Frankie the Fink

I DID do searches on this topic (forum and general Internet) and answers seem to be all over the map. Santa brought me an AEM UEGO wideband O2 sensor that I will install on a 396ci/375HP motor with a Holley dbl pumper 650cfm aftermarket carb (mechanical secondaries). Of course none of the instructions for these products give advice on optimal ratios. More like a thermometer-type gauge with green-yellow-red markings; pretty vague.

My reading says mid 13s to low 14s is a nice (somewhat 'fat') ratio for these GM motors considering modern gas; yet the "perfect" ratios is like 14.7. I also read too rich of a mixture eats O2 sensors pretty quickly.

I have 'tuned' by spark plug condition, vacuum and general running checks all my life so this is an exercise in new technology and I'm looking for advice from those that have, "....been there and done that"

cv67

Some may disagree but I wouldnt go by "perfect ratios" as some cyls run leaner than others dont want to go too far. Get it close then pay attention to how it runs ie "what it wants". Heard great feedback on the AEM system looking into one myself. Make sure your exhaust gaskets are fresh with no leaks

Frankie the Fink

Thanks! Yup...new header and collector gaskets installed by yours truly about two weeks back. O2 sensor bungs being welded in today...gauge will go in early next week.

Plasticman

Frank,

Based on my usage, I would use it to get into the "ballpark", and then let the engine tell you what it really likes.

As previous poster stated, don't get hung up on "perfect" numbers.

John (plasticman)

89onlyZ51

Shoot for 14.7 at low load/cruise. Under load/accelleration, you'll want to run richer, like around 13:1, to keep the combustion chambers cooler.

Tune for the smoothest idle, and go richer anytime you encounter a lean miss.

Are you planning on permanently mounting the afr gauge? Water vapor is what does in the sensor, and I don't know how long they last when permanently mounted. I use my wideband when tuning and take it out when I'm not fiddling.

wmf62

taking it out isn't a bad idea but that sensor is no different than the ones that are OEM.


Frank
as for tune, try 14.7 and see if you experience any surge or other ill-effects... too lean should give a lean surge at cruise, too rich will give dark plugs and smelly exhaust.

i have my EFI set at 14.7 and Jim Lockwood has his right around 15ish. Matt Gruber has his even higher....

Jim and i don't have to worry about lean cylinders as we both have forms of FI and so are 'immune' to carburetor manifold induced leanness (different length runners and relationship to jets) and, Matt is Matt (need i say more... )

lean it till it surges then back off and check plugs for leanness.

it will be interesting to see what it is running now before you do anything.

Bill
Bill

jim lockwood

In the interest of doing "good science", I'd make a lot of baseline readings before even thinking of making any changes.

Jim

waltonb123

I'm still playing with mine. My first reading at 3000 cruise was around 16.5, I changed the 64 jets to 68 and got a reading of 15.5. I installed 72 jets and now read rich at 13.5. Just picked up 70's but won't be home till Tues to see what they read. I always have had an issue with exhaust that burns my eyes and stinks up the place. I don't know what to try next for that issue.

wmf62

try my idea of tailpipe extensions that i suggested to you a while back...
Bill

waltonb123

I plan on it Bill, holidays are getting in the way. I have a beach house in the Outer Banks of NC and the only road that runs down to my house was washed out by hurricane Sandy. Well they just opened it back up so I can actually get down to see if I have any damage. I'll be down there until Tuesday so when I get back I plan on fine tuning the carb and putting the extensions on.
Bob

devildog

Frank,

On my 61 with the 400 DART engine and my old 2 x 4 WCFB's I have a bung in each exhaust and alternate the insertion of the O2 sensor.

It is surprising how precise you can tune even with swapping around the metering rods in those WCFBs.

One key point, with todays gasoline having high aromatics (toluene, xylene, etc) and ethanol content, the stochimetric ratio is more like 14.4 than 14.7 with real gasoline.

Like the others said lean it to where it feels right. I have some general information about setting that i will send you...I seem to run 13.8 at idle and 14.5 at cruise.

If you go to the INNOVATE website, I think they have many articles posted by users about their units, should apply to your brand as well.

Next step you put an EFI unit on it like I did my 400 SBC Avanti

Joe

65tripleblack

The AEM UEGO kit does not appear to be an effective tuning tool. It is akin to an idiot light and has nowhere near the accuracy required to do anything meaningful. It's amusing to watch your "ballpark" ratio on the gauge while you drive/idle, etc., but that's about IT, and you can get the same idea by watching a dashboard installed vacuum gauge.

The sensor/controller/gauge is meant to be permanently installed and powered, so fouling does not enter into the picture because the Bosch wideband sensor is continually being burned off/cleaned.

Here, YET AGAIN, is a "screenshot" of one frame of the scrolling real time output of my Zeitronix ZT2 unit:



The ZT2 is SELF CALIBRATING. The plot line scrolls to the left as new data is displayed on the right, and earlier data drops off the left edge of the screen. The entire sessions are stored as "ZTF" files which are easily retrieved for review/display/manipulation on your laptop or desktop computer. It's also less expensive than the Innovate because it does not come equipped with a output device (display), which is your laptop.

I assume that the Innovate tool has similar output graphics, although on a much smaller display. This is an example of a useful tuning tool, made to be removed when not being used. It is meant to display output versus time on a laptop computer carried onboard the vehicle while monitoring state of tune.

Return it and exchange for a more useful tool.

1snake

It's funny that when I suggested that FTF get a LM1 or 2 to correctly tune his Holley, he wasn't willing to ruin his STOCK exhaust by adding an O2 bung or learning some new hi-tech instrument even though he's a computer expert..
How things change.

Jim

Frankie the Fink

I don't know why you feel the AEM is not an effective tuning tool. It's a wideband that uses a very common O2 sensor that is self-calibrated as well. Lots of folks have had a good experience with it on the Chevelle forum and elsewhere. There is nothing 'magic' required. The sensor supplies a voltage and the gauge interprets it. I could see where the case can be made that a narrow band is ineffective for tuning since it's more like a 'switch' ping-ponging between rich and lean conditions. The vendor's claim is that the AEM is accurate to 0.1 AFR. It also can be used to 'datalog' to a laptop if that is required.

89onlyZ51

The issue is you need something that can log data (aka "record"), and do it with a few other parameters like time, rpm, vacuum, etc. Staring at a gauge can be useful for cruise speeds, but when you're hammering it, and a lot of things are changing rapidly, it's impossible to keep track of things with the single gauge.

There's nothing wrong with the AEM setup, you just might need more pieces to do full tuning. I use the innovative setup with datalogging, but they also offer just the sensor, interface and gauge. I'm sure AEM is similar - at least I thought so when I was shopping for my wideband setup.

I'll stand by my comment about temporary use, particularly with a carb'd motor. You'll probably be OK if you can mount the sensor between the 10 and 2 o'clock positions in the exhaust, but older carb'd motors don't heat as quickly and aren't as controlled during the warm-up cycle as newer EFI motors. It's an expensive sensor to go through every year or two.

65tripleblack

If you can't see the difference between the output of the ZT2 and the analog gauge face of the AEM, then I can't explain it to you.

cv67

Makes sense, maybe the AEM is just a little "dumb" in comparison wiht more expensive ones but still leads you in the direction to where youre not lost.
Kinda like TBI injection compared to Multi port.

Frankie the Fink

I worked in a test equipment and calibration lab in the aircraft industry and used a ton of test/troubleshooting equipment and can read a graph.

I can see the difference..I don't think ti disqualifies the AEM as a tuning tool. I'm not tuning a 700HP fuel injected beast with OBD-II outputs...just need to get in the right range for an old Holley. Perfection is the enemy of good enough.

I got my AFR range question answered and really didn't want a debate on equipment selection.
Thanks all.

Matt Gruber

Dumb is good. There is huge variation cyl to cyl, so with an average in the collector, how in the world can the reading be smart? It is like saying average tire pressure is 30.3 psi while 1 tire is 10 psi another tire is 40 psi and 2 are 31. how is an average ever all that smart?
Any AFR gauge can be a FANTASTIC diagnostic tool. How many times have u been diagnosing a problem, and wondering is it RICH or LEAN? And how many times does anyone guess wrong? Any afr gauge at least points u in the right average direction most of the time.

waltonb123

With it connected to a laptop, of course depending on the program, why wouldn't you get the same kind of data?
My Innovate also enables me to connect to a laptop although I haven't felt the need yet. Sometimes you can be paralyzed with too much data, and quite frankly, I think your graph is pretty useless to 90% of the guys here. I'll admit that I'm not an engineer but the only thing that means anything to me is the 14.7! Just saying!
Bob