Air Fuel Ratio gauge and now have question?

[1986F150Six]

Just for reference [regarding 16 degrees BTDC static timing]...

Gary, at one point [2016/2017?], when my truck was being worked on by the guys at your house [before The Truck Shows], the timing of the 4.9L was at 17 degrees BTDC. That setting returned good MPG [without pinging], but did occasionally momentarily drag when starting.

You worked some magic on the vacuum diaphragm and the static timing ended up @ a "fat" 14 degrees BTDC for best overall results..

[Gary Lewis]

Good point, David.  So if Dave's 16 degrees works for starting it might be good for MPG.

[1986F150Six]

Look what I found [my memory was off as the initial static timing was @ 18 degrees BTDC and it was reported by Gary on 9/13/14]:

Gary Lewis
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Results
We played with David's truck today to determine what his AFR is and what his timing is. First, we installed my AEM wideband meter and looked at the AFR:
Idle: Once warmed up it was about 12.5:1
Cruise: At 62 where he ususally runs it was in the mid-15's on level ground, but climbing hills it got as high as 17.0 at one point.
Power: Once the throttle was open it went as low as 11.5 but normally at about 12.0 - 12.5.
That said the carb, a 1970 YF carb off of an F350, is jetted just right. It really shouldn't be any leaner, but the truck runs well so it isn't too lean. And it certainly isn't rich.

Then we checked the timing. The initial timing was set at 18 degrees, which was getting good MPG but made the engine slightly hard to start sometimes. And, it pinged at full throttle, so the overall timing was too much.

As for the mechanical timing, at 1700 RPM where David cruises it was giving 10 more degrees advance. Then we checked the vacuum advance and found that it was starting to advance at 10" and was giving a total of 18 degrees 16" of vacuum, and at the 14" of vacuum the truck had at 62 MPH the advance was 12 degrees. So, total advance at 1700 was 18+10+12=40.

Then we turned the vacuum advance two turns clockwise, which made the vacuum start coming in at 8", gave the full advance of 18 degees advance at 14". Then we set the initial timing to 17 degrees, and the drive determined that it pinged both at part throttle as well as full throttle. So we put the initial timing at 14+, giving a total of 14+10+18 = 42 degrees at 1700 RPM. And the truck felt happier with that setting than it has.

[Gary Lewis]

That's really good info, David.  The only concern I have is that Dave's AFR meter may give different results.  I was told that mine is likely to read lean.  And I know where you place the O2 sensor, meaning how far from the closest exhaust port it is, makes a big difference.

So Dave, I think your readings are still a bit rich but I may be wrong.

[FuzzFace2]

Thanks you David on that information,
It looks really close to what I have about now both on the gauge & for timing.

Gary I think you are right, so close yet so far
I want to get a little more "testing" in before I make more adjustments to the carb.
I may also work with the timing a little more before the carb but will see.

I power washed the motor / under side of the truck as I need to find and fix the oil leak so the truck is parked till I can find it, don't want to re-coat everything if I don't have to.

Thanks guys
Dave ---

[ArdWrknTrk]

You can just touch the (I) wire to the relay hot terminal while looking with a timing light.
You will see it jump back I millisecond (about 4*)

[ArdWrknTrk]

FuzzFace2 wrote

I power washed the motor / under side of the truck as I need to find and fix the oil leak so the truck is parked till I can find it, don't want to re-coat everything if I don't have to.

Up here that "coating" is passive rust prevention!  

[grumpin]

ArdWrknTrk wrote

FuzzFace2 wrote

I power washed the motor / under side of the truck as I need to find and fix the oil leak so the truck is parked till I can find it, don't want to re-coat everything if I don't have to.

Up here that "coating" is passive rust prevention!  

Ha! That’s what I was thinking!

[FuzzFace2]

If I can remember the next time I got the timing light on the truck I will test that retard.

If I still lived up north I would see it the same way on the rust LOL
Right now it is messing up the cement floor in the garage.
I have cardboard down, front to rear of truck, for it to drip on and when it gets to oily I lay down new cardboard.

It also makes the pretty outside look bad or is it the pretty outside making the oil leak look worst
Dave ----

[Rusty_S85]

FuzzFace2 wrote

Ok, Think Jim said something about the EGR may help with the pinging.
Well I cant hook it back up. A freeze plug was installed in the intake under the EGR plate, a plug where the tube would connect but nothing for the tube to connect on the exh. pipe side as I am running EFI exh. manifolds.

I must have gone the wrong way with the vacuum can adjustment it had the death rattle really bad all the time at speed. I had to pull off the first exit 10 miles from when I got on, road work so no place to pull over. I pulled the vacuum hose off the dist. and not being able to find anything on the ground at 1amI left it open.

No more rattle and it seam to run pretty good.
AFR was about 14.0 but I don't know if that is the open hose or change in timing?
I could not find anything before I left work to plug the hose so it was left open for the ride home.
I did find it odd that the AFR was about 14.0 going to work OAT was 61*f
On the way home the AFR was high 14's to low 15's with OAT of 48*f.

Normal driving keeping the RPM shift points to 2000 the truck felt good but I had to run her out a bit getting on the high way and it was a dog with no vacuum advance or was it just running that lean?

Someone wanted to know what the AFR was at WOT. From 65 MPH It went so lean the gauge went ----
only when it got up to about 75 - 80 MPH did I start to see any numbers, 16's & 17's.
It did have a little "miss" every now & then getting up to that speed.

Going to read up on re-curving the dist. as I feel this has to be under control first then the AFR.
Dave ----

EGR would help reduce pinging.  Running a richer fuel mixture will do the same thing or backing timing down.

I have a chart from toyota that lists air fuel ratio and it lists 12.5:1 as being best power, best torque 11.50:1 to 13.00:1.  14.7:1 is target and 16.25:1 best economy.

I plan to use that chart in conjunction with the local tuner I will be using to dial in my sniper stealth, great thing about efi over carb, I can set my Air Fuel ratio to 11.50:1 under heavy acceleration and 16.00:1 under low load cruise but thats in theory how ever, I have to see what my engine is going to want as I dont want pinging so I might have to go a little richer than the charts listing of best economy.

[ArdWrknTrk]

EGR is 'running a richer mixture'
Your engine is a positive displacement pump.
Your carburetor meters fuel to the volume of air flowing through it.

"Richer" can mean more fuel... or it can mean less oxygen.

When the EGR opens some of that charge is diluted with molecules other than nitrogen and oxygen.
This slows the flame front, and pressure rise after ignition.
Hopefully eliminating detonation and keeping chamber temperatures low enough to reduce oxides of nitrogen as well.