Notes on injector / maf scalining using full time open loop

[mad_sb]

Originally Posted by jamesm

the main difference between that and what i do is that i don't mess with the di stuff. my theory is 'didn't change it, don't touch it.' so i first log DI only, scaled the maf just generally up and down against that (always tuning larger maf housings lol), then log port only and tune latency and scaler from that (with a now known-good maf as far as the scaling for size), then combine and fine tune the maf.

you can get fueling error across the board within 3% in a couple hours this way. i'm not sure it's the best way, but it works for me.

For sure, it think we just have different approaches to the same end.

Here is why i started doing it this way, gdi scaling changes over the rpm range and can be fine tuned as needed.. port you are just stuck with, except for the MP comp table for port. Because of this, I would use port injectors for doing the maf curve then dial in DI once the maf curve is done:

[mad_sb]

Originally Posted by jamesm

because the ratio between them changes, and the amount of fueling error for each is different (until you fix it). the trims aren't aware of the ratio, so if you've got 20% port fueling error and -10% di fueling error in a given range and you pass in an rpm cell from using 50% port to 0% port, you can imagine what happens .

technically they only both need to be wrong the same amount and in the same direction, but ideally you just want them both right.

note that most of this only applies when tuning larger injectors and maf housings. if you don't change you're injectors, you don't have that variable to worry about as much.

^ this
It's more of an issue when you change injectors. If your ports are scaled wrong, they will throw off the trims when they are active. for any given maf voltage you can be in mode 1, 2, or 3 and as a result individual systems need to be balanced if you want consistent fuel trims.

[mad_sb]

Originally Posted by jamesm

the main difference between that and what i do is that i don't mess with the di stuff. my theory is 'didn't change it, don't touch it.' ....

What about E85? You scale the DI side for E85 no? I do, so I have been messing with the di tables for a while now. That may be why i started doing it this way... not sure anymore lol

[jamesm]

Originally Posted by mad_sb

For sure, it think we just have different approaches to the same end.

Here is why i started doing it this way, gdi scaling changes over the rpm range and can be fine tuned as needed.. port you are just stuck with, except for the MP comp table for port. Because of this, I would use port injectors for doing the maf curve then dial in DI once the maf curve is done:

i've definitely thought about doing that to get the di dialed in better but wasnt sure how to go about it. thanks!

i'm always tuning turbo kits so larger maf and injectors at the same time, so i use the still-stock di as the 'rock' in the process.

[jamesm]

Originally Posted by mad_sb

What about E85? You scale the DI side for E85 no? I do, so I have been messing with the di tables for a while now. That may be why i started doing it this way... not sure anymore lol

i use custom maps with a total fuel volume compensation for e85/flexfuel

[mad_sb]

Originally Posted by jamesm

i use custom maps with a total fuel volume compensation for e85/flexfuel

Ahh, gotcha.. i forget your using EcuTek. So yeah, lots of different tools and ways to go about scaling.

In my case i wanted to align the fuel map requested afr with the actual afr across the entire range of load and rpm without altering the calculated load (MAF scale) very much. I recently changed my intake setup and it drastically changed the load values and as a result threw my tune way off from where it was the last time i dyno tuned it. Plus i was not happy with how lumpy my fuel map was looking (as a result of the factory MP comp table).

I think if i were doing my own forced induction setup, I would just do course DI scaling changes then port scaling changes to get the trims dialed in tight, then do the maf scale in port only mode if needed, then do injectors and redo the injector scale and touch up maf scale then do the maf housing.

Of course most of the time if your tuning for someone else you don't have that luxury and just have to get it done quick and dirty. I think i would still force open loop and use afr error since that gives you one value you can use across the entire load and rpm range regardless of if you are working on maf scaling or injector scaling or both.

I'll hit you up for your notes when i finally decide what route to go for boost lol. I have not gotten into boosted tuning yet on this platform so your method may work better there.

[jamesm]

Originally Posted by mad_sb

Ahh, gotcha.. i forget your using EcuTek. So yeah, lots of different tools and ways to go about scaling.

In my case i wanted to align the fuel map requested afr with the actual afr across the entire range of load and rpm without altering the calculated load (MAF scale) very much. I recently changed my intake setup and it drastically changed the load values and as a result threw my tune way off from where it was the last time i dyno tuned it. Plus i was not happy with how lumpy my fuel map was looking (as a result of the factory MP comp table).

I think if i were doing my own forced induction setup, I would just do course DI scaling changes then port scaling changes to get the trims dialed in tight, then do the maf scale in port only mode if needed, then do injectors and redo the injector scale and touch up maf scale then do the maf housing.

Of course most of the time if your tuning for someone else you don't have that luxury and just have to get it done quick and dirty. I think i would still force open loop and use afr error since that gives you one value you can use across the entire load and rpm range regardless of if you are working on maf scaling or injector scaling or both.

I'll hit you up for your notes when i finally decide what route to go for boost lol. I have not gotten into boosted tuning yet on this platform so your method may work better there.

well i've never done anything but boost... so we can share notes . i don't fully understand your method, and would certainly like to.

[Kodename47]

Thanks guys, I think I'm getting my head round it. Questions:

I have not changed injectors, so is there any need to do full PI/DI sweeps? From this I can just run full open loop to dial in the MAF, correct?

Injector latency, again no need to be concerned? How do you calculate that?

Changing PI/DI ratio will have an affect on AFRs? If I do this with no injector change, is can this be overcome by pure MAF scaling?

[Kodename47]

Also I thought it might be worth tying in the ECUtek tables as they aren't labelled the same as in Romraider, just so I/others don't get wires crossed (mainly me). @jamesm is this correct:

@mad_sb's list:
GDI Pressure Multiplier A & B - DI Quantity Fuel Pressure #1 & 2
Closed loop Target Compensation A & B - Closed Loop AFR Adjustment #1 & 2
Engine Load Compensation (Manifold Pressure) - Calculated Engine Load Compensations #1 (what is #2 - it's a 2x2 table?).


When you stated to zero the Engine Load comp tables, do you mean to have 1 in every cell as I assume it's a multiplier?

[jamesm]

Originally Posted by Kodename47

Also I thought it might be worth tying in the ECUtek tables as they aren't labelled the same as in Romraider, just so I/others don't get wires crossed (mainly me). @jamesm is this correct:

@mad_sb's list:
GDI Pressure Multiplier A & B - DI Quantity Fuel Pressure #1 & 2
Closed loop Target Compensation A & B - Closed Loop AFR Adjustment #1 & 2
Engine Load Compensation (Manifold Pressure) - Calculated Engine Load Compensations #1 (what is #2 - it's a 2x2 table?).


When you stated to zero the Engine Load comp tables, do you mean to have 1 in every cell as I assume it's a multiplier?

i believe that is correct. i'm not sure what the second engine load comp table is.

[Luckrider]

I have kind of skipped the last several (alright probably 10 or more posts), but @jamesm, I have seen you post more than once that you don't touch the DI (which you repeat here). Do you think there is merit to @mad_sb's method of scaling DI and PI since it is know that the stock PI is a limit at some point for fueling the FA20 (granted, that is with e85 and some boost). Has anyone even determined what the effective limit of the direct injectors is?

[jamesm]

Originally Posted by Luckrider

I have kind of skipped the last several (alright probably 10 or more posts), but @jamesm, I have seen you post more than once that you don't touch the DI (which you repeat here). Do you think there is merit to @mad_sb's method of scaling DI and PI since it is know that the stock PI is a limit at some point for fueling the FA20 (granted, that is with e85 and some boost). Has anyone even determined what the effective limit of the direct injectors is?

I've read that they flow around 400cc/min but I can't remember where. I do think that raising di pressure targets could increase their capacity, but I don't think that's why he does it. I think his idea is to get fueling error on the di side as low as possible, which I've considered in the past and just never tried. You reach a point of diminishing returns around 3-5% error across the board in terms of low speed drivability, which is where low fueling error is very important.

Another reason that we employ different methods is that every car I've tuned has been turbocharged (cars don't seem to stay NA for long around here lol). When the maf and injectors are replaced at once, I need to use the di in its stock configuration as something to scale the maf against (just up and down for the larger maf housing, not fine tuning the closed loop portion, that's done later once the fueling systems are recombined). If I were tuning a car with a stock airbox and maf, that would be my approach. Keep the stock maf scaling and tune di and port injection both to it. The idea is that you can only solve for one variable at a time, and being that the di is the only known quantity in an aftermarket turbo install, I don't touch it.

I will definitely adopt his approach when I get a chance to tune a car with a stock airbox. It seems that you could ultimately achieve lower fueling error that way, though I'm not sure it'll be noticeable as <1% is very doable on the turbo setups with my method. It's two different solutions to different problems if I'm understanding it correctly. I'm sure we'll be collaborating on even better methods in the future. Were all just kinda figuring this out, and no one told me how to do it my way, I just came up with it by chasing my tail long enough and trying different things. There is no real 'right' IMHO, it's what works for your situation. In the end it's low error you're after, and if you achieve that you've done it right.

[pixel67]

I think i have learned more from reading this thread than i have on any other since I have owned the car. I can't begin to tell you how beneficial this type of civil conversation is for those of us that are new to tuning. It is exactly what i was hoping to gain from the other "commercial tuner" threads. Thanks for sharing!

[jamesm]

Originally Posted by Kodename47

Thanks guys, I think I'm getting my head round it. Questions:

I have not changed injectors, so is there any need to do full PI/DI sweeps? From this I can just run full open loop to dial in the MAF, correct?

Injector latency, again no need to be concerned? How do you calculate that?

Changing PI/DI ratio will have an affect on AFRs? If I do this with no injector change, is can this be overcome by pure MAF scaling?

if you've never changed injectors then you have the luxury of using them as your known quantity to scale the maf and di. in this case you'd scale the maf against the injectors in port only mode, then switch to di only and scale the di against the now-known-good maf. of course stock injector calibration leaves something to be desired, so you can go back in port only and tune the latency and scaler later if necessary.

similarly you could scale the maf using only combined logs, as both the di and ports are known to be at least as good as stock (because they are still stock lol).

injector latency issues will show up in fueling error charts as larger error at low maf voltage (corresponding to low injector pulse width) with smaller error as the voltage (and ipw) goes up. you can see my screencast on generating fueling error charts for a slightly more in depth explanation (though not much ).

again none of this is the gospel. it's just one man's way of accomplishing low fueling error with two fuel systems.