This is a little something I came up with - I've been trying to figure out how to make a nice electronic non-linear* AFR meter for a while until I finally realized that it's otherwise useless. It's almost impossible to watch a vacuum gauge, tach AND an AFR meter all at once, much less remember any of the data. As some of you know, I originated the idea of WinALDL for the fuel injected cars (including my '82) so you could actually *see* to some degree where you're running rich and lean. It plots the number representing how rich or lean you are against RPM and vacuum signal (MAP, or manifold absolute pressure.) This way you can see just exactly where you need to make changes in your ECM.

However, there's no ECM with a carbureted car. Nor is there a MAP sensor or oxygen sensor! So I devised a circuit that plugs into the parallel port of your laptop (I bought the parts, haven't built it yet) and I've spent the last 3 or 4 weeks writing this program.

The program not only has a 16-LED non-linear* AFR meter on it, but it also has a real working tachometer and vacuum gauge. Then it has the infamous grid of MAP and RPM to where the oxygen sensor voltage is displayed - but I went a step further and filled the cells with a color indicating rich/lean/stoich so that you could get an idea *at a glance* of where you needed to change things. (Rods, jets, idle mixture, etc.)

If there is enough interest, I will make more advanced versions - one that will do multiple O2 sensors, one that will read other inputs, graph out track runs, etc. If you have any ideas, please let me know!! There is also a "shift light" option I can make for an external shift light!

Here's just a simple screenshot so you have some idea of what it looks like:



If there's enough interest in the program, I can add features or change things. The idea is to make carburetor tuning a lot easier.

*Most AFR meters are LINEAR gauges, while the output of the O2 sensor is NON-linear. This meter follows the non-linearity of a standard O2 sensor. Only two bars represent the stoich range, while most linear gauges have as many as 7 or 8 (out of 10!) that represent the stoich range, while the other remaining 2 or 3 are for rich and lean. In this meter, there are 7 rich and 7 lean bars, providing for much more accurate representations of the air-fuel ratio.


[Modified by Ken73, 11:23 AM 12/28/2002]

 

I'm not sure what the question is, but I answered "YES" :D the program looks like a real winner! Just tell us how we can get it and what parts we need for the interface!
If you need any beta testers let me know! I have the new engine in and I'm trying to find the right carb combination.

 

The question is in the title.. ;) Are you interested?

BTW, I made the image clickable.. apparently the forum software doesn't compress .GIF images properly or something. You'll get a full-screen preview when you click on it.

 

Looks nice. Question: Is the "redline" of the tach display adjustable?

I'm very interested in the proggie and hardware. I have a linear AFR gauge and dual O2 sensors...so I'd like to see the 2 sensor version. Again, awesome work!

 

:yesnod:

Count me in...Nice work!!

 

I'm VERY interested in this tool. This thing could really shrink the gap between carburetors and fuel injection.

 

That sounds really cool. I wouldn't mind giving it a try if it wasn't too hard to hook up. So, I'd have to buy some O2 sensors and weld them into my exhaust? Are O2 sensors expensive?

 

Yes, the redline AND yellowline are BOTH adjustable! :)

I can also put in an external shift light very easily - if there is any interest in that.

I'm looking at building the circuit and selling it as a complete kit - sensors included.

In the kit you would receive an O2 sensor along with a bung to weld into your exhaust (you can take it to any exhaust shop and they'd weld it in for a few bucks.) The closer to the engine the better. A tailpipe (portable) version could be made but it would have a time delay (since the exhaust has to travel through the entire tube.)

A dual-O2 sensor version would just have two tabs, one for left, and one for right. (And two side-by-side AFR meters.)

 

So what sort of sensors would be required besides the O2? Wouldn't you need something to convert vacuum information to a digital format? And the tach reading, would you just convert the tach wire voltage to RPM using some decoding electronics? Would you just scavange these parts from EFI setups or would you make your own?

I'd be really interested in something like this as long is it isn't prohibitively expensive.


[Modified by Langadorf, 1:01 PM 12/28/2002]

 

Can you guesstimate the time remaining before completion of the prototype?
Being able to see graphical displays of fuel ratio and vacuum from idle to redline will be awesome.

 

OKay, somebody has to ask. How much?$?$?$

 

That sounds like a GREAT project. If you need any beta testers count me in. What price are you looking to attach to this? Its a great idea, keep us posted.

 

You'd need a MAP sensor froma FI car. All the O2 sensors are the same (except for wide band), most MAP sensors are the same (except for 2 or 3 bar maps which are on turbo/supercharged cars),.

Ken, wouldn't we need a throttle position sensor here?

Marck EDIT!! the :bs did NOT belong here ;) dunno how that got there (me clicking the mouse perhaps?) :p: :crazy:


[Modified by Twin_Turbo, 2:40 PM 12/28/2002]

 

Price? I want to keep the whole thing (sensors included!) under $200 - I want it to be affordable as well as powerful.

The sensors would be brand spanking new, NOT something out of a junkyard. A MAP (manifold absolute pressure) sensor and an oxygen sensor are the only two sensors needed. You'll have a small alligator clip that will clip to the points side of your coil to bring in the RPM. No special sensor is required; it will be part of the circuit. And Marck, you KNOW I plan on making it work for 2 and 3 bar MAP sensors, just for you. :D

A TPS sensor is not required - since this is only going to display results of an oxygen sensor, a TPS sensor won't be necessary.

The main reason I'd prefer to sell it as a kit rather than just the program and a DIY interface is simple - quality. Not everyone knows how to build a circuit. I'd rather avoid the headaches of trying to help someone build their own circuit and just build it for them up front, and test it myself. That way they just "plug and play" from there.

As for completion time, I've spent the past month or so writing the program. The program will probably go through various phases as people give their input, but as it sits, it's complete. I've already bought 95% of the pieces I need for hardware (I need an oxygen sensor and a certain IC chip) and I'm going to set it up on a breadboard first to see if it works. I'll probably test it on Aaron's car and my '73. I hope to have it to where I can make PC boards in the next month or so.

 

Sounds really interesting. How do you tune a carb though? I know a lot about EFI, nothing about carbs? There isn't any way to add or subtract fuel in a certain RPM range, is there? Can you do that somehow with the jetting?

 

I'm interested in it. If you need a beta tester, I would be willing to give it a go as well.

:cheers:

 

Don't forget those of us with MSD ignitions...There's a tach hookup on the box, since the new coil primary voltage is 400 V.

 

It won't matter with the MSD - you'll just hook it into the points side of the circuit, not the coil side. It should also work fine with HEI or optical pickups. (I have a Mallory optical unit in my '73, so I'll definitely be testing that.)

Tuning is something that some of the more experienced carb tuners might be able to tell you about. If it's rich or lean all across the board, you'd change jets. Too rich or lean in one vacuum area and it's more likely rods.

What would really be nice is if some of those guys would chime in. I'd really like to incorporate a program that could actually *tell* you what you need to change! :cheers:

 

I know what jets are regarding a carb, but what are rods?

 

Sounds cool, I'm interested as well. I'll also throw my name in the pot for Beta testing if you need it.

Thanks,
David