Northstar DIS

[1project2many]

So how exactly does the DIS module fire the coils? From the pictures there is only two wires going to the actual coil. So does one get power, and then the other get grounded when it needs to fire, basicly like the injectors? Or is there more to it than that? I am trying to learn here.

The coil is fired like most automotive coils. Power is applied to one wire of the coil's primary circuit. Before spark is needed, the other wire is connected to ground. This "charges" the coil and causes it to build a magnetic field. When spark is needed the ground connection is removed. The magnetic field collapses and as it does, a voltage is created in the secondary winding. When voltage is high enough, a spark is created.

All you need to focus on is that it's really just an electronic distributor. The DIS internal circuitry decides which coil to fire. You provide a good power and ground circuit, connect the 4 wires required by the ecm, and set up the calibration so it commands a spark at the right time and you're all set to go.

Northstar system has 2 crank signals plus a cam signal. From way back, if any single sensor is disabled the ignition portion works fine but the pcm does not receive the timing required for sequential injection.

This page is linked to in the thirdgen page: http://lukeskaff.com/?page_id=380" onclick="window.open(this.href);return false;
It's very good about showing which terminals need to be used or ignored, and it has dimensional info for the trigger wheel. Also, thee's good tech info from junkcltr starting here: http://www.thirdgen.org/techboard/posts ... st156.html

I've added relative info from the FSM just to put it into the archives here.

I would put the crank sensor wheel on the crank. It will work on the distributor but with the timing chain and cam moving around you're not getting any better accuracy than the distributor gives and you're doing a whole bunch more work to get it.

[JeepsAndGuns]

Ask and you shall recieve!
Gonna take me a day or two to read through all those links and other info. Then I'm sure I will have lots more questions!

[EagleMark]

I got a headache trying to figure it all out as far as changes needed in ECM...

The mechanical end seems pretty straight forward.

[Six_Shooter]

Here is a thread on code59.org about changing certain settings to gain the extra "timing" needed. While this is $59 specific, many of the same ideas and even tables that are adjusted could be used in other applications: http://www.code59.org/index.php?option= ... mitstart=0

[JeepsAndGuns]

That NorthStar module needs 2 crank signals and a cam signal. so there has to be an easier way to make the coils work with just a crank signal.

Am I just looking at that picture wrong, or does the cam sensor simply pass through to the pcm, with no real connection in the dis module other than power and ground?

[EagleMark]

I still have a headache...
< feels like something stuck me in the head...

[1project2many]

Am I just looking at that picture wrong, or does the cam sensor simply pass through to the pcm, with no real connection in the dis module other than power and ground?

The signal is processed and converted from the raw waveform to a digital signal.

I still have a headache...

Well, the mechanical bits can be set up with the desired timing you choose, if that helps.

[Six_Shooter]

It has been said that the cam position is just a pass through, but that also the N* ICM can lose any 1 of the 3 sensors and still continue to work, so it may be shared, but isn't absolutely necessary to have the N* ICM function.

[EagleMark]

Well, the mechanical bits can be set up with the desired timing you choose, if that helps.

I read the code59 link from Six Shooter and the headache subsided, a bit...

But what your saying is making the reluctor ring 70 degrees off? Or whatever number it was.

I'm really looking at this for a four cylinder so all this Northstar V8 info may be a bit off for my next project...

[Six_Shooter]

Well, the mechanical bits can be set up with the desired timing you choose, if that helps.

I read the code59 link from Six Shooter and the headache subsided, a bit...

But what your saying is making the reluctor ring 70 degrees off? Or whatever number it was.

I'm really looking at this for a four cylinder so all this Northstar V8 info may be a bit off for my next project...

The problem with setting the mechanical wheel off by 70*, is that starting will be hard, if not impossible. In the original installation/application, the DIS runs at 10* BTDC, until the timing signal is active (usually around 400 RPM), where the ECM takes over. It is under control of the ECM that the signals differ between a dizzy and DIS application.

There is some theory and in some MegaSquirt applications that enable ECM based timing control right from 0 RPM, by applying 5V to the bypass wire at key on, not once the 400 RPM threshold has been achieved.
Personally I'd rather set it up to have the ignition system work as it was designed to with the correct trigger wheel alignment, so that if a Limp Home Mode situation occurs, you can still drive it home on the base timing.

Yes, the 4 cyl application will be slightly different, in that the 4 cyl will only require 1 crank sensor and a much more simple wheel. The bin changes will be the same or similar however.

[1project2many]

The threshold can be adjusted so the ecm applies 5V practically all the time. The worry is that low cranking voltage will cause the ecm supplied voltage to be insufficient to switch to EST mode and the module would then be 60-70 degrees advanced. Supply 5V from an external circuit and disable EST code 42 or place proper resistance on bypass wire from ecm so monitored voltage looks correct.

FSM shows Northstar DIS will run without any 1 sensor. Without cam sensor the SFI turns to PFI as there's no timing to sequence the injectors.

The reluctor ring can be set up at a number you determine. If bypass is used as GM intended, any wheel timing which provides from 0 to 15 deg advance at cranking will work. Problem with using someone else's wheel is you have to determine the timing they've selected. Although that's not too hard to work out, either.

I have 4 cylinder appropriate info will post in 4 cyl thread.

[JeepsAndGuns]

FSM shows Northstar DIS will run without any 1 sensor. Without cam sensor the SFI turns to PFI as there's no timing to sequence the injectors.

So If the cam sensor fails, it just switches to batch fire? Thats a pretty cool failsafe.
Ya know, another thing I just thought of. The northstar crank trigger wheel doesnt look overly hard to machine, the system is crank triggered, DIS ignition, OBD-1, and sequencial injection. So why has no one hacked the northstar PCM? All I see on tunerpro is a datastream defination. Why is the northstar system a red headed stepchild? Its seems like it could be a possiably cheap way to get sequencial injection, and its already set up for this DIS system we are all wanting to swap to
I'm guessing there is a good reason no one has hacked it, anyone know why?

[EagleMark]

Probably because not many Caddy owners tune their cars... Just looked and TunerCat has a bunch of Caddy files, not sure what to look for in NorthStar for this DIS...

What's even stranger is they have a Caddy with Manual trans?

[1project2many]

I have some Northstar definition files. Northstar pcm's were tougher to hack because they're dual processor pcm's with 2 eproms full of calibration data and code. There are a few disassemblies around but I don't believe they were put in the public domain.

If a cam sensor fails while the engine is running the pcm can continue to use sequential injection. It already has the sequence and crank position. But at next startup it will fire in batch mode. Most of GM's gasoline vehicles with SEFI will revert to batch fire if the cam signal is missing.

[JeepsAndGuns]

I have some Northstar definition files. Northstar pcm's were tougher to hack because they're dual processor pcm's with 2 eproms full of calibration data and code. There are a few disassemblies around but I don't believe they were put in the public domain.

So is there just a lot of extra programing in the northstar pcm's thats not needed and is hard, or not able to be turned off? Are they flash memory pcm's or do they have removeable eproms? I have never looked at a northstar pcm.
Dont guess there are any tunerpro rt V5 definations? Would be fun just to look at one.


But back to the topic at hand. I have another question, it was touched on in that one thread on thirdgen. Did anyone ever work out a way to use the LS1/2 coils with the northstar dis in wasted spark mode? Now that would be uber cool.
I believe if I could do that, on top of my batch fire mpi, it would cure my desire to swap to a 411 pcm sequencial system. And I need something to get rid of that super expensive desire. My pocket book would thank me.