For those who werent following the previous thread, here's a quick background on what I was trying.

I wanted to "temporarily" install an 02 sensor to aid in carb tuning (Q-jet), but wanted to be able to return to stock appearance (this car is running stock exhaust manifolds).
I took an old EFE (heat riser) valve that would be bolted directly between the manifold and the pipe. I cut off the extra material where the valve shaft extends out of the valve, and pressed the valve shaft out. The I drilled and tapped the valve shaft hole to accept an O2 sensor. Now I can undo the exhaust from the manifold, put the valve/sensor in, and take readings. I may just leave the valve body in place and use a plug when I remove the O2 sensor. (I should say that I put the valve in a lathe and turned the I.D. of the bottom of the valve to be larger than manifold I.D. so that it would not be a restriction.)

Rather than using a volt-meter, I built one of those "homade" LED graph readouts referenced in the previous thread (with about $12 in parts from http://www.radioshack.com). I used a variable power supply to "calibrate" the guage by supplying different voltages and writting down how many LEDs were lit at each voltage. (There are still some issues with this meter, but it's working well enough for now).

Now, for the first results (I just drove the car to work at lunch with this setup for the first time).
The car has a "sag" when you first go WOT (for about 1/2 of a second). I assume this can be solved by adjusting secondary opening rates, but I wanted a better way to monitor the condition. When I go WOT, you can see the accelerator pump shot as the guage "blips" to full rich only for a slight instant. Then, the guage instantly falls to full lean during the sag. The guage then suddenly goes back to the ideal fairly rich setting right as the car comes out of the sag. Really nothing new learned here, other than confirming that I am way to lean during the transition to the secondaries. This is good, because it's so easy to see on the guage that it should be easy to see the effect of the changes I'll make. (Now I just have to figure out the best way to fix it).
I eventually plan to do more tuning, but the first step now is obviously to cure this problem. It's funny how I new the car had a sag, but it's so much more "in need of fixing" now that I can "see" it going lean.

That's all for now, just wanted to share my experiences for anybody who might be interested.

 

Very cool!
I want to do that too...as soon as I get time. :rolleyes:

 

Very cool, Now I might have something to do with my O2 sensor when I disable my computer and go with a new carb/distributer.

 

Isn't the end of the rams-horn exhaust a little too close to the engine for a true reading. I might be wrong but I thought it should be further down the pipe....

 

Kudos for entering the 21st century!
How many inches is it from the nearest cylinder?
How long until it starts reading from cold start?

 

I'm guessing it's about 6-7 inches from the nearest cylinders (4 & 6). Maybe a little less. It may not be "ideal", but the readings looked pretty good.
It began reading about 1 minute after start. Started car, idled about 30 seconds, then drove off. In another 30-45 seconds, it began showing some voltage.

 

Ingenious place to put the sensor! Please keep us posted with your progress. I'm especially interested in your setup's sensitivity to jet & rod changes. Good luck!

 

4 & 6?
a single sensor should be mounted on the left bank as 3 5 7 run leanest.
Just info for cf readers. The only risk is melting a hole in a piston if it goes too lean. i would never ever do just the right bank on a small block chevy.

 

drives61,
I agree, and for further tuning will likely move it to the drivers side. The reason that I started on the "even" side is simple, there was already a "dummy" EFE valve on that side (to match up the exhaust), so it was the easiest place to swap in the valve body with the sensor.

 

Warhovs, I'm in the middle of making mine right now; did you use any kind of voltage regulator to feed your meter? I burned up the LM3914 when I was testing it, unfortunately. I'm going to purchase a handful of the damn things and put a regulator (and IC socket) in my circuit.

From what I know of the O2 sensor itself, it's really not a true indicator - it's merely a "switch" that either shows rich, lean, or dead on 14.7:1 A/F ratio. You could almost get away with making a 3-LED meter, for that matter. I *have* however, come across a true wide-band O2 sensor/meter setup, but just the sensor itself costs in the $200+ range. (And that's DIY!) BUT, you can REALLY tune your engine with that, as opposed to the meter/O2 setup you (and I) have now.

The trick with the EFE as your temporary install is pretty slick, but only somewhat accurate. It'll definitely help you see what's going on though, which is a huge improvement over the the O1 sensor (olfactory!) :D

Do you have any pics of your meter and/or EFE setup??

Ken

 

Just bought the MSD A/F ratio meter and LED gauge. Now I am trying to figure out where I am going to drill a hole in my Hooker headers to mount the O2 sensor. Any ideas from you guys would be appreciated. I also bought the MSD adjustable timing module that allows you to turn the dial and advance or retard timiing 15 degrees. Can't wait to try all these goodies out and see how she runs.

 

Scuba
mount it in #5
i am writing an article, it's not done yet: http://community.webtv.net/MATTGRU/AFtesting

 

Drives61,

I have the same Hooker side pipes as Skuba, why not mount at the front of the collector?

Chuck


[Modified by Chuck Harmon, 2:39 PM 8/4/2001]

 

Chuck
Good question!
I revised my article to clarify.
Thanks

 

Ken73,
I didnt have any problems without a regulator. I believe the LM3914 is good with a supply voltage up to at least 16V (maybe more). I ran mine up over 15V in testing without a problem. But I did go with the IC socket as well, just in case I have problems.
I did NOT find a way to get the reference voltage below 1.25V, so I can only get 8 of the 10 lights at full rich (about 125mV per light, but I found some non-linearities).
I absolutely agree that you Must understand the limitations of the sensor to use it properly.
As for your last question, Sorry, no pics! I did decide that I wanted to keep it installed for a while, and since I've spent the last couple years doing a complete interior and exterior restoration on the car, I wanted to keep it "hidden". I re-routed the wires through the firewall to the cigarette lighter compartment, where the meter fits. Now it's completely hidden until you slide open the cig lighter door, and then you can see it while driving.

 

I would love to read more articles on this. Once you get the meter and sensor working, maybe you could write something up and post it to the tech section. There have been several posts on this and it would be great to have a single place to go to get the story.

 

Ha!
I just recieved parts from the shack for 4 meters:D:D
Now I can put one in each header primary ( one side at a time ) and look for lean clyinders :yesnod: :lol: :D :cool: :rolleyes:


[Modified by 427V8, 7:39 PM 8/6/2001]

 

Drives61,

For those of us that may have a problem mounting a sensor on every primary tube, are there any devices that could be strapped/clamped to the primary tubes 10" from heads to measure temperature? Hotter tubes should be more lean than the richer tubes, right? If all temps are close, the A/F ratio as measured for that side should also be close, right? A big difference in temperature would identify a problem.

You're doing great stuff Drives61, please keep up the good work and keep us posted with your comments.

Thanks,

Chuck

 

I'm not Drives61 but I play him on , Nah!

They make temperature sensors that can read exhaust gas temps, My engine builder uses them in each exaust port to monitor for lean conditions. He has holes drilled into each primary, but I suppose you _could_ just clamp them on.
Then you'd set the A/F ratio for the entire bank and just use the temperatures to balance things.

You'd never know the actual ratio, but you could see the difference...
:cool:

 

427V8

If you drilled them in and ran heavy wires to an empty (no guts inside) smog pump, you could probably tell a smog inspector that they are the air fittings!

Chuck