Just a question on the Wide/band O2 project

What would it take to have a led readout of the actuall Air fuel Ratio? I would Like to put in my car permently. How long does the O2 sensor need to run befor the car is started so it wont ruin the sensor?

 

So far all there is a bargraph circuit floating around.
Just going power on with the key is fine

Personally, I just use mine when tuning.

 

Thanks

Where Can the Bargraph be found? Do you know how many leds? Just want to know if it will be accurate enough.

So far I have two boards solderd up. Orderd the 02 sensor last night. Cant wait to try it.
Its an exciting time to be alive!

Grumpy, Did you try putting together The fuel injection kit. I missed the Group Buy

 

Probably not what you wanted but I thought I’d share.

https://www.safety-page.com/nedt/store.htm

 

Thanks for the link,

Thats kind of what I am looking for.
I would like a dash Display, like the one in your link, but It needs to convert the voltage of the Wide band O2 to the actuall Air/fuel ratio. It will probably have to be homemade just for the Wideband 02.

 

Odd, using my WB, 820mv was 12.8:1
Hmm, and my WB agrees with a NTK WB, and is really close to one that has been compared to lab gases.

 

20 LED I think it's at DIY-EFI Incoming.
I have something really neat in the works <G>. So I've just watched the Megasquirt from the side lines..

 

In the Works?
Can you say what yet?

 

I just read these posts, and checked out that link, and had to get my 2 cents in. A little digital meter (gage) that indicates the mV reading of your O2 sensor is fine, but still doesn't tell me the AFR. I guess I would need to do the conversion in my head really fast, in real time. My scan tool records the O2 mV output, and I am sure that is accurate down to 1mV, but come on. I kind of side with Austin on this. If you are going to go thru the trouble of using the WB sensor, then at least make the output in real numbers, as AFR.

The little bar graphs are kind of nice for viewing trends, seeing where you are and where you are going. The OEM O2 sensor is not that accurate, so I have read, and is basically used as a switching device. IE rich-lean back and forth.

I been thinking about one of those Autometer circular AFR gages. It would really tell you if your O2 sensor is working properly, and whether you were in a PE mode, or highway mode or stoic. That's kind of the way I look at it. Not really concerned what the actual AFR is I guess. Every motor runs different, and uses a different AFR. I suppose you could still use it to tune, but the stock O2 is not that accurate, right?

You can always burn a new PROM, changing things, and observing how the motor responds.

That digital NEDT gage costs 40 bucks more than the Autometer unit. Besides, how fast does the 3 digit mV reading change, too fast that you can't make heads or tails out of it?

I could probably do the same thing for $89!!!

Just my 2 cents, good topic though!!!

------------------
Best ET 14.413 @95.57 without
pulling valve covers or manifolds.
Also with stock 2.77 rear end!!!

 

I think it would make more sense to make a simple circuit that would connect to a parallel port on a computer(since most dataloggers that I've seen connect to the serial port). Then write a C (or whatever) program that would display the A/F ratio. This would also allow you to incorporate this data into a datalogger like Craig's program (modified obviously). Having the info in the computer opens a world of possibility and flexability. I suspect the circuit necessary for the computer would probably be simpler anyway. Correct me if I am wrong, I'm not an EE, just a ME in training.

------------------
**82' Z-28. 327" w/ flat tops. 216/228/112LS. Pocket ported 041 heads 1.94/1.50 SS valves. World Class T-5 from a 91'. Soon to be converted over to TPI 383 with ported Accel runners, plenum, base, heads ect.
**Supercharger along with a new supercharger engine now destined for the Chevelle with a T-56.

 

The simple thing is just using a DVM.
Simplicity is the key to design.

Data logging for the sake of data logging is more an ego item then a necessity of real life.

Remember you tune for performance, and monitor the results, not the other way around.

 

You'll note there is a voltage conversion chart. If I'm out tuning, I'll look to see first where I'm at, DVM outout, and then see where that is on the chart and proceed from there. ie 1.6V being were I'm starting from, and look to see where I wind up with the changes I make.
Like ANY tool once you use it you get familiar with it and its use.

Want a AFR display, fine design one and we'll all use it. There is a big step from talking to actually doing. If you look at the output you'll notice it isn't linear, and it will take something clever to do it simply.

 

If I could do It, You would be the first to know Grumpy

Some of us only have one car, I just thought, Leave the Wide band board in the car permently and Have a good looking led readout to go with it.

 

I would think you could use Edelbrocks LED bar system with some internal changes and such? Resistor changes? not an EE... They have told me that the inside of the box is pretty basic but that doesn't mean much to me. Never opened mine up...

 

On incoming at DIY EFI there is a schematic and parts list for running a LED bar graph for the DIYWB. Also, I think there is a schematic and parts list for running a LCD display. This is more expensive and complicated as I believe you must write a bit of code for the IC that drives the LCD but it is an option. Try to remember folks that this stuff is DIY and not for profit so it isn't always the best product but it is the cheapest and was done with the best intentions. Also one of the intentions was that if you come up with something better that you would share it with everyone else. After all, Do It Yourself does also imply that if someone hasn't done it to your liking you should take it upon yourself to improve on it.

 

I would be very careful to trust the A/F data presented for the O2 display on the NEDT website! If you actually review the datasheet for the Bosch ZrO2 based narrowband O2 sensors, you will see that the A/F ratio versus Vout does not agree at all with the table on the NEDT website. 14.2:1 A/F at 800 mV!!! Pleeeeeeeze!! Grumpy I agree with your findings. My engines O2 sensor has been showing me 820-840mV when I make best power. I KNOW this is nowhere near 14.2:1(what the web page shows) more like 12.5 to 12.8:1. Be careful of who and what you trust! Verify yourself!!!

------------------
Dave Zelinka

 

The oem ones are so sensitive to EGT and backpressure, there is just no way to say a particular mv output from a stock sender is X-Y or Z, as far as AFR.
My own car, in which I've done plugs cuts, etc, and read the plugs many times had me fooled. Perfect coloring, no trace of detonation and I was in fact lean. Mind you I been looking at plugs for like 35 years now. That's why I harp on this stuff so much.

 

It would take less work to design a new one, which in fact you would be doing

 

Those mv/AFR are way out of line from what I've seen, even allowing for EGT.

 

I have my *snow* car and the GN. I'm also cheap. I have to be clever to do the things I want to. So I had an extra bung welded in the exhaust and just use the WB when I'm tuning. $120 is alot for me. Why run it all the time to see that your at 15:1?.
The whole idea of the DIY WB is to make it affordable. Hence the DVM output. It could have been designed for the EEs to assemble, but the point was to get it available for everyone. And judging from the numbers, that is what's happening.

 

This is what I did:

http://w1.601.telia.com/~u60113742/gauges/gauges.htm

I modified a cheep auto volt-meter (removed the scale and an internal resistor)


And mounted it in a pillar-mount with my boost gauge.



I also made a simple op-amp circuit:




I don't have a scale, because I did not use a wide-band sensor. The simple type is only rich/lean. On my gauge green is rich and red is lean. I like the analog gauge because it is fast and you can check it at a glance.

I only use it to see that I am not running lean, not the exact A/F value.

------------------
Jonas Bylund

 

Grumpy: Does it matter Where the O2 sensor is, in the exhaust? Will it be able to see changes , of the engines A/F ratio, better and faster If it is located closer to the engine.

JoBy: Thats really a pretty good Idea. Wouldent it work Just to mark the gauge at different A/F ratios using a DVM?

 

Jonas, you never cease to amaze me...

Sorry that I don't have/know this but can someone post a link or a table of the approximate wide-band O2 voltage numbers to their corresponding AF ratios??? thx

[This message has been edited by fast_broker (edited November 29, 2001).]

 

I havent been able to get into the Diy-efi board for a while but I have the Conversions printed up
So here it goes,

Vout AFR
1.40 10.08
1.45 10.23
1.50 10.38
1.55 10.53
1.60 10.69
1.65 10.86
1.70 11.03
1.75 11.20
1.80 11.38
1.85 11.57
1.90 11.76
1.95 11.96
2.00 12.17
2.05 12.38
2.10 12.60
2.15 12.83
2.20 13.07
2.25 13.31
2.30 13.57
2.35 13.84
2.40 14.11
2.45 14.40
2.50 14.70*
2.55 15.25
2.60 15.84
2.65 16.48
2.70 17.18
2.75 17.93
2.80 18.76
2.85 19.66
2.90 20.66
. .
. .
. .
4.00 Free air

 

Sure, that would work.

Pehaps I should explain my circuit ...


The first three resistors (4k, 100 and 1000k) are a standard O2 sensor input. The 1000k and 100k resistors are a voltage divider to get 0.5 volts at the amplifier input. That is the center point of the sensor range ( 0.1 volt to 0.9 volt ). Before the sensor is heated the gauge will read 0.5 volts and that is in the middle of the scale. Once the sensor is heated the 1000k and 100k resistors are oblsolite and the sensor value will be dominant. If you use the same O2 sensor as the ECM those two resistors should be removed.

The first amplifier is just a voltage follower.

The second amplifier has one 50k potentioneter to adjust gain and another 50k potentioneter to adjust offset. So if you have a gauge with a scale you can adjust the amplifier to match.

The reson for connecting the other end of the gauge to 5 volts instead of ground was to invert left / right on the scale. I wanted green to be rich, not red.

To modify this circuit for a wide-band sensor I would replace the 1000k resistor with a 100k resistor. That would put the start value at 2.5 volts, wich is the AFR=14.7 point.


------------------
Jonas Bylund


[This message has been edited by JoBy (edited November 30, 2001).]

 

That is one bad-looking beach racing Vette!!!

 

The WB O2 output is not linear.
You'd need use a PIC or some little processor to take the 2 slew rates into account.

 

AustinT, your table of Vout/AFR is for the output of the wide-band O2 sensor, yes? The standard OEM sensor puts out 0-1.0 volt. The more I read this post, the more difficult I see that is to get a true AFR number from an O2 sensor.

Joby, I like your circuit. Shouldn't the midmpoint of the sensor be set to 450mV? I take it your circuit is for a stand-alone O2 sensor, not the stock sensor that the ECM uses. Is the 4kohm input resistor high enough NOT to load down the sensor, for normal input to the ECM? If you could fine a conveinent 0-1.0volt little (2-5/8") analog gage, that would fit into the A-pillar pod, that would make it real sweet!!

Grumpy's answer is the simplest, I had the same idea after I thought about it. But for conveinence, Autometer's gage still appeals to me. Anyone use that?

 

MikeT. Yes The Numbers I posted are for the Wideband O2

 

Can you guys help me out.

I have the PC board for building the Wide band O2. But one of the DIY guys made up some kits from Digikey for all the parts and I need to get two Kits. Can you get me in the right direction.
I emailed ciciora@ciciora.com, but havent heard any reply yet.
Thanks
John



------------------
91 vette, 363ci, Miniram, ZF, 4.09, 11.95@118
http://www.geocities.com/bowtie8

 

there have been alot of boards and parts kits sold. He'll get to you eventually. Remember this is just a few guys volunteering their time and energy to do this.

 

I have mine behind the cat converter. With a good scope you can see individual cylinders firing up to like 3K rpm.
The operating temp of the sensor is like 800dC, so temp doesn't matter.

 

Thanx Grumpy

I havent sent in any $$ yet, I wanted to confirm that Steve is still doing the Kits.

Hey Grumpy, I am doing a big block coversion to fuel inj for a buddy. What do you think about running parellel injectors for each runner. I dont believe the 7730 Transistors will handle the current.
But what about the DFI,Felpro, or Haltech, Have you ever worked with this?
John

------------------
91 vette, 363ci, Miniram, ZF, 4.09, 11.95@118
http://www.geocities.com/bowtie8

 

Yes, I use a stand-alone O2 sensor. I would remove the 1000k and 100k resistors but leave the 4k in if I would use the same sensor as the ECM.

450mV, yes you are right, but the sensor is never in the middle anyway. In closed loop it goes left-right with more than 1 hz using most of the scale. As I said earlier I only use it to see that I am not lean at WOT.

The input resitance of this circuit is not 4kohm, it is 4k + ( 100k parallell to 1000k ). 4k + (100*1000/(100+1000))k = 4k + 91k = 95k input resitance

With the 100k and 1000k removed it would be 4k + amplifier input resitance ( very high ).

------------------
Jonas Bylund


[This message has been edited by JoBy (edited December 03, 2001).]

[This message has been edited by JoBy (edited December 03, 2001).]

 

They did it in an interesting way in the ZR-1 vettes. When the *Secondary* butterfly opened, the turned on a second set of injectors that just ran at the same PW as the primaries. Really crude, but it worked, and as far as I know folks liked the setup.

I'm just too spoiled on GM ecms. I've owned a few of the others, but never installed one. They just are so primitive, in general.

I had the injector drives changed in my ecm, and I can't see a reason for doing things any other way in all honesty.

If you need more *drivers* how about just running another ecm for second set. For $35-50 a pop it's really hard to beat the oem stuff.

 

I have never changed the drives in the ECM, Is it pretty simple, and what am I looking for, something that will handle approxomently twice the current that the ECM currently is using? I would have to pull the DATA sheet on the current stuff and find a better replacement. Is that what you did?

Thanks Grumpy

John


------------------
91 vette, 363ci, Miniram, ZF, 4.09, 11.95@118
http://www.geocities.com/bowtie8

 

Thanks Joby for your post. The input impedance should be plenty high enough as you said. Roughly how much $$ did you invest into your AFR meter? I am still leaning towards the meter from Autometer. $54 from Summit.

Can anyone repost the link for the DIY-WB O2 sensor? Can't seem to find it readily, and I want to check it out. Thanks!

 

I had the injectors changed.
They were a Cherry Semi Conductor devise.

You might just by with a large Power MOSFET thou. talk is they work fine, but like I said it's a rumor. I did ecm bench test one for Hours and the temps were all reasonable, I lost track of the guy, but if it hadn't worked I wouuld have thought he'd write back.

 

www.diy-efi.org
go to
diy-efi
then under projects

 

Hey Mike T I havent been Able to get Into the Diy Site for a few days now. I wish I could tell you how well The W/B meter works but I havent recieved the Sensor yet. IF you go back and read some of the posts on the Sensor, I think you will see its worth it to build one.

And For the Led readout< I dont know what to do. I dont see why it would be hard to build a circut that would read the voltage and display The AF ratio. But then Again Im No EE, and if it was easy, the designers of the W/B probably would have built the W/B meter with a led readout.

[This message has been edited by AustinT (edited December 03, 2001).]

 

It cant be too hard. I bet it could be done with a PIC chip and 3 7 segment displays. I'm no EE either, and I dont have any experience with a PIC chip, but I've seen quite a few things done with these, and this seems like a real simple task. The PIC chip would have an array that stored voltages and A/F Ratios. It could take the reading and display the correct ratio. Doesnt sound too hard at all, maybe someone out there who knows how to program PIC chips can help out with this.


[This message has been edited by Scott_92RS (edited December 03, 2001).]

 

It gets to the point of why?.
You can build a LED bargraph, and at a glance tell where things are *out of the corner of your eye*, vs having to focus on it. If you want to better understand whats really going on then you need to catalog it.
Once you actually use it for a while, you'll be able to make sense of the voltages as well as true display. It doesn't matter what the output is so long as you understand what it means. Using a voltage for AFR display is no different then reading temp in dC or dF.
Personnally I consider the sensor too expensive to just have it installed all the time. I have a short harness and a bung welded in just behind where the converter was, and remove the plug, insert the sensor, loop the harness over the floor board and set the stuff on the passenger floor board, and then the meter in an easy to read area.
next up is adding a small data logger for recording the TPS and sensor output. Then I can compare that to a Diacom or some other engine data logger to see where things are.
this isn't an exclusive replay to you, just things as I see them.

 

Oh my sensor isnt working, I recived the O2 sensor today and hooked it up to the board. When I put power to the board the Led will not light up. The Vout reads a constant 12 volts.

 

I find the WB project at the DIY-FI website. Where do I find posts on the sensor, the same webpage? I looked at the parts and some of the schematics, just couldn't view the circuit on one page to get big picture of what it does. I could get all the parts from work, and make up a little wire-wrap board to build the circuit. But the sensor cost really got me. I think I will pass on this project. I am sure it is an accurrate sensor, but for $50 I can get Autometer's AFR gage, which has 20 LED's ranging from .050v up to 1.00v, in 3 colors. I am not really concerned what the AFR really is.

I just want to see what the O2 is doing, how it is working, and where I am in the AF spectrum. Also helpful in telling open loop closed loop, and highway mode/ WOT conditions. Anyone have experience with it?

 

If you want to just see flickering lights there used to be a diagram for one at the GnType site, and for less then $10 you can make one of those. Won't tell ya a darned thing about open loop closed loop, just if the O2 is kinda wake.

 

What about my int guage idea.I have outlined it in my "two major questions" post.

[This message has been edited by formula5 (edited December 06, 2001).]

 

Here is my idea for actual a/f readout for w/b.Have bright leds behind a piece of transparent plastic.Black out the plastic and make a/f ratio numbers transparent.Then the leds will light up the correct a/f ratio.