Wideband O2 Tuning

[jdeignan]

It looks like a few of you have added a wideband for carb tuning.. can anyone post what their target AFRs are at different phases of driving?

I have an Edelbrock 1405 with auto choke added that I am trying to tune as best as I can. Its a street driver, but id like it to land somewhere between economy and best power, with a bias towards power.

The cam in there (lopey, no idea type) likes manifold vac. And runs super hot on ported.
Initial is 15
Vac Adv is a B28 can that gives me 15”
Total is 36 by 3000rpm
MAD 6al, MSD 8479 dizzy.


Vacuum at idle is 15, in gear around 11” (C4)
Idle RPM is 725 in park, 585ish in gear.
Carb has the stiffest springs

She sounds great, but I want to swap rods and jets to tune it best.

Right now I have it set to:
Idle- 14.2
Part throttle 13.8-14.7 range
70mph cruise- 13.3
WOT- 11.2

Any thoughts on where I stand here so far?

One weird issue I noticed:
Idle is 14.2, but after drive it around the neighborhood is sits around 12.5. If I restart the truck, it will go back to 14.2. Is something sticking?

Thanks! Looking forward to hearing your advice!

Joe

 

[T-7ToNewOldB]

I have pro-flo 4 on mine. Truck isn’t at my house right now. When I get it back I’ll post what it has it running at.

 

[jckkys]

I found this article;https://www.onedirt.com/news/how-to-fine-tune-your-carb-using-holleys-tuning-dvd-and-wideband/. It's geared for Holleys but describes the desired results. I'll be using the info to tune an Autolite 4100 with a wide band. Those are more similar to a Holley, but the desired A/F ratios are the same for all 3 carbs.

 

[jckkys]

Timing is another tuning area to consider. I like this article;http://vb.foureyedpride.com/showthread.php?22229-The-Ultimate-Duraspark-Distributor-Timing-Guide

 

[Broncobowsher]

My Sniper on a low compression big block is set for part throttle light cruise target of 14.9:1. Lean it out a little for economy and not enough compression for detonation issues.

Your 70 MPH cruise might be a little rich, depends on how much vacuum you are pulling at that time. The WOT is rich and there are gains to be had my going a little leaner.

This is where I like EFI, I am not a good carb tuner. Outside of the idle mix screws I tend to get lost.

 

[pcf_mark]

I tuned a few cars with a wide band and carbs and it is a perpetual compromise. But you can make improvements in the smell, mileage and performance but do not get too wrapped up in what the O2 tells you. It is a tool not a magic box.

First is your vac advance connected to ported or manifold vacuum? I could not discern that from your post. If ported great skip the next few sentences. If manifold it may be adding to your stress. With a C4 when it goes into drive the converter is tight and the rpm drop is strong. When the rpm drops the vacuum drops and if you have your vac advance on manifold vacuum it drops a lot and your timing is retarding. Then the idle gets lower because it has less timing and you are on this see saw. Stick shift use manifold vacuum, automatic use ported. Too much idle timing causes the exhaust to really stink too making you think it is rich but it just unburnt because the timing is wrong.

Idle is really about smooth idle than it is about a specific number. You will find that if you go from park to drive a few times the numbers jump around. This is the vacuum load changing and fuel gets pulled out of the carb and wets the intake runners. It takes a little time at idle for this to be burned up I just blip the throttle. I set the idle at my target rpm then start leaning the idle mixture out until the engine starts to idle rough then richen it back up. Repeat on both sides. You may be around 14.0-14.4 for a smooth idle on an old style engine. 14.7 will be a rough idle and run hotter. What is important is that it is stable. If it is jumping around you have a vacuum leak or lumpy cam giving you fits. You should be able to make a tiny adjustment (1/16 of a turn on a Holley) and see the O2 changed on the gage on EACH side. If one side is more or less sensitive you have another non-carb problem. Once you get around 14-14.4 and a smooth idle recheck your idle speed and you may need to go back and do them again. Your vacuum should come up from doing this process. If using manifold vacuum you may need to revisit your timing now.

When it comes to cruising down the road at part throttle you can get really lean and the engine will not care. Lean as in 16-17:1. This makes the engine more crisp, saves gas and the exhaust won't stink. But you need to get your accelerator pump right on the money. I suggest you lean it out 14.5-15.0 and see what happens when you try to roll on the throttle. If it lean pops or stumbles you should look into the accelerator pump. If you get really brave and go to 16-17:1 you need your vacuum advance (like 40 degrees of timing at light throttle) and accelerator to be right on the money or it won't climb a grade in gear or accelerate away when driving from 40-60 mph just lug along.

When it comes to power rich there are two parts. What the accelerator pump dumps in and what main fuel circuit is bleeding out. The accel pump will blind the O2 for a second or two and show a huge lean spot (when it is not tuned right) or a rich spot (good). Then it will taper off to what your actual ratio is. People see 11:0 when they hit the pedal and freak but if you let the engine build rpm it should flatten out to 12.5-12.8. If it is above 13 you may be lean for power but the parts will not die. Under 12 and you are throwing fuel out the tail pipe.

Use the numbers to inform what you are doing but do not get too wrapped up in hitting 14.7 at the perfect idle. Also if you have E10 in your area or have a winter fuel blend all of these ratios will be off a few.

 

[jdeignan]

Thanks for replies and articles.

Going to disable the secondaries and see what numbers I get for tuning the mains.
For WOT, My plan is to start at the secondaries and see if I can get that leaner without affecting any of the cruise numbers.

Any idea why she runs rich at idle after I drive it around, until I turn off and restart engine?
Thinking it could be the sensor? Could be the primary rods not reseating in the jets properly and reengaging the idle circuit? Any other easy things to check?

 

[jdeignan]

First is your vac advance connected to ported or manifold vacuum?

I’ve tried both. I have manifold vacuum now, because I noticed my idle engine temps were really high sitting at stop lights etc. Also, the 15 initial+15 advance at idle pulls 15” hg steady and provides a very stable idle compared to ported.
If I went ported, my initial would have to be significantly higher.

That said, solid point on the C4. Totally understand whats happening there. My vac drops to about 11”, but the B28 advance canister is fully deployed around 5-7” hg, so I shouldn’t be seeing timing jumping around with a loss of vacuum in gear. I will check this on a timing light asap.

Thanks for the data points and advice- I will play around with ported again, and see to tuning this thing correctly.

 

[pcf_mark]

Overheating by changing the vac source is very strange. If you set the initial with the vac connected to manifold you are going to end up with timing that is less than you expect. I am not sure of your level of tuning experience so if this is too basic just ignore it...


Engine warmed up
Vac can disconnected and hose plugged
Set base timing at 15
Rev engine to 3k and check total timing. If 32-36 great, if not you have two choices - reduce initial (drop your 15 - 12 for example) or get an bushing for the distributor to reduce total timing
Reset idle speed
Plug the vacuum advance can to ported vacuum.

If the idle speed picks up when you plug the vac can then you are on the wrong port of the carb.

As I noted the C4 and manifold vacuum is a challenge. If you timing is not on the carb is going to make you work hard to tune.

Different afr at idle (assuming the vehicle is in drive for both tests) can be wetting of the manifold walls while driving finally being burned. When you go from drive (loaded) to park (unloaded) the engine is going to go rich. It should settle out with a throttle blip in a few seconds.

 

[jdeignan]

Mark,
Thanks for the post- I’ve def got the timing basics down- but I appreciate the post nonetheless! At this point, Ive read a billion threads that spun in to arguments over ported vs manifold- I dont want to start another either! The truck runs better and cooler on full manifold- who knows why. Just trying to tune the carb so its not too lean or fat

I couldnt get out there to check the timing in gear, but that early deploying vac can should negate timing changes as my vacuum signal drops when I put it in gear. I will still test it for good measure and post it here.

The rich condition/throttle blip fix makes sense! Thanks for the info!

 

[jdeignan]

Ok shes tuned up! Sorta

Cruise at 70 is around 14
Moderate load 13.7 (0-40mph light accel)
Cruising highway is around 14
WOT- 12.5-12.7

BUT- I still have my original problem at idle. Even if i blip the throttle.
I set the screws to 14.7ish, its great, throw it in gear, holds 14.7.. Drive down the street, that 14.7 changes to 12.8 every damn time! Clockwork!
If I shut down and let it sit, itll go back to 14.7 again (until I drive)
I called Edelbrock and the guy basically said “meh, i dunno man”

Needle/float? just replaced and reset
Fuel Pressure? 5psi
Step springs? silver, verified down in place
Idle screws moving from vibrations? Checked
Choke plate moving and richening the mixture?
I cannot figure this out!
Any thing I am missing?

 

[pcf_mark]

You may need an insulator under the carb like this:

https://www.summitracing.com/parts/...MI4rPkjYSk7AIVjIvICh3zQAMoEAQYASABEgIXfPD_BwE

What you describes sounds like the carb is getting hot (really hot) or the fuel is getting hot. Then it actually dribbles out the boosters or the overflow. When it get hot and the AFR rises stop and shut it off. I bet you get vapor coming out of the carb. That vapor is fuel dripping into the intake and them evaporating. This gets worse if you live in an area with E10 winterized fuels.

 

[gr8scott]

Here's the one you want for your Eddy 1405. It does raise it up 0.5 inches...

https://www.summitracing.com/parts/edl-8722

 

[m_m70]

Here's the one you want for your Eddy 1405. It does raise it up 0.5 inches...

https://www.summitracing.com/parts/edl-8722

Used this one for years and has been great!

 

[rmk57]

My warm/hot idle is 14.2 to 14.5. Light cruise (35-40 mph) I can get it around 15.5-16.5. WOT is 12.2-12.5.

Engine is a 514 c.i BBF. 10.1 c/r, Holley 950HP, moderate cam, headers. Not in a Bronco but a 50's Ford.

I've found a fairly big difference in afr readings and engine temps so keep that in mind. As mine heated up to operating temps it would get much leaner, 18-19 at idle. After much messing around with the carb I got fairly street friendly.

 

[jdeignan]

RMK- Thanks for the numbers! I think if I go leaner on the primaries I can get similar numbers.

Mark and gr8scott- Ordered the part today! hope that fixes it! Thanks

 

[gr8scott]

Mark and gr8scott- Ordered the part today! hope that fixes it! Thanks

Good deal, it should help.

So based on your current rod/jet combo, where are you on this chart?

EDIT: posting 1405 chart.

 

[jdeignan]

Its a 1405 with the elec choke added. But Im at the stock config (1) with the secondaries set 1 stage lean.
I tried going 1 stage lean on the primary rod but ended up with a stumble off idle.

I’ve been getting pretty good AFR readings. Part throttle is where I want it around 14.7, acceleration is around 13.5, WOT is 12.5.
Its really just the idle that is killing me. It just somehow goes rich to 12.5.
If I set the idle in the 16s, itll hold around 14.5 after driving it around.
I am thinking:
-Maybe the vac is pulling fuel from the nozzles?
-Maybe the sensor is wrong? Dont think so. I put new plugs in so I will check them soon


I added the spacer- HUGE temp difference, but no AFR difference.

 

[gr8scott]

I tried going 1 stage lean on the primary rod but ended up with a stumble off idle.

that's strange...I haven't experienced that with all the rod/jet changes I recently made. The first picture is the chart for my 1905.
It's a AVS2 650 cfm carb. I went all the way to #15 on that chart and it was still running a little too rich. I ended up on #16 from the
1825 chart. It's one of their original AVS series carbs, also 650 CFM. I'm sure Edelbrock would say that I totally screwed up their
"new tune", but I sure as hell didn't like my plugs turning jet black.

I think your idle issue is a symptom of how your timing is set up. What is your initial timing with the advance can disconnected and the
full manifold port plugged?

 

[jdeignan]

that's strange...I haven't experienced that with all the rod/jet changes I recently made. The first picture is the chart for my 1905.
It's a AVS2 650 cfm carb. I went all the way to #15 on that chart and it was still running a little too rich. I ended up on #16 from the
1825 chart. It's one of their original AVS series carbs, also 650 CFM. I'm sure Edelbrock would say that I totally screwed up their
"new tune", but I sure as hell didn't like my plugs turning jet black.

I think your idle issue is a symptom of how your timing is set up. What is your initial timing with the advance can disconnected and the
full manifold port plugged?

15 initial
36 total

With it all hooked up, vac advance gives me 30 at idle- and it sounds healthy. Timing does not change in gear when the vacuum drops either.
At idle/red lights, Eng temp goes to 210 and fan kicks on to hold it there. Whenever I swap to ported timing, the fan struggles to hold 210 which I dont love.

Of note, my timing marks are setup for passenger side, but the marker is on driver side. So I validated TDC with the piston stop and made a mark on the drivers side so I can read using the marker. Using a dial back light too.
Next step is to pull the cover and checkout the timing chain condition.

I am beginning to think its a fuel pressure reg/carter pump issue.
Running a Holley FPR (mr gasket gauge) and the Carter isnt always a steady whine. It fluctuates a little after sitting at idle. Sometimes itll sit at 5psi, sometimes itll drop to 3 at idle. New gauge on the way to see if thats an accurate reading.

Sorry for the rant! Hope it makes sense. Thanks man!