AFM Redux

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Amskeptic
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AFM Redux

Post by Amskeptic » Wed Jul 10, 2019 5:34 pm

aircooledchris wrote:
Amskeptic wrote:
Sat Jul 06, 2019 7:44 pm

I have been fooling with the air flow meter. Right when I am about to rewrite the AFM article because I have a new insight, some thing or another blows me off the path. I have tried this matrix:

A) Weak Cog Spring ................ Lean Wiper
B) Strong Cog Spring ............... Rich Wiper

A) Better Fuel Economy and cooler DD readings, but only to a point, 17 mpg 410* but too lean skyrockets the CHTs to 430+.
B) Better Power Worse Fuel Economy and certifiably cooler DD readings at 12 mpg.
Anytime I ponder the eventual move back to the midwest (it's happening sooner than later) - I remember the damned bugs. Yea, there's some nice warmer weather than we get here on the coast, but camping still sucks with all of the friggin bugs.

Anyway, I am happy to hear there's progress with figuring these AFM's out further. I recently buttoned up a bunch of leaks in the system and needed to lean out the AFM. I went about as far lean as you can put the silver wiper and it's still pretty darned rich. I need to revisit just how the cog is set now and see if I can find the happy medium again. It's running cool, but it's cold startup/idle is around 9.2 AFR currently...
Hello Chris,
I have never seen a wiper so lean that you were running out of room on the board. If the silver fuel pump break is about to go around the other end of the fuel pump contact, you just carefully bend the wire to only open the contacts about 1-2mm.

I think you are a candidate for setting the cog tighter until the mixture is clearly lean when you take off the reference hose. A tighter cog may mean that you need to richen the wiper a bit so you end oup with a leanish idle and known good mixture at speed ( established because your CHTs are normal).
BobD - 1978 Bus . . . . . . . . . . . 112,660 miles
Chloe - 1970 bus . . . . . . . . . . . 206,820 miles
Naranja - 1977 Westfalia . . . . . 112,220 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 1991 Lexus LS400 . . . 78,885 miles

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airkooledchris
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Re: AFM Redux

Post by airkooledchris » Tue Aug 13, 2019 12:39 pm

Admittedly, I did forget to return to this for a VERY long time. The issue was baffling to me, so I threw the kitchen sink at it and have no idea where I am at anymore. My AF-R gauge has since gone into an error state, so it may not have been as accurate as id hoped. I am looking forward to finding what the mixture is now though - as the head temps have been terrific with the current mixture.

I finally got my electronic ignition system back up and running again this past weekend, so I will be revisiting the mixture fully in the next few days. I removed a working system and incorrectly assumed it should still work when I reinstalled it - but apparently I killed the electronic ignition module that mounts on the firewall during that timeframe.

Anyway, i'll report back once I can get the AF gauge removed and re-calibrated in the next few days.
1979 California Transporter

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Amskeptic
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Re: AFM Redux

Post by Amskeptic » Mon Aug 19, 2019 6:42 pm

airkooledchris wrote:
Tue Aug 13, 2019 12:39 pm
Admittedly, I did forget to return to this for a VERY long time. The issue was baffling to me, so I threw the kitchen sink at it and have no idea where I am at anymore. My AF-R gauge has since gone into an error state, so it may not have been as accurate as id hoped. I am looking forward to finding what the mixture is now though - as the head temps have been terrific with the current mixture.

I finally got my electronic ignition system back up and running again this past weekend, so I will be revisiting the mixture fully in the next few days. I removed a working system and incorrectly assumed it should still work when I reinstalled it - but apparently I killed the electronic ignition module that mounts on the firewall during that timeframe.

Anyway, i'll report back once I can get the AF gauge removed and re-calibrated in the next few days.

Chris! Incremental and note-takey wins the race!
103* Texas today, 410* @ 65 mph and a fabulous 11.8 mpg! See?
Colin :blackeye:
(I say we tear out the fuel gauge and the CHT gauge!)
BobD - 1978 Bus . . . . . . . . . . . 112,660 miles
Chloe - 1970 bus . . . . . . . . . . . 206,820 miles
Naranja - 1977 Westfalia . . . . . 112,220 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 1991 Lexus LS400 . . . 78,885 miles

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