DIY EFIE for less than $5.

[csrmel]

x

[Sigifrith]

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

[csrmel]

x

[beatr911]

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.

[beatr911]

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.

[MY02WRX]

Ok lets reconsider this, a VX o2 sensor is a wideband, thus it does take the inputs in differently, rather than a narrow band.

Ok NOW, your going to be telling your ecu your running rich all the time. Your o2 is not your only form of a/f to the computer. An obd1 computer has a set map every time you start your car, it basis your fueling by 1st your map and tps sensor, then immediately (mostly when its cold) by your iac valve, which causes fast idle, when you start your car on a cold day it leans the **** out of your fuel mixture to increase warm up time, most obd - obd2 cars are set up this way.

By you fooling the ecu into thinking its rich all the time, will potentially damage your engine. Your a/f through the rpm range at different throttle posistions is not consistently rich, no way no how.

So say at 3500 with 40% throttle your running a bit lean, by you changing your o2 to constantly lie you will go to a dangerous lean level. Just leaning out your o2 will temporarily help your fuel mileage, but will cause long term damage, I can promise you that.

By telling your car you are running rich all the time it will advance the ignition (this is natural, this keeps the car from loading up) once that happens and you at the given RPM you are running lean you will have a mis-fire or post fire. In no way shape or form would I ever do something like this without a way to fine tune it. When leaning your fuel supply you should also retard your ignition, you should have a way to alter your map/maf sensor inputs.

If you want to save fuel, your best bet is to find a chip that includes a data port for a laptop, you should have a wideband o2, a laptop, and datalog in real time the inputs of all your sensors, and tune your ecu with your laptop accordingly.

An engine is MOST efficient in every single way is 14.7:1, however, that is speculation, I've heard an engine is at its highest performance peak at !3.9:1, if an engine is at its peak performance, its fuel economy will be at its highest performance.

I'm just saying, lying about 1 single sensor to alter fuel with no exact a/f ratio, its not a good thing.


I understand that in a seriously lean situation the o2 will actually send a lean signal to the computer, but your going to have so many peaks and valleys in your a/f curve that the engine will become choppy, it will loose power and gain power at certain rpm's and throttle positions. I understand that this is all for saving $$$$ but in the long run, is saving $20 bucks every six months worth the damage that you take the risk of causing upon your engine? The chance of blowing a ring land, the cost of ruined plugs? This is why fuel management systems are so expensive, their ability to alter a signal of MANY sensors at the same time having the ability to be variable, by rpm and throttle position.

[skewbe]

If I remember correctly, the wideband puts out a low volatge when it is rich, so you should be able to put in a high ohm potentiometer as a voltage divider to lower the voltage output so the computer thinks it is running rich and leans out the mixture.

If you want to richen the mixture then you need to amplify the signal.

If I remember correctly.

[rh77]

Yikes...the only time I might see this to be useful for me, is possibly on cold starts where rich is the name of the game. The cat gets hot fast, so why so rich???

I'm quite concerned about running lean, and consequent internal engine wear, so bear with my alternative proposal.

So, if this system could be switched to force a closed-loop and O2 sensor offset shortly after startup, would the inefficiency be reduced, but retain engine longevity? Of course once the vehicle is warmed, a bypass directly to the stock closed-loop system would be required to go back to "normal". So much fuel is burned on cold starts, and driving warmup...

Any thoughts?

[MY02WRX]

That doesn't make sense to me, on initial start up yes you would be dumping fuel, however, the computer should lean your fueling out to create heat, running rich will create your engine to run cooler, running lean creates alot! of heat! As far as everything I've read and monitoring a/f after initial start up the engine leans out to create heat, and thus warm the engine up quicker. Post cat o2's mostly monitor cat heat, which would be a lean situation, running rich will not cause near the heat as running lean will.


Internal wear is not an immediate issue, unless the a/f rose 18-20:1 and then damage, mostly from heat and mis-fires would occur.


I have not done a ton of research in the differences between closed loop and open loop, i understand the difference, but do not know exactly what engine functions are changed and what sensors are used as primary and what ones aren't. I know in warm up, your a/f is based off of the IAC valve on a Honda, that and a few others, but that controls the amount of air going into the engine, and when that sensor is switched off the fuel mixture richen.

Actually the fuel is never really cut, it allows more air to bypass the throttle body, allowing for a lean situation, thus creating heat, and then warming your engine up quicker. Cutting fuel to an engine is not always safe, Honda tuned their engines to work properly at all temps, and altitudes, by faking the o2 to the computer and not changing anything else could be harmful......

[csrmel]

x

[MY02WRX]

I am also NOT saying that long term engine damage WILL occur, I'm just simply stating that you will be walking the fine line of long term damage. The same goes for over fueling as well, causing pre-det, or pinging. There are so many variables that have an effect on a/f besides just the o2. I guess I'm just pretty picky on what I do to my car as though. Basically, if you can increase airflow to and from the engine (hopefully keeping it quiet) and keeping good back pressure, and then lean your engine out, your efficiency will increase alot! More unused power means less engine effort and less fuel used. Don't believe me, how do cummins desiels make 1400fptq and get 2+ miles per gallon better than stock? Because they have less load on the engine itself. Or ok, thats wrong, the same load, but the engine is only working at way less capacity than with less power.


I can't explain things, I wish I could explain better, but I pretty much suck at it.

[SVOboy]

Having a small background in tuning, it is my gut to say not to do it, because not only do you not really know what you're doing changing it, you don't know what X changes will actually do to the car. It's like taking a shot in the dark and then not being able to turn the lights on to see if you even hit anything.

Besides, emissions increases from running lean are t3h suck.

[omgwtfbyobbq]

Originally Posted by MY02WRX

That doesn't make sense to me, on initial start up yes you would be dumping fuel, however, the computer should lean your fueling out to create heat, running rich will create your engine to run cooler, running lean creates alot! of heat! As far as everything I've read and monitoring a/f after initial start up the engine leans out to create heat, and thus warm the engine up quicker.

All newer cars I've heard of run deliberately rich on startup to light off the cat quickly. Emissions and all that.

[Erik]

What about the VX lean burn mode? Is that harming the engine?

I would like to lean out my carburated 87 civic, but I too am concerned about engine damage.

I can tell that the engine sometimes runs a little richer and other times leaner (I suppose the crude electronic control box is trying to do its job). Sometimes when fully warm, I get a little spark knock climbing a hill on my way to/from work, other times, I get no spark knock on the same hill, even when I purposely lug the engine a little and when it the same outside temp and same engine temp.

By the way, is there anyone out here that knows how the honda feedback carbs richen/lean the mixture? It is not electronic (I have rebuilt the carb) so it must be a vacuum bleed to lean it out or somehow keeping the power valve from richening the mixture via a vacuum line.

[rh77]

Originally Posted by theclencher

also running lean from cold just doesn't work- stumbing, hesitation, dieing and all that. needsta be warm enuf ta vaporize afor switching to lean

So is that the main reason for the ramped-up operation on cold starts?

I want to understand why. According to the shop manual, coolant temp determines idle speed via the IAC valve (on a modified S-like curve).

I want to minimize emissions, but at the same time minimize fuel consumption -- am I asking of a tall request of a modern ICE? On cold starts, I can shift the gear selector to '2' and idle along at 20-25 mph. 2500 RPM is the magic number to shift the auto into higher gears when cold -- that sucks (fuel...literally).

Let's say the coolant mod is introduced. Can I expect rough idle, and possible a stall on a shift into 'D'? Is this something you have to live with, and rely on the grille block to keep things toasty???

RH77

[omgwtfbyobbq]

Most cars have a high idle with less load to warm up the engine as quickly and safely as possible in order to minimize wear, on automatics this corresponds to different shift points, since too much load isn't necessarily beneficial for the car when cold. Essentially, everything has to warm up to minimize wear, and the best way to do this is run the engine relatively quickly with little load in order to generate heat. The mixture is also richened to start up the emissions system as quickly as possible.

[MY02WRX]

Ok... Everyone consider this, the more efficient you make your engine, the better mileage your going to get, no if ands or buts. The more useful power your engine makes at its median engine speed the better mileage it will recieive, the smoother your torque curve/a/f curve is the better mileage you will get.

I called my buddy, who has a ba in automotive engineering, told me cold starts are so rich because A. running a lean cold start the fuel is less combustible b. to increase heat in your emissions c. because a lean situation causes combustion chamber heat, but also causes a pollutant called nox, which is worse than unburnt fuel.

He told me if you want to know why running lean is so horrible try finding information on the tests manufacturers did in the 70's when unleaded fuel came out, it created a bunch of stink. Mainly HORRIBLE fuel mileage and horrible emissions.

[skewbe]

Hmm... I know "cold starts" are an issue, where the engine has been sitting overnight and the oil has all run out of the rings and bearings. But cold oil is generally thick oil and possibly a better protector of metal as a result.

Except for real high performance machines with very tight tolerances, is there any evidence that a cold engine is going to wear faster, assuming the oil is flowing? The cold metal will be less likely to gall anyway, no?

[MY02WRX]

yea running a lean cold start is hard on everything, does not idle high enough, and low amounts of cold fuel does not combust as well as a bunch of cold fuel. Also high performance machines use dry sump with perfectly precision oil sprayers/jets. Trust me Honda/nissan/toyota/ect. would not do alot of the things they do if it would harm the engine. They get what they can out of it SAFELY, there are things left untouched that do not pose a threat to longevity, but not single sensors.

[csrmel]

x

[omgwtfbyobbq]

Originally Posted by skewbe

Except for real high performance machines with very tight tolerances, is there any evidence that a cold engine is going to wear faster, assuming the oil is flowing? The cold metal will be less likely to gall anyway, no?

And Bob's yer uncle.

Cold Start" can destroy bearing surfaces and lead to progressive failure. "Cold Start" failure is caused by lack of lubrication and running up to full RMP before the engine is warm.

It is well known in the automotive art that wear in automobile and other vehicle engines of the internal-combustion type is not simply related to the number of miles driven, but depends upon the conditions under which the vehicle is driven. For example, it is recognized that an engine of a vehicle which is utilized for frequent short trips will wear faster (on a per-mile basis) than the engine of a vehicle which is driven less frequently but longer distances. This difference in wear life can be explained, at least in part, by the fact that friction is at its maximum value during the first few minutes after a cold engine is started and that, after the engine has warmed to its normal operating temperature, friction within the engine drops substantially. Some workers in the automotive art have estimated that up to ninety percent (90%) of the total mechanical wear of an engine occurs within a relatively short time after starting the engine cold. In one article on this subject, workers in the art estimated that an automobile engine undergoes the same amount of mechanical wear during the first thirty seconds after it is started cold as the engine would undergo if driven fully warm for five hundred miles. In otherwords, according to this source, the wear during a thirty second cold start of an engine may equal approximately the wear undergone by a fully warm engine over a nine hour period of normal operation. Similarly, The Society of Automotive Engineers has determined that up to eighty percent of the wear on vehicle engines occurs during the first ten seconds of operation. Accordingly, it is clear that critical times for engine wear occur during the period that the engine is being cranked by the starter motor and before the mechanical oil pump of the engine has had sufficient time to fill the oil galleys of the engine with oil at the normal operating pressure.

Etc...

[rh77]

So, let's say it's 20F. I start the car, and immediately place it in "D4". Ker-chunk, and we're off. Letting the vehicle idle along until some signs of warmth has been my style since I started tracking mileage. Cold start idle guzzles the fuel, but is the engine taking a huge hit then?

[theclencher]

best warmup is via gentle use NOT sitting there idling NOT hard use

engines coolant heaters

in fact i'm considering penning a "public service announcement" for the local paper regarding proper use of heaters, proper warmup, and how evil all these dod gamn autostarts are (need to counteract all the stupid shops advertising now to install those stupid things)

[skewbe]

"Accordingly, it is clear that critical times for engine wear occur during the period that the engine is being cranked by the starter motor and before the mechanical oil pump of the engine has had sufficient time to fill the oil galleys of the engine with oil at the normal operating pressure. "

Surely someone has tried an electric oil pump and possibly heater prior to startup then?

[skewbe]

Or an accumulator might be even better

Add a valve to trap some pressure for the next start, maybe wrap it in a blanket?

http://www.moroso.com/articles/artic...&catcode=13600