AFM Adjustment

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SlowLane
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Re: AFM Adjustment

Post by SlowLane » Mon Aug 05, 2019 5:05 pm

We're rather spinning off from the "AFM Adjustment" thread topic here.

New thread justified?
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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Amskeptic
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Re: AFM Adjustment

Post by Amskeptic » Tue Aug 06, 2019 7:10 pm

SlowLane wrote:
Mon Aug 05, 2019 5:05 pm
We're rather spinning off from the "AFM Adjustment" thread topic here.

New thread justified?
Oh yes .... people just walk all over these threads in single-minded pursuit.
Colin
BobD - 78 Bus . . . 112,660 miles
Chloe - 70 bus . . . 206,845 miles
Naranja - 77 Westy . . . 129,490 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 91 Lexus LS400 . . . 94,225 miles

Kossco
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Re: AFM Adjustment

Post by Kossco » Wed May 13, 2020 4:24 pm

Thanks for this solid write up. I have read thru all the replies and see numerous AFR readings provided and am wondering if there is a guideline that an ameuter could follow in regards to what the AFR to road speed to head temp relations should be?

Something like -
Warm idle - 13-15 AFR
Highway no grade, cruise 55mph - 12.1-12.6 AFR - no higher than 400F* CHT
etc etc

Or AFR readings through the revs on each shift point like -
1st-2nd gear, should be between 10.9-12.3 AFR
2nd-3rd, between etc etc.

Or AFR numbers and what state the engine should be in to see that number like -
AFR 8-10 - Very rich, shouldnt be seen while driving under proper conditions
AFR 11-12 - Rich, seen during heavy load acceleration and before shift points
AFR 13-15 - Nearing/past lean stage, should only see when cruising under light loads at 1/2-3/4 throttle
Etc etc.

I have been tweaking and making adjustments based off the LM-2 readouts but am not certain on what ideal AFR readings should be so I guess I am just looking for clarification/confirmation of what makes our T4 engines happiest with quantifiable numbers.

72Hardtop
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Re: AFM Adjustment

Post by 72Hardtop » Wed May 13, 2020 7:47 pm

If your 1/2 - 3/4 throttle (in a bus) you best be on the mains (if carbed) and AFR should be no richer (ROP) than 12:5 13:2 or so. Part throttle would be up to 1/3rd throttle or so.

Bus will run cooler with AFR of 16:0 at part throttle. Cooler than 13:0
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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Re: AFM Adjustment

Post by Kossco » Thu May 21, 2020 10:07 am

Thanks Hardtop. What do you mean by 13:2 AFR? Iv tried running around 16 but am hitting 430*CHT too easily when I go above 55mph. Being in the AFM topic, this is not a carbed engine, all though I imagine AFR correlations to CHT wouldnt matter if it was carbed or FI.

I have fought high head temps whenever over 50mph in the FI vanagon westfalia for years now. After melting a few valves out I opted for a CHT gauge and am now keeping my valves intact but find I am driving by CHT readings rather than speed limits now. The engine can move the van no problem, but the CHTs climb above 400* and stay there far too easy. I have played with the AFM the last few days trying to move it rich and lean etc to see how it affects CHT. Interesting how everything works together. But I have yet to find a combination that allows me to cruise without raising over 400*. So I guess I am looking for a good breakdown of what AFR # should be in relation to the driving condition that I should be in to obtain that number and what I should see my CHT do in response to that driving condition change.

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Re: AFM Adjustment

Post by 72Hardtop » Thu May 21, 2020 12:06 pm

AFR.jpg
AFR.jpg (23.95 KiB) Viewed 3003 times
Kossco wrote:
Thu May 21, 2020 10:07 am
Thanks Hardtop. What do you mean by 13:2 AFR? Iv tried running around 16 but am hitting 430*CHT too easily when I go above 55mph. Being in the AFM topic, this is not a carbed engine, all though I imagine AFR correlations to CHT wouldnt matter if it was carbed or FI.

I have fought high head temps whenever over 50mph in the FI vanagon westfalia for years now. After melting a few valves out I opted for a CHT gauge and am now keeping my valves intact but find I am driving by CHT readings rather than speed limits now. The engine can move the van no problem, but the CHTs climb above 400* and stay there far too easy. I have played with the AFM the last few days trying to move it rich and lean etc to see how it affects CHT. Interesting how everything works together. But I have yet to find a combination that allows me to cruise without raising over 400*. So I guess I am looking for a good breakdown of what AFR # should be in relation to the driving condition that I should be in to obtain that number and what I should see my CHT do in response to that driving condition change.
Being stock configured you'll be pushing the bus (working hard). Get the AFR (Air fuel ratio) down to 13 - 13:5 range when working hard. 12:5 or so WOT (Wide open throttle).

Cruise would be on the flat scenario. No hill, grade/s. The hottest AFR range is 14 - 15 AFR. Get above it...16 and it will run cooler (on the flats). You using a VDO gauge or a digital gauge? Where do you have the sender placed? How well is it placed (installed).

Tells us more of the engine specs, distributor etc...
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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Re: AFM Adjustment

Post by 1jmpshot » Sat Aug 08, 2020 12:03 pm

Following the original directions for the AFM Adjustment, I attempted to "bottom out" the mixture screw C. This is on a 1981 Vanagon, Federal model. I have rotated the mixture screw CW, in my case a 5mm hex, until it just rotates, never stopping. Now I'm attempting to rotate the mixture screw CCW, and it does not return to the original position. I can see the threads on the side of the chamber but the screw does not engage them. I have tried putting pressure on the hex wrench trying to force the screw to engage the threads. I have removed the AFM and held it upside down while rotating the mixture screw with no movement in the screw up the chamber. I have removed the air cleaner housing from the AFM and removed the two screws on the bottom of the AFM. I was unable to pry the bottom plate off the AFM in order to see inside the chamber. Previous to this issue, I had managed to adjust the AFM so I had steady idle and good power up through 3rd gear, before power fell off in 4th. Now, the engine starts but runs rough to the point I'm not comfortable in trying to make adjustments. Any suggestions on how I can adjust the mixture screw C?

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SlowLane
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Re: AFM Adjustment

Post by SlowLane » Sun Aug 09, 2020 8:36 am

1jmpshot wrote:
Sat Aug 08, 2020 12:03 pm
I have rotated the mixture screw CW, in my case a 5mm hex, until it just rotates, never stopping. Now I'm attempting to rotate the mixture screw CCW, and it does not return to the original position. I can see the threads on the side of the chamber but the screw does not engage them. I have tried putting pressure on the hex wrench trying to force the screw to engage the threads.
Oh, dear, that's a tough one.
Maybe a narrow-nosed pair of snap ring pliers could be inserted into the hex socket and used to pull upwards while rotating CCW to catch the threads. You would need to be very careful to not let the jaws slip out lest they damage the threads in the bore.
Good luck.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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Re: AFM Adjustment

Post by 1jmpshot » Sun Aug 09, 2020 2:27 pm

Hey, thanks for the quick reply SlowLane. I decided to try a fix last night and just tested it. I cut off a hex key, that fit the mixture screw, so that it would clear the engine lid when closed. I super glued the hex key to the mixture screw opening and let it cure. I have successfully turned the hex key while lifting it so that the mixture screw has moved part way back up the chamber and seems to have engaged the threads. The hex key did separate, but a regular hex key seems to be moving the screw CCW. I will spend more time, at a later date, in adjusting the AFM, but for now I'm a happy camper that the fix worked. If I need to make the hex key more permanent, in order to lift and turn, I'll try JB Weld the next time.

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SlowLane
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Re: AFM Adjustment

Post by SlowLane » Mon Aug 10, 2020 9:37 am

1jmpshot wrote:
Sun Aug 09, 2020 2:27 pm
I cut off a hex key that fit the mixture screw, so that it would clear the engine lid when closed. I super glued the hex key to the mixture screw opening and let it cure. I have successfully turned the hex key while lifting it so that the mixture screw has moved part way back up the chamber and seems to have engaged the threads.
Very creative. Glad you got it sorted.
'81 Canadian Westfalia (2.0L, manual), now Californiated

"They say a little knowledge is a dangerous thing, but it is not one half so bad as a lot of ignorance."
- Terry Pratchett

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Re: AFM Adjustment

Post by Kossco » Tue Oct 06, 2020 4:49 pm

72Hardtop wrote:
Thu May 21, 2020 12:06 pm
AFR.jpg
Kossco wrote:
Thu May 21, 2020 10:07 am
Thanks Hardtop. What do you mean by 13:2 AFR? Iv tried running around 16 but am hitting 430*CHT too easily when I go above 55mph. Being in the AFM topic, this is not a carbed engine, all though I imagine AFR correlations to CHT wouldnt matter if it was carbed or FI.

I have fought high head temps whenever over 50mph in the FI vanagon westfalia for years now. After melting a few valves out I opted for a CHT gauge and am now keeping my valves intact but find I am driving by CHT readings rather than speed limits now. The engine can move the van no problem, but the CHTs climb above 400* and stay there far too easy. I have played with the AFM the last few days trying to move it rich and lean etc to see how it affects CHT. Interesting how everything works together. But I have yet to find a combination that allows me to cruise without raising over 400*. So I guess I am looking for a good breakdown of what AFR # should be in relation to the driving condition that I should be in to obtain that number and what I should see my CHT do in response to that driving condition change.
Being stock configured you'll be pushing the bus (working hard). Get the AFR (Air fuel ratio) down to 13 - 13:5 range when working hard. 12:5 or so WOT (Wide open throttle).

Cruise would be on the flat scenario. No hill, grade/s. The hottest AFR range is 14 - 15 AFR. Get above it...16 and it will run cooler (on the flats). You using a VDO gauge or a digital gauge? Where do you have the sender placed? How well is it placed (installed).

Tells us more of the engine specs, distributor etc...
Ok so engines in 1980 Vanagon Westfalia (Canadian model, Federal Mogul, F.I.). Its still in stock configuration as far as I know. Previous owner who was original owner had the van maintained by the dealer and kept all the records. The engine was rebuilt by the dealer around 200k KMS. I now have it at 570k KMS and have done 1 full rebuild myself and several head replacements. I used all OEM parts on my rebuild and had a local shop polish the crank and regrind the cam. I am becoming most suspect of the cam grind thru all of the testing I have done. I have become very familiar with the engine since living in the van for the last 10 years and suffering many breakdowns. I have been thru it meticulously and this high head temp seems to be the only issue I cannot win on. All tins are in place and holes sealed with engine bay seal in good condition. Vacuum leaks addressed. Flaps are functioning correctly with a new thermostat. All F.I. components are functioning and testing accurate as per the AFC manual. Timing has been varied thru the process numerous times in attempt to see different head temps. When I bought the van it had a 009 dizzy on which I replaced with a rebuilt SVDA (205/034 spec) from Bill(sparxwerks) off the Samba. Should be between 27-28* currently. Ignition would be the WR7CC plugs (have run both 8's and 7's without any noticeable change in CHT) with Bremi wires, rebuilt SVDA dizzy, bosch cap and rotor and p&c replaced with electronic ignition unit running from a proper Bosch blue coil. I have played with a wide range of timing settings to try and lower head temps and I currently have it sitting in the coolest head temp location. I find I still have plenty of power when loaded up a grade but drive to the head temps as they will continue to climb above 430* if I let them. Current timing keeps me coolest as long as I adjust throttle as needed.

Ill try some more test runs soon with your latest advice. Thought I would throw out my engine details in the mean time...

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Re: AFM Adjustment

Post by Amskeptic » Tue Oct 06, 2020 8:03 pm

Kossco wrote:
Tue Oct 06, 2020 4:49 pm
72Hardtop wrote:
Thu May 21, 2020 12:06 pm
AFR.jpg
Kossco wrote:
Thu May 21, 2020 10:07 am
Thanks Hardtop. What do you mean by 13:2 AFR? Iv tried running around 16 but am hitting 430*CHT too easily when I go above 55mph. Being in the AFM topic, this is not a carbed engine, all though I imagine AFR correlations to CHT wouldnt matter if it was carbed or FI.

I have fought high head temps whenever over 50mph in the FI vanagon westfalia for years now. After melting a few valves out I opted for a CHT gauge and am now keeping my valves intact but find I am driving by CHT readings rather than speed limits now. The engine can move the van no problem, but the CHTs climb above 400* and stay there far too easy. I have played with the AFM the last few days trying to move it rich and lean etc to see how it affects CHT. Interesting how everything works together. But I have yet to find a combination that allows me to cruise without raising over 400*. So I guess I am looking for a good breakdown of what AFR # should be in relation to the driving condition that I should be in to obtain that number and what I should see my CHT do in response to that driving condition change.
Being stock configured you'll be pushing the bus (working hard). Get the AFR (Air fuel ratio) down to 13 - 13:5 range when working hard. 12:5 or so WOT (Wide open throttle).

Cruise would be on the flat scenario. No hill, grade/s. The hottest AFR range is 14 - 15 AFR. Get above it...16 and it will run cooler (on the flats). You using a VDO gauge or a digital gauge? Where do you have the sender placed? How well is it placed (installed).

Tells us more of the engine specs, distributor etc...
Ok so engines in 1980 Vanagon Westfalia (Canadian model, Federal Mogul, F.I.). Its still in stock configuration as far as I know. Previous owner who was original owner had the van maintained by the dealer and kept all the records. The engine was rebuilt by the dealer around 200k KMS. I now have it at 570k KMS and have done 1 full rebuild myself and several head replacements. I used all OEM parts on my rebuild and had a local shop polish the crank and regrind the cam. I am becoming most suspect of the cam grind thru all of the testing I have done. I have become very familiar with the engine since living in the van for the last 10 years and suffering many breakdowns. I have been thru it meticulously and this high head temp seems to be the only issue I cannot win on. All tins are in place and holes sealed with engine bay seal in good condition. Vacuum leaks addressed. Flaps are functioning correctly with a new thermostat. All F.I. components are functioning and testing accurate as per the AFC manual. Timing has been varied thru the process numerous times in attempt to see different head temps. When I bought the van it had a 009 dizzy on which I replaced with a rebuilt SVDA (205/034 spec) from Bill(sparxwerks) off the Samba. Should be between 27-28* currently. Ignition would be the WR7CC plugs (have run both 8's and 7's without any noticeable change in CHT) with Bremi wires, rebuilt SVDA dizzy, bosch cap and rotor and p&c replaced with electronic ignition unit running from a proper Bosch blue coil. I have played with a wide range of timing settings to try and lower head temps and I currently have it sitting in the coolest head temp location. I find I still have plenty of power when loaded up a grade but drive to the head temps as they will continue to climb above 430* if I let them. Current timing keeps me coolest as long as I adjust throttle as needed.

Ill try some more test runs soon with your latest advice. Thought I would throw out my engine details in the mean time...

I have been excitedly experimenting out here on my tour. I've been practicing with "starve the heat" by running my engine so damn lean that it can't even make enough heat to run hot. I let the idle be rich enough for a good pull from the stoplight, but that is it.

Yes, I lose a good ten percent of my available power. I don't care!

17-20 mpg @ 55-60mph attack the bottom of the hill at 398* CHT, full throttle for three mile hill and the temp drops as the speed drops, say to 396* @ 52mph. I like it.
Colin
BobD - 78 Bus . . . 112,660 miles
Chloe - 70 bus . . . 206,845 miles
Naranja - 77 Westy . . . 129,490 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 91 Lexus LS400 . . . 94,225 miles

Kossco
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Re: AFM Adjustment

Post by Kossco » Tue Oct 13, 2020 12:50 pm

Amskeptic wrote:
Tue Oct 06, 2020 8:03 pm
I have been excitedly experimenting out here on my tour. I've been practicing with "starve the heat" by running my engine so damn lean that it can't even make enough heat to run hot. I let the idle be rich enough for a good pull from the stoplight, but that is it.

Yes, I lose a good ten percent of my available power. I don't care!

17-20 mpg @ 55-60mph attack the bottom of the hill at 398* CHT, full throttle for three mile hill and the temp drops as the speed drops, say to 396* @ 52mph. I like it.
Colin

What sort of AFR #s are you seeing thru your throttle positions/engine load?

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Re: AFM Adjustment

Post by Amskeptic » Sat Oct 24, 2020 12:31 pm

Kossco wrote:
Tue Oct 13, 2020 12:50 pm
What sort of AFR #s are you seeing thru your throttle positions/engine load?

Absolutely nothing. I do not have an afr meter set up. This has all been intuitive, and I like the freedom from numbers dogma. But, it is time to record what those numbers might be!
Colin
BobD - 78 Bus . . . 112,660 miles
Chloe - 70 bus . . . 206,845 miles
Naranja - 77 Westy . . . 129,490 miles
Pluck - 1973 Squareback . . . . . . 55,570 miles
Alexus - 91 Lexus LS400 . . . 94,225 miles

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Re: AFM Adjustment

Post by sgkent » Fri Oct 30, 2020 11:25 pm

Bit of technical help offered. The average engine guy or gal is looking for power and smooth running. Some folks are looking for efficiency. Some are looking for it all. A water cooled steel block is a lot more forgiving with heat than an air cooled motor because it transfers the heat more efficiently. WWII aircraft engine designers discovered that in WWII.

Simply put, the combining of O2 and fuel makes heat, and that heat drives the pistons. The greater the heat the greater the power. The more fuel and O2 that can be crammed into an engine the more power it will have. Unfortunately, VW engines were made lightweight and they don't like excessive heat so the designers made a choice to detune them and not to over cool them like 911's etc. The fans are smaller for one. It was a tactical decision on VW's part to keep the buses utility vehicles. As a result VW DETUNED their engines to put out less power - the exhausts are lengthy and convoluted, the carbs and FI plenums are under flowed, the heads do weird things from the heat. In the end they had a well engineered engine but one that reduced power. The 2L GD and GE engine put out 70 HP - maybe 80 - 85 with a better cam. The same basic engine as a European 914 GA motor is 95 -100 HP. It isn't as detuned.

When fuel molecules are leaner they are farther apart, and that not only lowers power because they are farther apart, but the burn being slower extends into the exhaust valves and ports if it is too lean. The exhaust ports, seats, guides, and valves are the most vulnerable parts of the 2L head. The head at the combustion chamber may see less heat because of less fuel, but the exhaust ports, ports etc cook. Conversely, when one runs a too rich that extra fuel also leaves an incomplete combustion, and the mass of the fuel helps lower combustion temps, especially in the ports. Too rich however and the unburned fuel shows up in the catalytic convertor to make it glow and shorten its life. Generally speaking, one wants a burn that is as rich as it can be without washing fuel down the cylinder walls, or destroying the catalytic. At light cruise a 14.5 - 15.0 mixture is fine because one is not asking the engine to produce all the power it can. The advance is ramped up due to higher vacuum signals and that gives the burn longer in the cylinder, reducing heat in the ports. But too much heat can be hard on pistons too. When a bus engine is at WOT, which is just about anywhere above 65 mph, the fuel mixture should move richer to about 12.5 - 13.0. Once one gets between 13.5 and 14.7 heat starts to come up. Were it me I would not be tuning my engine so lean into the 15's unless I also had an EGT gauge to set the mixture to where EGT was not at peak. Keep in mind that these were air cooled aircraft engines when they were born, and the air is less dense and cooler at 10,000' ASL than at sea level. Aircraft engines are constant speed as well, and they run at lower RPM's than a bus engine does. As a automotive machinist involved with some well know racing teams in the 1970's and 80's, I have seen the effects of over stressing valves and seats in an aluminum head. A good friend, now deceased, was the head guy for VWOA's racing teams designing the T4 Super Vee engine. He found that the only way to make power and keep the heads, pistons, and oil cool was to ceramic coat them to slow heat transfer. ANY ONE trying to set the mixture on a T4 2L engine is doing a dance between too much power, too much heat, and when the burn begins and ends. Last time I spoke with Colin he told me he was running ceramic coated heads so automatically that puts him in to a different situation than those of us with uncoated heads. I don't think Len coated the pistons for him. Good luck to all tuning their AFM's. Your goal is basically 14.7:1 at lite cruise and richer down to mid to high 12's at WOT. Even at that it will be hard on catalytics and the ZDDP oil won't help either. VW went to square port heads for additional cooling when the laws forced them to maintain 14.7:1 across the RPM range. Ethanol in the gas carries its own O2 to a degree so it screws up the mixture and makes it run leaner than non-ethanol fuel. It also has less C molecules so it needs less 02 for complete combustion. Good Luck.
Thank You -

Merlin The Wrench

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