Supercharger questions

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May 21, 2003
I've been working on my Cruiser electrical. When I bought it the LEAN-STOICH-RICH gauge wasn't working at all. I traced the wires finally and noticed that it draws power through the same source that the front spots do, replaced that fuse and I'm back in business with both. :D The problem is that the gauge reads all over the place. When I start the engine, the gauge starts up and indicates a very RICH condition. As I drive around the neighborhood, it mostly bounces between the RICH and STOICH area. If I give it gas very gradually, it seems to stay pretty stable, but if I give it a bit more, it dips into the LEAN area for a sec and then comes back up. Is it supposed to bounce like that? I haven't tried romping the gas at all for fear of the unknown, but from what I understand from Christo, it doesn't take much to burn one of these things up. It also died on me once when I abruptly let off the gas. Does this indicate anything?
Now I'll mention two things:

1. The L-S-R gauge has 3 thin gauge wires, two for power, and the Purple wire for the voltage signal from the Diag Port. (I'm only guessing this from following the wires around.) But in following them I noticed that the Purple wire had been spliced with another wire of considerably thicker gauge to reach the Diag box. Is this a problem? Could this be adding to my woes?

2. My cruiser is also equipped with an APEXi Super Air Flow Converter, does anyone else run one of these things, or know anything about them? I read a 45 page PDF on it last night and from what I can tell, it's a "middle-man" that sits between the air flow signal and the ECU. You can then use it to "trick" the ECU into providing more fuel at given RPMs and throttle conditions. Not sure if I'm right in this or not, but that's what I gathered. Could this be causing/adding to my problems?

Any ideas? I consider myself pretty good with electrical systems, and capable in the mechanical areas, but this whole fuel mixture/air flow thing is just not my forte. Just thought I'd throw it out there to see what y'all thought. Thanks.
I recently had the same problem with my turbo charged 3FE, i have an Air/Fuel Ratio gauge on mine and when i'd hit the gas it would drop into the lean, ended up being a fried 02 sensor so i'd check those.
Sounds like you've got an Autometer model. They read in " real time ", so they read right off the 02 sensor, and will show current status of your a/f mixture. They should hold @ cruise and idle, but bounce around @ varying throttle positions.

I have an S-AFC on my turbocharged eagle talon. We have what we call a "blue wire mod" The blue wire from the AFC harness can be spliced in to the wire coming out of your ECU that reads O2 voltage. (at least that was it's color on my AFC). I did this years ago, so i'm a little rusty. Anyhow, tap this wire into the input 2 (get to it from the etc. menu -->> Sensor check). Anyhow, on the DSM's this input 2 has no other use, so we use it to read our O2 voltage. This is useful. Those blinky gauges are not. The only time you will see them be useful is at WOT. Even then, they're not really useful. The gauge's line that runs to the AFC will give you a digital readout of your voltage. There's also a company called jumptronix, which if still in business, sells a digital O2 gauge that will read voltage, and I believe also tell you if your battery system is charging properly. If it drops lean for an instant and then goes rich for the duration, it may be normal.

What the AFC does is basically "fool" the computer. It modifies the air flow signal. It makes the computer think that you're only taking in X number amount of particles of air, whereas you're actually taking in X++++ particles of air. This keeps your computer from freaking out on you and (in my case anyway) fuel cut (shutting down the engine because she think's she's gonna blow). This allows you to run more fuel, not sure about your case, but I have larger fuel injectors and a large fuel pump. If I didn't ahve the AFC, the car would be blowing even more black smoke at WOT (not fully burned fuel) than it does already. So what I've done to the car is tell it that i'm pulling in 40% (this is just my setting on my AFC, not to be copied) less air than I actually am. Because if the car knew I was running 23psi on a turbo that flows about twice as much air as the factory turbo flows it would $hit a brick. So this is basically what you're doing. I'm sure you upgraded your fuel system and you're now trying to make the computer live with all the extra air that the MAS (MAF, not sure what these run) is pulling in (you're modifying this signal).

I don't know superchargers, I know turbochargers. I know vaguely how superchargers work, but I couldn't tell you why your vehicle is dying, as I don't even ahve one yet. If you had a turbo car i'd say that you have a boost leak somewhere, as they're notorious for occuring. I'd say check all your plumbing, make sure there's not lose pipes anywhere allowing air to sneak in/out of the system un-noticed.
It is completely normal for the A/F gauge to contantly sweep from rich to lean. This allows the catalytic converter to operate correctly. Read the "autoshop 101" series it explains that very good
At idle the sweeps are long in duration and at high RPM it is very fast. If it stays in one position for long the computer and/or O2 sensor is having a problem determining/controlling the correct parameters.
[quote author=Bradass80 link=board=2;threadid=6800;start=msg55842#msg55842 date=1067295075]
I recently had the same problem with my turbo charged 3FE, i have an Air/Fuel Ratio gauge on mine and when i'd hit the gas it would drop into the lean, ended up being a fried 02 sensor so i'd check those.

turbo charged 3FE? let me in on the secret. does that work with my fj62? if so i want it now. please fill me in.
Thanks for all your responses so far, I went out driving it a bit more last night to see how things behaved. I was driving down the freeway last night and when I took my foot off the gas at the exit, the light went all the way to LEAN, and almost appeard to be off it was so low. Is that just how it acts? I decided to get on it a bit more to see where the gauge would monitor, and it was in the heavy RICH field. I imagine this is not ideal, but better than the lean that I was expecting.


I was reading the manual the other day as I mentioned, previoiusly, can't you just measue the O2 voltage on the ETC menu as you mentioned? Or was your modification to display it at all times from the standard display menu? BTW, what is WOT and DSM? You lost me there. Any online help on the "blue wire mod"? From the few that I've read, I guess I may already have the mod since I can see it under the ETC menu. Thanks for your experience.
First of all, lean condition whne you're off the gas is normal, there's no risk of "knocking" when you're not even in the throttle. So don't worry about that.

Now, sorry for my poor grammar. DSM stands for Diamon Star Motors. It was a joint venture between mitsubishi and chrysler back in the early 90's. From 1990-1999 us enthusiasts who own Turbocharged Eclipse's, Talon's, and Laser's refer to them as DSM's as they're all exactly the same car aside from labeling and minor cosmetic details. WOT = Wide Open Throttle. This is the only time that you need to be worrying about how rich you're running if you're worrying about running a lean condition. Cruising and at idle is not a worry as far as "am I going to blow up my cruiser" sort of worry, but if you tune for lo throttle settings, the better you tune, the better your gas mileage will be down in the lower range.

As far as measuring the O2 sensor goes, here's what us "DSMers" do. Since our turbo/fuel systems on our ECU's don't require us to use the input2 in the ETC menu on the AFC, we hook the In-2 wire into our O2 wire running out of our ECU so we can read the signal on the In-2 screen.

Did you hook up the AFC or did someone do it for you? If you have the manual, see which wire is the one used for the "In-2" (or whatever they call it, input 2) and see if this wire is being used. If it's not, then find out from (C-Dan) someone what color your ECU wire is that handles the O2 reading. Then splice into this wire for your input 2 sensor and you will be able to read your O2 voltage from the sensor check screen.

This probably won't be much help, but here's a wiring diagram for my car's ECU.

here's a site where you could pick up an O2 sensor gauge itself...

Here's a long dissertation on tuning with the AFC. Again, this is a turbo application, but you might find some useful information here as well.

Good Luck. I'd love to have a supercharger on my cruiser (when I find it) but I couldn't handle another hit on the mileage loss.


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