AEM A/F Gauge Behavior

[gludlow]

Quick question guys, hope this is the right section. I have the typical AEM A/F gauge. I've made some changes to my car (CAI, etc) and noticed at very high RPM the AEM fuel gauge goes down to the 10s, then goes three dashes (- - -), the same as when I'm coasting off the gas. It seems to be running a little rich.

Does this mean it's gone rich beyond its ability to read, or lean beyond its ability to read? Or could there just be a problem?

I seem to remember from before that if it reads rich, it just displays "10." I didn't hear any pinging or anything.

Before I start messing with the cards, I'd like to know if I should add or remove fuel at the high end. Don't want to explode the engine :no:

Thanks, guys!

(On a side note, under 3,500 RPM, the cards don't seem to be adding any fuel at all, even under boost; the gauge "bounces" like at idle, but doesn't go lean. Is that typical?)

[FormerDatsun510Man]

If it goes either way rich or way lean it will display three dashes. From the sound of it, your setup was going rich beyond 10:1. Sounds like the fueling is off. Well, it is better to be rich than lean at high rpm that is for sure.

It is normal to see stoich or close to it below 3500rpm... especially on the '01-'05 models. This is what you want with the FFS setup because otherwise, the stock ECU will pull fuel (like in the other thread) to 16-18:1 and you will experience low rpm knock. On your setup it sounds like all you need to do is adjust the top end fuel to get the A/F ratio back in the mid 11:1 range. Before you do that though, make sure mechanically there aren't any problems causing the high rpm to be rich. Since you did a CAI, I would check for any intake or vacuum leaks and also check the boost at high rpm. Also make sure all the sensors are connected and there are no codes on the ECU. If everything checks out ok, then adjust the cards.

As far as adjusting the cards, I suggest leaving E-Cool at the default setting of 3.5 lights and adjust the high rpm fuel with the Y-B and R-B on the Main Card only. Adjust the Y-B first, by checking the fuel at 4000rpm at WOT. You should see 11.5-12:1 at that rpm. Next, adjust the R-B to get the fuel at 11.5:1 at 6000+ rpm. Also note to keep the Timing Card at 6 lights on the G-B setting (default) during this tuning.

[gludlow]

Thank you, sir!