Air Fuel Ratio gauge and now have question?

[Gary Lewis]

I hope this works out for you, and you're able to tune out your knock.

Yes, I hope it solves lots of problems. MPG, AFR, etc.

[ArdWrknTrk]

Yes, the "best" AFR for 10% ethanol blend is 14.04:1, not 14.7. So you may not be that far off.

But, I suspect that your pinging problem is due to having a vacuum advance can that was designed for EGR, which was meant to come in at high vacuum. But the exhaust gas slowed the flame front such that they had to give it a whole lot more advance, which they did with the vacuum can. So if you are running w/o EGR but with an EGR vacuum unit you have too much advance at high vacuum. And while you can determine when it comes in you can't change how much you get.

I don't know what the options are from Crane, but I'd be looking for a vacuum unit that gives less advance.

Well if 14.04 for blend then I am not off all that much as you say.

I did 1 full turn of the rod / seat on the carb to get were I am at now and that was before I had the gauge. It did seam to help with a little more power and the motor ran smoother just nothing on the MPG front

As for the "while you can determine when it comes in you can't change how much you get." from what Jim is saying below I need to slow down the mechanical. I was all in by 2500 RPM so if I slow this down and / or limit it I would be changing the total.

My thinking is keep the vacuum to come in as it was, low vacuum, and install heavy springs so the mechanical will come in later. It is rare it get the RPM up to 3000 RPM, I shift between 2000 & 2300 RPM and maybe 2500 RPM but the truck does not shift well (NP435) at the higher RPMs.

Limit stops affect mechanical advance.

Bending the spring tabs affect spring preload.

With no EGR you probably don't want the mechanical advance 'all in' until 3,600-4K

Go to Kegs.

Find the Crane advance for '68-80 Ford's and look in the listing for the instruction sheet link.

Print it and read it.

Go to Scotty's old pages and find the two pages of distributor recurve instructions.

Both will help you understand what you are doing.

I will look up the information to get a better grip on this timing thing

So right now my mechanical is all in by 2500 RPM and as I posted above if I was to install heavy springs and return the vacuum can back to where it was that would limit the total timing, remember I have 46* BTDC @ 2500 RPM.

The vacuum timing would kick in as soon as the carb was off idle but the mechanical would not start to come in till say 2000 rpm.

Now this is just numbers I am throwing out and would be adjusted for best running and no pinging.

Remember I shift around 2000 RPM and cruse RPM is around the 1800 in OD in the high way and under 1400 RPM on back roads.

Or am I way off in my thinking before I read up on this

Dave ----

I was re-reading Dave's post here, and realized he has two fallacies.

A) Alcohol brings it's own oxygen.

Where Gary says stochiometric mixture for 10% is 14.04:1, that's chemistry. (by mass)

While what counts in an engine is heat and generated combustion byproduct (pushing on the piston.

Alcohol burns very cool.

Cool enough to light your hands on fire just for show.

You wouldn't do that with gasoline.

The Oxygen sensor is reading residual oxygen in the exhaust.

The AFR is inferring a ratio based on combustion byproduct.

But this isn't accurate when you're getting a bunch of oxygen from your fuel, and not just the ~20% of our atmosphere.

While it is reflecting how complete the combustion is, it's not giving an accurate idea of how much fuel you're flowing.

.

[Gary Lewis]

I was re-reading Dave's post here, and realized he has two fallacies.

A) Alcohol brings it's own oxygen.

Where Gary says stochiometric mixture for 10% is 14.04:1, that's chemistry. (by mass)

While what counts in an engine is heat and generated combustion byproduct (pushing on the piston.

Alcohol burns very cool.

Cool enough to light your hands on fire just for show.

You wouldn't do that with gasoline.

The Oxygen sensor is reading residual oxygen in the exhaust.

The AFR is inferring a ratio based on combustion byproduct.

But this isn't accurate when you're getting a bunch of oxygen from your fuel, and not just the ~20% of our atmosphere.

While it is reflecting how complete the combustion is, it's not giving an accurate idea of how much fuel you're flowing.

.

That's a very good point, Jim. I'd not thought about that.

So I Googled it and found this, which seems to make sense and fits with what you are saying. Basically it says to monitor lambda instead of AFR since the meter is assuming gasoline because it doesn't know what is in the tank.

So if Dave is running 10% ethanol his reading of 17 is actually ~16.24. (14.04/14.7*17 = 16.24)

[ArdWrknTrk]

That's a very good point, Jim. I'd not thought about that.

So I Googled it and found this, which seems to make sense and fits with what you are saying. Basically it says to monitor lambda instead of AFR since the meter is assuming gasoline because it doesn't know what is in the tank.

So if Dave is running 10% ethanol his reading of 17 is actually ~16.24. (14.04/14.7*17 = 16.24)

Which gives us a more accurate picture of fuel consumption, but not power generated.

Whether you want to measure in joules, BTU, Calories, watts or whatever.

[FuzzFace2]

Which gives us a more accurate picture of fuel consumption, but not power generated.

Whether you want to measure in joules, BTU, Calories, watts or whatever.

New carb showed up yesterday bit did not open the box yet. No time before bed time.

I am thinking of digging into the old carb a little for 2 reasons.

Just to see if the avcel pump tube is still in place and working. Same with the high speed rid & jet.

And last time I had the carb top off to adjust the rod & jet I found the bowl floor covered is rust. I would need to address this issue before the new carb goes on.

Got to work part of Saturday so see if I have time over the weekend.

Dave ----

[ArdWrknTrk]

New carb showed up yesterday bit did not open the box yet. No time before bed time.

I am thinking of digging into the old carb a little for 2 reasons.

Just to see if the avcel pump tube is still in place and working. Same with the high speed rid & jet.

And last time I had the carb top off to adjust the rod & jet I found the bowl floor covered is rust. I would need to address this issue before the new carb goes on.

Got to work part of Saturday so see if I have time over the weekend.

Dave ----

Are your tanks rusty Dave?

It certainly can't hurt to have an easily changed filter up near the carb.

And thanks for the reminder. I found that my filter coupler was looking a little frayed yesterday.

[FuzzFace2]

Are your tanks rusty Dave?

It certainly can't hurt to have an easily changed filter up near the carb.

And thanks for the reminder. I found that my filter coupler was looking a little frayed yesterday.

When installed they looked good from what I could see but with rust in the carb it has to be coming from some where?

I pulled the carb off motor and pulled it apart for a look-see.

It did have a little rust but not really bad.

The accel pump did not work when on the motor, 1 reason it was pulled other the rust.

On the bench it worked?

I also pulled out my Motor's book for professional that gave a better write up of the YF carb than the rebuild kit sheet.

The carb is missing a spring for the rod / jet but seams to be ok with out it. Made adjustments as per the book and carb went back on.

I did install a see through filter and will keep an eye on it when running off each tank to see what one has the rust issue.

I also adjusted the vacuum can on the dist. So it pulls in at a higher vacuum. I also bumped the timing up to 16 BTDC, total is about 48 BTDC now.

Took truck to work this morning and it ran great. My gage was 14.5 to 15.5 but most of the time 14.7 to 15.3.

WOT I did not see it drop leaner than 16.7.

So the old carb is working again and will run it till I am sure no rust will hurt the new carb.

Dave ----

[ArdWrknTrk]

Are your tanks rusty Dave?

It certainly can't hurt to have an easily changed filter up near the carb.

And thanks for the reminder. I found that my filter coupler was looking a little frayed yesterday.

When installed they looked good from what I could see but with rust in the carb it has to be coming from some where?

I pulled the carb off motor and pulled it apart for a look-see.

It did have a little rust but not really bad.

The accel pump did not work when on the motor, 1 reason it was pulled other the rust.

On the bench it worked?

I also pulled out my Motor's book for professional that gave a better write up of the YF carb than the rebuild kit sheet.

The carb is missing a spring for the rod / jet but seams to be ok with out it. Made adjustments as per the book and carb went back on.

I did install a see through filter and will keep an eye on it when running off each tank to see what one has the rust issue.

I also adjusted the vacuum can on the dist. So it pulls in at a higher vacuum. I also bumped the timing up to 16 BTDC, total is about 48 BTDC now.

Took truck to work this morning and it ran great. My gage was 14.5 to 15.5 but most of the time 14.7 to 15.3.

WOT I did not see it drop leaner than 16.7.

So the old carb is working again and will run it till I am sure no rust will hurt the new carb.

Dave ----

Wow, 16 seems a lot of initial timing.

If you had spark knock before I don't understand how that would help.

But, it certainly has to help with power.

Do you find it cranks slow or kicks back when starting?

Is the timing retard while cranking functional on your truck?

[FuzzFace2]

Wow, 16 seems a lot of initial timing.

If you had spark knock before I don't understand how that would help.

But, it certainly has to help with power.

Do you find it cranks slow or kicks back when starting?

Is the timing retard while cranking functional on your truck?

Normally I would say the same thing at 16* BTDC.

When I had it set to 10*-12* it would crank a long time before starting.

Now some of that could be the accel pump may have stopped work at the same time I don't know?

I get no kick back when starting, 1 pump and it lights off with a tap of the key. Real close to what my 02 Durango EFI 5.9 dose on starting.

I don't know if the timing retard works or not?

How would one go about checking if it did or not?

Guessing check timing at idle and say its 16* BTDC.

Then with a helper have them start the motor and when checking with the light see if it starts at say 8* BTDC?

Oh I also did not have any pinging and that was a vary good thing!

With the run to work yesterday morning (1am) it was about 45*f out and the AFR was high 14's to low 15's at 65 - 70 MPH and was happy with that readings and the truck ran great.

On the way home (4pm) it was about 70*f out and the AFR was high 13's to low/mid 14's at 45 - 55 MPH (back roads) wish the readings were like on the morning run but the truck still ran great.

Right now I am keeping an eye on the see through filter to see what tank may have rust issues before doing much more with tuning for MPG and a carb swap.

Dave ----

oh wait to reading are off because of the 10% gas I run so it is running richer right?

Darn it

 

[Gary Lewis]

Wow, 16 seems a lot of initial timing.

If you had spark knock before I don't understand how that would help.

But, it certainly has to help with power.

Do you find it cranks slow or kicks back when starting?

Is the timing retard while cranking functional on your truck?

Normally I would say the same thing at 16* BTDC.

When I had it set to 10*-12* it would crank a long time before starting.

Now some of that could be the accel pump may have stopped work at the same time I don't know?

I get no kick back when starting, 1 pump and it lights off with a tap of the key. Real close to what my 02 Durango EFI 5.9 dose on starting.

I don't know if the timing retard works or not?

How would one go about checking if it did or not?

Guessing check timing at idle and say its 16* BTDC.

Then with a helper have them start the motor and when checking with the light see if it starts at say 8* BTDC?

Oh I also did not have any pinging and that was a vary good thing!

With the run to work yesterday morning (1am) it was about 45*f out and the AFR was high 14's to low 15's at 65 - 70 MPH and was happy with that readings and the truck ran great.

On the way home (4pm) it was about 70*f out and the AFR was high 13's to low/mid 14's at 45 - 55 MPH (back roads) wish the readings were like on the morning run but the truck still ran great.

Right now I am keeping an eye on the see through filter to see what tank may have rust issues before doing much more with tuning for MPG and a carb swap.

Dave ----

oh wait to reading are off because of the 10% gas I run so it is running richer right?

Darn it

Yes, running ethanol means your true AFR is richer than what you are seeing on the gauge. But you aren't too far off now.

On the retard, you can test it by starting the engine and then pulling the R/LB wire from the starter relay/solenoid and turning the key to Start. As seen below that will send 12v to the ignition module telling it to retard. If you have a timing light on it you should see the timing retard, or at least hear the RPM drop.