AFM Adjustment

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midatlanticys
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Post by midatlanticys » Thu May 13, 2010 4:55 pm

Amskeptic wrote:Maybe you could help me find a proper environment to do the book. I have been unable to.
Colin :blackeye:
OK =D> what criteria are we using to define *proper?*
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Post by Ashtarot » Thu Jun 17, 2010 9:19 am

I just want to say, this post really helped me understand the wizard!
And it's the reason I wanted to join to thank whomever is responabile.
Thanks again.

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Gypsie
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Post by Gypsie » Thu Jun 17, 2010 2:03 pm

That would be Mr. Amskeptic (AKA Colin)

This little bit of info has helped me immensely as well.
So it all started when I wanted to get better gas mileage....

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Post by Ashtarot » Thu Jun 17, 2010 2:39 pm

Haynes, Bently, nor Idiots guide made it as easy to understand as Colin did,
Where did he "get it" from, if I can be so bold?

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hambone
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Post by hambone » Thu Jun 17, 2010 2:48 pm

Madness.
http://greencascadia.blogspot.com
http://pdxvolksfolks.blogspot.com
it balances on your head just like a mattress balances on a bottle of wine
your brand new leopard skin pillbox hat

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Gypsie
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Post by Gypsie » Thu Jun 17, 2010 9:36 pm

Methinks it be a quest for understanding.

And it's the appreciation of the engineering that makes him want to share that understanding with us.


That and the diet-coke-gumout-fueled madness...
So it all started when I wanted to get better gas mileage....

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AFM Adjustments

Post by jlaudin » Mon Sep 13, 2010 11:54 am

I have read this thread carefully and have made said adjustments.
What is your interpretation of these readings for a VW type IV engine in a Baywindow Bus with L-Jetronic?

I have a narrow band O2 sensor in my headers, at highway cruising speeds of 60 MPH about 2,400 RPM I get readings on my voltmeter of .885 to .895 with some spikes to .90. At idle around .47-.52.

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Amskeptic
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Re: AFM Adjustments

Post by Amskeptic » Tue Sep 14, 2010 8:19 pm

jlaudin wrote:I have read this thread carefully and have made said adjustments.
What is your interpretation of these readings for a VW type IV engine in a Baywindow Bus with L-Jetronic?

I have a narrow band O2 sensor in my headers, at highway cruising speeds of 60 MPH about 2,400 RPM I get readings on my voltmeter of .885 to .895 with some spikes to .90. At idle around .47-.52.
You are providing numbers that I cannot relate to. Can you give me Lamba numbers where 14.7 is equivalent to your 1.0 I believe.

As a general rule, we are shooting for 12.0 - 12.5 under full acceleration at 3,000 rpm, and a cruise around 13.5.
The rest is more flexible, I shoot for 14.5 under light load 15 + under deceleration and an idle at 14 to 14.5 at ambient of 70*+ . . . depending on driveability.
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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AFM Adjustments

Post by jlaudin » Thu Sep 16, 2010 1:09 pm

If we assume output from an O2 sensor to be .100 to 1.100 than Stoich is
between .700 and .200 which on an x/y axis is a horizontal line. Above .700 to 1.00 is rich, below .20 to 0 is lean. Ideally at idle stoich would be 14.7 at .4500.

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drober23
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Re: AFM Adjustment

Post by drober23 » Fri May 04, 2012 8:54 am

Colin,

You had a post on that other site, where you listed a bunch of combinations of static, dynamic, and mixture screw settings along with CHTs and MPG for a few settings. In that post you expressed astonishment that you got better fuel mileage at a very rich (11.3) AFR ratio.

Did this ever lead to a change in some of the procedures called out here?

I have been running a bit hotter than I would like, and after dialing in everything else in my FI system, I am now meddling with the AFM. I burnt up my last set of cylinder heads, and have some trepidation about running hot now.

So... it was time to buy some toys! I installed DD CHT, Oil temp, and Oil Pressure gauges. Then when I noticed higher CHTs than I would like, I invested in a PLX Wideband AFR sensor and gauge. This led me to believe I was running lean (AFR around 13.8 - 14.0 when cruising at 70 mph).

Now the brain is open, and I have been performing surgery on it. I marvel at your precision in being able to adjust the static screw precisely. I find it difficult to make minor adjustments, as it wants to jump a lot when I loosen it. Glad I marked that starting position before changing anything!

One of my adjustments left me at that real rich setting (11.5 or so at highway speed for me), so I rolled with it a while. Got terrible gas mileage! (14.7 mpg for 120 miles). Although my CHTs seem to be about 20 degrees lower than when it was at the leaner setting.

I really appreciate this post! Playing with the AFR has really helped me understand the whole FI system better. After reading a bunch more, and experimenting, my big lesson is that what I thought was too hot is probably about what everyone else gets driving that fast. I was getting about 405 - 410 at 70 mph. But that was hotter than I like. If I can get it below 400, i will be happier.

Got kind of rambly here, but any input is welcome.
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 » Sun May 06, 2012 7:19 pm

drober23 wrote:I was getting about 405 - 410 at 70 mph. But that was hotter than I like. If I can get it below 400, i will be happier.
We often get into numbers games, where we shoot for numbers we know nothing about. Others throw numbers around in a big marketing campaign to buy their stuff. Some throw numbers around just because they are seized with their own conclusions. Some numbers are generated falsely, gauges can have discrepancies between vehicles due to wiring variables, placement variables (with vdo non-compensated gauges), and engine variables.

I say drive, do not be happier with better than factory fuel mileage, understand that today we get to run our buses richer than when new, so don't worry so much.
Colin
(I do run a tad rich because I am driving sometimes 10 hours a day flat out in summer, experiment, keep records, don't shoot for arbitrary numbers. 400-410 at 70 with mild cool-downs to 375 on downhills, good)
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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drober23
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Re: AFM Adjustment

Post by drober23 » Mon May 07, 2012 9:45 am

Thanks,

I understand you are a DOOG (doesn't obsess over gauges) kinda guy. I obsess over the gauges until I really understand what they are telling me. Once I have a good handle on things, then I find I stop obsessing. This whole CHT thing is still new to me, and bit by bit I am starting to internalize what is going on.

For now, I have set the AFM following the method outlined here, then adjusted it so I am getting close to 13.1 AFR at 65 - 70 mph. I will have to get a tach out, as I do have trouble hearing "what the engine wants" at the higher speeds. I do most of my driving on the highway. 26 mile (one way) commute, 24 of which are on a highway. So getting in a comfort zone for highway driving is very important for me.

The only thing left that has me scared is I get a big difference between chilly days and warm days. For instance, on my way to work this morning, it was 55 F, and my CHT never rose about 360. But a 25 degree increase to 80 F would have CHT more than 25 degrees warmer (closer to 400). I am afraid of what will happen on the hot days soon to come.

Anyway, the plan is to leave it at the setting I have it at now for a while and try to get a better feel for how the numbers jive with the conditions, and to try to hear what the engine is telling me.
DJ

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

In a time of chimpanzees I was a monkey

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Gypsie
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Re: AFM Adjustment

Post by Gypsie » Mon May 07, 2012 12:05 pm

drober23 wrote:
Now the brain is open, and I have been performing surgery on it. I marvel at your precision in being able to adjust the static screw precisely. I find it difficult to make minor adjustments, as it wants to jump a lot when I loosen it. Glad I marked that starting position before changing anything!
Well since you said "any input" if figgered I'd chime in....

Adjustment of the static screw portion is a tad easier using the following steps.
1. Confirm where you are at...(eyeball the location of the fuel disconnect arm when everything is at rest. I use the end of the control arm as it is further from the center point and makes it easier to 'measure' the amount of change being made). This will be your starting position. I even take a picture to reference.

2. Loosen the screw. Do not loosen so much that the arm is loosey goosey, but loose enough that it can be moved by wedging a small screw driver into the toothed arc and mount area to create a small 'fulcrum and lever'. You can use this to move the arm "just a leeetle beeet' whichever way you want. It is a much more precise adjustment. I have found that movement of 1/8" as measured at the tip of the fuel disco arm has a significant impact on the all over mix and is practically imperceptible to the eye when looking at the teeth of the partial cog.

3. Adjust and tighten. Remember to keep an eye on the arm as you tighten. Mine won't stay still unless I hold it in place when I tighten. It wants to lean it out (ie shift the arm toward CW) as I tighten the set screw.


Lather rinse and repeat. Remember that when you adjust the static, you may need to adjust the dynamic and idle mix.

Have fun.
So it all started when I wanted to get better gas mileage....

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drober23
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Re: AFM Adjustment

Post by drober23 » Mon May 07, 2012 3:20 pm

Good stuff Gypsie! Thanks!

My next adjustment is likely to richen the static screw "just a leeeetle beeeet", and I have been fretting trying to get it just right.
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 » Mon May 07, 2012 3:53 pm

drober23 wrote:Good stuff Gypsie! Thanks!

My next adjustment is likely to richen the static screw "just a leeeetle beeeet", and I have been fretting trying to get it just right.
Dakota Digital gauge gave you that discrepancy between 55 and 80 ambient? A VDO will play all kinds of games.
Do not worry about readings you currently have.

If you have an AFR gauge, your adjustments need to bend around the superior information at your disposal.
Maximum torque is at 3,000 rpm, so get there in 4th gear (50-55 mph) and let me know what your readings are at 50 then 55 then 60 then 65 then 70 at whatever temp you are testing at.
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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