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Old 07-08-2013, 02:59 AM   #1
digger440 OP
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Question Electronic ignition Hall waveform shenanigans

So some questions for you electronic guys, techs, and airhead gurus, on my current project, an 1982 R100RT I am using two Accel 140032 coils. I purchased a WeaponX single channel coil driver in order to drive the coils.
So here are my questions

1. The Hall Generator produces a square wave which is sent to the ICM. The ICM in turn uses logic circuits to trigger the factory coils with a specific dwell and saturation time. Does anyone know how far off the wave length of the Hall signal is versus if you were to measure the dwell time with a lab scope on the trigger side of the module?
The reason I ask is that the coil driver is a slave unit and relies on the falling edge of a square wave to trigger the coil. In its normal application the driver would get a signal from a PCM which contains the programming for correct dwell (on time) and coil saturation. If I were to wire the Driver directly to the Hall signal generator I am not sure if there would be enough wavelength to have the correct dwell time and saturation, thoughts anyone?

2. If there is not a long enough of a signal coming from the hall sensor to make the correct parameters for the driver could I wire reduced voltage through a very small load or resistor to the trigger side of the factory ICM and then wire the driver in parrallel between the two thus artificially producing a high-low-high square wave as the ICM triggers the reference voltage to ground? Even with a very small load would inductive kick screw with my pattern?


3. If I were able to make option 2 work would varying the voltage amount aid in extending dwell or saturation time or would only wavelength do that? The driver triggers on a square wave from 2.8 to 12 volts and the factory ICM triggered 12 volts (two 6V coils in series) to ground. This would give me approx. 9 volts of amplitude to play with.

Here are links to the rather lackluster technical documentation for the driver module and to the wiring schematic for it (all of three wires)


http://www.weaponxperformance.com/manuals/Ignitor_Manual.pdf
http://www.weaponxperformance.com/technicalPDF/Ignition%20Module%20Specs.pdf



And for those that have absolutely no idea what I just said above


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digger440 screwed with this post 07-08-2013 at 03:17 AM
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Old 07-08-2013, 06:01 AM   #2
StephenB
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Soooo ...

You are trying to make the WeaponX work on your airhead? Or you are just looking for option to replace the factory EI?

First off: the Accels #140032 have a primary resistance of 0.66Ohm @ 12V so if you would install two in series, each of them only gets 6V, not enough juice to get them charged. If you'd install them in parallel, you would draw double the current and most likely kill the ignitor in a very short period of time.

As for the general function of the unit: unless the PCM works with the mechanical advance (like a Boyer), I would assume that the PCM triggers the ignitor based on a digital "map" that is programmed in. The PCM sends pulses to the ignitor based on the rpm and that specific map. The higher the frequency, the shorter the time between signals the shorter the time for the coil to charge (dwell) hence variable dwell time. It is possible for the "intelligence" to be in the ignitor but the wording suggest the PCM to have the smarts.

As for the dwell time: there is a note on the drawing saying "typical dwell time to be between 1.8 and 3.2". The dimension is missing (ms ?), so you better go back to the manufacturer and ask.

As for the PCM output signal: "2.5-12V, square wave" is specified, it is missing the required current (or permissable inner resistance); the output specification of the PCM must meet the input specification to the ignitor, is this where your question #2 stems from?


I am not familiar with the internals of the WeaponX but I wouldn't do anything as suggested in #1, #2 or #3 without prior discussion with the manufacturer.
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Old 07-08-2013, 04:55 PM   #3
Warin
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Dwell is a left over from the points system. I prefer not to use that term as it simply confuses the issues.

In a points based system the coils are selected to obtain the minimum amount of energy required to fire the spark plugs at maximum rpm. At slower speeds the coils will saturate and the excess energy is simply dissipated as heat (thus the coils get hot). The dwell is expressed as a % of one crank shaft revolution.

Now in an electronic system the coil is on for the required TIME to obtain the energy required to fire the spark plug at ANY speed (you might call this saturation time). Thus the dwell % will change as the engine speed varies. Ok? Some talk of dwell without % or time terms - very confusing. Thus I don't use the dwell term! I'd recommend you do the same.

The time between the hall effect (or other) engine position signal and the spark plug being fired depends on the ICU, different ICUs have different characteristics to suit the engine and the engine position sensing system.

I'd NOT wire it as per WeaponX instructions. And having looked at their 'manual' I'd NOT BUY their product!

---------------------------------------
The standard bmw hall effect signal is a square wave (50% duty cycle) voltage should be around 8~10 volts (from the standard ICU) and IIRC a maximum current of 100mA. The output is open collector, if you understand the term. The relationship between the signal and engine position changes with engine rpm ... a simple centrifugal relationship set within the 'bean can'. You cannot change the engine position relationship by trying to change the output voltage!

Warin screwed with this post 07-08-2013 at 05:03 PM
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Old 07-09-2013, 07:14 PM   #4
Warin
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The standard BMW/Bosch system is very simple on these bikes!

The advance is a simple mechanical centrifugal advance within the bean can.

Then a hall effect switch generates a 50% duty cycle square wave.

The a ICU unit fires the coils for a set time.

The single coil connects to both spark plugs.

------------------------
The delay between the hall effect signal and the ICU output would be in the order of micro seconds - simply the delay through the electronics? There is a circuit in one of the Bosch books (blue or red?)... it does have at least one basic error in that circuit.
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Old 07-12-2013, 03:44 PM   #5
digger440 OP
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Quote:
Originally Posted by StephenB View Post
Soooo ...

You are trying to make the WeaponX work on your airhead? Or you are just looking for option to replace the factory EI?

First off: the Accels #140032 have a primary resistance of 0.66Ohm @ 12V so if you would install two in series, each of them only gets 6V, not enough juice to get them charged. If you'd install them in parallel, you would draw double the current and most likely kill the ignitor in a very short period of time.

As for the general function of the unit: unless the PCM works with the mechanical advance (like a Boyer), I would assume that the PCM triggers the ignitor based on a digital "map" that is programmed in. The PCM sends pulses to the ignitor based on the rpm and that specific map. The higher the frequency, the shorter the time between signals the shorter the time for the coil to charge (dwell) hence variable dwell time. It is possible for the "intelligence" to be in the ignitor but the wording suggest the PCM to have the smarts.

As for the dwell time: there is a note on the drawing saying "typical dwell time to be between 1.8 and 3.2". The dimension is missing (ms ?), so you better go back to the manufacturer and ask.

As for the PCM output signal: "2.5-12V, square wave" is specified, it is missing the required current (or permissable inner resistance); the output specification of the PCM must meet the input specification to the ignitor, is this where your question #2 stems from?


I am not familiar with the internals of the WeaponX but I wouldn't do anything as suggested in #1, #2 or #3 without prior discussion with the manufacturer.


Sorry for the delayed response work has been hell this week.

Anyhow I did not put the specs found for the coils in my post as I do not think the primary resistance given is correct. I measured both the coils I have and they are 2.4 ohms primary each. So at 13V they should pull about 10A.

In their factory setting all 8 (or 10) coils, in addition to the pcm are fed off one 30 amp circuit in parallel and there are 2 capacitors bolted to the intake, one for each bank.

So forget questions 2&3 as I was thinking out loud and it wont work.

I am just going to have to place a phone call but I hate company tech lines as there is usually just some guy reading from a FAQ sheet and you just get transferred to some other person voicemail when you confuse the first guy
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Old 07-12-2013, 04:00 PM   #6
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Quote:
Originally Posted by Warin View Post
Dwell is a left over from the points system. I prefer not to use that term as it simply confuses the issues.

In a points based system the coils are selected to obtain the minimum amount of energy required to fire the spark plugs at maximum rpm. At slower speeds the coils will saturate and the excess energy is simply dissipated as heat (thus the coils get hot). The dwell is expressed as a % of one crank shaft revolution.

Now in an electronic system the coil is on for the required TIME to obtain the energy required to fire the spark plug at ANY speed (you might call this saturation time). Thus the dwell % will change as the engine speed varies. Ok? Some talk of dwell without % or time terms - very confusing. Thus I don't use the dwell term! I'd recommend you do the same.

The time between the hall effect (or other) engine position signal and the spark plug being fired depends on the ICU, different ICUs have different characteristics to suit the engine and the engine position sensing system.

I'd NOT wire it as per WeaponX instructions. And having looked at their 'manual' I'd NOT BUY their product!

---------------------------------------
The standard bmw hall effect signal is a square wave (50% duty cycle) voltage should be around 8~10 volts (from the standard ICU) and IIRC a maximum current of 100mA. The output is open collector, if you understand the term. The relationship between the signal and engine position changes with engine rpm ... a simple centrifugal relationship set within the 'bean can'. You cannot change the engine position relationship by trying to change the output voltage!
Quote:
Originally Posted by Warin View Post
The standard BMW/Bosch system is very simple on these bikes!

The advance is a simple mechanical centrifugal advance within the bean can.

Then a hall effect switch generates a 50% duty cycle square wave.

The a ICU unit fires the coils for a set time.

The single coil connects to both spark plugs.

------------------------
The delay between the hall effect signal and the ICU output would be in the order of micro seconds - simply the delay through the electronics? There is a circuit in one of the Bosch books (blue or red?)... it does have at least one basic error in that circuit.

Warin,

You are right Dwell is not the correct term and a throwback to the days of points.

I am familiar with how the factory system works, it is prety much exactly like all the other transistorized units of that time period. I was just curious as to if anyone knew the difference of how long the ICM grounds the coils in relation to the length of the digital wave generated by the hall sensor.

As I told StephenB forget questions 2&3 as I was thinking out loud and it wont work. Sleep deprivation and IPA do not make for a clear head

And could you please expound why you would not wire the module as per the Manufacturers specs to satisfy my curiosity? My background is in the testing and replacement of this stuff not building it.


And sorry for the delay in responding
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Old 07-12-2013, 05:05 PM   #7
Warin
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Quote:
Originally Posted by digger440 View Post
I was just curious as to if anyone knew the difference of how long the ICM grounds the coils in relation to the length of the digital wave generated by the hall sensor.
No relationship between those two.
The ICU grounds the coils for a set time at any speed, so any input times will change for no change in the output ground time.

Quote:
Originally Posted by digger440 View Post
And could you please expound why you would not wire the module as per the Manufacturers specs to satisfy my curiosity?
1) Not safe. Connections to the battery should be through a fuse, any connection not made through a fuse is a fire risk. You allready have unfused connection to the starter motor and the alternator, why increase the risk by running more?

I'd have to relook at their diagram to do more.
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