AFM Adjustment

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Kossco
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Re: AFM Adjustment

Post by Kossco » Wed Dec 16, 2020 2:25 pm

Wow, thank you for that amazing reply!

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tommu
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Re:

Post by tommu » Wed Mar 24, 2021 7:30 pm

Gypsie wrote:
Wed May 12, 2010 12:18 pm
airkooledchris wrote: On a side note id love to get a larger clearer file from the original post. the images and text are great, but it's a real strain to be able to make out all of the text and fine details. if the originals are larger/clearer id love to see them sometime.

Me too. Maybe you could put them in a book...
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Amskeptic
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Re: Re:

Post by Amskeptic » Mon Apr 19, 2021 3:56 pm

tommu wrote:
Wed Mar 24, 2021 7:30 pm
Gypsie wrote:
Wed May 12, 2010 12:18 pm
airkooledchris wrote: On a side note id love to get a larger clearer file from the original post. the images and text are great, but it's a real strain to be able to make out all of the text and fine details. if the originals are larger/clearer id love to see them sometime.

Me too. Maybe you could put them in a book...
Bump

:flower:
I will be working on the illustrations at some point and will try to improve clarity.
How many DPI shall I save them at? How many pixels you all want?
Colin

p.s. no Steve Kent, no. A lean mixture that is real lean does NOT extend the burn into the exhaust causing Armageddon, because the whole point of this exercise (that shows up on the CHT gauge, hello)
is that we are starving the burn. There is no further combustion left by the time the exhaust is going out the port. My late model bus exhaust system with the headless bolt flange on the left manifold is now at 133,000 miles since new, 70,000 miles past when I dremelled all the bolt heads off, it is terrible to look at, but not a wisp of soot leaking from the gasket. Let's chill on the catastrophisizing shall we?)
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 206,865 miles
Naranja - 77 Westy . . . 132,040 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 91 Lexus LS400 . . . 94,225 miles

72Hardtop
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Re: AFM Adjustment

Post by 72Hardtop » Sun May 09, 2021 12:51 am

Nothing wrong with running 15-16 afr at cruise. It is actually cooler than 14.7 at cruise. The added heat comes into play with throttle position (excess) not part throttle condition/s.
1972 Westy tintop
2056cc T-4 - 7.8:1 CR
Weber 40mm Duals - 47.5idles, 125mains, F11 tubes, 190 Air corr., 28mm Vents
96mm AA Biral P/C's w/Hastings rings
42x36mm Heads (AMC- Headflow Masters) w/Porsche swivel adjusters
71mm Stroke
Web Cam 73 w/matched Web lifters
S&S 4-1 exhaust w/Walker 17862 quiet-pack
Pertronix SVDA w/Pertronix module & Flamethrower 40K coil (7* initial 28* total @3200+)
NGK BP6ET plugs
002 3 rib trans
Hankook 185R14's

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sgkent
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Re: Re:

Post by sgkent » Mon Sep 06, 2021 10:37 am

Amskeptic wrote:
Mon Apr 19, 2021 3:56 pm
tommu wrote:
Wed Mar 24, 2021 7:30 pm
Gypsie wrote:
Wed May 12, 2010 12:18 pm
airkooledchris wrote: On a side note id love to get a larger clearer file from the original post. the images and text are great, but it's a real strain to be able to make out all of the text and fine details. if the originals are larger/clearer id love to see them sometime.

Me too. Maybe you could put them in a book...
Bump

:flower:
I will be working on the illustrations at some point and will try to improve clarity.
How many DPI shall I save them at? How many pixels you all want?
Colin

p.s. no Steve Kent, no. A lean mixture that is real lean does NOT extend the burn into the exhaust causing Armageddon, because the whole point of this exercise (that shows up on the CHT gauge, hello)
is that we are starving the burn. There is no further combustion left by the time the exhaust is going out the port. My late model bus exhaust system with the headless bolt flange on the left manifold is now at 133,000 miles since new, 70,000 miles past when I dremelled all the bolt heads off, it is terrible to look at, but not a wisp of soot leaking from the gasket. Let's chill on the catastrophisizing shall we?)
a overly lean mixture places the fuel molecules farther apart. As a result the burn is much slower. As a result the exhaust port and stack temp WILL go up as the burn extends into the exhaust port. Google "Lean backfire".
Thank You -

Merlin The Wrench

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Amskeptic
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Re: Re:

Post by Amskeptic » Mon Sep 06, 2021 12:10 pm

sgkent wrote:
Mon Sep 06, 2021 10:37 am
a overly lean mixture places the fuel molecules farther apart. As a result the burn is much slower. As a result the exhaust port and stack temp WILL go up as the burn extends into the exhaust port. Google "Lean backfire".
Yes, thank-you for the explanation, now talk to Len Hoffman and the guys over at Lycoming and the graphs that *show* EGTs dropping as you lean past lean.

Image

Image
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 206,865 miles
Naranja - 77 Westy . . . 132,040 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 91 Lexus LS400 . . . 94,225 miles

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sgkent
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Re: AFM Adjustment

Post by sgkent » Mon Sep 06, 2021 12:56 pm

the egt will drop once you get really lean but the burn will continue into the port and overheat the exhaust valve. On an air cooled VW engine your best mixture is not the most efficient one. That is why VW discontinued their air cooled engines in smog countries. If you read the Lycombing literature you will also see that any head temp over 380F - 400F is considered damaging to the engine. There is a reason drag racers burn alcohol - it burns really rich so they can use the extra fuel to cool the engine. When that un-burned fuel hits the outside air it creates the flames you see. The moral is don't run your air cooled bus engine at 14.7 or leaner unless you are on flat and level at low speeds. Waste the fuel and run in the low 13's except at light cruise which 14.5 - 14.7 is ok, no hills no headwinds. At light cruise the EGR will add inert air and let the engine run more efficiently and cooler. Like Len, I raced and won plenty of trophies in GP and FP also. Built heads like Len does today.
Thank You -

Merlin The Wrench

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Amskeptic
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Re: AFM Adjustment

Post by Amskeptic » Wed Sep 22, 2021 9:05 am

sgkent wrote:
Mon Sep 06, 2021 12:56 pm
the egt will drop once you get really lean but the burn will continue into the port and overheat the exhaust valve. Like Len, I raced and won plenty of trophies in GP and FP also. Built heads like Len does today.

... but did you like my photographs? Those bleached intake valves? The white frosted pistons?
Now at 142,000 miles.
Colin

Image
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 206,865 miles
Naranja - 77 Westy . . . 132,040 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 91 Lexus LS400 . . . 94,225 miles

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