123 distributor ignition curve, new install in 1.7 djet Options

[jhynesrockmtn]

I just got my 1970's engine back in after procrastinating with finishing up this project. Engine came out to address RMS and trans fluid leaks and a bunch of other stuff. I installed a 123ignition distributor. Stock 1.7 djet. It started right up and seems to run well. Idle settles in at 900 once warm. I need to address the AAR as it does not work. I took it for a 30 mile drive yesterday.

I wanted to ask about the curve on the distributor. I haven't changed it. The distributor is the bluetooth version. Pics of the curve and dashboard during the drive. Any input on what might need changing? Engine runs so much better. It does have new injectors as well. The old ones were not able to be serviced and one was from a 2.0. That cylinder was fouling.

[mgphoto]

Curve is a misnomer, they are straight lines for the most part, 29* will produce ping at high engine stress ie up hill full throttle, 27* will run cooler.
The lower end of the curve controls idle in concert with fuel mixture, for FI, air screw, ECU knob and MPS all contributing factors.
Most common problem with an incorrect curve is over heating usually when the onset of advance is too high, I tried to pull extra advance using the vacuum it did not go well, maybe the reason factory went to vacuum retard?
With a curve keep I it simple 4 points total, 2 control the idle to prevent hunting, a point for max advance at 3400 RPM and 8000 RPM also at maximum, all straight lines.
I’ve pulled my max advance back to 26* to run on regular octane, the 123 has made it really easy to tune, I used the non-blue tooth version of the 123 with the B curve and when I set the advance to 27* factory spec I needed to run 93 octane to prevent ping.
Your on the right track.




I have the vacuum line attached to monitor manifold vacuum but zero out the curve

[JamesM]

With a curve keep I it simple 4 points total, 2 control the idle to prevent hunting, a point for max advance at 3400 RPM and 8000 RPM also at maximum, all straight lines.
I’ve pulled my max advance back to 26* to run on regular octane, the 123 has made it really easy to tune, I used the non-blue tooth version of the 123 with the B curve and when I set the advance to 27* factory spec I needed to run 93 octane to prevent ping.
Your on the right track.

Guessing your motor is not stock or your mixture is lean? Never seen a stock motor (1.7 or 2.0) need 93 to not ping.

Retarding timing increases EGTs and can burn exhaust valves. Need to be careful on that side of the curve as well.

[mgphoto]

With a curve keep I it simple 4 points total, 2 control the idle to prevent hunting, a point for max advance at 3400 RPM and 8000 RPM also at maximum, all straight lines.
I’ve pulled my max advance back to 26* to run on regular octane, the 123 has made it really easy to tune, I used the non-blue tooth version of the 123 with the B curve and when I set the advance to 27* factory spec I needed to run 93 octane to prevent ping.
Your on the right track.

Guessing your motor is not stock or your mixture is lean? Never seen a stock motor (1.7 or 2.0) need 93 to not ping.

Retarding timing increases EGTs and can burn exhaust valves. Need to be careful on that side of the curve as well.

Not stock, 8.4:1 Nickies, 95mm x 71mm stroke Raby 9550 cam, with custom cut push rods and MPS tuned with LM-2 using a 1974 version D-Jet. My vision of what a type iv should have been.