LM-2 readings

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72Hardtop
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Re: LM-2 readings

Post by 72Hardtop » Sat May 17, 2014 6:29 am

Here is the chart Colin I tried to send you. Stoich (14.7) is the center dashed line.
Attachments
AFR chart.jpg
AFR chart.jpg (40.29 KiB) Viewed 7091 times
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

72Hardtop
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Re: LM-2 readings

Post by 72Hardtop » Sun May 18, 2014 4:01 pm

The following videos were shot a little while ago. They show the following:

Speed

Vacuum reading/s

Air fuel ratio (LM-2)

Video was taken going south on 167 from 405 the back from Central on same highway (167). Fairly level stretch of highway.

https://www.youtube.com/watch?v=0ObUMPC ... e=youtu.be

https://www.youtube.com/watch?v=4ZGLD67 ... redirect=1
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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Amskeptic
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Re: LM-2 readings

Post by Amskeptic » Mon May 19, 2014 9:50 am

72Hardtop wrote:The following videos were shot a little while ago. They show the following:
Speed
Vacuum reading/s
Air fuel ratio (LM-2)
You are close . . .

I would like to see a little lower A/F numbers at speed, unless you are off throttle.
14.3 at 70 mph at partial throttle is a bit lean.

Regarding plug reading, by the way, there is nothing to be learned from filing away the threads/shell to see the center ceramic. We can *assume* that plugs will be clean and porcelain will be whitish.

The useful warning is actually the perimeter ring of the plug metal, right where the threads are. If the perimeter has a whitish powdery look, that is too lean. Normally they are black carbonish and the ceramic is a brown to whitish.

If you are getting 18 mpg at 70, that is leanish. With the aerodynamic load at that speed, the factory emissions-saddled engines would only get 16-17. Performance carbs, should be equivalent. Get thee a Dakota Digital.
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

72Hardtop
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Re: LM-2 readings

Post by 72Hardtop » Mon May 19, 2014 10:47 am

Opening the plug was suggested by John from Aircooled.net he stated that with today's fuels the base of the ceramic where it meets the steel is where the fuel ring if any will show.

The plugs looked good no signs of overly lean as you described. I noticed as you probably did as well that at 60 mph and below the LM-2 readings were great high 12s - low 13s. Its after 60mph they started there way to the high 13 - 14 range. At that speed/rpm I believe the air corrector jets determine mixture. What do you think/suggest?

My last trip to Vancouver BC I averaged 20.6 mpg at 60 mph. I checked the valve lash a few days ago (after 1,109 miles) and none were snug and only 3 were at a loose .006 (intakes) cylinders 1,3 and 4. Likely my doing from a previous check & adjust. Nothing pointing at running too hot. But I to would like to see the AFR at those speeds at least no higher than 13.5.

Off the throttle the AFR readings drop from the low 14 range. What do you think of my vacuum readings? I've confirmed the advance plate starts to move right from 0 and stops at 4+ or so. I wasn't even sure my carbs would even offer up a signal. I'm also using a anti pulse valve to dampen the signal pulses.

Given my confirmed vac readings is it safe to say the vac advance is functioning?

Much appreciated

PS...its looking like I'll be in southern cal during your time there. Well have to meet up? Going to drive the bus down. Will also be home in WA. During your visit here as well. Will be in Huntington Beach, CA. During our stay. Looking to be down there for 2-3 weeks.

Talk soon and stay safe

Jim Floyd
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

72Hardtop
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Location: Seattle, WA./HB. Ca./Shizuoka, Japan
Status: Offline

Re: LM-2 readings

Post by 72Hardtop » Fri May 23, 2014 3:43 am

Update:

Dropped in 125 mans and LM-2 readings at 60, 65 and 70mph are settled in the low 13's or so (depending on foot). Heavy accel mid-high 12s low 13's. Vacuum readings went as high as 5-6inHg (depending on foot).

Final jetting:

50 idles
125 mains
180 air correctors
F11 E-tubes
28mm vents
float height 10.45mm
float drop 32mm

Did notice that after resetting for LBI from mid 11's to ~13-13.2 that on decel down steep grade (city street) I get subtle popping. This is in 3rd gear high RPM foot off gas. Made check of exhaust and everything looks great (pulled lower tins) no signs of carbon tracking around manifold-head joints and no signs of carbon tracking elsewhere very clean. No popping at any other times idle, accel or decel. Best guess:

1. I know to a degree it can be normal with IDF's

2. Or exhaust (S&S 4-1 w/Walker QP) might be big enough that it's reduced back pressure just enough that getting rid of popping on decel may be difficult (certain conditions).

3. Overrun condition...glanced over at LM-2 when I heard the subtle popping and it was in the 14-low 15 range. Transition range from progression-main coupled with steep downhill high RPM condition.

Thoughts?
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

luftvagon
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Re: LM-2 readings

Post by luftvagon » Fri May 23, 2014 6:29 am

Can't help you with the carb... but did you calibrate your LM-2?
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

72Hardtop
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Location: Seattle, WA./HB. Ca./Shizuoka, Japan
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Re: LM-2 readings

Post by 72Hardtop » Fri May 23, 2014 11:04 am

Yes, LM-2 was calibrated.
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

72Hardtop
Old School!
Location: Seattle, WA./HB. Ca./Shizuoka, Japan
Status: Offline

Re: LM-2 readings

Post by 72Hardtop » Fri May 23, 2014 2:28 pm

Yeah, the LM-2 doesn't lie which is great. It'll also tell you/one if you have any exhaust leak/s upstream from the sensor by showing lean. LM-2 doesn't show AFR #'s to indicate that I'm running lean during idle, acceleration, steady speed or decel (without steep grade/overrun) it shows no lean conditions.

I know that at certain conditions deceleration... (overrun) is when one could/can expect some light/subtle popping when the throttle is closed (high RPM) and the mix goes lean coupled with the fact that there is no added advance to help with the lean mix burn. As John said there is no load...so no worries.

One other thing that would point to an exhaust leak would be how often it's occurring and at what state IOW...if it's happening at other points of engine operation such as acceleration, idle or normal decel (no overrun) it's likely one has an exhaust leak or a combination of a lean/plugged idle jet combined with an exhaust leak...but of course the LM-2 would tell one this.

I could try to tune it out perhaps with the A/F screws...
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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Amskeptic
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Re: LM-2 readings

Post by Amskeptic » Fri May 23, 2014 2:40 pm

72Hardtop wrote:Yes, LM-2 was calibrated.
Rock . . . hard place.

Too lean causes misfires which do not make noise but leave a nice little cloud of unburned fuel that will ignite at the next cycle.

Volkswagen + emissions laws had to do all number of tricks to reduce backfires. They all add air.
Throttle Positioner ........'68-'70
Dashpot ......................... '70-'74
Gulp Valve...................... '73-'74 dual carb bus
Decel Valve ................... all L-Jets
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

72Hardtop
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Re: LM-2 readings

Post by 72Hardtop » Fri May 23, 2014 3:11 pm

Amskeptic wrote:
72Hardtop wrote:Yes, LM-2 was calibrated.
Rock . . . hard place.

Too lean causes misfires which do not make noise but leave a nice little cloud of unburned fuel that will ignite at the next cycle.

Volkswagen + emissions laws had to do all number of tricks to reduce backfires. They all add air.
Throttle Positioner ........'68-'70
Dashpot ......................... '70-'74
Gulp Valve...................... '73-'74 dual carb bus
Decel Valve ................... all L-Jets

If one is too lean wouldn't adding more air make it more lean resulting in more of a likelihood of exhaust popping under certain conditions such as overrun?

Something those with IDF (or aftermarket perf. carbs) would likely have to live with...given they have none of the above devices.
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

User avatar
Amskeptic
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Re: LM-2 readings

Post by Amskeptic » Fri May 23, 2014 8:36 pm

72Hardtop wrote: If one is too lean wouldn't adding more air make it more lean resulting in more of a likelihood of exhaust popping under certain conditions such as overrun?

Something those with IDF (or aftermarket perf. carbs) would likely have to live with...given they have none of the above devices.
They had to go balls-to-the-wall lean, we're talking so lean that it is virtually just air.
Your option is to go up rich in the idle circuit, it won't affect fuel economy, it will give you a floor under the rest of your mixture map.
Make a nice sensible flexible series of compromises and you'll do fine.
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

72Hardtop
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Location: Seattle, WA./HB. Ca./Shizuoka, Japan
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Re: LM-2 readings

Post by 72Hardtop » Fri May 23, 2014 9:32 pm

Used the bus to go to work but noticed it seemed a little more missy than usual after starting while idling . As bus warmed up it idled better. Ran great down the highway (no miss/es). But on decel (off throttle in gear) just a touch poppy if listening very closely. I did a lash check last week and none were snug and reset (3) that were a loose .006. I'm thinking that perhaps I misjudged on one of the adjustments. While checking/listening to the engine after starting # 3&4 side carb snorted a couple of times...plugged jet, snug valve or A/F mix screw off. I'm going to check them again before leaving work to be sure.

After getting to work I decided to do a little test. With a small sheet of paper ~ (5in x 4in) I held it up to the exhaust and it would occasionally pop inward rather than continually be pushed away. Ding..Ding..Ding..a miss. Hmmm...now we're onto something. Possible snug/loose valve. Definitely going to check the lash again.

If that doesn't do it I'll check the following:

1. Check for plugged idle circuit...again (pulled and cleaned last night) but did not run bus afterwards...tired.

2. Possible ignition issue...spark plug wire/s or fouled plug (just changed plugs a couple weeks ago) Wires ~ 2 years old (Bosch)
Cap & rotor is new.

3. A/F mixture adjustment
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

72Hardtop
Old School!
Location: Seattle, WA./HB. Ca./Shizuoka, Japan
Status: Offline

Re: LM-2 readings

Post by 72Hardtop » Sat May 24, 2014 9:40 am

Fixed:

First checked valve lash. All valves ok (.006)

Next start bus still running funky. Warmed up a bit and #3-4 side would spit/huff a bit. Hmmm.ok start checking mix screws...#3 first. Bang! #3 mixture was too far in 1/4-1/2 or so.

Drove home. Bus ran great. Once home rechecked LBI (all screws) and all seems well now.

Figure it had to be something simple. Best guess...while adjusting them the other day I turned #3 in further than usual and lost track of how far I turned it in an inadvertently did not return it far enough. This would definitely cause the popping at idle while coasting downhill in gear (overrun).

Bad hand...bad hand!
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

72Hardtop
Old School!
Location: Seattle, WA./HB. Ca./Shizuoka, Japan
Status: Offline

Re: LM-2 readings

Post by 72Hardtop » Sat May 31, 2014 10:22 am

Update:

Driving home from work there is a good 6-7% grade (1.5 -2 miles length) from Redmond - Seattle on the 520 towards Seattle. Hit that at 60+mph and the bus held easily the AFR was 12.6 - 13-13.2, mostly 13 - 13.2.

Cresting the grade it creeps to high 13' low 14's then settles back to low 13's. At times depending on load (slight decline/feathered) throttle the AFR will creep to low 14's. Adding any throttle however slight and it drops right back to low 13's.

Once crested the freeway has gentle up & downs during this time I can see the AFR fluctuate between high 12's - low 13's to 14 - 15.1 depending on throttle position & load (incline vs decline).

Idles at high 12's - low 13.1 - 13.2

Thought I tackled the subtle popping during heavy downhill decel. Still there. Not going to worry given it's under a no load condition and I'm optimally tuned according to the LM-2. Prior to hooking the LM-2 to the bus my LBI would be at ~ 11.0 - 11.5...too rich for me. With that AFR at idle I wouldn't hear (or couldn't) the subtle popping on heavy downhill decel.

So goes the life of aftermarket performance carbs when dialed in without any of the added luxuries to prevent such occurrences.
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

User avatar
Amskeptic
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Re: LM-2 readings

Post by Amskeptic » Sun Jun 01, 2014 6:25 am

72Hardtop wrote:With a small sheet of paper ~ (5in x 4in) I held it up to the exhaust and it would occasionally pop inward rather than continually be pushed away.
With any performance exhaust, you will be more aware of combustion irregularities because the exhaust is coming out more freely. You literally hear up the pipe to the combustion chamber, instead of hearing the cancelled out noise from endless baffles. With a performance cam, you lose idle efficiency, again combustion irregularities. Now you have a lopy idle with awareness of every combustion miss. The best way to know if your combustion is regular, is to get an HC reading.

You have heard many muscle cars trying to idle at a stoplight, right? They are popping and shaking and loping all over the place. Do not chase your tail if the engine starts well, idles at a consistent rpm when warm, moves out and pulls you up to speed, runs cool enough and gives decent economy. Some roughness around the edges is unavoidable. VW detuned their engines to pussycat status for a smooth idle and tractable performance.

Smaller spark plug gaps can improve combustion regularity. Are you at .028"? VW allows .024-.028"
Many performance ignition system ads tout their sooper-zinger 30,000 volt sparks, and everybody then assumes that you should open up the spark plug gaps to .045" or whatever, but that is not really how this is supposed to work. The spark plug gap needs to be small enough for reliable sparks with the ignition system you have, but as importantly, the flame propagation needs to be a nice linear burn. If you have a half a mile long spark and initiate a large wall of combustion, you are not getting the smooth progressive burn that reaches the piston at the all-in point.

Awaiting your update,
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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