Technical AF Meter?

It uses the venturi effect from exhaust flow. As long as exhaust gas is under positive pressure and is passing over the venturi it draws gas through the sensor.

It works at any condition above idle speed.

This device is used by rolling road tuners when there is no lambda plug

 

I bought an AutoMeter that reads in actual numbers plus has the dancing wrap around LEDs to show lean/ok/rich graphically. It doesn’t fit the overall look I want for the car, so I didn’t want it permanently mounted. I got a single pod gauge mount from Amazon and a medium sized magnet from Harbor Freight and stuck it to the bottom of the dash. It’s useful for tuning and information, but also easily removed.

 

I use that adapter, as well. After a while, you can kind of sense what the AF numbers are going to be based on the car's driveability, and the numbers on my meter seem to align with that (even when using the tailpipe adapter). Even if it's within a half a point, you're close enough for most of the driving a non-racer will do. Additionally, I know from experience that the adapter will hold up to being dragged down the freeway because the user didn't clamp it down tightly enough.

 

Thank you, I like the tail pipe adapter idea allows use on several vehicles.
Dan

 

You do not want a bung near header flange. I have an Inovate and and it specifies bung must be a minimum distance away. I think it is 36" but I do not remember the exact distance.

John

 

He might have meant the header collector flange, eh?

 

Yep... been there. I have developed the process of lashing the cables to the fender to limit the amount of travel of a lose clamp.

 

I have the exact same gauge and mounted it the same way. A rubber coated magnet with a 1/4 20 threaded insert. When not needed it just goes under the the dash.

 

You want the O2 sensor bung to be about 36 inches or so back from the header flange at the block. I prefer to have it in the merge collector. Also, you want the sensor bung at about the 10 o'clock or 2 o'clock angle. Lastly, if you are going anywhere past the header-collector flange, make dang sure you have no exhaust leaks!

I've seen a lot of cars with leaks at their header/collector gaskets - and that screws the readings all up. This is particularly important if you are using the tailpipe mounting shown earlier. If you have any leaky "slip connectors" or joints - fix them before messing with an AFR meter.

 

As someone who has used one, they work phenomenally.

 

Here is the instructions from SpeedHut, it shows mounting the O2s.
Standalone AFWB LED.pdf
" Recommended 40" from closest exhaust valve "

 

Modern fuels will show a clean plug, even with a radically incorrect mixture.

Light almond colored porcelain with a cruise AF ratio of 12.9:1 is possible.

I saw it.

The previous shop said the tune was "perfect".

+45 wheel HP, and 11MPG later, it was perfect, but that took a wideband O2 sensor.

 

Exactly, that is what I experience with my blown SBC mill.

 

Bored, have you ever heard of a way to use a meter with zoomie headers ?

 

I guess it depends on whether or not you want individual readings or all on a side? I've seen plenty of zoomies with EGTs in them, I can see no reason you can't put O2 bungs in them as well. It also kind of depends on whether this is for initial tuning - vs something you want to have running all the time (like for an EFI type situation). If it was for initial tuning, I'd make a slip-fit pipe about 24" in length with a good quality band-clamp on it where it slips over the zoomie tube. You cannot have ANY oxygen leaks - you might even need to use some temporary header wrap to guarantee a seal at the slip joint. I'd put the bung close to where the slip-fit ends - with about 18" of tube past it. This helps to insure there is no oxygen reversion hitting the sensor.

If you're running EFI and need to have dual sensors in all the time, then things get a bit more complicated. I would probably put the bungs about 12" from the end and at the 10 or 2 o-clock angle. What I can't tell you is if there will be any issues with how long a sensor lasts this close to the block . . . you won't know until you try. With that said, high performance exhaust systems can get plenty hot even after a header collector, so maybe it isn't an issue.

If I was running dual sensors, I'd probably put one in a middle tube on one side and one in a rear tube on the other side. You might think about some EGT bungs at the same time - up by the block, just plug them when you're not using them.

What are you trying to do this for?

 

Zoomies are going to be a difficult install. First, each cylinder is going to read separately. Second, if it's typical 2 foot length or shorter, there is going to be a high pressure pulse, followed by a low pressure, meaning it pulls in atmosphere (oxygen). This will be garbage info. You can hold a sheet of paper over each tube and if it doesn't consistently push out, it's going have this issue. Think about those old diesel stack flaps. Remember that the paper does have inertia, so even when it's just staying open, it's going to have some pull.
@pprather that CARBCHEATER looks like a cool setup. Kind of similar to the old feedback carbs with the duty cycle needles, except it's a duty cycle air leak. Too bad it's not currently available. Also, you want to start with things too rich on this. That is always the safe way to start, but if your setup is lean, this can't dial in more fuel that I can see.
I spent too many years bent over fenders trying to get stuff to pass smog, so I have that seat of the pants experience twisting things and seeing/hearing results. It has been a long time since, and today's 'gas' is not what it was even 20 years ago.

 

Another idea (if you need the O2's all the time) is to create a "H-Pipe" type of cross over between all four tubes on a side. It is essentially a shared "manifold" between the cylinders - which should reduce the chances for inversion of oxygen into the mix. One could do this quite easily and depending on the zoomies design, would be hard to tell you even had it in place. It would dampen the "sound" just like it does on a header car but it might be worth exploring if you're going EFI with zoomies. Also, it could get the sensor away from more direct flame/heat.

Just an idea that came to mind (and I might try it myself with a blown EFI setup!).

 

I added one to this pile as the four banger needs all the help it can get. Helped narrow down what size main jets to get it to run right. They carb comes stock with 45 and by the time it was in the right spot I'm using 33 mains.