1G Tuning With MAFT + SAFC

[Ski Bum]

I've recently installed 3" GM MAF with MAFT and a SAFC2 for a while and have been trying to get a "decent" tune. It has been VERY difficult as the car feels like it lost 100 horsepower from before using the stock 1G MAF setup. My question is do I just use the settings in the MAF mode for compensation and not bother with the RPM mode and use the SAFC2? Secondly should I set the MAF translator to compensate for the exact size of my injectors or a little smaller?

 

[MrdB]

having a wide band would help alot... did u set it for the right injectors.. i took me about 4 hours to finnaly get my tune down with my wide band

 

[Ski Bum]

having a wide band would help alot... did u set it for the right injectors.. i took me about 4 hours to finnaly get my tune down with my wide band

No wideband yet, I was having trouble justifying an innovate standalone but now the new NGK AFX seems pretty reasonable.

Originally I had it set for my injectors but I was over 100% IDC, and over 100% in the medium and high fuel trims so I figured i'd try setting it at 50cc less and see what happens.

Did you use the RPM mode settings at all or just corrections in the MAF mode?

 

[MrdB]

i have 780cc injectors.. i set a base with the maft... WOT @ 2 and MID @ 1... thats how mine is set up.. then on my afc.. i added fuel in LO and took away in HIGH

 

[Ski Bum]

So you didnt do any settings in the RPM mode of the MAFT, just in MAF mode?

 

[Bmxr152]

set the maft to what size injectors you have, then tune the rest of it out with the afc! Thats what i did with mine, i did the same thing as you too.

 

[Ski Bum]

set the maft to what size injectors you have, then tune the rest of it out with the afc! Thats what i did with mine, i did the same thing as you too.

Originally that was my plan but with the MAFT set at zero I couldnt adjust the AFR rich enough to idle correctly using just the SAFC for corrections. At 50% correction it still was very close to being too lean. I ended up setting the MAFT at 20% for idle, mid and WOT and adjusted the SAFC accordingly, which ended up around 24%, giving me a total correction of 44%, right? . Although now I think I only need to adjust the idle, keep the mid at zero, letting the SAFC adjust the mid through the interpolation of the high and low and set the WOT on the MAFT at zero as well.

Is there any reason to set the injector size smaller on the MAFT then what your actually running?

 

[MrdB]

that i dont know, that is a good question though

 

[Ski Bum]

I have been having a tough time tuning my car since I installed a 3" GM MAF and MAFT. The car feels much less potent than it did with the stock 1G MAF. Anyways there have been some strange things happening along with just difficulty establishing a decent tune.

My profile has the full list of mods but this is basically what I'm working with:
E316G
rewired walbro 255
Aeromitive FPR
650 cc inj.
FMIC
2.5" turbo-back exhaust (catless)
2.5" open element intake
3" GM MAF with MAFT in blow through configuration
Tial BOV
SAFC2, datalogger, EGT, boost gauge

With the MAFT installed and only set to compensate for my injectors I had to set the SAFC low, 1k rpm at 44% in order to idle correctly. I have since changed the idle setting on the MAFT to 20% therby alllowing me to bring the SAFC down to 24%. With that I established a nice FTRL of 100-110%. I set the remaing low trim by the standard stationary rpm holding. With those settings the low trim stayed in that range and my high trim hit 104% from playing around a bit with the logger and held there. However during WOT runs the injector duty cycles would hit over 100% toward the top of the rpm band. I figured 650's would be enough for my setup? The mid trim hit 125% for whatever reason. I figured if the low and hign trims were in the right range the mid would fall into place there as well. Since there is no way of directly adjusting the mid trim with the SAFC, other than changing the TH points I adjusted the mid setings on the MAFT +5%. The next day my mid trim went up to 133%

Along with the lean mid trim the car would knock during cruising in 4th or 5th gear, low rpm rolling on the throttle. It also knocked when accelerating from a standstill. As soon as I release the clutch and begin to bring the rpms up I see 7-15 counts of knock. While this happens the timing drops to 22*, which is still ok, I think. It will knock, then as soon as I begin moving and the rpms get above 1500 or so the timing shoots back up and the knock goes away. Is this related to the lean mid throttle condition?

While trying to figure out why the mid trim was lean I decided to run a boost leak test. I found a couple small leaks, one at the TB where the FIAV connects and between the two sections of the GM MAF. I have since fixed those and can now hold a fairly steady 18psi. With those fixed the same knocking and lean mid trim are present. I reread the MAFT manual and saw a few interesting points. The changeover points for the trims based on the airflow signal that the ECU uses are much different than the MAFT uses.

The approximate airflow ranges the ECU uses are:
Low: 0-125 Hz
Mid: 100-175Hz
Hi: 175+ Hz

This is the airflow chart provided by the MAFT:

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As you can see the mid range of the MAFT is well into the high range that the ECU sees. It looks like low is set 0-180hz and mid at 500-700?hz interpolating in between and wot is set at 1000+hz and also interpolating the in-between points. It would sem that the overlapping trim levels would cause problems with tuning.

What I'm wondering is if the MAFT should even be used at all if the SAFC is available? With the differing airflow/trim points the setting might end up working against each other? Also, with the TH points set with the SAFC who knows what airflow signal is being seen at 30% or 70% TPS when there are 5 poosible gears to be in and numerous levels of boost pressure added to the mix. Anyone have experince here that can chime in on their settings?

I have just reset my ECU in order to try a different approach with this all. I'm going to zero out the MAFT using only the injector correction and tune with the SAFC.

I'll also post some logs up later.

 

[timloomis]

On the maft:the low is 0-88hz,mid is 88-180hz,and hi is 180 to 500hz.500hz is when the ecu goes into open loop(or closed,i cant remember).The trims dont control anything after that.Set aux to 1 and base to 7 for your 650's.The richen the idle 2-3 clicks to make up for the deadtime.Go for a cruise and lightly step on the gas from about 50mph and look at your 02 trim.If it goes down from 100%,its rich.If it goes up,its lean.Use the mid knob on the maft to fix this.The mid knob adjust both mid and high trims.You can tune it like that and fine tune it with your safc,or just leave the mid and wot knobs to zero and fully tune with the safc.

 

[Ski Bum]

I just recalibrated both the MAFT and SAFC. I set the MAFT base and aux settings at 1 and 7 for the 650's and left the idle, mid and wot at zero. In order to hit the proper O2 trims for th elow settings on the SAFC I had to almost max out the corrections. The settings are as follows:
1k 45
2k 42
3k 37
3.6k 32
4k 32 and 32 is carried all the way to 7k.

During idle the O2 trim varies quite a bit. When the cooling fan turns on it goes fairly lean and wanders between 115-130% and when the fan is off it sits around 85-100%. With that the FTRL will rise from 95% to 115%.

I havent yet driven the car with these changes but am wondering if I should richen up the idle correction on the MAFT to give me a lttle more room to work with the SAFC since 50% is the max I can go and am fairly close to that. However I dont want the MAFT and SAFC to conflict with each other or make the tune more difficult with the different airflow points used.

Any suggestion on the TH points I should use to better suit the MAFT?

EDIT: What do you mean by deadtime? I have never heard that before. Also the idle trim seems very unstable. The O2 Trim changes from 85-120%.

 

[timloomis]

Bigger injectors have more deadtime.The ecu sends the signal to open them and it takes them a bit longer to open up.You have to actually drive around to set the safc.The engine needs a load for the 02 trim and the knock sensor to work correctly.The 02 trim will bounce around like that.You just want it going between 90-110% or so.If it's cycling between 70-80%,somethings off.Just set the afc back to zero,set the maft idle about 3 clicks clockwise and go for a drive.If you have your cruise control set,watch the 02 trim.You want it cycling around 100%.If its not,set your base accordingly.Then start tuning with the safc.

 

[Ski Bum]

I turned the idle adjustment on the MAFT 2 clicks clockwise, so 10% correction. This gave me a much more stable idle O2 trim. The FTRL is staying at 105-110%. During partial-throttle cruising the O2 trim sits around 60%. When I roll on the throttle it rises to around 70-80% before it reaches 100%. I played with the TH points on the SAFC and after adjusting them from 30% and 80% to 15% and 65% the throttle response seems much more responsive, however the O2 trim didnt seem to change much.

Let me get this straight, when cruising at partial throttle, below 4k rpms I should see 100% on the O2 trim?

I'll try what you reccomened, however I have a few questions and interjections. So I should set the SAFC back to zero across the board? If I do I will have to turn the idle adjuster on the MAFT 4-5 clicks counter clockwise in order to idle correctly. For whatever reason my setup requires about +45% correction to idle correctly. Once that is done I should drive, set the cruise and watch the O2 trim? When you say, set your base, do you mean the base/aux setting for injector compensation? If so and if my cruising O2 trim does not stay around 100% I should adjust the injector size input accordingly depending on a rich or lean condition?

 

[Ski Bum]

Just an update, I havent yet made the adjustements you reccomended timloomis, partly because I havent heard back from you and becuase I wanted to give the car a lttle longer to adjust. Where its at now is the mid and high trim have gone rich. The mid trim is down to 92% and the high is at 98%. The low stays right aroun 110%. My O2 trim while cruising still strays around 60% and upon rolling on the throttle shoots up to 75-80% for a second then holds 100%.

From an earlier post you made I should be able to bring up the mid and high trims by using the mid adjustement on the MAFT, right? So one click clockwise should bring those trims up slightly.

 

[Ski Bum]

Sorry to bump the thread but I havent recieved much feedback on this and was hoping for some help. It looks like there arent alot of experienced users of the MAFT and AFC together because 100 people have looked at this thread and only 1 person has responded. Did I choose an obscure tuning route here?

I tried zeroing out the SAFC across the borad and running only the MAFT correction and that will not work. With the idle set at absolute richest setting my O2 trims are still pegged at 167% and the car barely idles. I have to be at around +45% correction to idle correctly. Should that be the case with my setup? I am running extremely lean without ALOT of correction.

After I was able to get the idle decent with some AFC correction I tried some low throttle driving and the O2 trim was still pegged at 167%, extremely lean (I wish I had a wideband for this).

As of now I have the MAFT set for my injector size, mid and wot are both at zero and I'm just using the AFC to tune the lo trims for a base. One thing that seems odd is when tuning the low throttle trims there is a drastic change in correction needed within a 200 rpm increment. Between 3600 and 4000 rpms the correction goes from +5 to +19 in order to keep the O2 trims around 100%. I'm going to reset the ECU and see if that changes anything.

I'm really having a tough time tuning the car with the MAFT and AFC together. If anybody has experience with this or has a simialr setup please chime in and tell me whatever you can. Its so frustrating to know that I'm sitting on the potential fo alot of power but cant get up to use it.

Thanks in advance for any help.

 

[1Gdsmdriver]

Well i am running the maft in the blow through mode as well but i am running an afc2 W/550s. I had it running diecent but wanted to tweak the trims a little because there were a little high, and now i am hitting fuel kut bad and hitting alot og knock, so i am going to go back to the settings i had before. I will let you know how it works out, but i did end up setting the injector for like 480s to get it to idle and runs diecent last time. i think it had somthing to do with the dead time of the injectors from what i have read. sorry that i dont have much to offer you but i can give you what i had my old settings at before i adjusted.
bare in mind i am running 550s aux0 your will be 1 still but you might have to dile down the base for smaller inj. base5 idle7 mid1 highC I hope this will help but because you are running so much larger inj i doubt it will.