make sure that you make the necessary changes to your open-loop fuel maps, since the injector scaling change will change your AFR.
NOTE: Any changes to MAF Scaling will change your fuel trims. I suggest if your intake uses the STOCK OEM MAF tube as the housing. That you keep your stock MAF scaling and ONLY adjust the injector latency and scaling to get your fuel trims as close to 0 as possible and within +/- 5% of 0.