VX lean burn monitor - enhanced how to desired
 

I have read Krousdb's original post on TomO's VX links and info and need some assistance in understanding what it takes to tap into the ECU. I am somewhat fearful of cutting any of the wires at the ECU because some of them are shielded (to guard against stray EMF's I guess).

So, to those of you who have already wired up their lean burn monitor to D14 and D16, is there any way of doing this without cutting the existing wiring? As much as I would love to have this monitor to improve my mpg, I won't risk messing up my currently perfect PGM-FI without more knowledge.

careful with the lean burn, you could get detonation/pining and destroy your engine in short order. You should if you have a Honda check out Hondata for an ecu upgrade that lets you tinker with air-fuel and timing.

I disagree. Hondata is killing grass-roots tuning and PGM-FI.org. Don't use them.

I would also love a how-to on this so I could see when my car goes into lean-burn.

Ditto.

I carfully shaved the insulation off the two wires just enough to solder into them. Taped them up when i was done.

which ones??...pics??.. :confused:

Everything you need to wire a voltmeter, including wire color codes is in the main post, https://www.gassavers.org/showthread.php?t=2427

What I would like to implement instead of a voltmeter is a dash light that glows when in lean-burn mode. I noted when a new member from Portugal described his Civic has a Honda provided "ECONO" indicator that lights when in lean burn. Here's the post: https://www.gassavers.org/showthread.php?t=5535
Read the 5th paragraph and check out the 2nd pic.

A simple comparator circuit could be built to switch a dash mounted LED on whenever the monitored voltage is in the lean-burn range. I'll try and post back with a sample circuit next week.

Doug

That members car is an OBD2 version of Civic and that motor is a D16Y5. Different coding than our OBD1 VX so he has a little more bells and whistles from the factory with respect to indicators.
I'm in the process of getting a kit together that will do exactly that for the VX owners. I'm still amassing parts though. I'm thinking that I should be able to get a kit together and out the door this spring if things move smoothly.


Jadziasman is talking about monitoring the signal from the LAF (Linear Air Fuel) sensor currently found on all federal emission 92-95 Civic VX models. There is no modifying of the factory settings for lean burn and therefore no danger of ruining anything.

The P07 ECU that controls the D15Z1 motor is not "chippable" in the known sense of the tuner world. Therefor, Hondata wants nothing to do with the P07 ECU as it uses a 16bit code that differs greatly from the normal 8bit Honda coding.

I won't be able to take any pictures for a How-To for a while due to it being really cold out. But to let you know, you don't need to cut any wires, just shave off some of the insulation on the mentioned wires (D14 and D16) and solder on a lead to run to your DMM or just use some of those wire taps that don't cut the wire. I prefer the solder method though.

Thanks TomO, I figured you'd chime in on this sooner or later.

I was also kind of interested in if you had unfasten the ECU from the passenger side wall to get access to D14 and D16. I will wait for warmer weather as well before adding this "feature".

And, you will be helping out many VX enthusiasts if you decide to put together an installation kit.

TomO I'm down for a kit when it's ready.:cool:

I'll take one when ready.

I'm definitely interested.

When you have a schematic drawn up would you be willing to post it? I'm interested in how the comparator LED switching circuit should be wired. I can have a electrical design engineer look it over as well if this helps you.

doug

I would like to have light that tell me when the Lean Burn is on. I'm wondering why Honda didn't put one from the factory, still its a 1992 model...

I'm just going to modify the schematic found HERE at Autospeed.

The only difference for monitoring lean burn in the VX as opposed to a regular O2 sensor is figuring out if the potentiometer needs to be changed and if the comparator IC can handle the higher voltage of the Honda LAF.

Feel free to run it by your electrical engineer and post what he says.

BTW the operational voltage signal of the L1H1 tends to be 1.1V-4.6V IIRC.

Heck yeah! Put me down for a kit, too...I can figure this stuff out usually, but it makes my head hurt. And I don't mind paying for convenience :)

Tom, the article in your VX links says the ECU connector pins to monitor are D14 & D16. Monitored voltage will be from -1.4 to +0.8V. Lean burn is indicated by a steady voltage above 0.4 to 0.45v. Assuming the article is correct (I haven't personally monitored the voltage), then the LED will be constantly lit in lean burn and off otherwise. I think this is better than a distracting blinking LED anyway!. I'll try n get you feedback on the "autospeed" circuit later today.

doug

^^^ when you hook up the DMM to D14 and D16 you are watching the LAF signal compared to the Reference signal, not chassis ground. You can also hook up your DMM a different way and read the entire spread of the LAF signal. In which case the voltage will always be positive and anything above the reference voltage (2.7V measured from D16 to ground IIRC) will be lean burn. That is the way that I'm intending on setting up the comparator circuit.

I'm also looking forward to your input on ways to modify/use the circuit in the LAF sensory circuit.

Thx Tom, I also figured this out on my own by carefully reading-digesting & re-reading the original thread. I drew a schematic, based on the autospeed design and had a design engineer look it over. He said it should work fine, but there is a better way to do it. The 470 ohm resistor will be between +12v and ground in the non lean-burn state and as a result it will consume energy while performing no useful work. When in lean-burn, the output of the comparator is switched off (open-circuit) and the 470 ohm resistor serves as a voltage divider to get the LED input voltage into the proper voltage range (and brightness). Along with some schematic changes, if the comparator and LED are selected such that the comparator output current rating is capable of driving the LED on its own, the circuit may be designed to consume no energy in the LEF off state.

doug

If you like, PM me with a FAX number and I'll send you the schematics I've scratched off

PS: In the VX, the indicator will have only two states LED on and LED off, there will be no flashing mode, which I'd find annoying anyway.

Nice. I'll have to look into this post more when I get back from work.

any updates?

Parts are in hand and assembling might take place this week or next. My next offspring is going to be born this Friday. Expect to see kits for sale around March, maybe sooner if I can find free time.

Tom it's March & I just can't wait anymore!!!;)
Any idea on when the kits will be ready.

can't you use a VAFC, tune it, and call it a day?

I have a proto-board made up with the circuit and will be installing ithopefully by the end of March. After that, it's time to etch some traces onto a circuit board and get cracking on selling them. :thumbup:

Would there be a need for a SuperMID once I have my idiot light working?

The SuperMID would be of more help for an instant mpg readout. The Lean burn indicator is mainly for watching when the car is in lean burn.

:thumbup: :thumbup: :thumbup:

:eek:

I'm going to be doing a lot of driving soon, I hope I can get one of these once it's all tested and ready!

Ok, so for someone who isn't very technical at all (unfortunately). With this kit, after installation, you can see when you're in lean burn. What would you use this info for? To fine tune your driving habits to try and drive in such a way that the lean burn indicator is on as much as possible?

You pretty much hit the nail on the head with that one, McPatrick.

My Circuit would provide a means of showing you when you were in lean burn so that you may drive in such a manor as to maximize lean burn on time.

I know all about how much time babies/kids can take up, so you probably find yourself without much time on your hand, but do I dare ask if you have a new guestimate as to when you'd have your kit ready (which hopefully would come with a fairly idiot-proof how-to)?

And in what way do you expect would the info that this indicator gives you change your driving habits when it comes down to religiously obeying the shift indicator already present on the dashboard?

Should I think of a situation for instance when you're already in 5th gear, going up a hill and with the new indicator finding out that you can still drive in lean burn going 55 mph but not doing 60 mph? Or what other situations would the extra information be helpful for?

My new guestimate is going to be sometime after the middle of June.
That is when I am done with my school job for the summer and after I get my tonsils out and recovered from that. Then I'll have some time to get things finalized and get some nice instructions together. I'm trying to make it as idiot proof as possible without increasing price. I could go all out and make a connector system that just plugs into the ECU, but then it would be nearly $80 just so you could see if you were in Lean Burn..... not cost effective in my book.
That is pretty much it...that is why I'm trying to keep costs down as much as possible. So that the money you spend to get the monitor will help you recoup that money and start saving you more in a reasonable amount of time.

I'll be looking forward to buying one when it does come out. With all the highway driving I'll be doing this summer along with the gas prices going up so much right now, hopefully it will pay for itself quickly.

Edit:

Just saw your VX has the same lights as mine! I really like the projector lighting compared to the terrible factory headlights.

One suggestion for your VX is you might want to reinstall the factory intake if you still have it lying around. Mine actually only pulls air from the engine bay (right next to the radiator hose) so it functions as a warm-air intake, and the small diameter of the VX intake pipe really makes for some good throttle response compared to the three inch aluminum intake I had installed before.

Sorry about the off-topicness.

@TomO: great! Looking forward to the kit. Personally I wouldn't mind paying a bit more and being able to just hook it up easily. I'm just thinking; if the VX would have cost $100 more would you still have bought it and since the answer is yes I wouldn't mind the investment.
With the Lean Burn Indicator You pretty much have all the info you need to get the best out of your VX.

Tom, your VX-related posts have been very helpful to me. Thank you. I want to chime in with a question/suggestion.

jadz said: "is there any way of doing this without cutting the existing wiring"

McPat said: "Personally I wouldn't mind paying a bit more and being able to just hook it up easily"

TomO said: "I could go all out and make a connector system that just plugs into the ECU, but then it would be nearly $80"

Let me summarize what I think the issue is. There's a need to tap into D14 and D16. The main post on this subject, which is full of great information, doesn't address how to do this (how to physically tap the two wires).

I can think of several ways of doing this, which include the following:

A) carefully strip away some insulation; solder a lead to the exposed conductor; use tape to button it up

B) create a custom harness somewhat similar to the Honda test harness (I'm talking about the one illustrated on page 11-25 of the service manual)

I think the method you generally use and suggest is A. I see the merit of this method: it's simple and reliable, assuming you have some moderate dexterity. On the other hand, I could see how some people don't like the idea of cutting into factory wiring, and aren't comfortable with soldering.

I think the "connector system" you mentioned is probably more-or-less what I described as B. The good part of this approach is that it makes it possible for a user to install your device easily, with no cutting and soldering. The bad part is that it adds a fair amount of cost and complexity to your design. I understand why you prefer not to do it that way. I agree that it's not a good solution.

It seems to me that what's needed is a simple, reliable way to tap into the two wires, without having to make use of a knife or a soldering tool. What about using a device that's designed to pierce insulation with a needle? I'm thinking of something like this.

That device is pretty expensive, but maybe there's something similar that's cheaper. A device like this would also be relevant to someone who wasn't ready to install a permanent indicator light, but just wanted to do some temporary monitoring with a DMM.

Just an idea. Personally I really like the idea of chopping up the factory wiring as little as possible, and to do such things in a way that can be reversed with little or no trace. It's so hard to find an unmolested VX, so I like the idea of keeping mine as original as possible.

Monroe - you understand what I'm trying to do really well. The other issue that I have with my project though is the fact that there is a display device that is currently being constructed that will give you about as much information as a SuperMID does, but only cost around $70 total investment.... If I went through and made my lean burn monitor with the OEM style ECU connectors I would end up having to sell my monitor kits for that high of a price, if not more...not really worth it in my book.

So for now, my project is at a stand still. I have a prototyped board made and ready to be installed and calibrated. I fear that this will be all the farther that my project goes though. I will install and calibrate the unit and then most likely do a nice write up DIY for others that want to go this route with their VXs. And in the off chance that someone really wants this mod and does not want to assemble it themselves, I would then be able to build a unit for them.

"for now, my project is at a stand still"

Thanks for explaining. I understand your situation, and I think your plan makes sense.

"there is a display device that is currently being constructed that will give you about as much information as a SuperMID does, but only cost around $70 total investment"

That's very interesting. Can you say more? Or does someone (you or someone else) wish to not pre-announce what they're doing (more than you already have)?

TomO. I too would love to hear more about thsi device you are talking about. And as additional question: would this device also monitor lean burn?

A little tangent. I just ran into some interesting material.

That's an archive of messages of people discussing O2 sensors. Of course there's lots of material like that on the internet. But what makes this archive especially interesting (to me, at least) is that it's a collection from 1992-1994. This was an early and interesting time in the history of O2-sensor technology. Also, many of the people speaking seem to be very knowledgeable insiders, who were working on PGMFI/ECM/ECU technology at places like Motorola and Ford. This was also an early time in the history of internet discussion groups; at that time, participants in such groups tended to be insiders of some kind. Scientists/engineers, in either academia or industry, tended to have internet access several years before the rest of us.

Here's an example of a comment I found interesting, from a historical perspective: "I worked on such a circuit [advanced mixture-monitoring] for Ford a few years back with the intention of putting it into production vehicles. It turned out that it was not cost effective for the benefits (at least that was their reason for killing the project)."

There's also some discussion specifically about cheap/simple ways to monitor O2-sensor output. That's what this thread is about, so I figured folks reading this thread might be interested.

The archive includes some very clear explanations of how O2 sensors work, clearer than I've seen anywhere else (and I've looked around a lot). And with interesting details that I haven't seen explained elsewhere. Also some good info about how to test an O2 sensor, on and off the vehicle.

I have a solution for this exact problem. An inline 3M connector that costs less than a quarter.
https://www.discountcarstereo.com/detail.aspx?ID=531

These are very common in the car stereo installation shops. Great little bits of hardware.

Perfect! That's exactly what's needed.

Now that you mention it, I realize I have a dim memory of messing around with products like that, many years ago, in connection with doing a car stereo installation. There might even be some connectors like that buried somewhere in my basement. But I had totally forgotten, and definitely didn't know what they were called or how to find them. Anyway, I knew something like that must exist, and I hoped someone else would know the details. You've provided the answer.

Thanks for speaking up. Getting this kind of very practical help is one of the best things about a forum like this.