AFM Redux

Carbs & F.I.

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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 . . . . . . . . . . . 111,155 miles
Chloe - 1970 bus . . . . . . . . . . . 206,820 miles
Naranja - 1977 Westfalia . . . . . 103,007 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 1991 Lexus LS400 . . . 78,885 miles

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