Bullet Bob wrote:

HudginJ3 wrote:

The AEM that I have has two plugs that go into the back of it. I haven't tried but it looks like you can reverse them and put them in the wrong position unless your carefull. Mine read an average of 13.2 - 13.5 jumping all over the place. Today I put the next smaller jets in my carb and now it reads 13.4 - 13.6 still jumping all over the place. I don't know if it's broken or not. I think a jet change would make a bigger difference in the reading or AFR.

Hey Doug, are you  running an EB pot?  If so, what Jets did you change to and from.  I have a spreadsheet I ginned up that calculates the percent change between jet/rod combos.  Looks like your change was just over 1.5 %.  I'd like to stuff those jets/rods in my spreadsheet and see what it spits out.

BB1

 
Sorry for the late reply. Been concentrating on the bash thrash a little more diligently being it's a week earlier than I had planned. But I have the 1411 EB pot on my engine. I've always thought it was to rich. On the EB chart I went down to the .104 jets and 071 X 047 metering rod (19). From there on the advise of a friend I went to the .101 jets that you are inquiring about. With no significant change I went to the .098 jets and the 070 X 037 metering rods based on the 1406 calibration chart. Still no change on the AFR and it ran so crappy that I only drove it about 4 miles. But I dropped one of the metering springs and lost it. I put it all back to (19) position except for the springs which I need yet to fix. I just got back from a 104 mile drive looking at Blue Bonnets.  As expected it is still running too rich. The AFR is still showing in 13.5 area and it has a big hesitation leaving a stop I'm pretty sure because of the springs I put in it. I skipped the .100 jet. I think that might be the area I'm looking for but I don't know how to select the metering rod. I don't know the theory how to select them. That is why I got the AFR. My AFR is the same 30-4110 that you have. I think they are both broken.

HudginJ3 wrote:

Bullet Bob wrote:

HudginJ3 wrote:

The AEM that I have has two plugs that go into the back of it. I haven't tried but it looks like you can reverse them and put them in the wrong position unless your carefull. Mine read an average of 13.2 - 13.5 jumping all over the place. Today I put the next smaller jets in my carb and now it reads 13.4 - 13.6 still jumping all over the place. I don't know if it's broken or not. I think a jet change would make a bigger difference in the reading or AFR.

Hey Doug, are you  running an EB pot?  If so, what Jets did you change to and from.  I have a spreadsheet I ginned up that calculates the percent change between jet/rod combos.  Looks like your change was just over 1.5 %.  I'd like to stuff those jets/rods in my spreadsheet and see what it spits out.

BB1

 
Sorry for the late reply. Been concentrating on the bash thrash a little more diligently being it's a week earlier than I had planned. But I have the 1411 EB pot on my engine. I've always thought it was to rich. On the EB chart I went down to the .104 jets and 071 X 047 metering rod (19). From there on the advise of a friend I went to the .101 jets that you are inquiring about. With no significant change I went to the .098 jets and the 070 X 037 metering rods based on the 1406 calibration chart. Still no change on the AFR and it ran so crappy that I only drove it about 4 miles. But I dropped one of the metering springs and lost it. I put it all back to (19) position except for the springs which I need yet to fix. I just got back from a 104 mile drive looking at Blue Bonnets. As expected it is still running too rich. The AFR is still showing in 13.5 area and it has a big hesitation leaving a stop I'm pretty sure because of the springs I put in it. I skipped the .100 jet. I think that might be the area I'm looking for but I don't know how to select the metering rod. I don't know the theory how to select them. That is why I got the AFR. My AFR is the same 30-4110 that you have. I think they are both broken.

Out of curiosity, at 13.5 A/F ratio why do you think its running rich?  At idle or cruise I would agree that is rich, but on transition throttle or acceleration that is actually on the lean side.  The idea that the A/F ratio should be stoich at all times is incorrect.  Engines make max power at more like 12.5:1.  If you're experiencing a bog leaving the line hard this is most often actually caused by a momentary lean condition.  Often its assumed that the carb is going too rich, when its actually the exact opposite.  Trying to lean it out either does nothing or makes the issue worse.  My advice would be try going the other way and see if it improves.  BUT, on a bog like that I would look at the accelerator pump first.  The shot may be too small.  If that does nothing or has marginal effect go back to the stock setting and go up one rod size from stock and see if it gets better.  If that's better but not perfect try a bit more accelerator shot with that rod and see what happens.

If the carb is too big you'll often find that without a lot of real trickery you aren't going to get it perfect everywhere.  This is why a smaller carb has good street manners while leaving tope end power on the table and a bigger carb does the opposite.  If carbs could have been made perfect everywhere there would have been no reason for OEMs to go to EFI.  They had all the money and engineering people in the world and still found it an impossible task.  We often forget that coming from diving new vehicles. 

A/F ratio gauges are great for tuning EFI applications, but I've never been a fan in a carb application.  Reason being, you really need to datalog the results along with other operating parameters to get a complete picture and this is most easily done with EFI where you can log live sensor data along with A/F ratio. 

It's very hard to tune by watching the gauge and drive **and** as you noticed it will jump around especially at part throttle and cruise. I'd tune it to what the engine likes (reading plugs is great, as well as how it idles and SOTP in general) and then use the A/F gauge as a reference. I remember back when I would do tuning people would get hung up on numbers, they wanted their engine to be "by the book" and couldn't understand why theirs ran better richer or leaner than others or liked 30 degrees of total timing instead of 32, or 28, etc etc.

My sensors used to die regularly then I saw a write up on the problem. The bung in the headers were at almost exactly 90 degrees. I changed to rotate them up to more than 20 degrees. So no moisture could stay in the sensor. No problems since. You don't want the connector end pointing down at all but up at-least 15 to 20 degrees. 

DC wrote:

My sensors used to die regularly then I saw a write up on the problem. The bung in the headers were at almost exactly 90 degrees. I changed to rotate them up to more than 20 degrees. So no moisture could stay in the sensor. No problems since. You don't want the connector end pointing down at all but up at-least 15 to 20 degrees. 

Would you be able share that write up?
How did the sensors fail?...guessing the write up explains problem.

Well, I may have stumbled onto the problem...and why AEM is having it.  Modern Auto Perf. is probably...maybe...going to refund my $$$ and asked that I look on their website to see what I would like to replace it with.  I was checking out the Innovate stuff and can probably be happy with their MTX-L or MTX-L Plus.  While checking out the specs I noticed that it says it can be calibrated...hmmmm.  AEM says no cal required as the LSU 4.9 has a "laser etched" resistor installed that never needs to be calibrated in free air.   More Hmmmmm?
So I found and read the Install Manual for the Innovate unit and, sure enough, it requires calibration in the beginning and is recommended periodically thereafter.  Butt (TS&T) it uses the Bosch LSU 4.9 sensor just like the AEM. 
Apparently AEM is adding the resistor to the sensor pigtail and I'm wondering if that could be the cause of the issue.
I'll likely be ordering an Innovate setup and see what happens.  Re-cal could be a PIA but if it works as advertised and only requires it once a year or so it shouldn't be too much trouble with the lift, and the fact that I only plan to rely on the thing when messing with the tune.

More to follow, back to the re-loading bench.

BB1
 

Last edited by Bullet Bob (4/10/2020 11:02 AM)

I installed an AEM 30-0300 AFR gauge last year and used it to tune my 302 with an Edelbrock 1403 carb.  The AEM gauge is still working perfectly for me.  I am happy with it.  After looking at the reviews of the unit on Amazon, there are a few poor reviews; however, most experiences seem to be positive like my own experience has been.

I just looked at the 30-4110 on Amazon.  That model does not have a good review score.  The 4110 dial only goes from 11 to 17 and there are no selection buttons on the face.  My 0300 model dial goes from 8 to 20 and while I was tuning the carb I did see values below 11 and above 17.  Definitely looks like the 4110 model should be avoided.  Maybe all the batches with that model are "bad".  Even though the "0300" model number is smaller than the "4110" number, it looks like the "0300" model is a newer design.  Perhaps that is why my gauge has been fine.

It is helpful to be able to see the AFR, even when it is way out of target, so that you know you're seeing the changes as you tune the mixture back to where it should be.

When AFR is at either end, you have no visual indication or value doesn’t change?

Just trying to understand how they have it setup.

hey sally 6 i have set up same gauge in this days , works from 1 starts . Needs some help ?
 

Send the man a nice check Bullet Bob.........He  thinks you're ME!

Bullet Bob wrote:

I'll put some variations in the spreadsheet and let you know.  So, I think you are running 98 jets and #19 rods.  Correct?
Are you running a 351 or 393 or bigger engine?  I would think that part of the stumbling problem could be a bit too much carb.  For street work I always liked a the smallest carb that would give decent performance....off-idle performance is much better usually.

BB1
 

 
Thanks for the spread sheet. I don't know if it makes a difference, my pot is a 1411. I don't think so but I will do checking. I'm contemplating trading my AFR for a 30-0300. I think it's new enough to trade under warranty.