How to check AFR on a '79

[LIRS6]

I did a search, but what I found involved either O2 sensors (which my car doesn't have), or using the air sensor plate to try to get a feel for whether the ratio was where it should be or not. As a relative novice working in my home garage, is there a gauge that can be purchased/easily be utilized to measure AFR, and how is that achieved? In the case of the sensor plate test, is that test done at cold start or when the engine is warm (I suspect when warm)?

Thanks

Jason

[SkiVT]

I installed an Innovate Motorsports 3918 MTX-L Plus. My exhaust pipe/header had a bung so it was easy to install permanently. First decision is do you want to measure it periodically or always? I find always can help tell you if something is changing or deteriorating in the system, so I chose a permanent install. If you have a bung, it is easy. I believe its also easy to have someone install a bung. If you only want to check it periodically, you can find a sniffer (at a shop or buy one). Not sure which is the best cost decision. I also agree you set AFR based on warm but knowing AFR across warmup cycle doesnt hurt when making your setting.

[tirwin]

Agree with what SkiVT said.

I personally think if you are going to spend money it makes sense to install permanently. Why? 1) It’s a good bit of money to sink into something you’ll use once in a while 2) if you get a wideband AFR that can log it’s data you can see over time if something changes with the car.

What is your exhaust setup? Stock or something else? In most cases a muffler shop should be able to weld in a bung for the wideband O2 sensor.

[LIRS6]

Originally Posted by tirwin

What is your exhaust setup? Stock or something else? In most cases a muffler shop should be able to weld in a bung for the wideband O2 sensor.

Thank you both.

Exhaust is : SSI's into Dansk (2 in/1 out) muffler. No cat. (pic below)

Jason

[LIRS6]

[SkiVT]

What is that O2 sensor looking thing in the far/upper left of the pic? Almost looks like you have a pre-muffler before the SSI. I also have SSI 2in1out. The bung on mine is right after the three pipes turn into 1 on the SSI

[LIRS6]

Originally Posted by SkiVT

What is that O2 sensor looking thing in the far/upper left of the pic? Almost looks like you have a pre-muffler before the SSI. I also have SSI 2in1out. The bung on mine is right after the three pipes turn into 1 on the SSI

I see what you are looking at, but I don't have an answer - will have to check tonite. Edit : Ok, I think mystery solved - photo was taken at the shop with engine out, I think we are looking at photo of the engine on stand but the perspective is upside down; if I rotate the photo it seems we are looking down at my engine (proper perspective), and the sensor is a component of a different engine.

here are other shot's of my SSi's - I don't see a bung, unless photo angle hides it





Jason

[SkiVT]

Maybe the SSI install decided to leave part number 6 behind. I can't think of a way to connect it to the SSI piping but who knows. Should be an interesting investigation....

[Porchdog]

Originally Posted by SkiVT

Maybe the SSI install decided to leave part number 6 behind. I can't think of a way to connect it to the SSI piping but who knows. Should be an interesting investigation....

# 6 is the catalytic converter. Leaving that out is sort of the point of SSI's.

I welded a bung just behind the collector on the driver's side SSI (Near where the stock O2 sensor mounts).

[LIRS6]

Originally Posted by Porchdog

# 6 is the catalytic converter. Leaving that out is sort of the point of SSI's.

Right, as I noted in #4 above - cat is no more.

Originally Posted by Porchdog

I welded a bung just behind the collector on the driver's side SSI (Near where the stock O2 sensor mounts).

Can you clarify "behind the collector"? - Meaning just back of the 3 into 1?

thanks

Jason

[SkiVT]

Agree its part of the point of SSI which is why its surprising to see what looks like a cat in the picture.

[Porchdog]

That picture is the stock setup.

Mine is about 2" back from the 3 into 1. Angled up a bit so the nose of the O2 sensor is on a downslope into the pipe - I know that's important but don't recall why.

By the way - I used an AEM gage which failed after a couple years and their out of warranty repair is more than buying a new one. The Innovate requires that you remove it fairly frequently for "free air" calibration. I haven't replaced the AEM yet but I will likely buy a Daytona unit.

[LIRS6]

Originally Posted by SkiVT

Agree its part of the point of SSI which is why its surprising to see what looks like a cat in the picture.

As I expressed in #7, I believe the photo to be misleading; the photo was upside down, as my engine is actually on a stand rotated 180 deg, and the photo includes part of an adjacent engine (with sensor) - not part of my engine.

Look at it this way, and you will see the floor with a transmission on ground to the left; this is the proper perspective:

[SkiVT]

Now that makes perfect sense.

My mount is the same as Porchdog describes. I pull the sensor every two years to calibrate. It takes about 15 min.

[LIRS6]

Originally Posted by Porchdog

Mine is about 2" back from the 3 into 1. Angled up a bit so the nose of the O2 sensor is on a downslope into the pipe - I know that's important but don't recall why.

"Downslope" meaning angled into the flow of the exhaust, or away from the flow?

i.e. SSI 3-into-1 then ==== / === tail pipe (where the "/" is the O2 sensor angled into it at the top of the pipe) .... or the reverse of that angle?

[SkunkWorks]

I had the local shop weld a bung on the passenger side SSI - running an AEM wideband where the clock was.

My SC has lambda so there's already a bung on the driver's side for when I need to check both banks. There are multiple products now that are compatible with two wideband O2 sensors for one gauge. I'd do this if I had to redo it again.

[SkiVT]

This may help, from the instructions that came with my Innovate gauge:

"Using a clock as reference, mount the bung between the 9:00
o’clock and 3:00 o’clock position. Welding the bung in the lower
section of the exhaust pipe can result in sensor damage caused by
condensation making contact with the sensor’s internal heating
element."

[LIRS6]

Originally Posted by SkiVT

This may help, from the instructions that came with my Innovate gauge:

"Using a clock as reference, mount the bung between the 9:00
o’clock and 3:00 o’clock position. Welding the bung in the lower
section of the exhaust pipe can result in sensor damage caused by
condensation making contact with the sensor’s internal heating
element."

Got it, makes sense - thank you.

Jason

[wreckah]

i had a bung welded into my SSI's as well, mounted an AEM wideband kit to check up on my CIS system. Saw that things were terrible, and ultimately went to EFI. the AEM gauge is still on the dash, as well as a voltgauge.

[scarceller]

And in this thread I posted the table for CO to AFR mapping.
https://forums.pelicanparts.com/8922068-post8.html