AFM Adjustment

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AdreView
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Re: AFM Adjustment

Post by AdreView » Tue Jun 23, 2015 9:28 am

Latest post of the previous page:

Amskeptic wrote:
What vehicle are we dealing with?
Thank you for responding to my post....I hope to not offend anyone as I'm not a VW owner, but wish to learn from your knowledge base on a similar AFM system. Funny you ask, it actually happens to be a 1978 Datsun 280Z. Reason I joined is that I came across your AFM Adjustment write-up and it happened to be the only one on the web that explained everything which I was searching for...the Datsun world could benefit from your knowledge as we use the same Bosch system.
Amskeptic wrote:Reset all to original locations.

Turn mixture screw to 2 or 2 1/2 turns from the bottom.

With warm engine, adjust wiper to best obtainable idle. Now lean it about 25 to 50 rpm.

Check that the fuel pump shuts off when you kill the engine and turn on the ignition only. You can bend the shut off arm carefully, making sure that you do not accidentally move the wiper in its slot.
As a side note, my AFM has the fuel pump cut off switch, but the harness/ecu does not utilize it....there are no pins in those 2 locations. Do I still attempt the suggestion for the wiper to best idle and lean it out?
Amskeptic wrote:Your adjustment procedure inadvertently chased after a result that was just not forthcoming. The engine should have responded to your incremential adjustments long before you traveled around the whole cog.
Keep the cog on stand-by and get the wiper closer to optimum.
Perhaps I misinterpreted the results...I'll have to reference my notes, but I was testing the movement of the wiper/weight assembly CCW and CW after adjustment to the cog wheel and was attempting to achieve that slight change in RPM when fingering it CCW. When fingering it CW, it responded with the slight drop in rpm, instantly at one point (have to look again at notes). So I kept adjusting the cog wheel to keep that slight CW drop, but achieve the slight increase in RPM when going CCW to get it in the brink of lean.
Amskeptic wrote:Keep in mind that valve adjustments and ignition timing have great bearing on idle airflow. I sense that your engine is not breathing as efficiently as it should, taking into account that you declared no vacuum leaks. The end result does NOT require a "no change in rpm" when you nudge the wiper to check mixture. A little evidence of leanness is OK. How do you test your results? Do you have LM-1, CHT gauges, known performance benchmark? We also need to ask your spark plugs after a couple of hundred miles.
Colin
I'm going to re-verify my valve adjustment settings this afternoon prior to any AFM adjustments. Can you explain what you mean by "engine not breathing efficiently due to NO vac leaks"? I'm displaying healthy vac at idle with the AFM bypass screw set from full close up until about 4 turns out...then vac starts to dip below 17 In/Hg.

Most of my results unfortunately are having to go by reading the plugs after a country drive and listening/feeling what the motor is responding to. I have a non-catalyst exhaust and no bung for a wideband sensor unless I weld one in. I'm currently using a vacuum gauge, rpm/dwell tach meter, and my ear to get this motor in the ballpark. New spark plugs after a couple hundred easy driving miles of use started in the lean, I had some white deposits on them. Then I started to play with the AFM, which led me to you!

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Amskeptic
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Re: AFM Adjustment

Post by Amskeptic » Thu Jun 25, 2015 5:59 pm

AdreView wrote:
Amskeptic wrote:
What vehicle are we dealing with?
1978 Datsun 280Z.
Totally different animal. Water-cooling around the exhaust valves, a totally different torque/hp curve, Nippondenso interpretation of Bosch air-flow injection, I am not qualified to be tutoring you. Your internet resources are robust and specific to your car, fine thee them.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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asiab3
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Re: AFM Adjustment

Post by asiab3 » Tue Apr 12, 2016 6:43 pm

Amskeptic wrote:Vacuum leaks fool the ECU the same way. And if your AFM has the mixture screw bypass completely closed when you get to it, guess what? Someone else has been fooled too.
Well, apparently someone else has been fooled. Several cracks on my decel valve hose says a new hose is in order, followed by a retune just in time for Smog Celebration this summer. Hey Colin, want to work on fuel injection instead of a sliding door? :blackeye:

Robbie
1969 bus, "Buddy."
100k miles with me.
279k miles on Earth.

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Amskeptic
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Re: AFM Adjustment

Post by Amskeptic » Tue Apr 12, 2016 6:49 pm

asiab3 wrote:
Amskeptic wrote:Vacuum leaks fool the ECU the same way. And if your AFM has the mixture screw bypass completely closed when you get to it, guess what? Someone else has been fooled too.
Well, apparently someone else has been fooled. Several cracks on my decel valve hose says a new hose is in order, followed by a retune just in time for Smog Celebration this summer. Hey Colin, want to work on fuel injection instead of a sliding door? :blackeye:

Robbie
Sure. I can pedantically plough you through the worst of fuel injection arcana.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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asiab3
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Re: AFM Adjustment

Post by asiab3 » Tue Apr 12, 2016 11:13 pm

I am an "example 3" at the moment:
example 3
... lean idle
... rich high speed
*** adjust (A) CCW for perfect idle, then tighten (B) CW to help lean out the high speed mixture, then trim the unintended consequence (probably a tad leaner) to the idle with (C)

However, I am not trusting that vacuum leaks have been abolished. I will spend more time with an unlit torch, thorough hose inspection, and hose replacement until I have a trustworthy vetted vacuum network.

After all, my idle mixture screw was set at 1/2 turn from bottoming out, and my idle mixture was 15.1:1. Cruise was in the 11.5-12.5 range. :pale: At least that explains the poor fuel economy…

Robbie
1969 bus, "Buddy."
100k miles with me.
279k miles on Earth.

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Amskeptic
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Re: AFM Adjustment

Post by Amskeptic » Wed Apr 13, 2016 9:33 am

asiab3 wrote:I am an "example 3" at the moment:
example 3
... lean idle
... rich high speed
*** adjust (A) CCW for perfect idle, then tighten (B) CW to help lean out the high speed mixture, then trim the unintended consequence (probably a tad leaner) to the idle with (C)

However, I am not trusting that vacuum leaks have been abolished. I will spend more time with an unlit torch, thorough hose inspection, and hose replacement until I have a trustworthy vetted vacuum network.

After all, my idle mixture screw was set at 1/2 turn from bottoming out, and my idle mixture was 15.1:1. Cruise was in the 11.5-12.5 range. :pale: At least that explains the poor fuel economy…

Robbie
Not really. Yeah really.

Factory economy was 16.7 mpg mixed driving.

You can carefully get a cruise ratio closer to high 12 low 13 area, but the new benchmark is to perform a full throttle pull in 4th gear from 55 mph to 70 mph.
Set wiper to 11.7 at 55 and see if it leans to 12.3 at 70.
Check to see if the fuel cuts off at total decel from 70 down, you should see a 22 or so that "switches" back down to 15-16 or less when rpms drop below threshold.

Sure wish my LM-1 had not been stolen out from under me . . .
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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asiab3
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Re: AFM Adjustment

Post by asiab3 » Wed Apr 13, 2016 1:52 pm

Amskeptic wrote: Not really. Yeah really.

Factory economy was 16.7 mpg mixed driving.
I'm seeing single digits......

The AFM has a "remanufactured" sticker on it from a brand I've never heard of. I'll grab the name of it this afternoon. My spare AFM is Bosch remanufactured, but it came in a box of dusty parts with the cover off, so I'm not sure of the cleanliness level of the wiper and track. Perhaps I should install it, tune it, and keep it that way so I can hot swap it one day down the road if necessary.

You can carefully get a cruise ratio closer to high 12 low 13 area, but the new benchmark is to perform a full throttle pull in 4th gear from 55 mph to 70 mph.
Set wiper to 11.7 at 55 and see if it leans to 12.3 at 70.
Check to see if the fuel cuts off at total decel from 70 down, you should see a 22 or so that "switches" back down to 15-16 or less when rpms drop below threshold.

Sure wish my LM-1 had not been stolen out from under me . . .
Colin
I'll pull 55-70 and note the time, and do it in the opposite direction for an average. Power is GREAT in this bus; on par with the BobD, except I'm not afraid to play hard with BB. It keeps on pulling above 50 in third without protest or lethargy.

LM-1 gone with the Naranja break-in? You're welcome to borrow mine for a spell this summer if it will enlighten anyone. Comes with a factory 16' signal wire!

Robbie
1969 bus, "Buddy."
100k miles with me.
279k miles on Earth.

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SlowLane
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Re: AFM Adjustment

Post by SlowLane » Wed Apr 13, 2016 3:56 pm

asiab3 wrote:
Amskeptic wrote: Factory economy was 16.7 mpg mixed driving.
I'm seeing single digits......
.
.
.
I'll pull 55-70 ..., and do it in the opposite direction.
I'm not afraid to play hard with BB.
It keeps on pulling above 50 in third without protest or lethargy.
Connect those dots. :bom:

Kidding slightly. An "enthusiastic" driving style will certainly have an effect on fuel economy, but shouldn't drive you to the single digits range. Do you have a locking gas cap?
'81 Canadian Westfalia (2.0L, manual), now Californiated

"Wisdom comes from experience. Experience is often a result of lack of wisdom."
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Re: AFM Adjustment

Post by asiab3 » Wed Apr 13, 2016 6:03 pm

I do have a locking gas cap, why? I just ordered a non-locking cap because I'm tired of needing keys to fill my cheap-ass car that SHOULD have a filler door. :-({|= Something to do with it not venting? I drove a 10-gallon fill up with eggshell toes like my Type 1 that gets babied, and I still only netter 12mpg on the highway at 65. Boo.

I was able to nudge the static adjustment richer and blast my dynamic adjustment a dozen teeth or so leaner to get 12.5-13.5 cruise. Interestingly, a 55-70 flog at full throttle left me at 11.3 solid. So now my full throttle enrichment is putting me where I was at cruise before, and I have the upper teen to low 20's overrun shutoff option, whereas before I saw 14.2 on high RPM overrun. (Full throttle enrichment took me down as far as 9.5 before adjustments.) Do those adjustments seem reasonable? Is there such thing as too many teeth on the dynamic adjustment, as long as my entire fuel map is within a safe range? I was expecting three to six teeth to make a larger difference than it did, after seeing how sensitive the static adjustment is.

The drivability seems to have smoothed out some, but I still have a hunch that I have a vacuum leak somewhere. I want to hit 14.0 at 25mph before I even think about taking it to the smog ref. Interestingly, I've been driving at 28* btdc hoses off at max advance. This landed me at 4* idle, which is failing for smog time. I bumped up to "sticker-approved" 7.5* and my entire map was better; idle was close to stoich, light cruise was leaner, and mashing acceleration was the same.

So far so good.

Robbie
1969 bus, "Buddy."
100k miles with me.
279k miles on Earth.

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SlowLane
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Re: AFM Adjustment

Post by SlowLane » Wed Apr 13, 2016 7:05 pm

asiab3 wrote:Something to do with it not venting?
No, simpler than that. Something to do with gasoline growing legs and walking away. :angryfire:
'81 Canadian Westfalia (2.0L, manual), now Californiated

"Wisdom comes from experience. Experience is often a result of lack of wisdom."
- Terry Pratchett

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Re: AFM Adjustment

Post by asiab3 » Wed Apr 13, 2016 10:23 pm

SlowLane wrote:
asiab3 wrote:Something to do with it not venting?
No, simpler than that. Something to do with gasoline growing legs and walking away. :angryfire:
Fantastic! Ha! Typical me, overanalyzing and overthinking!

--
So I have to append most of my earlier posts. It took me three years to catch, but my vacuum system is a complete mess. The EGR vacuum signal hose and EEC signal hose are both hooked up to manifold vacuum when they should be off the ported vacuum advance line. I'm going to get everything plumbed correctly tomorrow and see how that affects mixture and cold start. I speculate the EGR contributes to my wandering idle, since it's being circulated when it shouldn't be. Maybe I'll have drastically different numbers, maybe I won't, but either way I'm getting closer to nailing down a smooth Volkswagen Experience.

Robbie
1969 bus, "Buddy."
100k miles with me.
279k miles on Earth.

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Amskeptic
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Re: AFM Adjustment

Post by Amskeptic » Thu Apr 14, 2016 10:09 am

asiab3 wrote: So I have to append most of my earlier posts. It took me three years to catch, but my vacuum system is a complete mess. The EGR vacuum signal hose and EEC signal hose are both hooked up to manifold vacuum when they should be off the ported vacuum advance line.
Three years, how?
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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asiab3
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Re: AFM Adjustment

Post by asiab3 » Thu Apr 14, 2016 11:09 pm

Amskeptic wrote:
asiab3 wrote: So I have to append most of my earlier posts. It took me three years to catch, but my vacuum system is a complete mess. The EGR vacuum signal hose and EEC signal hose are both hooked up to manifold vacuum when they should be off the ported vacuum advance line.
Three years, how?
Colin
I maintained the car for the family that owned it prior to me. The idle seems to float less now, with EGR being signaled by ported vacuum instead of manifold vacuum, but now the idle mixture is once again on the lean side with the idle mix screw bottomed out. (15.5:1)

If I richen the static adjustment to get the idle stoichiometric with the mix screw a few turns out, the dynamic adjustment needs nearly an entire turn lean to bring the fuel map into passable for normal driving. I have reset the AFM back to "where it all started" so I can try again after looking for more leaks.

Do you trust Python Injection? I'm not sure I do yet. Perhaps a short road trip is in order, at 8-12 mpg.

Image
1969 bus, "Buddy."
100k miles with me.
279k miles on Earth.

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Re: AFM Adjustment

Post by Amskeptic » Fri Apr 15, 2016 6:14 am

asiab3 wrote: idle mixture is once again on the lean side with the idle mix screw bottomed out. (15.5:1)

If I richen the static adjustment to get the idle stoichiometric with the mix screw a few turns out, the dynamic adjustment needs nearly an entire turn lean to bring the fuel map into passable for normal driving.
I have to update that stupid article.
Do not monkey with the wiper (static) for the idle mixture. The wiper's primary purpose is to give us the correct WOT mixture from torque to horsepower peak (55-70 -4th gear). In this situation, the spring effects are mostly out of the way, a nice opportunity to reduce variables. Vacuum leaks mean less at high rpm. It is here that we set the wiper for best mixture under load.

Then we set the spring for that nice lean out when you release the throttle at-speed, and you make sure it is giving the right overswing when you goose the throttle (its inertia is, after all, our "accelerator pump"). Set mixture screw is at 4 turns out and bring idle mixture to 14-16 with the spring. Then use the mixture screw to clean up your idle anywhere down to 1 1/2-3 turns out, it is not that important where. Chances are that the idle mixture will be adjustable to stochiometric range and that is fine! Generally, the leaner the idle, the better the cold start idle speed. These engines were designed to run pretty damn lean when new. The engineers gave a piggy cold start rich mixture to get it going, then let the engine go through a leanish bog for the five or so minutes to operating temperature. After I adjusted the BobD to give me desert survival mixtures, my cold start behavior got pretty rich and sluggish (pump the brakes rapidly during the first minute from cold and see if your idle smooths out and picks up a bit, that is your proof that your cold idle is too rich if anything).

We need to come up with an AFM adjustment system!
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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Re: AFM Adjustment

Post by asiab3 » Sat Apr 16, 2016 8:12 am

Amskeptic wrote: We need to come up with an AFM adjustment system!
I am not ready yet. As expected, I found my vacuum leak; the underside of the breather valve housing shows sign of melting from extreme local heat. It appears different from plastic burn tests I've conducted at work, but there are boil-esque bubbles that let air through, in addition to a large gap where plastic has melted away. Of course all of this is out of sight, and the diaphragm inside is ruptured too. (Blow-by, being mostly inert, is passed into the intake after the AFM, because it is not combustible enough to need metering from the AFM, otherwise it would have been plumbed into the air cleaner to be metered.) However, because I have a hole in the side of the breather tower, I have the vacuum leak messing with my mixture AND the excess oil consumption of a blown breather valve.

Chalk this one up to another case of "the symptom was only a path to the discovery of the real problem." Aren't these cars fascinating?
Robbie
1969 bus, "Buddy."
100k miles with me.
279k miles on Earth.

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SlowLane
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Re: AFM Adjustment

Post by SlowLane » Sat Apr 16, 2016 10:20 am

Robbie, since you've monkeyed around with the AFM spring, and also since you're unsure about the quality of a Python unit to begin with, perhaps it might be helpful to use Steve Kent's weight-calibration method as an initial starting point.

Steve basically used a 60g weight on the vane to set the spring pressure to where the vane would just start to open. He's posted explanatory photos several times on TheSamba.

Congratulations on finding that (hopefully) last vacuum leak.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"Wisdom comes from experience. Experience is often a result of lack of wisdom."
- Terry Pratchett

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