AFM Adjustment

Carbs & F.I.

Moderators: Sluggo, Amskeptic

Post Reply
slow.bus
I'm New!
Status: Offline

Re: AFM Adjustment

Post by slow.bus » Wed May 06, 2015 11:00 am

airkooledchris wrote:advancing the timing past the suggested marks will raise your head temps, and fast. every motor not being equal, I wouldn't rule out playing with the timing a little to see what the numbers tell you - but from what ive seen advanced timing gives more power and too much heat along with it.
That's exactly my concern ... and understand that too much advance or retard will also cause excessive heat.

ASSUMING the factory setting was the sweet spot ... (ie correct me here :)) ... what would be the sweet spot with a change in AFR ...
1981 Westfalia
Dents & Dings, but no Rust

User avatar
airkooledchris
IAC Addict!
Location: Eureka, California
Contact:
Status: Offline

Re: AFM Adjustment

Post by airkooledchris » Wed May 06, 2015 11:13 am

I've gone damn near pig rich with my AFM adjustment, but I still set my timing for 28* max advance.

I'm running 11.5 at part throttle low speeds and 10.5 at part throttle under load. I'm hitting 9.8 or so under serious load and Wide Open Throttle.
My head temps are in the 330's around town and about 390+ on the highway, unless hill climbing when it spikes.

No matter how rich I have setup this particular motor to run, the heads don't like the timing to be advanced past 28*.
1979 California Transporter

slow.bus
I'm New!
Status: Offline

Re: AFM Adjustment

Post by slow.bus » Thu May 07, 2015 5:15 am

airkooledchris wrote: No matter how rich I have setup this particular motor to run, the heads don't like the timing to be advanced past 28*.
Thank you for the details. By not liking, I am assuming ran hotter?

I am getting similar (but higher) temps right now, but am into the 30's for advance. Will try backing off timing over the next few nights and see if there is much difference
1981 Westfalia
Dents & Dings, but no Rust

User avatar
airkooledchris
IAC Addict!
Location: Eureka, California
Contact:
Status: Offline

Re: AFM Adjustment

Post by airkooledchris » Thu May 07, 2015 9:49 am

That's correct, it starts running hotter anytime I go past 28* advance (hoses off and plugged when checking) - almost no matter how rich ive got it setup to run.

Let us know what your numbers say after backing off the timing a bit...
1979 California Transporter

slow.bus
I'm New!
Status: Offline

Re: AFM Adjustment

Post by slow.bus » Thu May 07, 2015 5:26 pm

Stock is about 32.5 all-in (7.5 with 25 added), I was slighty more advanced (probably 33/34 ) and brought it down to 31 tonight with no material change - maybe 5 degree ... Cruise at 410'ish at 65mph on flat - seems about a normal number.

Will try 28/29 this weekend just to see any difference - but pretty happy where things are. 1st camping trip of season next weekend - with a few hundred miles of driving - so tuning has to stop.
1981 Westfalia
Dents & Dings, but no Rust

User avatar
airkooledchris
IAC Addict!
Location: Eureka, California
Contact:
Status: Offline

Re: AFM Adjustment

Post by airkooledchris » Thu May 07, 2015 9:00 pm

always give yourself a little wiggle room if your out testing with an empty bus and then you go load it to the gills to go camping.
410 empty is going to be 425 in a hurry once your loaded down and driving for an extended period of time.
1979 California Transporter

slow.bus
I'm New!
Status: Offline

Re: AFM Adjustment

Post by slow.bus » Mon May 11, 2015 6:16 am

Noticeable drop with 29 or so - below 400. Did not check exact timing, just gave it a quick twist (usually about 2 degrees). Am going to check exact timing and set it to 28 and run a few more tests - will also swap my cold plugs back in and add a cog of fuel to the top end cruise.

edit: long weekend runs with 27/28 advance was sub 400 (est 370-380) for all but hills and the speedo pegged at 60-65 mph, except hills where it maxed out at about 420 - never higher at 55 to 60 mph. Note, this is on a VDO in pretty much exactly 70 degree weather :). The drive is VERY hilly but mostly uphill on the way there and more downhill / flat on way back ... about 250 mile round trip
1981 Westfalia
Dents & Dings, but no Rust

Ballyhoo25
I'm New!
Status: Offline

Re: AFM Adjustment

Post by Ballyhoo25 » Tue May 12, 2015 9:52 am

Thanks for the write up on the AFM adjustment. I have a question about modifications to a VW Type 1 engine and the Fuel Injection System.
My car is a 1979 Super Beetle Convertible with the Factory L-Jetronic Fuel Injection System. The engine is worn out and I will be rebuilding it. I want to use larger pistons in the rebuild (stock engine 1600 rebuild 1776 or 1835).

From my limited understanding from reading the AFM Adjustment, the amount of fuel delivery can be increased to richen the air-fuel mixture.

My thought is that the larger pistons will need more fuel. With a carb engine you use a bigger carb and change jets. Using the AFM Adjustment you have written about, what I need to do is richen the air fuel mixture to get the engine to run well.

Is my thought process correct or did I miss something important ?

Do you know if the L-Jetronic system in the VW Type 1 engines provides enough adjustment to get the larger capacity engine to run well ?

The F.I. in my Super Beetle has served me well and I do not want to give up reliability or turn the car into a crappy backyard invention.

Do you know of others who have had success or failures with the larger engine displacement using the Type 1 F.I. System ?
The advice I have found around the internet all say the system has no adjustments and also that with the factory F.I. system the engine displacement is limited to the stock 1600cc.

Thanks in advance for any advice you may provide.

Victor

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: AFM Adjustment

Post by Amskeptic » Wed May 13, 2015 7:46 am

Ballyhoo25 wrote: 1979 Super Beetle Convertible with the Factory L-Jetronic Fuel Injection System. The engine is worn out and I will be rebuilding it. I want to use larger pistons in the rebuild (stock engine 1600 rebuild 1776 or 1835).


Do you know of others who have had success or failures with the larger engine displacement using the Type 1 F.I. System ?
The advice I have found around the internet all say the system has no adjustments and also that with the factory F.I. system the engine displacement is limited to the stock 1600cc.

Thanks in advance for any advice you may provide.

Victor
An amazing thing happens on the way to screwing up your nice Volkswagen. People give poor advice.
They might suggest a "performance cam" which indeed destroys the calibration of the fuel injection.

You have a tired engine. Why launch yourself into the endless variables and compromises of a larger displacement, when you haven't experienced a happy fresh 1600? Rebuild it correctly and everybody plays nicely. Then calibrate your mind and your outlook to the following fact. Stock late convertible might take 23 seconds 0-60. 1835 compromised bug with potential heat problems and less reliable cylinder barrels might take 18 seconds 0-60. Big Deal. Really. Have you driven a convertible bug with the top down? Who is in a hurry?

Go visit late model Bug shift points. Ask yourself if you have been extracting the power potential of the car. Most people are short shifting under heavy acceleration and they are hanging uselessly at high rpms under low-to-no load. Have you ever wound out a Bug to 34 mph in 2nd and 60 mph in 3rd?

That said, there is great adjustability in the L-Jetronic air flow meter. The injectors themselves can flow any fuel requirement for any VW engine up to high speed Porsche/VW 412 5,000 rpm cruising rpm.
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

Ballyhoo25
I'm New!
Status: Offline

Re: AFM Adjustment

Post by Ballyhoo25 » Thu May 14, 2015 10:11 pm

Thank you for your advice and insight. You are right about the little benefit of increasing the engine displacement.

What I remember most about my first classic VW convertible was that it was very reliable, got decent gas mileage, and parts were plentiful and affordable. I also remember that my 1971 convertible was slow but very enjoyable to drive.

Unfortunately the Fuel Injection System in the late model Super Beetles were perceived as being unreliable and expensive to maintain and repair. Many owners changed back to carbs and simply discarded the fuel injection components. This have made it hard to find good used fuel injection parts.

Thank you for your prompt response.

Victor

User avatar
Bleyseng
IAC Addict!
Location: Seattle again
Contact:
Status: Offline

Re: AFM Adjustment

Post by Bleyseng » Fri May 15, 2015 6:49 am

I have to agree that the way to go is a stock rebuild, plenty of HP/ torque when it is a new engine. Going to bigger pistons yields a slight increase in HP as most of the HP gains are in changing the cam. The stock VW cam is a mild cam for the Ljet FI and changing to a different cam requires lots of tuning on your part and the cam grinder.
Just Blueprint build the engine using the best quality parts you can buy and have it balanced.
Geoff
77 Sage Green Westy- CS 2.0L-160,000 miles
70 Ghia vert, black, stock 1600SP,- 139,000 miles,
76 914 2.1L-Nepal Orange- 160,000+ miles
http://bleysengaway.blogspot.com/

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: AFM Adjustment

Post by Amskeptic » Mon May 18, 2015 7:06 am

Ballyhoo25 wrote: Unfortunately the Fuel Injection System in the late model Super Beetles were perceived as being unreliable and expensive to maintain and repair. This have made it (easier-ed) to find good used fuel injection parts.
Gotta shake the trees a little. All of these nice fuel injection systems ripped off the cars means you just have to find them in their milk crates under the work benches of mechanics who couldn't figure them out.
Component parts, like AARs and injectors and series resistors and fuel pressure regulators and head temp sensors are interchangeable amongst the fuel injected VWs.
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

AdreView
I'm New!
Status: Offline

Re: AFM Adjustment

Post by AdreView » Fri Jun 19, 2015 8:06 pm

Amskeptic wrote:
(A) Static.
This adjustment repositions the wiper on the shaft that holds the flap. This adjustment richens or leans the entire fuel map.
Amskeptic, I have followed the steps you have outlined to calibrate my AFM and have some questions now based on my results.

History....AFM passed all diagnostic tests. Wiper was untouched, wiper trace in great shape-show normal wear, glue blobs all original/intact, clean guts, free moving flap, cleaned all connections, carefully wiped down guts with IPA/Q-tip, and set idle bypass screw to 4.5 out. No vacuum leaks on a healthy motor reading 18 in/Hg at idle and correct readings during revving.

Started with a extremely lean factory set AFM....questioning if it is reacting to "today's" fuel compared to when it was calibrated by Bosch back in the 70's since it's been untouched???

Started by moving the cog wheel 3 teeth rich, tested moving the wiper in both directions, fingering results pointed to go more rich. Continued to move the wheel 3 teeth at a time rich until I noticed I came back around full circle to my original starting point!
Started over, reset wheel to original starting point and moved the wiper "static" adjustment 1-tooth rich. Tested and results pointed to start going lean with the cog wheel. Adjusted and tested 3-teeth at a time and ended up with too loose a wiper, to where it was reading off the trace at full enrichment. I also noticed that the wiper now sits a good distance from its original starting point on the trace and way off the fuel cut off switch (not used anyway), which is why it's floating off the trace at full open flap. I read somewhere that the "resting" or starting point of the wiper on the trace should line up it's centered contacts with the corner of the first rectangle printed on the trace board.....I don't know if this is accurate or not???

So my question is where do I go from here? Any suggestions?

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: AFM Adjustment

Post by Amskeptic » Sun Jun 21, 2015 8:39 am

AdreView wrote: Continued to move the wheel 3 teeth at a time rich until I noticed I came back around full circle to my original starting point!

So my question is where do I go from here? Any suggestions?
What vehicle are we dealing with?

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.

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.
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
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

AdreView
I'm New!
Status: Offline

Re: AFM Adjustment

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

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!

Post Reply