AFM Adjustment

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Amskeptic
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Re: AFM Adjustment

Post by Amskeptic » Mon May 07, 2012 7:47 pm

1978 Bus AFM Adjustment Results

posted April 2011

This original factory build engine has original exhaust and fuel injection at 69,000 miles just this morning.
Compression most recently was 130/135/125/140. No valve seat migration noted in the before/after hydraulic valve adjustment check. (1 1/2 preload)

Ambient temps 84* no wind, Interstate 10 westbound in Florida and Interstate 75 northbound to Atlanta GA.

My original AFM adjustments were set in Yuma, AZ in February to yield a 12.5 air/fuel ratio at full throttle at 3,000 rpm and a 70 mph cruise at 13.5. The car has been driven hard for the last 4,000 miles with these settings.

The AFM adjustments below are in reference to the above "base line". The "A" adjustment is the wiper which has little teeth to reference (originally at 3-3/4 teeth from base point, so less than that is leaner), and the "B" adjustment is the black cog with the number of teeth increments from my baseline (+ is CCW towards rich). Idle mixture screw "C" number is from seated position, more is leaner.

....MPH........A........B.........C........CHT........A/F..........MPG.........notes
.....65........2.5.......7+.......2.5.......415........15.7........................pinging!
.....70.........................................435........15.6.....................................
.....75..........................................NO........................


....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65........2.5......14+.......3..........420.........14.4..................................
.....70...........................................430.........13.6..................................
.....75...........................................447.........13.4..................................


....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65.........3..........0........2.5........406.........14.1...................................
.....70...........................................435.........13.8...................................
.....75............................................NO................................ 450* CHT

....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65........3.5.......6+....................400.........11.9.....................idle 15.5
.....70............................................413................................................
.....75........................................................................................no test


....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65........3.75.....3+.......3.5........385..........11.7..................................
.....70...........................................400..........11.6..................................
.....75...........................................410......................................63*amb


....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65..........4........6-.........2.5.......400.........11.9........................idle 18
.....70...........................................416..........11.8.................................
.....75...........................................447..........12.0....(full throttle hill)......


....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65..........4........6+.......4.5.......393..........11.5.........17.5.....using the
.....70...........................................398.........11.3.......itinerant-air-cooled
.....78............................................424.........11.3.......................method


....MPH........A.........B.........C.........CHT.........A/F..........MPG.........notes
.....65..........4.........0.....................385.........11.4.........17.3........63*amb
.....70............................................395.........11.4.................................
.....75............................................415........11.4..................................
*************************************************** 81*amb
......65...........................................395.................................................
......70...........................................410.................................................
......75...........................................425.................................................

I have some guesswork conclusions from the above, but look forward to any wonks chiming in. The only critical conclusion I came up with was
Do Not Assume! I ran the LM-1 at a PigRich 11.4 expecting horrible fuel economy, and instead got the best fuel economy and the lowest CHT readings!

Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: AFM Adjustment

Post by Westy78 » Mon May 07, 2012 8:22 pm

Amskeptic wrote:1978 Bus AFM Adjustment Results
Colin


I've noticed that even the slightest incline/decline or head/tail wind can make a huge difference in the numbers I see on my CHTs. As well as ambient temps. The worst are those long stretches of road that only gain a few feet in a mile but you are constantly climbing even though the road looks flat.
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Re: AFM Adjustment

Post by RSorak 71Westy » Tue May 08, 2012 10:16 am

CHT's reflect engine load better than anything I have seen. They react almost instantly to the slightest change.
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.

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Re: AFM Adjustment

Post by Amskeptic » Wed May 09, 2012 7:40 am

Westy78 wrote:
Amskeptic wrote:1978 Bus AFM Adjustment Results
Colin


I've noticed that even the slightest incline/decline or head/tail wind can make a huge difference in the numbers I see on my CHTs. As well as ambient temps. The worst are those long stretches of road that only gain a few feet in a mile but you are constantly climbing even though the road looks flat.
If you are referring to your Raby engine, can you give us some hard numbers, including ambient temps?
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: AFM Adjustment

Post by Bleyseng » Wed May 09, 2012 9:46 am

For my Westy, coming out of Maupin up that long hill I hit 405F CHT's on a 85-90F day mostly in 4th gear. I did have to downshift to 3rd gear some cuz I was follow Wayne and Michelle .
Geoff
77 Sage Green Westy- CS 2.0L-160,000 miles
70 Ghia vert, black, stock 1600SP,- 139,000 miles,
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Re: AFM Adjustment

Post by drober23 » Sat Jul 21, 2012 12:44 pm

Adding one more bit of observed data:

My AFM changed a bit when I adjusted my valves on my last tune-up. No individual valve needed more than a 20° adjustment, but all the exhaust valves were just a little tight. Not sure if this is due to the way I adjusted them last, or other conditions (engine has 7,000 miles on it. I had adjusted the valves at 4500 miles, and now again at 7,000).

Anyway, "cruising" AFM dropped to about 12.7 (from 13.1). WOT AFM dropped a bit as well. Also, I realized I did not have my oil temp sensor all the way seated. I turned it tight (several turns) and it pokes into the oil in the sump now. So my oil temps read higher that before. My earlier temps were not reflecting the real oil temp.

That said: Ambient temp 103°, ~35% humidity. Drive home at 65 mph, little to no wind. At the end of the drive (26 miles, mostly highway) the CHT was 401° and the oil temp was 249°. Same drive 2 days later, ambient temp 76° and about the same humidity. CHT was 371° and oil temp was 221°. So the difference in ambient temperature resulted in about a 1-1 increase in CHT and oil temps.

I find that after about 20 minutes, the CHT and oil temps stabilize and do not continue to increase unless I drive harder. Did a ton of driving in the last few months, including about 1100 miles in 6 days (vacation trip). The biggest realization I came upon is that wind plays a bigger role in CHT than I first thought. I was getting to be able to predict what my temp would be without looking based on speed, grade, and wind.
DJ

'75 Westfalia, '79 Deluxe
(plus more busses than sense)

In a time of chimpanzees I was a monkey

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Amskeptic
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Re: AFM Adjustment

Post by Amskeptic » Tue Jul 24, 2012 9:22 am

drober23 wrote: I find that after about 20 minutes, the CHT and oil temps stabilize and do not continue to increase unless I drive harder.

wind plays a bigger role in CHT than I first thought.
Takes even longer to rise to the "homeostasis" point when driving all day.

Yes yes yes. My CHT gauge is both an altimeter and a windsock.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: AFM Adjustment

Post by luftvagon » Sat Nov 10, 2012 11:35 am

Colin,

I think we should work on providing the original specifications, and instructions on how to revert to OE.
I'm doing the research to find the original spring rate in grams, and the original wiper position. I believe the original spring rate is measured at full opening, and the original wiper position is measured by intersecting the closed voltage, and full open voltage.
In addition to, I will be trying to source the original board, wiper, and temperature sensor, should one feel the need to rebuild their own. The default factory settings will be a must.

I have already found some numbers, however, I will share them if my additional research proves to be accurate.
1981 Volkswagen Vanagon Westfalia - air-cooled Type4 1970cc CV (hydraulic lifters, 42x36 valves, stock cam, microSquirt FI with wasted spark ignition)
1993 Ford F-250 XL LWB Extended Cab 7.3L IDI

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Re: AFM Adjustment

Post by Amskeptic » Sat Nov 10, 2012 6:14 pm

luftvagon wrote:Colin,

I think we should work on providing the original specifications, and instructions on how to revert to OE.
I'm doing the research to find the original spring rate in grams, and the original wiper position. I believe the original spring rate is measured at full opening, and the original wiper position is measured by intersecting the closed voltage, and full open voltage.
In addition to, I will be trying to source the original board, wiper, and temperature sensor, should one feel the need to rebuild their own. The default factory settings will be a must.

I have already found some numbers, however, I will share them if my additional research proves to be accurate.
You can PM Steve Kent on theSamba, and he can provide you with spring load in grams at initial opening. Be forewarned, however, that you are barking up a tree whose leaves are all the variables that crop up and grow in an engine over its lifetime. These different variables, like valve guide clearances, piston ring gap positions, hose integrity, crap in the breather, EEC valve/charcoal tank HCs, timing curve variations, etc, will render any magical factory oe base point utterly moot. We want *your* engine happy, it will tell you what it needs. Every factory AFM adjustment I have ever run into near sea level is lean with a middle-aged-to-tired engine.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: AFM Adjustment

Post by slow.bus » Mon Mar 30, 2015 6:28 am

Hello,

Does anyone have some AFR guidelines for cold starts below freezing? ie what should my AFR be immediately after it starts - when it is freezing outside?

I modified a spare AFM in the early fall and had the camper running (and starting fine) just like I wanted (a bit richer on the highway etc) ... but as the winter hit and snow fell - the camper basically refused to start. I checked all temp. sensors, ignition, CSV etc etc and all is in spec.

When I am able to start it (more often now as the weather is getting better) it starts at about 10.5, then steadily climbs to 14.7 ... then to 15.6 or so (where it bogs down a bit) ... then settles to about 14.7.

My running assumption is that my changes are TOO rich at start up in cold weather - and interfere with the ECU's cold start routine. Once at temperature for driving, or for hot starts, or warm starts up to a few hours later - it's great.

Has anyone else dealt with this ... tuning the AFM / AFR and have it start fine in both warm and very cold environment start-ups?

Note, the camper never liked to start in freezing temperatures ... but I could always coax it to start with a little cold start spray. I almost never drive it when cold (salt on the roads) ... but would rather have the option if possible

Note, camper is a 1981 vanagon, federal model
1981 Westfalia
Dents & Dings, but no Rust

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Re: AFM Adjustment

Post by airkooledchris » Mon Mar 30, 2015 9:13 am

slow.bus wrote:Hello,

Does anyone have some AFR guidelines for cold starts below freezing? ie what should my AFR be immediately after it starts - when it is freezing outside?

I modified a spare AFM in the early fall and had the camper running (and starting fine) just like I wanted (a bit richer on the highway etc) ... but as the winter hit and snow fell - the camper basically refused to start. I checked all temp. sensors, ignition, CSV etc etc and all is in spec.

When I am able to start it (more often now as the weather is getting better) it starts at about 10.5, then steadily climbs to 14.7 ... then to 15.6 or so (where it bogs down a bit) ... then settles to about 14.7.

My running assumption is that my changes are TOO rich at start up in cold weather - and interfere with the ECU's cold start routine. Once at temperature for driving, or for hot starts, or warm starts up to a few hours later - it's great.

Has anyone else dealt with this ... tuning the AFM / AFR and have it start fine in both warm and very cold environment start-ups?

Note, the camper never liked to start in freezing temperatures ... but I could always coax it to start with a little cold start spray. I almost never drive it when cold (salt on the roads) ... but would rather have the option if possible

Note, camper is a 1981 vanagon, federal model

The short answer is no, not really. When it's setup just perfect for the highway and warm driving conditions, it will suffer when it's cold.

Here is my AFM readings for a short little run around the neighborhood last night. This is my highway and/or hot weather AFM, which is setup for max cooling at extended highway speeds:

Image


When it's cold outside this AFM doesn't want to start the engine. The AFR will be around 9 at first, which the motor dislikes. I can however still get it started so I just live with it. Over the winter months, assuming im not going on any long highway runs, I have a spare AFM that is setup more lean and I just run that.
1979 California Transporter

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Re: AFM Adjustment

Post by Amskeptic » Mon Mar 30, 2015 9:50 am

airkooledchris wrote: When it's setup just perfect for the highway and warm driving conditions, it will suffer when it's cold.
The AFR will be around 9 at first, which the motor dislikes. I can however still get it started so I just live with it. Over the winter months, assuming im not going on any long highway runs, I have a spare AFM that is setup more lean and I just run that.
Assuming that you have a too-rich when cold, can you bias your adjustments onto the wiper/flap to handle warmer conditions, and throw more lean down onto the mixture adjustment screw?
i.e.
Lean the mixture screw to 7 or 8 turns out.
Increase idle speed to 1,050.
Adjust wiper to compensate for the above leaning out.
Trim with cog.
You want as lean of an idle as possible, with as much air flow as possible. Then see if cold idle is somewhat improved. The factory has the cold idle mixture compensation pretty darn rich, don't they? That is because in the day, the rest of the mixture was pretty darn lean.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: AFM Adjustment

Post by slow.bus » Mon Mar 30, 2015 11:37 am

Amskeptic wrote:
airkooledchris wrote: When it's setup just perfect for the highway and warm driving conditions, it will suffer when it's cold.
The AFR will be around 9 at first, which the motor dislikes. I can however still get it started so I just live with it. Over the winter months, assuming im not going on any long highway runs, I have a spare AFM that is setup more lean and I just run that.
Assuming that you have a too-rich when cold, can you bias your adjustments onto the wiper/flap to handle warmer conditions, and throw more lean down onto the mixture adjustment screw?
i.e.
Lean the mixture screw to 7 or 8 turns out.
Increase idle speed to 1,050.
Adjust wiper to compensate for the above leaning out.
Trim with cog.
You want as lean of an idle as possible, with as much air flow as possible. Then see if cold idle is somewhat improved. The factory has the cold idle mixture compensation pretty darn rich, don't they? That is because in the day, the rest of the mixture was pretty darn lean.
Colin
Thank you both for the details - exactly what I was hoping for (the specifics) & I really like the idea of 2 separate AFM's.

The problem for me testing cold starts in the winter is that I really only get 1 shot at it each night ... I had it starting OK for a bit, but it got super lean in the late stages of the warm up cycle and I had to turndown the idle screw to prevent it from stalling ... which then prevented it from starting the next evening ...

I've been maintaining a low idle speed - for no logical reason, just habit I never thought to change. I will increase idle speed and make some adjustments as necessary and see how that works this week.

Funniest part, is that now that it is getting warm ... I cannot really test it anymore in 'like' conditions.
1981 Westfalia
Dents & Dings, but no Rust

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Re: AFM Adjustment

Post by Amskeptic » Mon Mar 30, 2015 2:08 pm

slow.bus wrote: Funniest part, is that now that it is getting warm ... I cannot really test it anymore in 'like' conditions.
. . . which, over in my lizard sunning on a rock universe is hardly the worst news.

These engines had no provision to improve cold air flow as the valve guides and other idle vacuum killers sprouted up during the aging of the engine. You need as much air flow as possible during cold idle.

The thing about these engines that fools people, is that they were hard-engineered (as in, you can't get to it) to *lean out* if a stall was imminent. You can see your ratio dive lean as you slow the engine down. Flooding is a much more horrible state of affairs when cold, ask us carbureted Porsche 911 owners. If you should flood the engine, you would have to pull clean and dry the plugs or go back to bed for another day.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Re: AFM Adjustment

Post by slow.bus » Wed Apr 01, 2015 6:35 am

... as much as I fantasize about an older (well any) Porsche ... my garage (nor budget) barely fits the camper. When I could actually get one ... I fear they will be priced near to 'unobtanium'

I changed the idle (1,000'ish) and opened up the idle Co2 and was able to get through a warm up cycle without any 'protesting' and with even higher than normal max AFR's (16.5) before settling down to the about 14.7. Note: at turnover it was 12.5, then down to 11, then climbed steadily from there.

More work to do, as top end AFR are high and such - but an improvement all the same.

A quick question: getting it to start happens on my second attempt ... 1 hr after 1st trying. I try turning it over 2 or 3 times, then if no start leave ... and come back in 1 hr. At that point it starts up just fine ... Any suggestions? My guy tells me it could be loosening up the oil (remember it's cold here ... just above freezing ... was about 3 degrees Celsius) or the excess gas that prevented me from starting before ... slowly vaporizing and filling the cylinders and creating a more combustible mixture ... but these may just be silly ideas.
1981 Westfalia
Dents & Dings, but no Rust

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