SAFC changes dont take affect immediately?

[Sayajin]

Hey guys. I am trying to tune with my new SAFC and let me say yes I am 98% sure all the connections are correct and yes so are the settings, and yes it does read RPM and crap like that. Well anway, I changed both the high and the low settings by +10% and then I checked it with my datalogger and no change. Still running rich, so then I figure maybe it takes a while for the ECU to detect changes so I wait about 4 days and then recheck it with my datalogger. No change at all. I am at a loss. Does anyone have any advice as to what my problem is? Also one more thing is bugging me, the SAFC reads changes in every other monitored aspect but Airflow, that single aspect of the monitor remains the same, it always shows 0. Any suggestions about this? Or can we just not monitor that? Thanks a lot for the help!


-Sayajin

 

[kpt4321]

If the SAFC reads 0Hz for airfow, you have a problem.

What changes ae you looking for on the logger? Fuel trims will always take a little while to update.

 

[Sayajin]

Yea, I am looking for fuel trim. The odd thing is though, when I change the settings on the SAFC there is a noticible difference in the sound of the engine.. so I know it is making the changes at least.. As for the Airflow reading, any ideas? I mean everything else that it monitors it reads just fine.. but airflow just remains at 0 on the SAFC.... im at a loss.



-Sayajin

 

[psychlow]

If you're going +10%, you're making it run richer. You're convincing the ECU the engine is getting more air so it dumps more fuel. You can't correct a rich condition by adding fuel.

And yes, you have a huge problem if you're not reading any Karman. Did you set up the unit for Karman Mass Air?

 

[Sayajin]

..... I thought that adding it made it run more lean? Beucase I was running rich in the first place. I am almsot positive that is what the tuning guide said.

Also sorry, I am reading Karman, I am not reading AFL, sorry I thought AFL was airflow.. but it seems its not. However, about this rich thing, does adding % really make u run more rich? Becuase I am trying to get lean! Alas....


-Sayajin

 

[Sayajin]

Ummm.. never mind.. im a dumbass... the higher the fuel trim reading the leaner I am running........ the lower the setting the richer I am running..... ahh well I am running lean then not rich. I did tune it correctly going +10% however I thought I was doing the opposite of what I really was. Anway, yea my low trim reading is 118% which means I am running lean correct? So I want to richen up the fuel by adding %? ....... to think I cant even read a damn paragraph properly... im sorry guys, im not usually such an idiot. But what is the deal with AFL or maybe its AFR? if its not airflow then?


-Sayajin

 

[kpt4321]

Whoa man, slow down and take it easy.

If the fuel trims are positive, then you are running lean (because the fuel trims show that the ECU feels the need to add more fuel). The way to counter for this is by going positive (+) on the SAFC. That way, the ECU sees more airflow (which does not really exist) and adds more fuel.

So, your SAFC *is* showing the Karman Hz airflow value? That is good news.

Can you check the SAFC again and clarify what it was you were confused about?


Oh, and can you please do me a favor and not use more than one period to end a sentence?

 

[psychlow]

Saya, are your high trims below 100%? If so, check for vacuum/boost leaks.

 

[Sayajin]

Ah sorry about that. Yea my Karman value does show, what it was that I was confused about was a AFL value. I thought that was airflow. Also seems I was setting the tunning right, meaning trim %, but I just had what the positive or negative trim reading meant backwards. Also I have not yet had a chance to set my high trims becuase I am waiting for my stupid ECU to adapt to the changes so I can read it in my datalogger and finish the low trim settings. I planned to do the high as soon as I completed the low. Thanks for the help guys. Been 4 days and just waiting on my ECU to change so I will know how my settings look!


-Sayajin

 

[Sayajin]

Umm, sorry but I have another question. Yea I can read and I see that if my trim level is above 100% I want to go + on the SAFC to make my fuel richer, however I just want to make sure I am reading you right? Because on my local board a lot of people are saying different. They say if you are running lean, im actually at 188% then you want to go -10% and not +10% like I did. I am just trying to find out what the truth is? Because in my research and reading I thought if your running rich then go + but I may be wrong, or these guys could be stupid? Thanks.


-Sayajin

 

[kpt4321]

With regard to the ECU taking forever and a half to update your settings:

You probably want to reset the ECU before you go tune. On a 1g, you can pull the lower right fuse in the driver's side footwell fuse box for a couple minutes. Then, when you start the car back up, all of the fuel trims will be set at 100%. That way, you can go and drive around at 2k-3.5k rpm and set the SAFC based only on the O2 trim. Those are the hardest rpm ranges to set right, and this makes it much easier.

The O2 trim will cycle up and down, but you just have to make it cycle around 100%.

Once you do this, you should be close. Then just leave it and drive the car for a week, and see what the fuel trims do.


With regard to fuel trims:

Sounds like the local guys are wrong, I am afraid. Let me explain why.

(all of the following applies in closed loop only)

When the MAF sends an airflow signal to the ECU, the ECU will calculate the amount of fuel it thinks it needs to get the A/F ratio to 14.7:1. It will then inject this much fuel into the intake ports. After this is done, the ECU will look at the O2 sensor to see if the A/F ratio is rich, lean, or dead on.

Let's take an example: You're at idle, and the ECU is seeing 35Hz of airflow. It decides that means a 1.5ms injector pulsewidth, so it shoots that in. However, then the O2 sensor sends a lean signal back to the ECU. The ECU will increase the O2 trim (just a short term, fast updating fuel trim), let's say to 120%. Then, the next time it does the calculations for the injector pulsewidth, it will add extra fuel in (longer pulsewidth) since the O2 trim is positive.

The same thing happens with the long term fuel trims. If the long term fuel trim in the range you are driving in is positive, then you will get a longer pulsewidth than the ECU originally thought it needed.

Now, think about what happens when you add correction on the SAFC. If you add correction so that instead of the ECU seeing 35Hz like it was, it is now seeing 40 Hz (keep in mind that the true airflow is the same, and the SAFC is just faking to the ECU that there is more), then the ECU will start with a longer pulsewidth. Since it's starting with a longer pulsewidth, then the O2 sensor isn't going to show the mixture being as lean as it was, and the fuel trims won't move as much.

Hope that helps.

 

[Sayajin]

Thanks a lot. It does greatly help. I think I will wait to pass emissions in about 2 weeks before I reset my ECU however, I heard it is quite hard to pass with it reset. Once I do pass however, I will just pull the fuse and tune based on FTRL02 and FTRH02, thanks a lot for the help.


-Sayajin

 

[kpt4321]

That's bull. If you reset it and then tune it, the car will be running better in 2 weeks than it otherwise would be.

 

[psychlow]

Some emissions places look for mileage ran since last ECU reset. If you reset it, they'll just tell you to come back once you've driven the appropriate mileage.

I think that's what he's talking about.

 

[Sayajin]

Actually it was a post here that got me thinking about it. Something about how is car died and the ECU reset and he took it for emissions and it failed because of the fact that the engine wasnt running optimized? It sounded like it could be true so I figured there is no harm in waiting 2 weeks to tune exact!


-Sayajin

 

[kpt4321]

Originally posted by psychlow
Some emissions places look for mileage ran since last ECU reset. If you reset it, they'll just tell you to come back once you've driven the appropriate mileage.

I think that's what he's talking about.

There is no way to check this, at least not on a 1g. It *might* be an OBDII thing.

 

[kpt4321]

Originally posted by Sayajin
Actually it was a post here that got me thinking about it. Something about how is car died and the ECU reset and he took it for emissions and it failed because of the fact that the engine wasnt running optimized? It sounded like it could be true so I figured there is no harm in waiting 2 weeks to tune exact!

If you tune it right now, 2 weeks is enough time for the fuel trims to settle.

The car will run better tuned.

 

[Sayajin]

oh. Okay cool. Thanks a lot guys.


-Sayajin