Datsun 1200

[ggzilla]

Engine Mfg: Nissan
Engine Code: A12
Cylinders: Four
Displacement (cc): 1171cc
Rev Limit: 6400
TPS or MAP: MAP
Boosted or Normally Aspirated: Normally Aspirated
Modifications: None
Chassis: 1972 Datsun 1200 (B110) USA model
Notes:
* Mimicing factory ignition curves
* 5 degree BTDC initial timing (emission controlled model), Ported Vacuum
* Factory curve is all in by 2200 RPM
* More optimization can be done starting with this map

I hope I did this right. It seems to drive nicely. Doesn't ping.

Here are the Nissan factory ignition curves:




The digital map points overlayed on the factory chart:

[ggzilla]

When I first made this map, I didn't realize the MJLJ would smoothly adjust the timing between the map-points. I figured it would 'step' at each RPM level. But it runs too smooth for that to be happening!

Also note that the Factory vacuum advance curve was designed for emissions control. So probably there is some power to be gained by modifying it.

[Yvan]

* Factory curve is all in by 2200 RPM

I am not an expert, and someone will correct me if I am wrong, but your centrifugal advance curve is for distributor rpm, and that is usually 1/2 of the crank rpm. Maybe it is different for your car, but if I am right than your centrifugal advance is not all in by 2200 rpm, it's all in by 4300 rpm.

I also checked your ignition map. If you wanted factory map you should have max 19 deg advance (5 initial +14 centrifugal +0 vacuum) at 4300 rpm for full throttle (no vacuum advance), or max 13 deg advance at idle (5 initial +0 centrifugal +8 vacuum). You have ~24 at idle and 32 at full throttle for more than 2200 rpm.

[ggzilla]

I think you are right, I'm still learning... I knew about "distributor degrees" being 1/2 of crankshaft degrees, but failed to notice it was quoted in "distributor RPM" and not crankshaft RPM. No wonder I had to change initial timing more than expected.

For the max I think 32 degrees is right: 13.5 x 2 = 27 crank degrees + 5 initial = 32?

[Yvan]

Correct, it's been a while since I was playing with my distributor.

[ggzilla]

Thanks for your comments. I did some more work on it, it runs a bit better.
I also found I had converted from mmHg to KPa incorrectly.
I have updated the Map file. New one is 712 bytes.