Wideband AFR Gauge

[Ernest]

Im seriously thinking about getting one, reading plugs properly has become somewhat of a hasle and time consuming, especially with todays fuel, its not the same as when we used to run leaded..... anyone currently using one and was it hard finding the correct mounting location with the tight room under malibus for the oxygen sensor?

The one im interested in - https://www.aemelectronics.com/prod...ies-wideband-uego-afr-sensor-controller-gauge

This will be for setting up my ZZ4 long block crate engine thats currently topped with a Holley 650(0-80783C) vacuum secondary 4150 style carburator. At the moment, im going by seat of the pants feel(butt dyno), since holley carbs are set at sea level @ 70degrees, im currently at 650ft above and 20degrees warmer here in TX, now 30degrees warmer, no thanks to this 100degree heat wave currently, so i went down just one jet size from stock in the primary and secondary side(67/73 to 66/72) and using the plain vac secondary spring for now. This is nothing more than just a conserative street tune, i havent done any WOT tests yet just to keep the engine safe, i wanted to see how it runs on the street as well as on the highway doing the posted speed limit. The GM recomended ac delco "mr43lts" plugs look great, the 10degree initial timing mark on the ground strap is where its supposed to be(tip above center electrode), the total timing mark comes later(idealy at the arch location) after a WOT run, the center porcelan is white(clean), the entire flat ring at the bottom of the threads that surrounds the center porcelan is a semi dark tan color, all good signs of not too rich and not too lean, like in between, from what i've read and seen online. Im using a 9.5HG power valve in place of the stock 6.5HG power valve, the lower numbered PV just wasnt opening for enrichment when the engine needed it too that made the engine somewhat sluggish and that lack of power feeling. If ya'll wondering how i came to using the current PV, i took my 60mph highway cruising speed vacuum reading of 15HG, divided that by two(7.5HG), then added two(9.5HG), found that info in other HiPerf car/engine forums, the holley method is incorrect(vacuum at idle in nuetral with stick shift or in drive with an automatic and divide by two), probably fine if you are using a much more agressive camshaft or otherwise near or at WOT all the time, mine is not(208/221@112ls). This alternate method has worked out perfect for me, now the highway throttle response is much better as the light cruising on the street, but overall, if feels great, with my foot barely on the pedal, i found myself doing 70mph quite easily now, almost effortless and secondaries hasnt begun to barely open yet, according to my RPM and holley's chart for the secondary springs.

Use the AFR guage to tune for jetting, and the vacuum guage for power valve tuning, both go hand in hand for those that are not ready for fuel injection or choose not too(like me), because we all know that is cheating and taking the easy way out. 😛


Thanks

 

[Ernest]

Well... i finally dropped the coin on the AEM(30-300 X series UEGO) brand directly from AEM through amazon, like the one linked above, and i cant wait to use it.

But now i have to make the descision on wether to get a bung welded in that comes supplied with the kit, or use AEM's no weld 02 sensor mount, which would make it easier for me to do the job myself.

 

[motorheadmike]

Either or on the bung. Learn to read it in Lambda, not AFR on the gas scale. Real men use Lambda.

 

[Ernest]

AFR vs Lambda is like standard vs metric to me.....so whats the difference?

 

[69hurstolds]

AFR vs Lambda is like standard vs metric to me.....so whats the difference?

Not much. They both do the same thing, well, not exactly the same thing, but they're trying for the same end result. AFR is fuel type dependent. Basically the amount of air ratioed to the amount of fuel. So if you were running diesel, for example, the AFR would be different than gasoline, as well as any other fuel. 14.7:1 is the gasoline's stoichiometric, or most efficient ratio balance for combustion, so 99% of your street engines are going to use this AFR as stoich. 15:1 is starting to get lean, 13.7 is starting to richen up. But if you wanted to know what your lambda is, you can simply take your AFR reading and divide by 14.7 and there you go. Lambda is more like a percentage of AFR. As long as you're at 1.00 you're at 100%, or stoichemistry for your engine.

Lambda is more like a readable O2 sensor in a way. Lambda references 1.00 as the fuel/air mix, and it doesn't care what fuel you're using. If there's not enough oxygen, you're running rich and it will read <1.00. If you're leaving oxygen on the table (or in the exhaust we should say) than you'll get a readout of >1.00, or lean. 1.00 would be perfect stoichiometric conditions meaning it was using the exact amount of oxygen to efficiently burn all the fuel. Of course, you have to calibrate the lambda to the natural "clean" air around you to make sure it knows what to reference. Conversely, if you wanted to know what your AFR was for a lambda reading, just multiply your current reading by 14.7 and that's your AFR.

Lambda is beneficial in "computer controlled" environments when using ethanol blended fuels because it didn't care WHAT fuel you were running, just worried about trying to maintain stoich at 1.00. Obviously E15, E85 would burn different than straight up gasoline because there's less energy in the ethanol. So unless you knew EXACTLY what your AFR was for the fuel in your tank, you might not be at 14.7 on the AFR as your optimum. So by using lambda, you take the worry out of it and can run whatever fuel you got, and just worry about how much O2 is left over.

Whichever type you use, it's fine. Your engine doesn't care. Personally, I'd probably go with the lambda readings and take the guesswork out of the fuel blends, unless you use the non-ethanol blended gas if you're worried about tuning to exactness.

 

[Ernest]

That explains alot, thanks.

Im currently using 93octane, but thats with the 10% ethanol blend... the AEM guage can also read Lambda, it has that function as well, then i'll just flip the face for that reading.

 

[69hurstolds]

Lemme just add, there's way more to sensor tuning than just tweaking on fuel curve to get 14.7 or 1.00 all the time. You have other conditions where you may want to fatten up the fuel a bit under load and WOT and such. I am not an expert on it by far. But depending on how many hp you're trying to extract from your combination, you could have some compromise on a street engine and still make it perform well. If in doubt, as a general rule, always tilt toward the rich side of the equation if you're going to need to compromise.

Not familiar with your gage, but I've heard it's one of the better ones out there. I'm sure there's tuners here that use widebands all the time and can give you way more accurate information that can help your situation. If in doubt, follow the manufacturer's recommendations. They do this stuff for a living.

I looked at the AEM package instructions you have and it appears there's a trim resistor in the circuit and it was factory calibrated. As the sensor wears, you still have the ability to do a free-air (hanging the O2 sensor out in mid air without fuel fumes around) calibration if you wish, but they recommend any new sensor replacement should do just fine with the trim resistor. Basically as easy as you can get it. Even if you did have to calibrate, it only takes a few minutes to do.

 

[motorheadmike]

For modern ethanol blended gasoline you'll probably find that the engine wants to be 3-6% richer than 1.00 at around 0.970-0.940. For best power you are going to be in the .860-.920 range. Happy cruise is going to be in that place between .920 and .970.

Anything closer/at/slightly over 1.00 is okay for cruising too... You just have to get the timing right.

 

[Ernest]

Thanks again for the info.

Figure for now, i'll run with the AFR readings, once the engine is set, i'll switch over to the Lambda setting and see how that fairs.