distributor based sparking questions

mikesb · Post by **mikesb** » Sun Mar 05, 2006 8:31 pm

I'm sorry to do this - I've read everything I could find, but I'm not sure I understand.

I've got a MS 2.2/MSNS-E 26h4 running on a 4 cylinder engine that I'd like to use with the spark feature too. I've currently got a Crane XR700 installed, so I've got an optical trigger and a module to drive the coil.

So, dumb questions:

Trigger angle, trigger angle additions - these are crank angles not distributor angles, right?

Is there a mode where I can leave my distributor timing where it is (10 degrees BTDC), use that signal for crank timing, and when the engine is running switch to a base timing angle which is 190 degrees BTDC of the next cylinder?

If not, it looks like I can use the trailing edge of my shutter to trigger the crank signal. Werner says on his site that's 30 degrees after the leading edge. So I could set that trailing edge at 10 BTDC, which would place the leading edge at 190-30 = 160 crank degrees BTDC. But that seems too far ahead for the settings available in megatune. Is my math right? How about my understanding of MSNS?

I know a lot of this has been answered from a dialog with Werner on another thread, but I didn't understand everything that was said there

.

MegaScott · Post by **MegaScott** » Sun Mar 05, 2006 9:03 pm

If you have your trigger output set to inverted you should have no problem leaving the stock 10dbtdc. The firmware will use "This Cylinder" during cranking and starting, once the RPMS go over ~400 "Next Cylinder" mode kicks in. The firmware does this automagically in MSnS modes, no other settings required.

The MS1 MCU is looking for a low to high transition to trigger the input IRQ, you can use the LEDS as described on the MSnS web site to setup your distributor.

mikesb · Post by **mikesb** » Mon Mar 06, 2006 11:48 am

Thanks Scott, this helps.

Again from Werner's site, it looks like Crane Opto-trigger goes high to low (high impedence, switched to ground when the LED shines through the shutter). So I think I do need to set my distributor up so that the trailing edge of the shutter opening to be somewhere between 0-10 degrees BTDC static to use in cranking mode.

Next cylinder mode - I've seen references to it but I can't find too much explaining it... Is there any more info around? Knowing that the leading edge of my shutter opening will be about 160 degrees BTDC, what do I use as my trigger angle and trigger angle addition? I can't enter 160. Should it be 160-90, or 70 degrees? It's just not clicking for me

.

I'll probably use the FIDLE output as my spark output since I'm not using it for anything else and it looks easy enough.

feck · Post by **feck** » Mon Mar 06, 2006 1:12 pm

I would leave your distributer set where it is and wire the MS as shown in the luminition diagram on the MSnS site (http://megasquirt.sourceforge.net/extra/setup-msns.html). I'm don't know if the wire colours are the same for the Crane ignition, but the High to low transition is. Note that this is effectively the same as the points diagram if that makes it easier to understand.

In Megatune set your trigger angle to 10deg. The MSnS firmware has something written in to it that when the trigger angle is set to <20deg then during cranking it fires the coil as soon as it is sees the trigger edge. Once the engine is over ~400rpm (or what ever your cranking speed is set to) then it uses that 10deg trigger as a 190deg BTDC trigger for the next cylinder. The spark cranking settings are only used if your trigger angle is over 20deg.

Hope that helps
Cheers
Daniel

woh · Post by **woh** » Mon Mar 06, 2006 1:39 pm

Mike

I have tried both this cylinder mode, and next cylinder mode.

Next Cylinder Mode
Setting up Next cylinder mode, you can leave the distributor as it works with the XR700. In this set up the leading edge of the opening will be at ~10 deg BTDC. (10deg advance) The trigger is set to 10 deg. In this mode the spark during crank comes from the leading edge of the opening (ie light shines on the optical sensor) and fires the spark immediately. During running, the advance is calculated for the 'next cylinder' or spark plug. When using next cylinder mode I had difficulty starting in very cold weather using older code due to missing sparks during cranking. I have not tried next cylinder mode since I switched to 'this cylinder mode'.

The 'next cylinder mode' will allow you to use the XR700 as a back up if you can get the connector (I could not get the correct connector)
These are the settings:

http://www.msefi.com/download.php?id=2851
http://www.msefi.com/download.php?id=2850

The value of the Trigger Angle determines that the above is next cylinder mode.

This cylinder mode
I have since switched to 'this cylinder mode'. In 'this cylinder' mode, the leading edge of the opening is set to 60deg BTDC. You need to turn the distributor. The Trigger Angle is set to 60deg. The spark for cranking is calculated. The spark for running is in 'this cylinder mode'. When using the CR700 optical trigger the trailing edge of the opening happens at about 60-30deg = 30 depending on the trigger wheel. This requires that the cranking timing is calculated since 30deg advance is too much for cranking. Set the Trigger Angle (Deg) to 60 and the Cranking Timing to Time Based (the rest as above)

When the Cranking Timing is set to 'Time Based' (and you are in 'this cylinder' mode) the the cranking spark timing is calculated and will take about 1-2 revolutions of the crank to figure things out. Due to cranking rpm variations, the cranking timing may not be consistent or accurate. To get better cranking, the 'Cranking timing' should be set to 'Return Trigger'. This means that the spark during cranking will be generated by the trailing edge of the opening of the shutter. For most Crane shutters, this will be 30deg advance. To get this to 10deg advance the shutter opening must be widened. see my web site.

mikesb · Post by **mikesb** » Mon Mar 06, 2006 7:19 pm

woh wrote:see my web site.

Yep, many times

.

I get it now! If it's too late to spark, the MSNS-E code waits till the next opportunity.

If the MS dies I won't be getting any fuel so having spark as a backup isn't much use

... I plan to use a pair of male/female bullet connectors to splice a bypass in the grey line of the opto-sensor. This'll let me test my setup before hauling out my distributor to lock the advance down.

Thanks guys!

mikesb · Post by **mikesb** » Mon Mar 06, 2006 8:17 pm

But wait, maybe I don't. Are you saying that in "next cylinder" mode, MS uses the falling edge of the signal to trigger both crank and running? It's this page that messes me up: http://megasquirt.sourceforge.net/extra/setup-msns.html. There's a signal trace that shows the signals (under the picture of the Bosch valve). That diagram says it's the rising edge (T) that'll trigger the spark once the engine is running, right? With my 30 degree slot that edge will be 20 degrees ATDC, or 160 degrees BTDC for the next cylinder.

woh · Post by **woh** » Mon Mar 06, 2006 9:54 pm

In next cylinder mode, you will be using the leading edge of the opening.

In the diagram, T is at the point when the full voltage is across the ignition input. This happens when the optical trigger goes to ground and the +12 (or +5) is at pin 24. Note that the waveform is at pin 24. You need to tie pin 24 to a + voltage, and the low (XG1) to the output of the opto trigger.

mikesb · Post by **mikesb** » Tue Mar 07, 2006 5:32 am

Ah, ok, I missed the point about the trigger going to XG1, that makes sense now, thanks!

So is the cranking spark is triggered on the trailing edge (R) or the leading edge (T) of the shutter in this mode? I hope it is the leading edge (T), same as the running trigger. I couldn't find any documentation (other than your post) that describes it working like that - did I miss it?

Post by **jsmcortina** » Tue Mar 07, 2006 6:18 am

mikesb wrote: There's a signal trace that shows the signals (under the picture of the Bosch valve). That diagram says it's the rising edge (T) that'll trigger the spark once the engine is running, right?

That diagram is very old and the code has evolved significantly since then. The whole page needs re-writing.

James

woh · Post by **woh** » Tue Mar 07, 2006 8:01 am

It's not very helpful to speak of the rising or falling edge at the input. It depends if the input is at pin 24 or XG1. For 'next cylinder' mode the cranking trigger and running trigger will be the same. This is the leading edge of the shutter opening. This is the time when there is full voltage between pin 24 and XG1 or current is flowing into pin 24.

mikesb · Post by **mikesb** » Tue Mar 07, 2006 8:47 am

woh wrote:It's not very helpful to speak of the rising or falling edge at the input.

Yep, that's why I switched to talking about the leading/trailing edge of the shutter - at least that'll make sense to you and I and anyone else using the Crane kit.

Just to confirm what Daniel has said before I get out my wire cutters and soldering iron:

In "next cylinder" mode, are both the cranking and the running spark signal are triggered by the same (leading) edge of the shutter? That is, a falling edge as seen on IRQ1?

woh · Post by **woh** » Tue Mar 07, 2006 8:59 am

In "next cylinder" mode, are both the cranking and the running spark signal are triggered by the same (leading) edge of the shutter? That is, a falling edge as seen on IRQ1?

yes

mikesb · Post by **mikesb** » Sat Mar 11, 2006 6:08 am

Fantastic! 30 minutes with a snipper and the soldering iron on my board, and I was ready to go back to the garage. 15 minutes later it was wired in, I held my breath and it fired right up! Another 30 minutes to lock the vacuum advance, set the timing. Next thing I knew I was driving!

Thank you gentlemen for your help!