Ignition Timing Mechanical Advance

[Zed Head]

Are those Celsius or Farenheit?

[jonbill]

Kelvin.

[Zed Head]

I love Kelvin and Hobbes.  Great cartoon.

[jonbill]

I love their social contract work.

[Zed Head]

So I've been browsing around the internet watching car videos and came across this guy who has a channel where he finds old cars and builds engines and stuff, and he built one then took it to the dyno for tuning.  A Chevy 307.  Guess what "best" timing was?  Weird.

It's at 31:30

 

[Captain Obvious]

Thanks for that. So I'm assuming that 34 degrees was total timing? But on the dyno at WOT, that would be all mechanical, right? No vacuum.

And our engines top out at just over half that for the "base" mechanical. Sounds low.

[Captain Obvious]

And on a related note, I've whipped up a little electronic gizmo prototype that applies the mechanical advance in an electronic manner. Reads an input pulse train and effectively outputs a pulse train advanced with respect to the input. The curve looks like the stock curve with a couple adjustments to the numbers to make the math work out easier.

10 degrees advance up to about 1200 RPM
Then 1.3ms of delay from 1200 up to 2500 RPM (which mimics the advance slope of the stock curve)
And then caps off at 19.5 degrees above 2500 RPM

Not sure there's any real value in what I did, but it was an attention diverting academic exercise. I think just that is worth something right now.

[240260280]

10 hours ago, Captain Obvious said:

And on a related note, I've whipped up a little electronic gizmo prototype that applies the mechanical advance in an electronic manner. Reads an input pulse train and effectively outputs a pulse train advanced with respect to the input. The curve looks like the stock curve with a couple adjustments to the numbers to make the math work out easier.

10 degrees advance up to about 1200 RPM
Then 1.3ms of delay from 1200 up to 2500 RPM (which mimics the advance slope of the stock curve)
And then caps off at 19.5 degrees above 2500 RPM

Not sure there's any real value in what I did, but it was an attention diverting academic exercise. I think just that is worth something right now.

WOW VERY COOL BRUCE!!!!!!

[Captain Obvious]

Haha!! Yeah, if I put in some provision for vacuum advance, I've re-invented the electronic ignition controller for the n+1000th time!!  

Completely remove or lock down the mechanical and vacuum advance mechanisms in the distributor and do it with a little module instead. I'll let you know when I've reached the point where I'm willing to put this thing on my car and take it for a drive. Haha!

[240260280]

I like it. What would be the trigger and how often does it need a trigger?

[Captain Obvious]

The design concept is three pulses per crank revolution. Right now it's just using a signal generator on the bench for proof of concept, but if I get energetic, I'll put a variable reluctor front end on it and connect it up the pickup coil on a distributor.

In theory, it should work with points. All the math is set up for six cylinders and three pulses per crank revolution. I can get those pulses from either points, or the VR pickup in the later distributors.      In theory.   Haha!!

[Captain Obvious]

So I did some reverse engineering of the stock ignition module and patched my contraption into the middle of the box, essentially using the stock module as my VR front end. Then I spun up a distributor on the bench with a variable speed DC motor. And it all seemed to work as intended!    

Hey... I got the time, right? It's not like I can drive my car!