AFC Neo for simple fuel management

[eTiMaGo]

To continue our old discussion of approaches to tweaking the AF maps...

To recapitulate, the ECU has two distinct operating modes: Closed loop and open loop.

Closed loop uses the AF sensor in the header in order to make adjustments to the injectors duty cycle to keep the exhaust gases at a normal mixture. Tuning the AFR in this mode is rather difficult but could potentially be done by intercepting the AF sensor's signal and reporting to the ECU that it is leaner than it already is.

But what's of interest here today is open loop tuning. From PK's data logging runs, we saw that the ECU seems to go to closed loop mode once the throttle reaches about 75%. When it's in closed loop, the ECU uses a fixed internal map, and calculates the injectors duty cycle based on RPM and MAF sensor signals. Thus in theory it is possible to make adjustments to the MAF signals in order to tweak the resultant AFR. This seems to be the way Blitz's fuel controller for the supercharger kit operates.

So what would be useful is a tuning tool that can adjust the MAF signal only once a certain throttle percentage has been reached. I've done some looking around and Apexi's AFC Neo seems to fit the bill.

http://www.apexi-usa.com/products/?id=5347

Two adjustment modes: Hi throttle and Lo throttle, with the ability to select the throttle percentage for each mode (i.e. we'd set Hi Throttle at 75% and make adjustments there, while leaving the Lo throttle mode at default unadjusted values)

up to 50% signal adjustability, plenty of headroom

It also has a mode to cancel out the wrong readings that a MAF might give when you close the throttle and blowback occurs, I think someone mentioned getting a CEL at a certain time because of this

Problem is, the device costs about $400, which is a bit hard to justify compared to just dropping in some bigger injectors. But, it offers a degree of adjustability, even for the non-turbo'ed ones with a lot of other bolt-ons.