air fuel ratio meter DIY

[dinghyguy]

So, has anyone built their own AFR setup? If so what did you use? where did you install the oxygen sensor or did you make something that can work up the tailpipe?

also i read that CO is sometimes used to help tune the carb, has anyone built one of those?

cheers
dinghyguy, asphyxiating in the dungeon

[rebar1111]

I just went through that process and here is what I found using an O2 sensor in the exhaust.
2L engine with 1800 head and intake with Weber 34ADF and 421 downpipes. 40-80-40 reground cam. No smog equipment. Manual transmission. Ambient air @ 65deg F. Eng temp @ 185 deg F. Timing @ 10deg BTDC.
Results were A/F between 14.0 and 12.5 from 1000 to 4000RPM
************************Primary *********Secondary
Idle Jet *******************60**************80
Main Jet******************130*************140
Emulsion tube***************F2*************F5
Air correction Jet************45*************180
Syncro Air Flow @ Idle********20**************2

[kilrwail]

I didn't build my own, but I do have an Innovate AFR system in the Porsche, with oxygen sensors in both headers, within about 6-8" of the collector joint. It's very useful for choosing the correct jets at initial engine installation. It's also very useful for tuning and balancing all six carburetors with each other and side to side. Just a note of caution - when you select your main jets, make sure they're sized to give an AFR reading of 90% Lambda (13.23 = 0.9 x 14.7) at maximum revs. Anything leaner than that would be dangerously hot. FYI in an air-cooled engine, that threshold is 85% Lambda.

[Nut124]

I have had a fuel/air ration readout on my dash for 20 years. It came from one of the US Fiat parts experts, not sure which.

It uses a standard O2 sensor. I had a nipple welded in the ex manifolf for the sensor.

It works well and is a must if jetting carbs.

[Nanonevol]

I just went through that process and here is what I found using an O2 sensor in the exhaust.
2L engine with 1800 head and intake with Weber 34ADF and 421 downpipes. 40-80-40 reground cam. No smog equipment. Manual transmission. Ambient air @ 65deg F. Eng temp @ 185 deg F. Timing @ 10deg BTDC.
Results were A/F between 14.0 and 12.5 from 1000 to 4000RPM
************************Primary *********Secondary
Idle Jet *******************60**************80
Main Jet******************130*************140
Emulsion tube***************F2*************F5
Air correction Jet************45*************180
Syncro Air Flow @ Idle********20**************2

A 45 Primary Air Correction jet? That's not a typo?

[bluespider262]

I have an innovate wideband on my spider. I welded a bung into the pipe right at the back of the wheelwell sticking straight up. Works great and easy to get to when I want to move it to one of my other vehicles.

[rebar1111]

Sorry that 45 should have been a 145. Thanks for pointing that out.

[dinghyguy]

Thanks to all of you
So I am sensing. Weld bung in. Use Bosch 02 sensor pick gauge and interface adapter and go for it.
Thanks
Dinghyguy

[wetminkey]

Gosh, and all of these years I've been tuning carbs by ear,...
Hee, hee!

[zachmac]

I've always used a colortune. http://colortune.net/

[rebar1111]

Gosh, wetminkey, maybe now even you can get it right.

[wetminkey]

Didn't say I wasn't getting it right,...

[dinghyguy]

ok so now i have learned something......not that wetminkey has a bad ear, but about colortune. Never knew suck a thing existed but it makes sense to me. so has anyone compared the colortune to the AFR meter results? If so what did they learn?

educated a bit , in the dungeon
dinghyguy

[wetminkey]

I recall a very primitive version of Colortune back in the 70's, I believe,...

[wetminkey]

Not quite 50 years ago, I was taught by a high school buddy how to tune a 4bbl by ear. I've been tuning single, 2bbl, and 4bbl carbs by ear for all that time. I can get power/emissions pretty accurate on my cars, trucks, and tractors,...
I can do single carb setups, but multi-carb setups cannot be approximated by ear.