HOW TO: Adjust Injector Latency & Scaling for Larger Injectors - EvoXForums.com - Mitsubishi Lancer Evolution X Forums
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Old 11-09-2009, 02:17 AM   #1
Clipse3GT
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HOW TO: Adjust Injector Latency & Scaling for Larger Injectors

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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.
Basic Info:

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.
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Last edited by Clipse3GT; 11-17-2009 at 02:03 AM.
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Old 11-17-2009, 02:02 AM   #2
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Quote:
Originally Posted by nj1266

EDITED BY: CLIPSE3GT

Injector Scaling

The stock injectors on the Evo are rated at 600. Generally speaking, the stock injectors will give you adequate fuel flow with a TBE, an intake, and 19-23 lbs of boost by redline. Once you get cams, then it is advisable to get bigger injectors. If you get a bigger turbo, then definitely get bigger injectors.

If you install bigger injectors, then you will have to scale them properly and use the correct injector voltage latency, otherwise your car will idle poorly and stall on occasion.

So how do you go about scaling your new injectors?

Scaling injectors is a PITA. It involves a lot of trial an error. It is not enough to simply put numbers in the rom tables and simply declare the injectors scaled. You must test and make sure that the scaling is accurate.

Here are the steps I follow when scaling injectors

1. Open Ecuflash and open your rom. Under fuel locate the Injector Scaling table and the Injector Battery Voltage Latency table. On a stock Evo they look like this:



The table on the left refers to the injector value that the ECU is using when making its fuel supply calculations. The number in the table is always smaller than the actual size of the injectors on the engine. For example, the stock injector size is ~600, but the number in the table is 532. As a general rule of thumb, enter a number in the table that is 15-20% less than the size of the injectors installed on your Evo.

EVO X: I found that the difference is about 11% in the OEM values.

Starting Point for DW Injectors:

800cc: ~713 Scale Starting Point

1000cc: ~890 Scale Starting Point


For example, let us say that you are using 680 size injectors. Then you enter in the injector scaling table a number between 578 and 544. Please note that this is only the starting point and not the end point of injector scaling. The final number will be determined through multiple sessions of logging and testing your fuel trims. More on this later.

The table to the right is the injector battery voltage latency table, aka, dead time table. The numbers in the right column are in milliseconds. The numbers refer to the amount of time that the injectors take to open completely and produce maximum flow. The numbers in the left column are in volts. As battery voltage decreases, the time between the injector receiving the signal to open and when it actually opens increases. Therefore, you must send the signal sooner to have the injector open at the appropriate time. The larger the injectors, the more time is needed for them to open. So you will have to increase the numbers in the millisecond column to compensate for larger injectors. The trick is to find the accurate numbers.

ou need to make sure that the numbers that you have entered are working properly. To do that you MUST log your fuel trims for an extended period of time. The trims to log are:

LTFT Idle = Long Term Fuel Trim Idle
LTFT Cruise = Long Term Fuel Trim Cruise

Both of these trims fluctuate between +/- 12.5%. The LTFT Idle is for idle and the LTFT Cruise is for cruising. Your aim is to keep both trim to +/- 5% or less. If the fuel trims are too positive, then the ECU will add fuel and this will royally make your AFR too rich. If your fuel trims are too negative, then the ECU will remove fuel and this will make your AFR too lean.

How do I log my fuel trims?

Logging fuel trims takes a lot of time and you will waste a lot of gas to get your fuel trims as close to 0 as possible.

Let us start with the LTFT Cruise. You must drive the car at a steady speed for at least 16 minutes. Why? The fuel trims cycle approximately every 4 minutes. You will need to have them cycle multiple times until they settle on a number in your log. 16 minutes will alow your trims to cycle 4 times. That will give them ample time to settle.

Let us say we had the scaling at 552 for the 680 injectors. And we cruised at a steady speed of 60 mph for 16 minutes. We found out that the trims went way negative and hit -10%. So we pulled over and incremented the injector scaling twice. The scaling went up from 552 to 572. We flashed the new numbers into the ECU. Then we went logging again for another 16 minutes.

We found out that the trims are still going negative but not as much as before. This time our trims hit -8%. We now know that we are on the right track. But we are nowhere near the +/-5% that we would like to hit. So we pulled over on the side of the freeway again. Incremented the injector scaling in the rom twice. This moved it from 572 to 597. We flashed the new scaling into the ECU and went for another 16 minute log.

The numbers in the log were very close to 0. The LTFT cruise registered around -3. We are almost there. So we pulled over on the side of the freeway and incremented the injector scaling one last time. The new scaling was 609. We flashed the scaling into the ECU and went for yet another 16 minute log. The logs showed a final fuel trim of -1.86. We have dialed the LTFT cruise to as close to zero as possible.

The next step was to log the LTFT idle. This is done by logging the car for 16 minutes at idle. We did that several times and found out that the LTFT idle stayed at the -1.66 level. This is a similar number to the one we achieved with the LTFT cruise trims.

We have finally dialed our fuel trims. Are we done done now? Not yet.

Now you MUST go back and adjust your High Octane AFR fuel map to fit the new injector scaling. You are basically going to have to re-tune your fuel map to fit the new injectors.

The whole process is very time and gas consuming and it can get very frustrating. But with time and patience, it can be done.
THANKS to: l2r99gst & nj1266
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Old 11-17-2009, 02:04 AM   #3
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UPDATED with more info!!!
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Old 12-10-2009, 04:07 PM   #4
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^^ thanks for this!
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Old 12-28-2009, 11:42 PM   #5
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Old 01-11-2010, 09:40 AM   #6
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Amazing. I am learning

Thanks!
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Old 03-23-2010, 03:47 PM   #7
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Quote:
Originally Posted by Clipse3GT View Post
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.

&

Now you MUST go back and adjust your High Octane AFR fuel map to fit the new injector scaling. You are basically going to have to re-tune your fuel map to fit the new injectors.
Clipse3GT - this may seem trivial, but can you briefly go over how this is done? Thanks.
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Old 03-23-2010, 04:02 PM   #8
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Wait you mean I am responsible for my actions. When did this happen. Anyway good Post.
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Old 03-23-2010, 04:12 PM   #9
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Quote:
Originally Posted by BADABING View Post
Clipse3GT - this may seem trivial, but can you briefly go over how this is done? Thanks.
Ideally, it would make more sense to dial in your injectors/trims BEFORE tuning your AFR map.

That is, get your trims 3, then dial in your AFRs.
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Old 03-24-2010, 03:06 AM   #10
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Quote:
Originally Posted by xPRimNT View Post
Ideally, it would make more sense to dial in your injectors/trims BEFORE tuning your AFR map.

That is, get your trims 3, then dial in your AFRs.
Yes, that is correct. Dial in your injectors first then do map tuning.
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