tuning the new 123 distributor

[vairter]

Stephen-

 

Yes, you should plug the carb vacuum port and use the one on the intake manifold (if it's there!), like in my earlier picture.

 

The 123 unit comes with software to monitor and write .csv files with the data.  I ran a laptop on the passenger seat and a long USB cable to the distributor to collect the data during test drives.  Then I plotted the .csv files when I got home.

 

Terry 

 

 

[John76]

On 5/26/2020 at 10:10 PM, vairter said:

manifold vacuum has the weakness of sudden surges of vacuum advance at each shift point.

Terry,

I've been thinking about the "pick your poison" option between ported or manifold vacuum advance.

Perhaps the dashpot solves this problem. When manifold vacuum spikes at each shift point (high RPM, closed throttle), the dashpot retracts the throttle very slowly (1/4" over 10 seconds) before it closes completely. This "dampening effect" prevents the spike that occurs when the throttle snaps back completely. 

I use a dashpot on my Weber 32/36 connected to manifold vacuum to minimize the exhaust smoke on deceleration. 

Your charting of kPa vs. vacuum advance for tuning your 123 dizzy is great. Thank you for the "brain food".

John

 

[BLUNT]

On 7/25/2021 at 3:37 PM, vairter said:

sczapiga-

 

I ended up pretty close to what I presented earlier in this thread.  I only backed off a bit on the vacuum advance.  The car has been driving for a year with no apparent issues.

 

My final curves are:

 

Centrifugal:

 

RPM limit: 8000

Point 1: 500 3.0

700   10.0

1000   20.2

1400   25.0

2000   30.0

2500   34.0

3000   36.0

3500   36.0

8000   36.0

 

MAP Advance:  (using port on intake manifold)

 

MPA start: 1500

Point 1: 0   0.0

29   0.0

30   5.0

65   5.0

70   0.0

100   0.0

200   0.0

 

Thanks for this. Made my install 10 minutes and car runs fantastic