Discussion
eliot said:
I think this is possibly where the confusion is stemming from. Even when using the snap-on light, I still had the dialback set to 0 - so its essentially the same as my cheapo light. I relied on my timing tape to get the actual advance figure.
I think the doubling of the advance value is only present when using the dial-back feature - right steve?
Good question, but TBH I doubt it. Ive only ever used a digital Snap On light.I think the doubling of the advance value is only present when using the dial-back feature - right steve?
I havent seen or heard any information stating different to what I already have with regards to the wasted/double scenario. And Ive never needed to try a 0deg flashing only light on my car.
I think, if it sounds right....its due to flashing crank degrees, as opposed to the correct dizzy degrees, which would automatically half things to the correct value we normally see.
This seems to be an inordinate amount of faffing about to resolve what's basically a very simple problem.
1) Verify the TDC notch on the crank pulley. Take the plug out of No1 cylinder. Bring the piston to TDC. Mount a dial gauge with an extension tube onto the piston through the plug hole and rock the piston over TDC. I usually make a little mark (tippex) at 2 thou BTDC on the dial gauge and 2 thou ATDC. True TDC will be halfway between them.
2) Measure the circumference of the crank pulley in mm with a tape measure (or the diameter and multiply by pi). Divide by 360. That's your mm per degree for that pulley size. Usually about 1.5 mm per degree. Now you can mark out in 4 degree increments with tippex or masking tape up to 40 degrees. Remember to mark out clockwise of your new TDC mark.
3) Strobe your advance curve in the normal way without using a dial back facility. If you like you can then check against the dial back to see how the wasted spark is affecting things. It would normally be doubling the advance on a 4 pot. I'm not sure how a V8 would be affected or what coil pack system you have.
Now you can correct any trigger offset in the MS system and hopefully both advance curves will match.
Dave
1) Verify the TDC notch on the crank pulley. Take the plug out of No1 cylinder. Bring the piston to TDC. Mount a dial gauge with an extension tube onto the piston through the plug hole and rock the piston over TDC. I usually make a little mark (tippex) at 2 thou BTDC on the dial gauge and 2 thou ATDC. True TDC will be halfway between them.
2) Measure the circumference of the crank pulley in mm with a tape measure (or the diameter and multiply by pi). Divide by 360. That's your mm per degree for that pulley size. Usually about 1.5 mm per degree. Now you can mark out in 4 degree increments with tippex or masking tape up to 40 degrees. Remember to mark out clockwise of your new TDC mark.
3) Strobe your advance curve in the normal way without using a dial back facility. If you like you can then check against the dial back to see how the wasted spark is affecting things. It would normally be doubling the advance on a 4 pot. I'm not sure how a V8 would be affected or what coil pack system you have.
Now you can correct any trigger offset in the MS system and hopefully both advance curves will match.
Dave
Edited by Daveuk9xx on Friday 11th July 10:32
Edited by Daveuk9xx on Friday 11th July 10:34
Daveuk9xx said:
This seems to be an inordinate amount of faffing about to resolve what's basically a very simple problem.
1) Verify the TDC notch on the crank pulley. Take the plug out of No1 cylinder. Bring the piston to TDC. Mount a dial gauge with an extension tube onto the piston through the plug hole and rock the piston over TDC. I usually make a little mark (tippex) at 2 thou BTDC on the dial gauge and 2 thou ATDC. True TDC will be halfway between them.
2) Measure the circumference of the crank pulley in mm with a tape measure (or the diameter and multiply by pi). Divide by 360. That's your mm per degree for that pulley size. Usually about 1.5 mm per degree. Now you can mark out in 4 degree increments with tippex or masking tape up to 40 degrees. Remember to mark out clockwise of your new TDC mark.
3) Strobe your advance curve in the normal way without using a dial back facility. If you like you can then check against the dial back to see how the wasted spark is affecting things. [b]It would normally be doubling the advance on a 4 pot. I'm not sure how a V8 would be affected or what coil pack system you have.[/b[
Now you can correct any trigger offset in the MS system and hopefully both advance curves will match.
Dave
It doubles the advance on a 4 stroke engine. Number of cylinders is irrelevant.
Coil type is irrelevant...wasted spark is wasted spark. 2 sparks, for every bang, just one in the wrong place.
It doubles the advance on a 4 stroke engine. Number of cylinders is irrelevant.1) Verify the TDC notch on the crank pulley. Take the plug out of No1 cylinder. Bring the piston to TDC. Mount a dial gauge with an extension tube onto the piston through the plug hole and rock the piston over TDC. I usually make a little mark (tippex) at 2 thou BTDC on the dial gauge and 2 thou ATDC. True TDC will be halfway between them.
2) Measure the circumference of the crank pulley in mm with a tape measure (or the diameter and multiply by pi). Divide by 360. That's your mm per degree for that pulley size. Usually about 1.5 mm per degree. Now you can mark out in 4 degree increments with tippex or masking tape up to 40 degrees. Remember to mark out clockwise of your new TDC mark.
3) Strobe your advance curve in the normal way without using a dial back facility. If you like you can then check against the dial back to see how the wasted spark is affecting things. [b]It would normally be doubling the advance on a 4 pot. I'm not sure how a V8 would be affected or what coil pack system you have.[/b[
Now you can correct any trigger offset in the MS system and hopefully both advance curves will match.
Dave
It doubles the advance on a 4 stroke engine. Number of cylinders is irrelevant.
Coil type is irrelevant...wasted spark is wasted spark. 2 sparks, for every bang, just one in the wrong place.
Coil type is irrelevant...wasted spark is wasted spark. 2 sparks, for every bang, just one in the wrong place.
deetes said:
These are the figures I got when using a dial back timing light:
RPM / MS / Actual
900 / 9 / 10
1500 / 21 / 29
1700 / 24 / 31
2000 / 26 / 35
2500 / 33 / 45
As you can see at no time was the difference double to that reading on the MS.
You obviously have some trigger discrepencies then, as your numbers dont appear to follow any pattern, assuming they are accurate.RPM / MS / Actual
900 / 9 / 10
1500 / 21 / 29
1700 / 24 / 31
2000 / 26 / 35
2500 / 33 / 45
As you can see at no time was the difference double to that reading on the MS.
Ranging from 1 deg difference, to 12 degrees....I would be very concerned if that was my engine, and sure as hell wouldnt be loading it up until my timing was known to be correct.
A strobe with the facility to move the strobe timing arbitrarily works in this manner: At e.g. 1000 RPM with conventional ignition, the strobe sees a trigger signal every (60/1000)*2 = 120ms. The strobe measures this period, and divides it by the angle it assumes the engine has turned within the period (720 degrees) in order to get a time/degree number, in this case 166us/degree. From this it can easily shift the strobe point by the required amount.
In a wasted spark system, you get a spark every 360 degrees, so for the engine running at 1000RPM, that works out to be 60ms. The strobe still assumes 720 degrees between sparks, so it calculates an angular period of 83us/degree. Thus you actually get half the change in angle that you dial in on the strobe.
As a (common) example, if you have a Ford EDIS system running the car with the ECU disconnected, you should get a static 10 degrees advance. If you dial in 10 degrees on your strobe, and assuming the crank pulley marking are accurate, you will actually see the timing mark at 5 degrees BTDC, rather than the expected TDC mark. Double the setting on the strobe to 20 degrees, and the timing mark should 'move' to TDC on the pulley.
If the angle is set to zero on the strobe light, it should work as a standard basic strobe and show the actual firing point on the pulley. This is the most reliable way of using the strobe on a wasted spark setup. Note however that the strobe is actually firing twice as often as it would be on a conventional system (and therefore illuminating the other 'side' of the pulley with no marks). Xenon flash tube strobes have a maximum frequency of operation before they start getting unreliable, with a wasted spark system you will hit this limit at half the RPM you normally would. Additionally any timing scatter caused by interference, poorly mounted crank sensors etc. will play merry hell with these timing lights.
In a wasted spark system, you get a spark every 360 degrees, so for the engine running at 1000RPM, that works out to be 60ms. The strobe still assumes 720 degrees between sparks, so it calculates an angular period of 83us/degree. Thus you actually get half the change in angle that you dial in on the strobe.
As a (common) example, if you have a Ford EDIS system running the car with the ECU disconnected, you should get a static 10 degrees advance. If you dial in 10 degrees on your strobe, and assuming the crank pulley marking are accurate, you will actually see the timing mark at 5 degrees BTDC, rather than the expected TDC mark. Double the setting on the strobe to 20 degrees, and the timing mark should 'move' to TDC on the pulley.
If the angle is set to zero on the strobe light, it should work as a standard basic strobe and show the actual firing point on the pulley. This is the most reliable way of using the strobe on a wasted spark setup. Note however that the strobe is actually firing twice as often as it would be on a conventional system (and therefore illuminating the other 'side' of the pulley with no marks). Xenon flash tube strobes have a maximum frequency of operation before they start getting unreliable, with a wasted spark system you will hit this limit at half the RPM you normally would. Additionally any timing scatter caused by interference, poorly mounted crank sensors etc. will play merry hell with these timing lights.
Mr2Mike said:
A strobe with the facility to move the strobe timing arbitrarily works in this manner: At e.g. 1000 RPM with conventional ignition, the strobe sees a trigger signal every (60/1000)*2 = 120ms. The strobe measures this period, and divides it by the angle it assumes the engine has turned within the period (720 degrees) in order to get a time/degree number, in this case 166us/degree. From this it can easily shift the strobe point by the required amount.
In a wasted spark system, you get a spark every 360 degrees, so for the engine running at 1000RPM, that works out to be 60ms. The strobe still assumes 720 degrees between sparks, so it calculates an angular period of 83us/degree. Thus you actually get half the change in angle that you dial in on the strobe.
As a (common) example, if you have a Ford EDIS system running the car with the ECU disconnected, you should get a static 10 degrees advance. If you dial in 10 degrees on your strobe, and assuming the crank pulley marking are accurate, you will actually see the timing mark at 5 degrees BTDC, rather than the expected TDC mark. Double the setting on the strobe to 20 degrees, and the timing mark should 'move' to TDC on the pulley
If the angle is set to zero on the strobe light, it should work as a standard basic strobe and show the actual firing point on the pulley. This is the most reliable way of using the strobe on a wasted spark setup. Note however that the strobe is actually firing twice as often as it would be on a conventional system (and therefore illuminating the other 'side' of the pulley with no marks). Xenon flash tube strobes have a maximum frequency of operation before they start getting unreliable, with a wasted spark system you will hit this limit at half the RPM you normally would. Additionally any timing scatter caused by interference, poorly mounted crank sensors etc. will play merry hell with these timing lights.
I believe that is an error ???In a wasted spark system, you get a spark every 360 degrees, so for the engine running at 1000RPM, that works out to be 60ms. The strobe still assumes 720 degrees between sparks, so it calculates an angular period of 83us/degree. Thus you actually get half the change in angle that you dial in on the strobe.
As a (common) example, if you have a Ford EDIS system running the car with the ECU disconnected, you should get a static 10 degrees advance. If you dial in 10 degrees on your strobe, and assuming the crank pulley marking are accurate, you will actually see the timing mark at 5 degrees BTDC, rather than the expected TDC mark. Double the setting on the strobe to 20 degrees, and the timing mark should 'move' to TDC on the pulley
If the angle is set to zero on the strobe light, it should work as a standard basic strobe and show the actual firing point on the pulley. This is the most reliable way of using the strobe on a wasted spark setup. Note however that the strobe is actually firing twice as often as it would be on a conventional system (and therefore illuminating the other 'side' of the pulley with no marks). Xenon flash tube strobes have a maximum frequency of operation before they start getting unreliable, with a wasted spark system you will hit this limit at half the RPM you normally would. Additionally any timing scatter caused by interference, poorly mounted crank sensors etc. will play merry hell with these timing lights.
Checking timing at only TDC is not reliable enough. It must be checked at at least a couple of different rpm's, and at least 2 different timing figures.
You could very easily have the trigger angle settings wrong where timing appears accurate at zero, but when revved, it can be a mile off, just as the previous timing check examples have been given. Huge discrepancies with timing compared to those displayed on ecu table.
stevieturbo said:
It doubles the advance on a 4 stroke engine. Number of cylinders is irrelevant.
Coil type is irrelevant...wasted spark is wasted spark. 2 sparks, for every bang, just one in the wrong place.
If the wasted spark system is conventional and operating correctly so it triggers every 360 degrees instead of every 720 then I agree. The number of cylinders shouldn't make any difference. However clearly something odd is happening here. Either the strobe is malfunctioning, the OP is a numpty or the ignition system is not working conventionally. Which of these is apposite I couldn't say.Coil type is irrelevant...wasted spark is wasted spark. 2 sparks, for every bang, just one in the wrong place.
Dave
PS - I have a hunch that maybe the Megasquirt is configured for a different trigger tooth pattern than exists which is confusing the hell out of it.
Edited by Daveuk9xx on Friday 11th July 18:24
I just love being called a numpty. So much for a forum that will discuss problems in a civilised manner!!!¬!!!!
Elliot, I got a tape from Real Steel and will check again when I get the car back from it's MOT.
If I can't get to the bottom of this, is it worth converting to EDIS and can you suggest a supplier for an EDIS 8 unit C/W connections?
Elliot, I got a tape from Real Steel and will check again when I get the car back from it's MOT.
If I can't get to the bottom of this, is it worth converting to EDIS and can you suggest a supplier for an EDIS 8 unit C/W connections?
I don't know if this has already been covered, but if that was me, I'd start by logging the tooth timing on the crank sensor to ensure it was getting a good solid consistent lock. For example if the input is inverted you'll see two small 'missing teeth' signals instead of one big one. Depending on the ignition configuration, that seems like the sort of thing that could have the ECU changing its mind about where TDC is. MS ignition configuration strikes me as hideously and excessively complicated and I bet there are loads of ways to set it up wrong which will run the engine but not produce the intended timing. But start by verifying the crank signal, if you haven't already done that.
GreenV8S said:
I don't know if this has already been covered, but if that was me, I'd start by logging the tooth timing on the crank sensor to ensure it was getting a good solid consistent lock. For example if the input is inverted you'll see two small 'missing teeth' signals instead of one big one. Depending on the ignition configuration, that seems like the sort of thing that could have the ECU changing its mind about where TDC is. MS ignition configuration strikes me as hideously and excessively complicated and I bet there are loads of ways to set it up wrong which will run the engine but not produce the intended timing. But start by verifying the crank signal, if you haven't already done that.
I'm realy going to show my ignorance now..... How do you:1) Log the tooth timing and
2) Verify the crank signal
Couldn't find anything about it in the MS1 Extra manual.
deetes said:
I'm realy going to show my ignorance now..... How do you:
1) Log the tooth timing and
2) Verify the crank signal
Couldn't find anything about it in the MS1 Extra manual.
Hardly surprising you don't know because it's next to impossible to find in the MS1/Extra documentation even if you know it's there. I've just had a search for it, and completely failed to find it.1) Log the tooth timing and
2) Verify the crank signal
Couldn't find anything about it in the MS1 Extra manual.
Basically you edit one of the INI files to make an extra memory table in the ECU visible to MegaTune, the table is one that records the time interval between adjacent teeth in real time. The missing tooth stands out because the gap is much longer than normal. If you get one big gap you know you're OK; two smaller gaps indicates a problem.
I'll have another look later on and see if I can dig out the details for this.
stevieturbo said:
Mr2Mike said:
Double the setting on the strobe to 20 degrees, and the timing mark should 'move' to TDC on the pulley
I believe that is an error ???Mr2Mike said:
stevieturbo said:
Mr2Mike said:
Double the setting on the strobe to 20 degrees, and the timing mark should 'move' to TDC on the pulley
I believe that is an error ???GreenV8S said:
Basically you edit one of the INI files to make an extra memory table in the ECU visible to MegaTune, the table is one that records the time interval between adjacent teeth in real time. The missing tooth stands out because the gap is much longer than normal. If you get one big gap you know you're OK; two smaller gaps indicates a problem.
I'll have another look later on and see if I can dig out the details for this.
Yes I recall such an option. I seem to recall having to use megatunix, I did try to install it - my my "tuning" laptop is way too slow - so i gave up.I'll have another look later on and see if I can dig out the details for this.
(And yes i did try searching for it lol..)
eliot said:
GreenV8S said:
Basically you edit one of the INI files to make an extra memory table in the ECU visible to MegaTune, the table is one that records the time interval between adjacent teeth in real time. The missing tooth stands out because the gap is much longer than normal. If you get one big gap you know you're OK; two smaller gaps indicates a problem.
I'll have another look later on and see if I can dig out the details for this.
Yes I recall such an option. I seem to recall having to use megatunix, I did try to install it - my my "tuning" laptop is way too slow - so i gave up.I'll have another look later on and see if I can dig out the details for this.
(And yes i did try searching for it lol..)
Find the .INI file that defines the memory page configuration. In my installation this is defined in C:\Program Files\MegaSquirt\MegaTune2.25\mtCfg\msns-extra.ini and it contains something like this in the [Constants] section at the top of the file:
#unset MEMPAGES ; set to enable all 13 pages for full debugging
#unset LOGPAGES ; set to enable 11 pages for trigger/tooth logging
Change the LOGPAGES line from 'unset' to 'set' i.e.
- set LOGPAGES ; set to enable 11 pages for trigger/tooth logging
; Pages 10 & 11 are special read only pages that can be used to view realtime logged data
; of inter-tooth or inter-trigger times. Primarily for code devel or checking your trigger
; wheel is giving normal pulses.
;At present you can only access this data by using the Table Editor and viewing the data directly
;Page 10 contains the time between each tooth in the generic (missing and/or 2nd trig) and Neon
;Page 11 contains the time between "triggers" and will work for all ignition types
;93 big endian 16bit numbers are returned. The 188th byte is the address of the _next_ byte to
;be written. The code logs continuously once the page is selected so you need to start from the
;next byte and wrap around to the beginning to get the data in the right order
;The 189th byte indicates the time units. 0 = microseconds, 1= 0.1ms units
;After you've selected the page, pause a little then hit Fetch, you'll get 93 new samples.
;Then somehow get them into a spreadsheet and plot a graph.
;i.e. if the data is (decimal) 52, 45, ....
; convert those two numbers -> (52*256) + 45
;page 12 = RAM bytes $0000 to $00FF ($0000 to $003f return zeros)
;page 13 = RAM bytes $0100 to $01FF
The Table Editor referred to in the comments is under the 'Tools' menu. I seem to remember being confused about the table numbering initially, I forget whether it starts from 0 or 1 and I assumed the opposite, so check to make sure that the contents are consistent with the description above. When I went through this it was quite obvious with a screen full of similar values and one much bigger value in the middle so you could see almost at a glance whether there was a problem.
Edited by GreenV8S on Sunday 13th July 10:41
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