DIY LTCC or similar system for LT1s

[spfautsch]

Couple questions arise, please humor me as I'm terribly unfamiliar with the Northstar system.

1) what would be the advantage(s) of using the Northstar ICM (and I'm assuming the "old" gm waste spark coil setup that bolted directly to the ICM)?

2) is there any reason other than lack of programming expertise, that the arduino couldn't do your minimalist version (my personal preference)? Assuming we're letting the ECM control timing and only need to sequence which FET is enabled next, the code for something like this should be fairly minimalist.

This idea has completely piqued my interest. I'm going to be pulling my freshly built LT1 out this winter to fix an oil leak and possibly fit EGT sensors on my headers. I might be willing to serve as a volunteer guinea pig for your minimalist rendition. My only concern is coil selection - the size of the LT1 / 2nd gen HEI coil pack (x8) is going to require some creativity for mounting and secondary wire routing in a factory LT1 install environment.

[vilefly]

1) the northstar system has more parts availability, and is still fairly compact. not much more.
2) should be no problem for the arduino to do minimalist data distribution for the 8 coils.

The coils we will probably use are the LS engine coils (4.8L, 5.3L, 6.0L, 6.2L). They are fairly small, and mount on the valve covers with short plug wires to the spark plugs.
There are aftermarket coil mounting kits from EFI connection, and some others.

I hope I will be able to make a prototype this winter, but my toddler might be busy distracting me. 3yr olds....all energy, no focus.

[spfautsch]

The coils we will probably use are the LS engine coils

I thought you were opposed to using the LS coils because of the built-in FET drivers. Looks like they could possibly be driven directly from an arduino output. I've got a bunch of projects waiting for me this winter, but this is one I would love to try my hand at.

I hope I will be able to make a prototype this winter, but my toddler might be busy distracting me. 3yr olds....all energy, no focus.

Been there, I completely understand. Thankfully (or maybe unfortunately) my youngest will be of legal drinking age this year.

[vilefly]

yup. I had said I didn't want the "smart" LS coils, but they are quite readily available as was pointed out to me. So, I will set it up to use the LS coils anyways, since they are easy to find and have nice brackets to hold them. I had thought there was an early "dumb" version of the LS coil setup, but I was wrong. My alternate Ion Sense Ignition circuit might still work with the LS coils.....maybe. Depends if they like running on 300v on the primary or not. The built-in transistors might not be rated for the increased kickback.
However, I have tons of ford ignition COP coils at work. Most from people who "shotgun diagnose" their triton engines. I might use those or whatever I can find when I go to Ion Sense Ignition later.

[spfautsch]

Most from people who "shotgun diagnose" their triton engines.

Last year I broke my moral code and took wrench to one of those, and can tell you the most useful way to "shotgun diagnose" a VVT triton engine is with a real shotgun. Load it with slugs or steel buckshot and stop shooting when there's both oil and antifreeze pouring out. Whoever designed the cam phasers for that application should also be likewise "diagnosed".

Has anyone positively determined the signal alignment of the low-res circle? I'm curious because the ECM needs only to sequence the injectors so the TDC signal might be a full crank revolution out of phase with the ignition sequence.

[vilefly]

You forgot that the optical disk turns a 1/2 crankshaft speed since it is connected to the camshaft. yes, it has 360 slots in it, but the computer turns it into 720 by counting both edges of the square wave signal coming out of it. This gives you 1 degree accuracy with respect to the crankshaft. 180 degrees out of phase is impossible. I did confirm rotor position with my spare optispark I will be using as a signal generator for my circuits.

As to the triton VVT woes.....I was tasked with finding out the real source of the cam phaser problems. The oiling system. Starting with the oil pump, it has an aluminum backing plate that flexes at 1700 rpm or earlier, bleeding off oil pressure. Melling has fixed this problem with a cast iron backing plate. The oil pressure sending unit position only lets you monitor oil pressure right at the pump outlet, not at the upper end. There are orifices in the heads to limit inlet flow to the camshafts, then to another orifice in the front cam bearing, then to the cam phasers, then lastly to the chain tensioners. Nice fault tolerant design. pffff. Then there is the 2 piece spark plugs that seize in the head and break off. The special tool used to extract the piece works perfect, because it came out 3 months after this design rolled out to the public. They knew. The repair manuals don't show the oiling diagram......interesting, yes?
oil-flow.jpg
This is a 1st generation diagram, it still tells the story.

[Aroberson77]

The leading edges of the low res circle are 45 degs from each other. We are assuming that the leading edges trigger a counter for the high res signal that is stopped by the trailing edge of the low res signal. I believe this tells the ECM what cylinder is combusting. I know in EE Hack you can turn cylinders on and off, I assume that this shuts the spark and the injector off, does anyone know?

[spfautsch]

You forgot that the optical disk turns a 1/2 crankshaft speed since it is connected to the camshaft. yes, it has 360 slots in it, but the computer turns it into 720 by counting both edges of the square wave signal coming out of it. This gives you 1 degree accuracy with respect to the crankshaft.

No, I assure you I didn't, just explained my thought process poorly. I have my doubts about the meaningfulness of the high resolution signal to the ECM. The amount of slop introduced by the timing chain at lower engine speeds makes it all but useless in detecting misfires, so what is it used for? I would venture a guess this is why GM went to crank mounted sensor wheels for obd-2 as it mandated monitoring crank angular velocity to detect misfires.

180 degrees out of phase is impossible.

What I was trying to get across here is the ECM doesn't care about sequencing anything but which injector to fire. By my understanding, because the distributor handles sequencing, spark is controlled as a single signal that pulses 4 times per crank revolution at varying degrees BTDC - i.e. in "batch" mode. Essentially the point I was trying to make, which after some reflection I think wasn't very meaningful is if we knew how the ECM decoded the opti signal it would be doing so with the sequencing geared around the intake stroke. Since no-one has yet to dump the code that this third processor runs, we don't know.

I did confirm rotor position with my spare optispark I will be using as a signal generator for my circuits.

With a degree wheel? Is it signaling at TDC or at some fixed advance point such as 15 degrees?

As to the triton VVT woes.....I was tasked with finding out the real source of the cam phaser problems. ... Nice fault tolerant design. pffff. Then there is the 2 piece spark plugs that seize in the head and break off.

Funny you also have such experience. One other thing not to discount is people running cheap oil that turns to the viscosity of water when it heats up. The one I had the displeasure of working on belonged to my daughter's at the time boyfriend. I found it odd when the kid called the spark plugs "two piece", but I soon realized it was sarcasm. The OE phaser design is lacking in that it resembles a vane pump, and is extremely fragile when the oil pressure drops, the proportioning valve can no longer control the cam but the pins are unlocked, and it starts banging back and forth in 60 degree strokes. Patent stupidity. Then there's the soft camshaft material and the pathetically inadequate indexing pin location. The whole design was just one poorly engineered stupid idea after another. When I pulled the one phaser off and realized the driver side cam had excreted the indexing pin and spun 180 degrees I told the kid to get it running and sell or trade it immediately. He did not heed my advice, so I later told him maybe he should replace the cams and oil pump and plan on keeping it. When I talked to him after replacing the cams and asked about the oil pump he said he hadn't got to that yet, but did change the oil. Just not the filter. Sometimes it's worth re-engineering the stupid in machines, but the only way to fix it in humans is with a bullet.