Retrofit 24x reluctor to early V8

[Jim Blackwood]

What would be good with that is if you could use a mirror to show the sensor lined up with the hole and then a shot down the #1 cylinder showing the crank throw. I know it isn't as good as dialing it in but if the camera is on the bore centerline the crank throw should be centered. Either from the deck or the pan should work. If you feel like it.

Revisiting the relationship of the pulsetrain, CMP signal and #1 firing pulse, I realized that there is indeed a delay between zero on the pulsetrain and the #1 ignition event. That delay is most of the first rotation of the crankshaft. During the first full rotation the cmp signal is high and goes low on the second but the coil fires a bit before the second rotation begins. The first rotation makes up the intake and compression strokes. So based on zero the firing pulse is delayed until near the end of that rotation depending on advance. This can be viewed as consistent with industry practice provided one of two things. If the timing of all events begins at zero on the pulsetrain then the delay is nearly a full rotation rather than a sector such as 60 degrees, and due to the sequence of pulses the ignition events for selected coils can be triggered as soon as the crank begins to turn. I have not confirmed that this actually happens though. But I think it is important to recognize that zero on the pulsetrain coincides with the beginning of the #1 intake stroke and not with the firing of #1 cylinder.

Jim

[kur4o]

I will do my best to get more accurate measurements but it is really hard to turn that piece of iron in any other directions than straight on the ground.

Don`t forget that you have at least 14* spark advance + dwell time[charge time for the coil] that will be likely 10ms. Zeroing crank spark advance will get you #1tdc with firing the coil.
Speaking of dwell time, the on time for the coil before it fires. Can you take some scope measurements of the dwell time during cranking.

[Jim Blackwood]

I'm not sure how dwell time is dealt with in a COP setup. I was finally able to get scope traces of the trigger pulses along with the crank and cam signals and verify that my timing is spot on. The width of the trigger pulses at cranking speed is 7-1/2ms but with an independent power source and ground I'm not sure that has any effect on dwell time.

My ignition trigger pulses don't appear to be as consistent as they should though and this could be the reason for the no-start. To properly troubleshoot this I will need to complete the build on my benchtop simulator to include the cam sensor at a 1:2 ratio with the crank trigger and I would like to have a speed range from 200rpm up to as high as 8K but at least 2K. It's going to take me a few days to put that together but then I should be able to put the ECM through it's paces on the bench. I seem to be fighting this every inch of the way.

Jim

[In-Tech]

Jim,
I couldn't help myself, just ordered one of those Perytech U2200's
-Carl

[Jim Blackwood]

I think you will like it Carl, for a 2 trace scope it is pretty handy. It gets complicated when you start stacking them and then I think it's probably better to look for something else. But I did get a pair of them to work acceptably. I just prefer my test equipment to be more or less bulletproof.

I'm machining some parts today to build the simulator, I think I have all the pieces I need now. Had to wait on the timing set to come in. Should be able to get 2 or 3 speeds out of it. I'll post photos once I have something worth looking at.

Jim

[In-Tech]

Nice, keep us posted on progress. I have my Rigol DS1054Z 4 channel but as mentioned it's kinda a pain to have to unhook and cart it around besides the fact that it is super powerful and way smarter than me.

I just built a crank/cam signal generator on an arduino thanks to a guy on the net that donated the freeware code(David J. Andruczyk, code is called Ardu-Stim). Here's a couple screen shots, encoded 24x 1x(LS1) and 58x(60-2) 4x(LS3). I am looking forward to having it run a pcm on the bench as soon as I get time to play.

[Jim Blackwood]

Very nice.
I want the actual parts for my simulator. I even went so far as to order the LS timing set (which sets me back to Thursday to start building, oh well.) because it has the flag cast into the cam gear. But the pulses coming out of the CKP sensor concern me a little, as what I am seeing is not a true square wave pulse. If you look at the trace I posted you should see that. I suspect it is due to the characteristics of the pickup (since it is a pulse generator also). Not sure if that has anything to do with my erratic spark outputs or not. I suspect a wiring issue will end up being the cause and if the simulator works correctly on the bench that will confirm it. That would be the simple solution.

Another possibility has to do with rotating speed. I want to see what it does at running speeds. We already know it acts a bit different when cranking.

Jim

[lionelhutz]

Did you post a waveform with a short enough time scale to tell how clean the signal was?

[Jim Blackwood]

Maybe not. The one on page 3 is the closest but still not great and I don't know what was going on with that wavy top line. I've attached one below. It includes the CMP trace and two coil outputs, #1 and probably #2.

On the CKP trace you can see steps in the verticals. This is more pronounced as the time base is stretched out and the pulse top and bottom get more noise. #1 coil trigger has an extra pulse and the 2nd regular pulse isn't quite where it is expected to be. #2 is flat, no pulses. #3 and 4 did have pulses but they were irregular, sometimes there, more often not.

Jim

[lionelhutz]

That 24x signal looks fine. The 1x signal looks fine too. I didn't double check the timing between them.

The steps are the scope sampling.

[Jim Blackwood]

That sorta makes sense I guess. I checked the timing and it is right. I misstated the coil spikes as what I had connected was the first 4 in the firing order, and at one point I was looking for 1 and 6.

Am I correct in thinking that with just the CKP input the ECM should put out coil pulses? Is there any other input that it absolutely has to have first?

Jim

[kur4o]

You can monitor the coil firing at the PCM coil control pins.

pins connector c2 [RED]
26 cyl1
67 cyl2
69 cyl3
29 cyl4
68 cyl5
28 cyl6
27 cyl7
66 cyl8

It is 0-5v signal. When the signal goes high the coil starts charging. When it goes low the coil fires. The high time [charge time] is the dwell time of the coil. At startup it should be around 10ms. When the engine runs it will drop to 3-4ms.

I will be really glad if you can measure it.

Each coil fires once per 2 crank revolutions, so you will get 1 coil pulse every 2 crank rotation for a given coil.

[Jim Blackwood]

I will be really glad if you can measure it.

I got 7.5ms while cranking.

Jim

[kur4o]

Thanks for sharing the measurements. I guess you have a constant power supply at fixed voltage. Do you remember what is the voltage reading during the test, and if you can vary it, a test in the 9-10v range will be awesome. I need that data for another project for retrofitting ls1 coils on older engines.

[Jim Blackwood]

That was on the car with the plug disconnected from the coil and cranking on a fully charged battery. I really won't have anything further until the simulator is built, and my power supply for that is a wet cell battery for emergency lights and a 15v laptop brick that I use to recharge it. I expect to upgrade to a trickle charger but have no plans for a variable supply voltage at this time.

Jim