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Dangermouse Samba Member
Joined: November 23, 2005 Posts: 1266 Location: Beautiful New Zealand
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Posted: Sun Sep 17, 2006 4:25 pm Post subject: Measuring dwell - having difficulties :-( |
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I have an electronic, automotive multimeter, like this one...
I want to use it to measure my dwell angle, so I hook up the red lead to the #1, negative post on the coil, ground the black lead and start the car. The meter just seems to go nuts, screen flashes on and off, displays gibberish, seems to stablilise for a few seconds and then blanks again. Not at all happy.
I don't think the meter's faulty as the other functions seem to work ok.
But - the coil is 6 volt; is this causing the problem? |
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glutamodo The Android
Joined: July 13, 2004 Posts: 26297 Location: Douglas, WY
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Posted: Sun Sep 17, 2006 4:30 pm Post subject: |
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I've got one of those meters too. Never have been happy with its dwell (or tachometer) readings. I found that keeping the probe wires as far away from the coil and the spark plug wires helped a little but, but I don't even bother trying to use it for tach/dwell anymore, I've got a couple of other digital meters that work OK, plus an old analog meter that I think works the best of them all.
Oh, and the 6V part shouldn't really make a difference to a self-powered or unpowered meter.
-Andy |
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atye Samba Member
Joined: September 02, 2004 Posts: 580 Location: Peachtree City, GA
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Posted: Mon Sep 18, 2006 6:40 am Post subject: |
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I have one of the old analog type dwell meters. Found it in a buddy's tool box a few years ago, he had no idea what it even was. I've used it many, many times and the car runs noticibly different when the points were set by the dwell meter vs a feeler gauge. Not sure if a DMM would work right on 6v or not, good question there. |
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gt1953 Samba Member
Joined: May 08, 2002 Posts: 13842 Location: White Mountains Arizona
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Posted: Mon Sep 18, 2006 7:03 am Post subject: |
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I have and old analog meter with the needle type. It is for 6 cyl and 8cyl and says double the reading for 4 cyl. it works pretty good for my aplication. _________________ Volkswagen: We tune what we drive.
Numbers Matching VW's are getting harder to find. Source out the most Stock vehicle and keep that way. You will be glad you did.
72 type 1
72 Squareback
({59 Euro bug, 62, 63, 67, 68, 69, 73 type ones 68 & 69 type two, 68 Ghia all sold}) |
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rsperko Samba Member
Joined: May 22, 2006 Posts: 119 Location: Milwaukee, WI
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Posted: Mon Sep 18, 2006 7:48 pm Post subject: |
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atye wrote: |
I... runs noticibly different when the points were set by the dwell meter vs a feeler gauge ... |
Which was better for you? I have been setting mine by dwell lately, but really do not know.
Thanks,
-Rick _________________ 63 Ragtop - L380 |
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Dangermouse Samba Member
Joined: November 23, 2005 Posts: 1266 Location: Beautiful New Zealand
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Posted: Mon Sep 18, 2006 9:15 pm Post subject: |
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Quote: |
Not sure if a DMM would work right on 6v or not, good question there. |
Oh yeah, if its some weird problem that noone's ever encountered before; that'd be me all right
Anyone wanna buy a multimeter? One careful owner, used once... |
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atye Samba Member
Joined: September 02, 2004 Posts: 580 Location: Peachtree City, GA
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Posted: Tue Sep 19, 2006 5:53 am Post subject: |
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rsperko wrote: |
atye wrote: |
I... runs noticibly different when the points were set by the dwell meter vs a feeler gauge ... |
Which was better for you? I have been setting mine by dwell lately, but really do not know.
Thanks,
-Rick |
I noticed that the car ran LOTS better after setting the points with a dwell meter than a feeler gauge.
The dwell (to my understanding) in simple terms, is a measurement of the amount of spark it takes to jump the air gap of the open points. If you use a feeler gauge on worn points, there may be small ridges that will affect the measurement, but the dwell meter will not have the same problem because it does not physically touch the worn surfaces.
I would put the meter on the coil, remove the cap, and have someone spin the motor over while I tweaked the adjustment on the points. |
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doug Samba Member
Joined: September 03, 2003 Posts: 48 Location: dunedin, fl
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Posted: Tue Sep 19, 2006 8:42 am Post subject: dwell |
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dwell or dwell angle is how many degrees your points are closed in relation to the rotation your rotor. This determine how much time your coil has to energize. |
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atye Samba Member
Joined: September 02, 2004 Posts: 580 Location: Peachtree City, GA
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Posted: Tue Sep 19, 2006 9:04 am Post subject: |
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I was close, right?
LOL
I'd swear I read that somewhere (about the air gap)... maybe that was too many brain cells ago.
Regardless, dwell is the way to go! |
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Buggeroff Argumentative Bastard
Joined: October 16, 2004 Posts: 1124 Location: Lake of the Ozarks, Missouri
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Posted: Tue Sep 19, 2006 10:54 am Post subject: |
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Why don't you just use a six volt bulb and a couple of wires across the coil feed and ground ?
Set your points, set your timing marks, switch on ignition, rotate distributor untill the bulb lights up and voila, dwell is done.
BTW, that big black clamp looks like it is for measuring current draw.
Chris. _________________ "Chris of the Ozarks"
Headlinerless 57 Ghia
Thread deleter extrordinaire. |
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UncleBob Grease Midget
Joined: August 21, 2002 Posts: 2862 Location: Northeast Florida
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Posted: Tue Sep 19, 2006 11:48 am Post subject: |
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crtclff wrote: |
Why don't you just use a six volt bulb and a couple of wires across the coil feed and ground ?
Set your points, set your timing marks, switch on ignition, rotate distributor untill the bulb lights up and voila, dwell is done.
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Because that is 'Static Timing' and not checking Dwell Angle? _________________ OG JHC
don't worry, the ciggaret is fake. |
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KTPhil Samba Member
Joined: April 06, 2006 Posts: 33875 Location: Conejo Valley, CA
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glutamodo The Android
Joined: July 13, 2004 Posts: 26297 Location: Douglas, WY
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Posted: Tue Sep 19, 2006 1:17 pm Post subject: |
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Maybe it is a 6V problem - although I've had some problems in the past checking the dwell with my meter, I just threw my meter on my 12V cars and it was working fine. (I do know the inductive tachometer sensor is useless on my cars though, no matter what wire or where I move the adjuster thingy on the inductive pickup)
Now that I think back again, I'm not sure if I ever used this particular meter on a 6V car before, I got it only a few months before I quit being a mechanic and I may not have got the chance to then. Could be that 6V isn't strong enough for this meter to get a good enough signal to read reliably.
NOTE: I just realized there's something else you might be able to try with this meter: Dwell is a duty cycle measurement, transformed into the traditional "dwell angle" range depending on how many cylinders you have. Now, if your meter is the same type as mine, there will be a separate duty cycle setting that might work for you. On mine, it's 3 clicks to the left of OFF, and says %duty. This gives duty cycle based on a 100% scale. Use the same connections, the positive/red lead to +1 on the coil, negative/black lead to a good ground on the car, (I often clip mine to my rear bumper and keep that wire out of the engine compartment) And if yours will read a steady duty cycle, then all you have to do is multiply your reading by 9/10 (0.9) to get the dwell. Or, go in reverse, and make it even simpler, VW speciifies dwell to be 44 to 50 degrees, and to translate that 44-50 degree range for a duty cycle, you'd multiply by 10/9ths (1.11) and get 48.8 to 55.5 degrees, aiming for the middle of that range. I'd try that and see if it works.
-Andy |
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Dangermouse Samba Member
Joined: November 23, 2005 Posts: 1266 Location: Beautiful New Zealand
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Posted: Sun Sep 24, 2006 4:46 pm Post subject: |
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Thanks for the suggestions folks, just for the record, my digital multimeter couldn't read duty cycle either - I guess they're just calibrated to measure 12V outputs.
I'll have a look at setting dwell statically as KTPhil suggests, or try and find myself an OLD meter.
(Keywords for future searchers: 6 volt, 6V, dwell, digital multimeter, crappy). |
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glutamodo The Android
Joined: July 13, 2004 Posts: 26297 Location: Douglas, WY
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Posted: Mon Sep 25, 2006 3:27 am Post subject: |
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I tried mine on the duty cylce measurement the other day and it worked, but it's 12V, so maybe 6V isn't strong enough after all. At least it was worth a try.
FYI - whenever I've set my dwell to the 47 degrees the factory recommends, and have double checked it with a feeler gauge, I've found the gap to be .017-.018, that's within the .016-.020 range the Bentley states too. |
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Dangermouse Samba Member
Joined: November 23, 2005 Posts: 1266 Location: Beautiful New Zealand
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Posted: Thu Oct 12, 2006 3:21 pm Post subject: |
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So, I acquired an old, analogue-type dwell meter and hooked that up and it seemed to function fine so I guess at this stage I'm prepared to resign myself to the fact that 6 volt systems bring some 6 volt problems. I still wouldn't be tempted to change it over though, I like it running 6 volts.
BUT - in order to get a dwell reading of approx. 50 degrees (25 degrees on an 8-cylinder scale), I had to gap my points to .035 rather than .016; should I be concerned about this and what does it say about the condition of my distributor?
After I did this the engine wasn't running too well and I returned the point gap to .016 (but I have a nagging suspicion that that might be because I timed the engine on cylinder #3 instead of #1 'cos I forgot to check the position of the rotor . I'll have to go back and repeat the exercise). |
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KTPhil Samba Member
Joined: April 06, 2006 Posts: 33875 Location: Conejo Valley, CA
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Posted: Thu Oct 12, 2006 3:41 pm Post subject: |
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Something ain't right, and it seems everything is off by a factor of 2...
6V vs. 12V
0.016' vs. 0.035'
50 degrees vs. 25 degrees (normal for the 8 cyl scale)
Do yourself a favor, use my static method (only requires a light bulb) and then see what the dwell meter reads. |
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Dangermouse Samba Member
Joined: November 23, 2005 Posts: 1266 Location: Beautiful New Zealand
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Posted: Wed Jan 27, 2021 10:00 pm Post subject: Re: Measuring dwell - having difficulties :-( |
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I learned something today that I wish I had known when I first posted this thread and thought I'd share for those as quick on the uptake as myself
I know, from searching, that many folks have struggled with getting an accurate dwell reading on 6V cars running points. Feeler gauges will get you close but correctly points gap should be set using a dwell meter. Old, analog equipment is exactly that and fancy digital meters often don't appear to work correctly with the 6V signal, or so I long thought...
Maybe everyone already knows this and I just didn't pick up on it correctly.
I have a nice digital meter that I have used for tach, timing advance, voltage etc, everything except dwell reading as when I tried it it just bounced numbers around which didn't make any sense and I put it down to 6V oddness as I have before. On my 6V car, I have powered it directly from a 12V battery source and it works fine like that for everything, except dwell...
BUT, if like I did today, I add an additional ground wire from the 12V battery source negative terminal to a ground point on the car itself - it works perfectly!
Who knew! Maybe everybody except me
Anyway, I'm posting this because it would have been useful information to have at the time. _________________ Do not follow me, for I may not lead. Do not lead me, for I may not follow. Do not walk beside me either; actually just bugger off and stand over there will you. |
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Wayne S. Johnson Samba Member
Joined: April 12, 2006 Posts: 1265 Location: GILROY, CA
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Posted: Wed Jan 27, 2021 11:40 pm Post subject: |
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Print a pic of a degree pulley and taped it to the pulley.
Connect a small lamp from the points to ground and turn on ignition sw.
Rotate the pulley, when the light goes off record the position, when the light goes on record the position.
Subtract the two numbers (Correction: "the values shall be divided by 2 to have the real dwell angle"). Thanks Herby 1200.
Useful to test the accuracy of your dwell meter.
_________________ Additional products https://www.thesamba.com/vw/classifieds/search.php?username=Wayne+S.+Johnson
Additional products with Bluetooth http://www.thesamba.com/vw/classifieds/detail.php?id=2097231
Last edited by Wayne S. Johnson on Sun Jan 31, 2021 11:41 pm; edited 4 times in total |
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herbie1200 Samba Member
Joined: April 27, 2006 Posts: 832 Location: Rome - Italy
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Posted: Thu Jan 28, 2021 4:16 am Post subject: |
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glutamodo wrote: |
NOTE: I just realized there's something else you might be able to try with this meter: Dwell is a duty cycle measurement, transformed into the traditional "dwell angle" range depending on how many cylinders you have. Now, if your meter is the same type as mine, there will be a separate duty cycle setting that might work for you. On mine, it's 3 clicks to the left of OFF, and says %duty. This gives duty cycle based on a 100% scale. Use the same connections, the positive/red lead to +1 on the coil, negative/black lead to a good ground on the car, (I often clip mine to my rear bumper and keep that wire out of the engine compartment) And if yours will read a steady duty cycle, then all you have to do is multiply your reading by 9/10 (0.9) to get the dwell. Or, go in reverse, and make it even simpler, VW speciifies dwell to be 44 to 50 degrees, and to translate that 44-50 degree range for a duty cycle, you'd multiply by 10/9ths (1.11) and get 48.8 to 55.5 degrees, aiming for the middle of that range. I'd try that and see if it works.
-Andy |
This is correct, let me explain why.
Dwell angle is related to distributor rotation (not the crankshaft rotation!).
Distributor, in a complete revolution (360°), has to spark 4 cylinders, so it has 90° available for each cylinder.
So the idea is, to have the coil energized for about one half the time available, to set dwell at the half of degree available, i.e. 90°/2=45°.
If it was an 8cyl engine, the degrees available for each cylinder are 360/8= 45° so the dwell for 8cyl engine is about 20-30°.
The dutycycle is a percentage of a square wave: how many time it is "on" respect to the full period.
So 100% duty cycle corresponds to 90° dwell in a 4 cyl engine. And 50% duty cycle corresponds to 45° dwell. This is why 9/10 is the factor between dwell and duty cycle.
Pay attention that duty cycle is the ON time of the square wave, so the multimetr shall be connected on +15 and 1 of the coil.
If connected on ground and the coil it measures ON when the coil is OFF so you have the opposite of the dwell angle.
A dwell meter is good to check the variable-dwell distrubutors (accuspark, etc.) to chek how the dwell angle is adapted to the engine speed. |
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