Air/Fuel Ratio Tool - Home Built? - Ford Truck Enthusiasts Forums

Go Back  Ford Truck Enthusiasts Forums > General > Garage & Workshop
Reload this Page >

Air/Fuel Ratio Tool - Home Built?

Notices
Garage & Workshop Tips & Ideas for the garage or workshop. No Truck Tech Discussion

Air/Fuel Ratio Tool - Home Built?

 
  #1  
Old 09-10-2018, 01:46 PM
Rusty_S's Avatar
Rusty_S
Rusty_S is online now
Postmaster
Thread Starter
Join Date: Apr 2007
Location: Houston
Posts: 4,450
Rusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to all
Air/Fuel Ratio Tool - Home Built?

Has anyone on here ever built a Air/Fuel ratio tool for their garage use?

I found some videos on youtube but they were almost as pricy as the datalogger and surely there has to be a cheaper way to build a home built reader to help with diagnostic as well as tuning on your vehicle.
 
  #2  
Old 09-10-2018, 03:03 PM
Tedster9's Avatar
Tedster9
Tedster9 is online now
Post Fiend
Join Date: Apr 2002
Location: Waterloo, Iowa
Posts: 14,852
Tedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputation
It's easy to install a "narrow band" 1-wire O2 sensor and read it using a voltmeter, very inexpensive. Standard brand SG-12; The reason it's called narrow is because it basically revolves around stoichiometric (14.7 parts air to 1 part fuel by weight) and "rich" and "lean" conditions on either side of that in a narrow range. While "stoich" AFR is theoretically perfect, in practice it isn't seen very often.

http://www.bob2000.com/carb.htm

What you want in my opinion for tuning is a wideband O2 sensor and display, don't really need a data logger and graphing programs and all that. Not for carbed engines probably. It will also convert the voltages to actual AFR for you, and adjust AFR display for different fuel types -E10 for example as well. I think the problem with the narrowband setups is they won't display down to 12.5 - 13.0 AFR (full throttle) nor up to 15 - 16 AFR (lean cruise); I'm sure a narrowband could be made to work and is far better than nothing, but the prices have come down quite a bit on the wideband kits. The fuel savings alone after a roadtrip, it will pay for itself. EFI modern engines run as high as 18 to 1 on the highway, don't try this at home kids! But if you really want to get a carb dialed in it's the way to go. Plugs don't "color" the same since leaded gas went away.
 
  #3  
Old 09-10-2018, 03:24 PM
Rusty_S's Avatar
Rusty_S
Rusty_S is online now
Postmaster
Thread Starter
Join Date: Apr 2007
Location: Houston
Posts: 4,450
Rusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to all
Originally Posted by Tedster9 View Post
It's easy to install a "narrow band" 1-wire O2 sensor and read it using a voltmeter, very inexpensive. Standard brand SG-12; The reason it's called narrow is because it basically revolves around stoichiometric (14.7 parts air to 1 part fuel by weight) and "rich" and "lean" conditions on either side of that in a narrow range. While "stoich" AFR is theoretically perfect, in practice it isn't seen very often.

http://www.bob2000.com/carb.htm

What you want in my opinion for tuning is a wideband O2 sensor and display, don't really need a data logger and graphing programs and all that. Not for carbed engines probably. It will also convert the voltages to actual AFR for you, and adjust AFR display for different fuel types -E10 for example as well. I think the problem with the narrowband setups is they won't display down to 12.5 - 13.0 AFR (full throttle) nor up to 15 - 16 AFR (lean cruise); I'm sure a narrowband could be made to work and is far better than nothing, but the prices have come down quite a bit on the wideband kits. The fuel savings alone after a roadtrip, it will pay for itself. EFI modern engines run as high as 18 to 1 on the highway, don't try this at home kids! But if you really want to get a carb dialed in it's the way to go. Plugs don't "color" the same since leaded gas went away.
i agree, thats why i really want to go with building one of these tools so i can set my timing get it locked out to not pull more than i think it is 35* of total advance then i want to set the idle mixture and main and secondary jets.

i thought of using my vacuum gauge to set the carb but found out that setting for max vacuum could still be rich.

i was looking at some gauges to install in a small box with wires but the digital gauges are over $150 without 02 sensor. I dont mind spending the money just dont want to spend too much.

i could get a summit gauge with the bars cheap but i was advised to set it a little richer than ideal by .5 to 1.0 ratio. Hard to do that with just little dashes in red, yellow and green.
 
  #4  
Old 09-10-2018, 06:43 PM
Tedster9's Avatar
Tedster9
Tedster9 is online now
Post Fiend
Join Date: Apr 2002
Location: Waterloo, Iowa
Posts: 14,852
Tedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputation
Idle mixture doesn't really matter too much. (Though it does if you have to pass a smog check) What happens is the most efficient burning of fuel skews the NOX emissions very high relative to CO and HC. That's a whole different deal there, and probably not what you're concerned with.

While the idle mixture setting does affect the overall AFR in the other circuits - transition, cruise, power, etc, it's like pissing alongside a firehose. Adjust it where it idles good, slightly lean. If it's too rich it will tend to load up the plugs after a few minutes and the idle will suffer, and also contribute to fouling.

Where the wideband makes your money is in determining optimum cruise jetting. A carbureted engine in good shape will cruise on level ground around 15.5 to 16.0 AFR or so, this requires experimenting. The trick is to then monitor the WOT AFR, it will likely need adjusting after jetting down. In many carbs this is a little tough to do, as the power valve channel restrictors are basically jets, but they are fixed in size. Simply going with a different power valve will change when the extra fuel comes in, but not how much, it is limited by the PVCRs. The key thing is never go too lean on power. It's OK to lean it out quite a bit when cruising, but never under load or acceleration. I bought an Innovate LM2 kit, it works slick I gotta say. It allows you to see exactly what's going on in real time. The stock Y Block isn't a performance engine but I don't need to have a fuel tanker follow me around anymore. It is truly amazing how much fuel can be wasted out the tailpipe with no noticeable change in performance.
 
  #5  
Old 09-10-2018, 08:49 PM
Rusty_S's Avatar
Rusty_S
Rusty_S is online now
Postmaster
Thread Starter
Join Date: Apr 2007
Location: Houston
Posts: 4,450
Rusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to all
Originally Posted by Tedster9 View Post
Idle mixture doesn't really matter too much. (Though it does if you have to pass a smog check) What happens is the most efficient burning of fuel skews the NOX emissions very high relative to CO and HC. That's a whole different deal there, and probably not what you're concerned with.

While the idle mixture setting does affect the overall AFR in the other circuits - transition, cruise, power, etc, it's like pissing alongside a firehose. Adjust it where it idles good, slightly lean. If it's too rich it will tend to load up the plugs after a few minutes and the idle will suffer, and also contribute to fouling.

Where the wideband makes your money is in determining optimum cruise jetting. A carbureted engine in good shape will cruise on level ground around 15.5 to 16.0 AFR or so, this requires experimenting. The trick is to then monitor the WOT AFR, it will likely need adjusting after jetting down. In many carbs this is a little tough to do, as the power valve channel restrictors are basically jets, but they are fixed in size. Simply going with a different power valve will change when the extra fuel comes in, but not how much, it is limited by the PVCRs. The key thing is never go too lean on power. It's OK to lean it out quite a bit when cruising, but never under load or acceleration. I bought an Innovate LM2 kit, it works slick I gotta say. It allows you to see exactly what's going on in real time. The stock Y Block isn't a performance engine but I don't need to have a fuel tanker follow me around anymore. It is truly amazing how much fuel can be wasted out the tailpipe with no noticeable change in performance.
I was looking at the LM2 kit but couldn't justify the $400ish for the kit. I would like to build my own to try and set this carb. I really want to maximize power on acceleration and maximize economy when cruising. Gotta do what I can to get the most out of my setup considering I only have a 16 gal tank.

This is one of the ones I really would like to get almost $200 with 02 sensor. All I would need to do is use some bulk wire and clips to connect to the battery for my tester.

If I go cheaper I can get the summit air/fuel gauge without the digital read out but I rather have the digital read out so I know what the number is and not try to figure out based on a multi bar red/yellow/green scale.

https://www.summitracing.com/parts/avm-30-4110

It has good reviews but not too sure on how accurate.

Figured it should be a good foundation for building a stand alone box to put in my truck and run the cables to the 02 bungs in my y pipe for road testing then remove the sensor and install the 18mm plug.
 
  #6  
Old 09-10-2018, 09:58 PM
Tedster9's Avatar
Tedster9
Tedster9 is online now
Post Fiend
Join Date: Apr 2002
Location: Waterloo, Iowa
Posts: 14,852
Tedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputation
Originally Posted by Rusty_S View Post
I was looking at the LM2 kit but couldn't justify the $400ish for the kit.
The LM-2 is a little spendy, but not that bad. Should be able to pick up the basic kit under $200 if you dig around. I don't remember what I paid, just under a couple hundred. Used units pop up now and then too. The LM-1, the earlier basic unit works just as well for what you want to do, these used units are up for auction now and then, I just got impatient. Snag one if you can.

I would like to build my own to try and set this carb. I really want to maximize power on acceleration and maximize economy when cruising. Gotta do what I can to get the most out of my setup considering I only have a 16 gal tank.
That is exactly where O2 sensors shine. Everybody seems to think they are only for EFI but they will really help dial in a carbureted engine. I would suggest getting one that has a numerical display of AFR. Innovate has the gauge and wideband sensor under 200 bones. I think that's all you need.

I'm not sure you can "get there from here" with a 1 wire O2 sensor is the problem. Maybe....

Find out what the total range of voltage output is with the SG-12 for example, and convert these to the AFR numbers. If a 1-wire narrow band sensor actually has an equivalent range of say, 12 to 16 AFR, you can make it work (I think) just fine. You'll just have to convert voltage numbers on the fly to AFR is all, no biggie.

Get the jetting dialed in and plug fouling is a distant memory, plenty of power when needed etc, and should see a significant fuel economy increase, at least on the highway. Your vacuum gauge is also useful here. Make certain if the carb has a Holley type power valve that it is closed when cruising or measuring AFR at cruise, otherwise correct jet selection will be impossible. That's the lesson O2 sensors teach, each carburetor circuit is tuned separately, they all work together but each has to be measured and adjusted in isolation, if that makes sense. Short version: lean it out till it sqeeks on the highway, fatten it up on the acceleration & power, done.

One thing - the ignition system has to be in top condition to properly tune, it's easier to light off a rich fuel mixture. Also, if your engine has an intermittent misfire - the gauge will show lean, not rich, as one might expect. These sensors measure oxygen only, if the plug isn't firing, the fuel isn't being burned... but neither is the oxygen. So make sure the ignition timing and distributor bushings and secondary voltage and everything is 100% first before tuning the carb.

I shoot for about 15.5 to 1 at steady level cruise on the highway and WOT is 12.5 to 1 Mileage about doubled. Hope this helps, let us know what you find.

 
  #7  
Old 09-10-2018, 10:43 PM
Rusty_S's Avatar
Rusty_S
Rusty_S is online now
Postmaster
Thread Starter
Join Date: Apr 2007
Location: Houston
Posts: 4,450
Rusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to all
Originally Posted by Tedster9 View Post


The LM-2 is a little spendy, but not that bad. Should be able to pick up the basic kit under $200 if you dig around. I don't remember what I paid, just under a couple hundred. Used units pop up now and then too. The LM-1, the earlier basic unit works just as well for what you want to do, these used units are up for auction now and then, I just got impatient. Snag one if you can.



That is exactly where O2 sensors shine. Everybody seems to think they are only for EFI but they will really help dial in a carbureted engine. I would suggest getting one that has a numerical display of AFR. Innovate has the gauge and wideband sensor under 200 bones. I think that's all you need.

I'm not sure you can "get there from here" with a 1 wire O2 sensor is the problem. Maybe....

Find out what the total range of voltage output is with the SG-12 for example, and convert these to the AFR numbers. If a 1-wire narrow band sensor actually has an equivalent range of say, 12 to 16 AFR, you can make it work (I think) just fine. You'll just have to convert voltage numbers on the fly to AFR is all, no biggie.

Get the jetting dialed in and plug fouling is a distant memory, plenty of power when needed etc, and should see a significant fuel economy increase, at least on the highway. Your vacuum gauge is also useful here. Make certain if the carb has a Holley type power valve that it is closed when cruising or measuring AFR at cruise, otherwise correct jet selection will be impossible. That's the lesson O2 sensors teach, each carburetor circuit is tuned separately, they all work together but each has to be measured and adjusted in isolation, if that makes sense. Short version: lean it out till it sqeeks on the highway, fatten it up on the acceleration & power, done.

One thing - the ignition system has to be in top condition to properly tune, it's easier to light off a rich fuel mixture. Also, if your engine has an intermittent misfire - the gauge will show lean, not rich, as one might expect. These sensors measure oxygen only, if the plug isn't firing, the fuel isn't being burned... but neither is the oxygen. So make sure the ignition timing and distributor bushings and secondary voltage and everything is 100% first before tuning the carb.

I shoot for about 15.5 to 1 at steady level cruise on the highway and WOT is 12.5 to 1 Mileage about doubled. Hope this helps, let us know what you find.

Will do. I am using a mix of oem 82 and oem 96 parts so I want to go this route to try and tune everything together properly. I figured with my Y pipe having a o2 sensor bung in the Y where the two pipes merge I can read both bank 1 and bank 2 with this sensor. I will check out the LM2 on ebay see what I find but I found a wide band Autometer Phantom air/fuel ratio which is listed as a street gauge with 8 - 18 full sweep digital on sale now with 02 sensor for $179.96. Think this might be the one to go for. Once I build this if I go the build route I will probably be posting a topic on seeking help on fine tuning based off the air/fuel ratio I am seeing. I will try to do as much as I can on my own before seeking help.
 
  #8  
Old 09-10-2018, 11:28 PM
Tedster9's Avatar
Tedster9
Tedster9 is online now
Post Fiend
Join Date: Apr 2002
Location: Waterloo, Iowa
Posts: 14,852
Tedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputation
Yeah, there's not too much info on actual AFR "how to" and tuning in terms of what to tune for, the instructions that came with the innovate didn't say anything about that. Basically though, a carbureted engine cannot run as efficiently as EFI. Also keep in mind the AFR displayed is an average of several cylinders, individual cylinders will vary a bit. So it's possible one cylinder is running too lean even if the overall AFR is OK. Don't get too hung up on chasing the numbers, and as always inspect the plugs. They will really help you take your tuning to the next level safely and you'll understand a lot better how carburetors actually work. Definitely a lost art these days.
 
  #9  
Old 09-11-2018, 01:00 PM
Rusty_S's Avatar
Rusty_S
Rusty_S is online now
Postmaster
Thread Starter
Join Date: Apr 2007
Location: Houston
Posts: 4,450
Rusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to all
Nope there really isn't. I saw some claim shoot for slightly rich at cruise and at power and others ive seen state to go lean on cruise slightly and go fairly rich on power.

Part of me is tempted to just leave the carb as is out of the box but I know that wont give me the most benefit. My only option is to build this or buy a used scanner so I can have a tool to help figure out where I need to make changes.
 
  #10  
Old 09-11-2018, 01:56 PM
Tedster9's Avatar
Tedster9
Tedster9 is online now
Post Fiend
Join Date: Apr 2002
Location: Waterloo, Iowa
Posts: 14,852
Tedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputation
If the goal is to improve the truck range or fuel economy on a tank of juice then jetting down is where you "make yer money". Do this first. Jet size, in turn, affects the WOT air fuel ratio. I had to enlarge the PVCRs slightly, with a pin vise drill. This brought the wide open throttle AFR back into safe range. It went leaner as a result of jetting down to the edge of "safe" but it's important to never go lean under power, under load. Think of what happens to a cutting torch when oxygen is fed to the acetylene.

On level ground at highway cruise there is hardly any load on the engine. If you go too lean here, at a certain point the fuel mileage actually starts to decrease. In a carbureted engine about 16-1 AFR is best economy. In the old days people would just jet down till it started surging or bucking at level cruise and jet back up two sizes. For wide open throttle, inspect the plug ring color deep inside, where the porcelain transitions to plug shell. Each jet size change flows approx. 2.5% difference.
 
  #11  
Old 09-11-2018, 02:42 PM
Rusty_S's Avatar
Rusty_S
Rusty_S is online now
Postmaster
Thread Starter
Join Date: Apr 2007
Location: Houston
Posts: 4,450
Rusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to all
Originally Posted by Tedster9 View Post
If the goal is to improve the truck range or fuel economy on a tank of juice then jetting down is where you "make yer money". Do this first. Jet size, in turn, affects the WOT air fuel ratio. I had to enlarge the PVCRs slightly, with a pin vise drill. This brought the wide open throttle AFR back into safe range. It went leaner as a result of jetting down to the edge of "safe" but it's important to never go lean under power, under load. Think of what happens to a cutting torch when oxygen is fed to the acetylene.

On level ground at highway cruise there is hardly any load on the engine. If you go too lean here, at a certain point the fuel mileage actually starts to decrease. In a carbureted engine about 16-1 AFR is best economy. In the old days people would just jet down till it started surging or bucking at level cruise and jet back up two sizes. For wide open throttle, inspect the plug ring color deep inside, where the porcelain transitions to plug shell. Each jet size change flows approx. 2.5% difference.
i went ahead and ordered the air/fuel gauge set for $179 on sale and will make my own.

nice thing is im running a summit vac secondary 600 crm so my secondaries have jets as well. Can lean the primary jets down and keep the secondary jets on the rich side and adjust the vac secondary to kick in when under proper load to enrich the mixture.

at least that is my line of though.
 
  #12  
Old 09-12-2018, 12:37 AM
Tedster9's Avatar
Tedster9
Tedster9 is online now
Post Fiend
Join Date: Apr 2002
Location: Waterloo, Iowa
Posts: 14,852
Tedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputationTedster9 has a superb reputation
Wait. For $179, it doesn't include the O2 sensor itself?? That sounds nuts.
 
  #13  
Old 09-12-2018, 02:29 AM
Rusty_S's Avatar
Rusty_S
Rusty_S is online now
Postmaster
Thread Starter
Join Date: Apr 2007
Location: Houston
Posts: 4,450
Rusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to all
Originally Posted by Tedster9 View Post
Wait. For $179, it doesn't include the O2 sensor itself?? That sounds nuts.
No for $179 it comes with the autometer digital gauge, a bosh wide band 02 sensor with a 8 foot cable. 8 foot should be enough to go from the bung in the y pipe up out the hood and inside the truck through the door. It also states 8 - 18 full sweep which I take it to mean it will read 8:1 to 18:1 air fuel ratio. I planned on breaking a sheet metal box and for the gauge so I can also sit it on my seat and take a look at it while cruising and seeing what it does while driving.

This is it here, it is a Phantom II Autometer gauge. I could have got a cheaper one but the cheapest one was only $174.99 with 02 sensor so I said screw it ill go with the autometer one that stated it comes with a bosh 02 sensor.

https://www.summitracing.com/parts/atm-5779/overview/
 
  #14  
Old 09-13-2018, 01:58 PM
Rusty_S's Avatar
Rusty_S
Rusty_S is online now
Postmaster
Thread Starter
Join Date: Apr 2007
Location: Houston
Posts: 4,450
Rusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to all
Got the autometer gauge in today. Going to take it back to work with me after lunch. Will see what I can come up with for a box for mounting it in.
 
  #15  
Old 09-13-2018, 11:38 PM
Rusty_S's Avatar
Rusty_S
Rusty_S is online now
Postmaster
Thread Starter
Join Date: Apr 2007
Location: Houston
Posts: 4,450
Rusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to allRusty_S is a name known to all
For those that want to build their own here is a break down of my parts list as I have it now.

1) Autometer Phantom Wide Band Air/Fuel Gauge Kit - Part #5779
2) LeMotech Waterproof Plastic Project Box - 7.9" x 4.7" x 2.95" - Part #lm2lm201709251049
3) Mictuning 12V DC Waterproof Volt Gauge - Part #mic-vm-blue
4) Carviya LED Dot Round Rocker Switches - Blue and Red
5) Techflex General Purpose Braided cable sleeve - 1/4" 20ft roll
6) Plasti dip spray - Blue

The goal is to install the Phantom Wide band A/F gauge at the top center of this waterproof box with the wires coming out the top with a rubber grommet with the wiring from just inside the box out to the ends being covered in the 250* braided cable sleeve. The box is white to allow less of the Plasti-dip to be used to get the blue coloring I want. The rocker switches will be blue for power for activation which will switch on the A/F gauge as well as the volt gauge. The red rocker will be used to close the circuit for the 02 heater circuit. It has that feature and I want to fill up some of the empty space for such a large box. I couldn't find anything smaller that had the 2 3/4" internal depth for mounting the gauge.

I haven't bought it yet but I am going to see if I can source some battery clamp style alligator clips for attaching to the power and negative wires for temporary attachment to the battery of the vehicle the testing is being done on which would be my truck.

By time I am done I should have $250 or less in this box. Could have built it a bit cheaper but I really wanted to do the volt gauge as it would serve as a dual purpose tester for me as I can see what my alternator is doing basically.
 

Thread Tools
Search this Thread

Contact Us About Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.