Gen 4 crank & cam signal waveform

[takid455-2]

Looking for Gen 4 crank & cam signal waveforms. Preferably laid on top of each other as the ECU would receive when running. Found the Gen 3 patterns, but not the Gen 4. Mainly looking to see where crank & cam TDC #1 are & the rise & fall of each of the 4 cam triggers.

[edcmat-l1]

I have that on one of my much older hard drives. I've got at least a couple hundred really interesting multi-channel O-scope screen shots and that was one. It would probably take longer to find it than to run another one LOL

I can get you one in the next couple days. Have multiple GEN4s here just need to spend the time and do it. If you can wait til the weekend maybe.

[takid455-2]

That'll be great!

[edcmat-l1]

Here ya go buddy.

First shot channel 1 crank, channel 2 cam, channel 3 injector 1. I used number 1 injector for the trigger source to keep everything stable for a screen shot.

Second shot includes channel 4 and that is number 1 coil primary current. The plug firing would occur on the falling side of the current ramp.

Hope this helps.

If they don't come out clear enough shoot me a pm with an email address and I'll email them to you.

[hjtrbo]

If you don't mind me asking, what scope are you using? Nice signals.

[edcmat-l1]

If you don't mind me asking, what scope are you using? Nice signals.

That's a Snap On Zeus. I had a 4 channel Vetronix since the late 90s but it needed some updating, and I need a really good general-purpose scanner as well as a scope update so ended up trading in several diagnostic tools towards the Zeus.

The scope feature although full color is not quite as nice as the Vetronix was. Especially trying to do low amperage waveforms. And the secondary ignition probe doesn't work well at all. Need to get with one of their tech reps about that.

I am a scope geek since way back in the day.

[takid455-2]

Great shots! Couple questions.

1) What's the timing advance at the rpm recorded?

2) Are the signals relatively the same as in the rise is actually the down on the trigger wheels respectively? Crank channel has the missing tooth (down) as an up. This the same for both can & crank? Just crank?

3) Reading the coil firing relative to TDC & advance. The highest amplitude is the firing at advance BTDC or is the the start of the coil rise? If at the start, then the actually firing would be less than requested advance, no?

4) #1 TDC correlate to an edge (rising or falling) of the cam trigger or is it between 2 edges? Haven't pin pointed it down, but thinking #1 is somewhere around the 12 or 13th tooth on the crank after the gap. This would place it at the rise of the 2nd long per the scope.

[blindsquirrel]

The crank wheel just tells it where it is and then it calculates timing, there isn't a specific spot where it fires anything.

The Gen 3 is actually much more sophisticated - the dual tracks are really more like a resolver than a plain position sensor.

[edcmat-l1]

OK, if we plot out either the injector to injector (then divide that by 2) time frame or the crank sensor gap to gap, either or, we come out to right at 85-90 ms equals 1 rpm. Do a little math 60/.085=705.88. That's idle speed.

The red trace (Ch 4) is the coil primary current. The length of time from the beginning of the ramp to the falling edge is roughly 4 ms. That is your coil dwell time. The falling edge is the primary side of the coil collapsing and firing the plug. That's when your spark is occuring.

OK, if we do a little more math, 85/36=2.361, we know that every 2.36 ms equals 10 degrees of crankshaft rotation. If we measure the rising edge of the crank gap to the falling edge of the coil ramp (spark) we come out with about 16 -17 ms.

16/2.361 ms=6.77*10 (degrees of crank rotation)=67.7. Take into account the system probably has a 50 degree inductive offset or delay, and that puts our timing advance right at 17.7 degrees. Close enough to the commanded 18 degrees.

Think I did most of that right LOL I'm sure if I didn't someone will be along soon to correct me LOL

[gtstorey]

Take into account the system probably has a 50 degree inductive offset or delay,

Is this delay part of the scope measuring?

[edcmat-l1]

Is this delay part of the scope measuring?

Has nothing to do with the scope. It is a built-in delay in the ECU. You're only using the scope to measure these different events.

[takid455-2]

pm sent