Toyota 4AGE - MS3X - Stable on Drill to 80rpm - Crank unstab

[suberimakuri]

Hi everyone,

Struggling a bit with rpm sync when cranking, but not on the drill.

Car has dual VR:
24 tooth cam wheel (NE). Wired to V3 board main VR in +
1 tooth cam wheel (G). Wired to MS3X board cam input.
Shared ground (G-). Wired to V3 board main VR in -.
Shield connected to v3 board ground as per docs.

With a battery drill, rpm is solid to 50rpm or so.
When cranking at I think normal 200rpm, the rpm sync comes and goes.

Pots seem to all be at their lowest resistance when measure with meter (in circuit).
Had rpm on old VEAL board with dual VR.

Composite log shows:
- on drill rising or falling edges or any combination, stable with 24 teeth crank and 1 tooth cam, all the way from 50rpm to max drill speed.
- on crank (starter), groups of 5 crank teeth 4 times then 1 cam tooth. Sometimes slight variance but typically this pattern.

With Audacity and soundcard probe on Tachsel or VROUT it was maxing the amplitude with minimal mic gain so couldn't really gauge individual pulses.

Can't seem to get datalogging to stay on during cranking.
Jumpered with good battery, crank speed should be okay.
I'm tempted to put LM1815 in the proto area for the crank signal...

Any ideas or suggestions much appreciated.

[DaveEFI]

I tend to look at the output of the VR conditioning circuit (Tsel) on the V3 board with a scope, to make sure there is the correct pulse present. It's not usual here to see none at all until R56 is adjusted. R52 rarely needs touching here.

If you have some form of pulse at low revs, but not at higher, I'd turn R56 1/2 turn clockwise at a time until it comes good, if you don't have a scope.

If I were to guess at a default setting for R56 based on the sensors I've seen here, I'd make it 6 turns clockwise. But others way well say otherwise, as it will depend on the individual sensor.

[suberimakuri]

Thank you.
The problem seems to be at low rpm only and only when cranking from starter rather than off drill.
I'll sort scope and try tsel.
I'm a bit puzzled by the functions of the two resistors.

[billr]

Post a couple of tooth-logs, one with the drill and one with actual cranking.

[suberimakuri]

Tooth logs attached, thank you.

[suberimakuri]

Looking at the cranking log.
There is some lope to the pulses timing.
It shows a longer pulse every 6th pulse. 6 is 24/4, and it's a 4 cylinder so that matches with each cylinder compressing and slowing the crank speed.
If this long 6th pulse is filtered out, then that would match with the composite log showing 5 then a gap.

Going to change to higher power starter to try get cranking speed up. Fit better battery and earth's..

Is there anything I can do for this?

[suberimakuri]

So. Changed battery and redid earth's. Cranking now 250rpm and sync is sweet.
Car runs and is super smooth. Bring on 20lbs!
Thanks everyone!