BV1

I have been doign some reading on the S-AFC and I have heard that the ECU will after time learn to compensate for the S-AFC by monitoring the o2 sensor voltage. Is this true, any expereicne with this? Red have you dynoed your car a week after tuning and still found the gains?

In some tuning sections

www.roadraceengineering.com/newafc.htm

they suggest to lean out the mixture until the ECU is at such a point that it cannot compensate for the S-AFC and then adjust your settings as you desire in that point (around -30%).

Does anyone have any experience with the tuning? What did you set your Hi-Lo %'s to and at what RPM's did you find you had to lean out or richen up. I know its different depending on mods, but I am trying to get a feel.

Thanks,

-Steve

Decker

remember that they're talking about a eclipse ecu. Ours probably behaves differently. I'd still be interested in seeing what people have for settings out there?

ChaosThom

It depends on the ECU. I don't know about our specific ECUs. When I was competing with my Impreza, I learned that the ECU would adjust and nullify the S-AFC in the '00-02 models, but not the previous year models.
Somebody is going to have to test it before we know.

Cheuk in Seoul

Usually OBD II + ECU's will adapt for rich / lean conditions.

When making changes to the fuel mixture, I recommend it being made only in the WOT. OBD II will not use the O2 sensor values during WOT / near WOT for global adaptation.

neal

So does this mean getting an SAFC is kinda worthless for OBD II cars?

Cheuk in Seoul

Depends,

If you tune it so that the AFC only makes corrections to the fuel maps when you are at or near full throttle the OBD II will not use these "rich" values to correct the global fuel map.

So think of where in the AFC correction map that you will be only in full throttle for.... such as 5000+ rpms... hopefully you will only be there during WOT runs... and make fuel changes there. Do not make fuel changes in locations where you will be "putt-putt"ing around in.

neal

This is somewhat pertinant to me because of a modification I have planned. I am going to get a twin throttle body intake manifold from RPW and they say it needs a piggy back computer. Can anyone elaborate why - I have the new MAP Beta engine.

Random

Call me crazy...but why not ask them why it needs it?

I would "guess" that it needs it for 2 main reasons.

#1. The MAP sensor values for pressure are based on the amount of air flow that enters the IM from ONE SIDE. If you allow air in both sides of the IM, you are changing the air flow volume at a given pressure reading. This needs to be compensated for.

#2. You will now have 2 throttle position sensors (unless they somehow get by with just one). Somehow those two signals need to be combined and "averaged" so the ECU (or piggyback) knows how fast you are trying to go.

ECU's differ in regards to how much control they have over spark timing and fuel delivery. The New Suby's have an UNGODLY ammount of control. If you read last issue of Sport Compact Car they install the Uni-Chip (PROgram) on a 2002 Suby. They see something on the order of 17 HP gains. Then they reset the stock ECU...and only gained 5 HP. Why? The Suby Stock ECU has such control over the engine, it can effectivly over-ride even the UniChip. The car in question was also a sea level car (LA Based) driven to Colorodo (5000+ elevation) so the ECU learned how to deal with high altitude driving. After reseting the ECU, it went back to sea level base maps.

Our Stock ECU does not have the same measure of control that the Suby unit does, but it does have a some degree of control. This is the drawback with "ECU piggybacks". The only way to elimate this problem is to elimate the stock ECU altogether and go with a stand alone system.

The S-AFC does allow you to adjust the system from the cockpit, so if you notice yourself running rich or lean you can attempt to adjust it yourself. Of course, do not attempt this unless you have a damn good idea of what you are doing.

neal

Why dosen't this apply to a bored IM/TB. Dosent this increase the air flow compared to the pressure that the MAP sensor would read?

Random

Simple, the BTB/BIM combo is still air coming in via ONE opening. Yes, the opening is enlarged, but it is still one opening. By doubling NUMBER of openings, you add about 75% to the total air flow. The BTB/BIM combo only add about 25%, if that.