re: bad oil ring, fwiw - I had one and the behavior was: light smoke on cold start up but once the compression rings were warm the smoke went away. The only time it would smoke when warm was between shifts at high revs. It did consume oil.

 

Just out of curiosity, how did you know specifically that it was the oil ring and not a combination of all of them, or something else?

 

So does this mean you have permission to grind things now?

 

Sadly no. Even though they showed me how it was done, it was made clear that was not one of the things the engineers can use.

 

Engine was tore down for rebuild.

 

What ended up being wrong with it?

 

^What Aidan said. I say this because, oil rings are very tough to tell that they have gone bad, unless they are broken or packed with carbon. Usually oil rings require measurement to see if there is a lot of rail or tab wear on them which results in loss of function. Like gauging the gaps in the bore might work.

 

The bottom ring was cracked and the top ring gap wasn't too far offset from that crack. This was a super low mile 1.6- head had no staining, but it had been sitting for a very long time. I think I cracked it when I hand rotated the crank. Guessing it was stuck on residue, or caught... Lesson learned- I now let cylinders soak with ATF or mystery oil on engines that have sat for a an extended, then use discretion on the first rotation. Oh well, learn from my mistake.

 

Hmm. Well I'm not tearing this down. So I guess I just wont let it idle...

 

Set idle to 2k RPM. Problem solved.

 

Remove throttle plate. Drive car with brakes.

 

Ah, the go kart method.

 

Basically anything better than 0.001-2" in accuracy, you should be banned from. This is why you can borrow my calipers, but not my mics or bore gauges.

 

 

That was going to be my reply.

 

Turns out it looks like I was losing cam sync and thats what was causing the issue.

Megasquirt Support Forum (MSEXTRA) ? VVT with Flying Miata 36-2 wheel (View topic)

First I switched to updating the VVT angle based on timing instead of cam events, and that worked, then I swapped out the .22uf cap for a .001uF cap and now it seems like everything is working fine.

Soldering is ugly but I've got shakey hands.

 

So does the car smoke? That is what we really care about.

 

It didn't yesterday. But that means nothing.

 

We also care *what* it smokes. Or, is that just assumed?

 

In general theory, sure. But what actually happens if the oil control rings are not seated correctly, is they do not 'wipe' the cylinder walls completely and leave some amount of oil residue behind, which then burns and we see as smoke. And no, the compression rings will not do this 'wiping' task.