Megasquirt Ignition Options (falling edge, stock distributor, etc)

[Ondonti]

Unfortunately, it's been a couple years so I can't remember. You'll have to get out the degree wheel, mark the spark tower positions on the distributor and mess around with MS and your distributor position until you find something that works. I was using MS1 which is a real pain for this stuff. MS2 is better so you might have more luck.

I honestly think you'll spend less time adding a crank sensor... You could probably get away with only adding three "teeth" to your crank pulley which would give you the same resolution as the stock distributor but with the freedom to choose your trigger angle. Six teeth will give better starting performance, though.

BTW, is there a good way to make the cam signal useful in sequential setup?
I will definitely mess with the degree wheel because I will at least get a better idea of what is going on. I don't mind spinning my wheels on some of this stuff as its helpful for others.

[87turbodance]

BTW, is there a good way to make the cam signal useful in sequential setup?
I will definitely mess with the degree wheel because I will at least get a better idea of what is going on. I don't mind spinning my wheels on some of this stuff as its helpful for others.

You can block off all the openings in the high res section of the shutter wheel and then use a sharp knife to cut out one section in the spot you want the cam pulse to be. You could also do the same thing with the low res area of the wheel but then you won't be able to use it as a crank trigger anymore.

If it was me, I'd use a crank sensor and then use some foil tape to block off all but one cut out in the low res shutter wheel to use as a cam sensor.

[crusty shadow]

if I were you I would add a 36-1 wheel on the crank, then do a half moon shutter wheel on the distributor. best possible signal setup for MS- no limitations on timing. I made a jig for the 36-1 wheel to align it with the crank pulley and welded it on- worked perfectly and was not hard to do. for the half moon cam shutter wheel I just took a N/A distributor and cut all the teeth off the shutter wheel, made a half moon shutter wheel out of a 2" exhaust pipe connector that I bought from Autozone PN 17504 cut it to size with a chop saw and welded it to the original shutter wheel base. that was also pretty easy.



the end result is nearly instant sync as soon as you hit the key, and the most accurate timing setup you can get

[Ondonti]

I would not attempt to use two sensors at the same time from the distributor. If I wanted to be that accurate I would want to take out the timing belt deflection from the equation.

[87turbodance]

Well, you could easily convert the distributor pickup to the half moon style mentioned above. Then add some manor of crank position sensor. A 36 tooth wheel is overkill for ms2 but can be bought off a shelf but as I've mentioned i found it super easy to mark up my damper with some ink and a scriber and a drill press. A 6 or 12 tooth wheel would work great a six cylinder without putting much effort into it. i used a piece of angle aluminim to mount a crank sensor towards the front of the motor under the distributor. I found that a hall effect cam sensor from a 2000ish madza 2.0 worked great as a low resolution crank sensor; salvage yard parts work great for mockup and testing. The half moon distributor and a 12 tooth crank gives all you need for a great wasted spark setup..... or just run the crank sensor and the distributor/single coil.

[Ondonti]

Well, you could easily convert the distributor pickup to the half moon style mentioned above. Then add some manor of crank position sensor. A 36 tooth wheel is overkill for ms2 but can be bought off a shelf but as I've mentioned i found it super easy to mark up my damper with some ink and a scriber and a drill press. A 6 or 12 tooth wheel would work great a six cylinder without putting much effort into it. i used a piece of angle aluminim to mount a crank sensor towards the front of the motor under the distributor. I found that a hall effect cam sensor from a 2000ish madza 2.0 worked great as a low resolution crank sensor; salvage yard parts work great for mockup and testing. The half moon distributor and a 12 tooth crank gives all you need for a great wasted spark setup..... or just run the crank sensor and the distributor/single coil.

I found today that my setup as is was able to physically spark farther then -10 ATDC timing and ~50 degrees BTDC.
Now I am going to mess around with adjusting things. I don't know if it was the reasoning behind your original plan to run trigger return but that suggested setup of yours is supposed to provide the good starting of cam phasing around 5-15 degrees BTDC and have the good running and adjustability of setting it between 60-90 BTDC.

I only see upgrading from camshaft only to include all the mods required to run sequential fuel injection and coil on plug ignition. I really don't think I have the ability around here to get a spark tune close enough to need greater accuracy without spending the money that would make a weaker ignition setup pointless. So I think if I get stuck someday with ignition blowout (especially caused by high rpms) then I will then move to upgrade my Tach In setup.
My distributor setup right now really kills off my dwell time at higher rpms. Not sure what rpm it will have problems at without boost but I have a feeling that boost + 8500 rpms (goal) will not work. I will probably try boost a coil first and run the coil at higher voltage when I get there before upgrading the entire ignition system. I think I would also give a hotter coil a chance.
3000gt guys have problems with their wasted spark blowing out in many 500+whp setups but its hard to say how good of a job they are doing to minimize problems on the setups in the lower range of HP. I had to use small spark plug gaps with OEM ignition and then had to go even smaller as HP rose. Alcohol injection also makes spark blowout happen at even lower HP levels. Spraying 3 nozzles makes it really bad.

[Ondonti]

I really failed at this.


Pretty sure there is a typo for falling edge instructions from 87turbodance but...
I was lazy so I only put my degree wheel on and set it to zero based on the camshaft arrow to timing cover mark.
================================================== ===========================================
Then I put the crankshaft to 10 degrees BTDC

Forced to enter trigger return spark mode and enter an offset higher then 60 or it caused configuration errors in ms2/extra 3.3.1, Set offset to 75

Falling edge

Set middle LED indicator to Ignition trigger indicator
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Now, turned back distributor backwards until LED turned off. Slowly turned forward until it turned on. Its almost exactly where it was when I used a 15 degree offset and a timing light to set things up with basic trigger. Locked down the distributor.
-----------

Set fixed cranking timing to 10
Set fixed timing to 10
Left predictive timing on.

Verified rotor was just about to leave #1 terminal at 10 degrees BTDC
-----------------------------
Left in trigger return mode and falling edge
Tried to start and got a few nasty backfires. Tried again and it started.
================================================== ===========================================
Megasquirt is commanding 10 degrees timing BUT my timing light indicates something like 30 degrees ATDC (retarded).

Should have taken a datalog.
Seems like a big failure.

[Ondonti]

Here is the only description I have read of trigger setup that has actually been clearly explained.


This refers to setting up an Audi distributor but its basically the same as the 3.0 12 valve SOHC distributor except the inner optical data is from 5 small and 1 large window slots while 3.0 6g72 12 valve is 6 equally spaced large slots. Both have outer 360-10 slots.
Looking into this also lead me to the Nissan CAS which has replacement distributor (50 and 54mm) slotted discs available on DIY's website that are megasquirt compatible with full sequential. I might try one of these in the future. I don't think the ECU can handle our high data 360-10 slot setup. I did think that we could just cut out groups of slots in the OEM and create a 36-1 wheel. I did not measure our OEM wheel to see if its 50 or 54mm. They mention possible compatibility with Mitsubishi applications.
http://www.theprojectpad.com/viewtopic.php?f=14&t=796

Re: Anyone else running MegaSquirt?

Postby vt10vt » Tue Jun 24, 2014 12:04 am
MS1/2/3 this doesn't matter. I'm on MS2, ran the same setup on MS1. It's all the same except that MS1 uses trigger angle additions but that's not relevant here or to most anyone so I'm not even going to get into it.

I'll give you the long of it, if you want the short of it skip to the end for the easy/copy cat answer. But that's not what some of us are about is it?

By setting your trigger angle you are telling the ECU the relationship between when it sees events from the hall effect sensor in the distributor and the rotor being "centered" on the post for the respective cylinder you are firing.

The first thing is that the trigger angle requirements are determined primarily by the processor speed and by the desired range of advance. So if you had an ECU that could do calculations at the speed of light and wanted a maximum advance of 40* Before Top Dead Center (BTDC) then your trigger angle could be only 40*. But math takes time (especially for me ) so you need some space and time built in there for Megasquirt to do it out.


*ASIDE/IGNORE* VEMS still needs the same minimum trigger angle (---- whatever VEMS calls it, it's Megasquirt based and you know it; it's a trigger angle). I don't know if it's processor limited or not, you wouldn't think so because it can read fast enough to keep up with a 135 tooth flywheel but I'm not sure.


So if you were to set your trigger angle at, say, 60* in TunerStudio, you are telling Megasquirt that when it sees a pulse from the hall sensor it is 60* from the next time the distributor rotor is centered on a post. Couple important things to remember here are that in basic trigger mode like you're running Megasquirt has no idea which cylinder it is actually firing, all it knows is that 60* from when it sees that pulse the rotor will be centered on a post. The rotor making contact with the distributor cap is the only thing that dictates which cylinder the coil ignites. Second is that with the motor set at TDC the rotor is centered on the distributor post for cylinder number one. In reality you don't really want the rotor centered on the post at TDC but we'll get to that in a minute. Third is that you are primarily dealing with the relationship between the sensor and the windows in the distributor. The position of the engine does come into play but trigger angle is primarily the relationship between the sensor and windows.

Megasquirt will then make calculations based on the current engine speed to tell how long it will take for that 60* to happen, and based on that time calculation it can adjust timing. Using arbitrary numbers for example's sake, if you're at idle and the hall sensor is moving 60* every 6 milliseconds, and you want the cylinders firing 10* BTDC the ECU would calculate the distributor is moving 10*/1millisecond based on the speed it is seeing events from the hall sensor and would fire 5 milliseconds after the pulse from the hall sensor comes. Thus the rotor would have moved 50* in that 5 milliseconds igniting your cylinder 10*BTDC. So if you commanded 0* advance at the same RPM Megasquirt would wait 6ms after it sees the pulse from the hall because in that 6ms the rotor would have moved 60* and thus be firing directly in the center of the rotor, which means our engine would be at TDC. Remember that when set at TDC our theoretical engine will have the rotor centered on the post attached to cylinder 1. Thus when cylinder 2 is set at it's "TDC" the next window will have sent it's pulse 60* and 6 milliseconds ago giving Megasquirt that 6milliseconds advance warning to calculate how fast the engine and thus the rotor are moving, time out dwell and then fire at whatever angle.

So hopefully what the trigger angle is doing makes sense, if not go read the megamanual front to back again a few times haha. Now on to where to set it.

This is where the theoretical engine needs real world tweaks. If you look at a spark map, you generally run 10-50 degrees of spark advance (ie degrees BTDC/Before Top Dead Center) depending on RPM, manifold pressure, temperature etc. The angular relationship between the rotor and points is the limiting factor here. Look the outer circumference of the rotor edge in relation to the entire 360* of the distributor and you'll see it only makes up a fraction of that total 360* of rotation. The size of the rotor edge dictates available engine advance. Thus the angle of the rotor on the point for cylinder #1 with the engine at TDC needs to be adjusted to compensate for the degrees of timing you actually want to run. About -19* is the angle the megamanual recommends for this ("-" =BTDC). The closest your timing will get to TDC is usually at idle, so 10-15* BTDC meaning you need to offset your rotor to allow for more BTDC timing because you won't use much (any?) positive timing. So with the engine set at TDC, your distributor rotor should actually be 19*BTDC or 19* counter clockwise prior to the actual center of the rotor.

So the process would be set the engine at TDC/Top Dead Center, center the rotor on the point for cylinder #1, then rotate the distributor housing counter clockwise (against it's running rotation) 38* to "center" the rotor relative to the angles of desired spark advance while allowing the shaft and rotor to stay in the same position. Then you would turn the engine backwards and measure the angle it takes to trigger the hall sensor. However, what you will end up with is actually in the unacceptable range, so you need to go back an extra window. Megasquirt needs either 0-5* or 60*+ and the OEM Audi distributor will fall in the range of 5-59* which won't work. So if you just keep going backwards to the next window you end up with a very high angle. In MS1 this is dealt with via trigger angle additions but in MS2/3 it's straight up trigger angle.

So set the engine to TDC. Center the rotor on the point for cylinder #1. Turn the distributor housing counter clockwise ~19*. Then turn the engine counter clockwise until a vane is at the sensor. This will be between 5 and 59* which won't work. Keep rotating backwards until you're at the edge of the next vane. Remember, the ECU only knows what you tell it so if you say 115* it knows to start calculating for the rotor it will see 115* after it sees the hall pulse, it doesn't matter if it sees another pulse/vane before it fires from the last one it saw. Overlap doesn't matter. This will work but your angle will be very high somewhere between 110* and 120* which is fine. This is where trigger angle additions come into play with MS1 but you don't have to deal with this. So that angle you measured is your trigger angle. Bam. Done. Wasn't that easy? Now you just need to use either the timing wizard in tuner studio or manually set the spark angle and use a timing light to dial in your timing exactly which can be done either by rotating the distributor or by changing your trigger angle. I recommend rotating the distributor with the engine running and a timing light on the flywheel with the timing locked at 10*BTDC in tuner studio and an adjustable timing light set to the same 10*.

And something that bothers me with what I am doing right now,

Also you dont need to be running trigger return, that setting determines which edge of the distributor sensor the ecu uses during cranking. I dont remember which I'm using atm but it only relates to trigger angle in that your trigger angle will dictate if you can run one or the other or both interchangeably.

Guy who is said to be THE Audi megasquirt guy with additional electrical engineering background

You want "basic trigger" mode. Trigger-return is evil... it does a lot of weird things, like trigger on one edge while cranking then the other when running.

Trigger return is supposed to be good in that it allows you do use one side of the slot for cranking and another slot for running. That avoids the tradeoff where trigger angles of 0-5 degrees BTC only provides high quality starting and 60-90 provides the best running characteristics.

This might be why so many people were running rising edge instead of falling edge...So the 3.0 megasquirt install guide by 87turbodance still does not make sense for rising vs falling edge. I know Kyles MS3 functions with 75 offset, his distributor alignment looks the same as mine, and he uses falling edge and trigger return. Mine does not work as is.

I need to go record what angles the Middle LED trigger indicator turns on and off at in the 0-100 BTDC range. Then figure out if I can use trigger return or if I have to use basic trigger and also figure out if I need to use rising edge instead of falling. Having had apart my messed up optical setup in my He341 3.0 Spirit, I know there is some adjustability in the slotted disc and also the rotor if I really needed to. I could force more adjustability in worst case scenario.

[Ondonti]

With distributor setup to be about "normal" compared to 2 other 3.0s,
--------------------------------
Trigger turns on with falling edge trigger return

ON 130 to 75 BTDC

Off 75-10 BTDC

ON 10 BTDC - 45 ATDC

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So I think I need to use rising edge since the setup instructions want your LED to turn "on" during the 75-10 window, not off.

[Ondonti]

This is kinda making me grumpy with megasquirt even more since the best descriptions date back to MS1 stuff and it seems that people are given less and less "why" along with the newer stuff, even when the same circuitry is used.



http://www.msextra.com/doc/ms1extra/...ED_for_IRQ.htm

You can monitor and test the Optical or Hall input for proper operation by setting the center LED on the MegaSquirt front panel to show the state of the IRQ-1 inside MegaSquirt.

First set up TunerStudio to help you time the distributor. Set the center LED on the MegaSquirt front panel to show the state of the IRQ-1. These settings will be under Menu Basic Settings > Codebase and outputs Function.

To do this set Distributor to MSnS^ LED 19(D16) to IRQ trigger. This LED is usually set to Warm Up. Click on Send to ECU. Here is a subset of the settings in the dialog box.


Center LED indicates the state of the Trigger

LED is OFF; MS opto-isolator is off, IRQ-1 is high.
LED is ON; MS opto-isolator is on, IRQ-1 is low.
LED transitions from Off to On, this is the Trigger Angle at the crank.
LED transitions from On to Off, this is the Trigger Return Angle at the crank.

[87turbodance]

You can setup MS to "trigger" on either the slots on the pickup wheel or the filled in parts of the trigger wheel. The trigger angle will be the beginning of the opening or gap and the trigger return will be either the ending of the opening or gap. Try to get the of transitions of the beginning or ending of the gap to line up with about 0 degrees btdc - this will make a great trigger return angle for starting. Then rotate the motor backwards until the middle LED changes to indicate that you have reached the other end of the opening or gap - this will become your trigger angle. Then get your spark tower terminals to line up with the trigger range you've setup.

[Ondonti]

I have to change my chart now to reflect that those #'s were taken with falling edge and maybe make another showing rising edge. I changed the setting to rising edge and then my 10-75 degree BTDC window is ON instead of off. Falling edge vs rising edge just changes weather megasquirt is looking for voltage to be high or pulled low so changing the setting will "flip" the range that is considered "ON"

Now timing sets at 10 degrees with a slight distributor adjustment (could have used trigger wizard and changed my crank offset).

Very happy.

Then took a datalog of some 4th of July antilag afterfires.

My timing is now able to go to -10 degrees during antilag (when not cutting sparks). Idle timing control is now also able to go below 16 degrees (previous limit with basic trigger settings at 15 degrees offset) so my idle is very happy.