Thread: Why the SAFC II is so awsome..article by Big J

http://twofivetuning.com/smf/piggyba...ome/?topicseen

I don't know how people can hate on the SAFC II other than they don't have an indepth understanding of how it works AND HOW it interacts with the Spec V's ECU.

Most people don't tune the low throttle maps because they have been told for so long you can't tune in closed loop. True, you can't adjust the air fuel ratio but what you can and do do is shift the entire range of the MAF scaling.

The second part of this rumor is that making too large of corrections throws off ignition timing. True to a point, but the timing is too conservative on a the QR, at least if you can get good 93 octane gas, and the ECU relearns the adjusted range and adapts to the scaled MAF. You get a lot more MAF range w/o anything crazy going on.

While you can only tune the low and high throttle maps, there is a third map that is there and is used if your SAFC is set up correctly. When you run your low throttle maps at at 45% throttle and under, and then set you high maps at 46% and above you cut this middle map out entirely, which is a really shitty transition for the factory ECU to have to deal with. Think about it, if you have no corrections under 45% throttle and then have a big jump at 46% to big corrections the ECU hates it. The SAFC will interpolate the entire area between the low and high maps if you give it the range to do so.

You can get some detonation at part throttle low RPM if you take out too much MAF voltage in the low RPM ranges too soon, typically 20-30% throttle with corrections around 15-20% in the 2300-2800 RPM range. I found if I extend the low throttle cut off % to a higher throttle %, around 20% it takes this away, it also takes away the rich dip I get with a part throttle stab, which really helped the gas mileage. My high throttle transition point is still a little on the low side around 60%, I'll play with that later.

The main benefit to not following the "guidelines" that are out there for setting up SAFC for a QR are that you get better fuel control, less tune drift, better ignition and cam timing and an extended MAF voltage range. High throttle I'm currently running about 25-30% - corrections across my entire high throttle maps, and I can manipulate how large the high throttle corrections will be by changing how my low throttle corrections are set up. I get a good transition between my high and low maps because the SAFC calculates them for me, and the ECU handles it better. I could conceivably tune the car to subtract 50% MAF voltage and really extend the MAF range.



I'm back up to 9psi, still no meth, my base timing is 17*, which is fully advance, and the car is running just as strong as ever.

The ECU has what I'm going to call a natural fuel curve. The AFC is used to add corrections to this curve to get the AFR you're looking for. Most people typically only modify the end of the natural fuel curve that is in the range of open loop, when you start modifying the whole curve and figuring out how the ECU responds, that's when the SAFC becomes a great tuning tool. It's not trial and error, it's trending data. But to trend data you need a good datalogging program that logs more than just AFR. You have to be able to look at timing, cam advance, and fuel table corrections.

On top of that I still don't tune my Spec like most people as far as RPM correction points spacing ETC. My correction points are set to the natural fuel curve, meaning I set points at the RPMS where the AFRs come to high and low points. If you have a high point, and put a correction on the peak it will bring the peak down between the points to the left and the right of the point set on the peak. Because of this I also put a point where the curve starts to go up to the peak, and where the peak starts to level out, the same for a low point. This way instead of having to make a correction at an interval of xxx rpms, I can move one point and address the problem area, without having to hit points all along the way. I think I have a total of 6 correction points from 800 RPMs to 6400, the rest are stashed above 6400 so I don't ever have to adjust them. I can make big changes in my fuel curve across a big rpm range moving just one or two points, as opposed to a point every 200-400 rpms. It make spot tuning much easier, like when you go to the track and you up the boost, screw a second map, tweak 2-4 correction points and be done with it. You can pretty much tune in 1-2 pulls.

If I ever tune my car UpRev Osiris, I'm going to leave the SAFC in place and rescale the MAF using the SAFC. The datalogging of corrected MAF voltage vs. uncorrected MAF voltage will be invaluable to figuring out how to make hard corrections to the MAF tables and load tables. In the limited time I had MAF scaling was about the only thing I didn't have the chance to really figure out with the UpRev software.

I <3 the SAFC II

wow thats alot to read, i started to but ill have to finish it later..haha

Will this info apply to a Apexi NEO as well as the SAFC II

they NEO is almost the same thing. The differences areL the neo has more tuning points, and a knock readout.

SAFC II has a knock readout as well.

Originally Posted by limp_noodle

they NEO is almost the same thing. The differences areL the neo has more tuning points, and a knock readout.

Are you sure the NEO does knock? I keep hearing otherwise...

I hope so.

my bad. it doesn't. i meant the safc-II does