DIY EFIE for less than $5.

[csrmel]

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[Sigifrith]

There are a lot of Civic VX owners here. We have 5 wire sensors.

[csrmel]

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[bones33]

Thanks for the design! Sounds plausible though I do not understand the ground voltage idea, (I'm electronics challenged).

When the EFIE was designed, probably most of the O2 sensors were single wire. For newer vehicles this design makes much more sense.

Thanks again! You just saved me $60, I was just about to buy another EFIE for our '02 Honda.

[bones33]

If you have some ideas on adjusting MAF outputs I'd be really interested. On both of our vehicles monitored with an A/F gauge, they run pig rich at WOT. This is both common, and intended by most manufacturers to cool the engine at sustained WOT with excess fuel. In autocrossing days the honda guys used to lean out WOT a little and got like 8hp on the top end from the 1.6 from fuel trim alone.

[MY02WRX]

Ok, first off thats great, but your messing with possible spark knock, pre-ignition, timing MUST come into play when leaning your fuel mixture. also vx's have a 5 wire sensor because it is a wideband sensor, which is much more accurate in realtime then a standard narrow band sensor. Leaning your fuel mixture blindly is a potentially dangerous thing.

1. Without proper tuning, and exact a/f ratio your engine will run hotter due to its lack of fuel, fuel does cool the combustion chamber.
2. You will eventually a. burn a valve or piston, b. blow a ringland. Running leaner won't neccesarily net you better fuel mileage.

For instance, I had a 2001 GSXR 1000 sportbike. In stock form it made 144 rwhp on 2 different dynos and consistently got around 35mpg.
I put on a full titanium exhaust (header back, very very expensive) and a fuel controller, I wanted more power not fuel mileage. Without the piggy back tuned, I was getting around 24mpg and made right at 155rwhp, HOWEVER, when it was tuned the final result was 166.9 rwhp and I was getting in the low 40mpg.

Now, consider this, less power, more engine effort to general power, more fuel consumption, even though your lying to your computer and telling it to give less fuel, naturally without PROPER tuning your going to have high and low spots in your torque curve, thus making the engine have to work harder to accelerate to the same speed. Also what comes into play as well, is your injector duty cycles, even though your telling your computer your running rich and to lean it up a bit, there are other ways the computer computes your a/f mixture. MAP or MAF baro. pressure, engine temp. oil pressure (not all the time just when its low). TPS, all of these come into play, the 02 is basically used for emissions, it is however, a confirmation to the computer that the fuel mixture is right or close to right.


It is a good idea, however, your going to hurt yourself in the long run. Just because your engine is getting less fuel does not mean that it will get better mileage. Less power=more engine effort. More power used properly=less engine effort, less workforce less load. So more power is NOT ALWAYS a bad thing, if used properly.


And again VX's have 5 wire o2's because they are wideband, which makes them more expensive to buy, but very useful when it comes to a/f monitoring.

Please read more into what happens when you lean an engine, by a constant, not by a variable adjustment.

I have been around engines all my life, read alot, and have learned on my own, mainly from my bike, but now from my subaru. Also consider this, what makes you wear out quicker, lifting the same box with less energy or lifting t he same box with more energy, it takes less work when you are more energized, and you can use your energy more efficiently without tiring out. I know it is a bad analogy, but it does make sense.

Efficiency is key, being efficient isn't always cutting fuel to the engine, it is having the optimum fuel/air mixture at the lowest load possible with the least resistance possible, that is efficiency.


my .02

Jerod

I understand your concept, but you have no variable control, it is fixed, that will create high and low spots in your a/f curve. that is why fuel controllers, are expensive, they alter the signal of the map/maf tps ignition and o2 not just one sensor, and they do it in conjunction with each other.

[jeffreymccoy]

Originally Posted by MY02WRX

Please read more into what happens when you lean an engine, by a constant, not by a variable adjustment.
...

I understand your concept, but you have no variable control, it is fixed, that will create high and low spots in your a/f curve.

I will admit to knowing nothing about this than what I have read today, however one thought comes to mind regarding these statements... It apears that the concept maintains the variable adjustment of the original sensor output signal.

If the OS was .47 before the mod, and fluctuates between .47 and .55 lets say, wouldnt this mod change the OS output to .52, fluctuating between .52 and .60? The dynamic change is still there, relative to all the other sensors - just with an offset? Am I interpreting this correctly. Thanks for the discussion on this, im learing more every day!

[jeffreymccoy]

Here are 2 pics of my wiring diagram for the 2 HOSs before the cat converter. There are 2 more after each, but Im sure that these are the ones upstream. I have visually confirmed that it is a 4 wire HOS.

Which one of those is ground? If this isnt enough information - what else should I look for?

Also, could I use the single 1750ohm resister to connect to the ground wires of both the HOSs, requiring only 3 resisters? Or do I need to find 2 switched power sources and use 4 resisters?

I thought I would do this as close to the PCM as possible, since I have more room to work there. One of the HOSs connectors is impossible to reach with any tools, barely enough room just to disconnect the thing.

Thanks!

Wiring Diagram 1

Wiring Diagram 2 (offpage references)

[csrmel]

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[skewbe]

The typical o2 sensor is a glorified switch and the computer has to cycle between rich and lean to know that it is somewhere near stoichiometric. The sensor does not put out specific voltages for specific o2 content, it will only tell you if it is rich or lean.

I have one of those cheesey fuel air ratio gauges and you can see it jumping up and down, sometimes only like once a second.

The computer *shouldnt* be making any specific interpretations on the voltage it sees from the o2 sensor. It should only be seeing if it is above .45 volts or below .45 volts, therefore adjusting the voltage bias will not have the effect you intend.

The EIFE should be analyzing those pulses and creating a new set of pulses to send back to the computer to fake it out, I.e. it should create a pulse with more high time than the input pulse to make the computer think it is running rich so it will respond by leaning the mixture.


Let me know if this makes any sense.