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.

[JamesM]

Advance ramp up seems a little slow to me, especially for a 1.7, you want it all in by 3000 RPM

Factory max advance is 27 degrees, Jake says he usually sees best power with 28

[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.

[JamesM]

This pelican article has 3 point curves for various stock 914 distributors
https://www.pelicanparts.com/techarticles/9.../914_timing.htm

As you can see all except the 75-76 cars are 27deg by 3000 RPM

the 75-76 cars retarded the entire curve to run up the EGTs for emissions and addition of a CAT, this is part of why they lost so much power and ran HOTTER.

For a 1.7:
Keep somewhere in the range of 1000-1200 RPM and below set to your idle advance, generally you want this as low as possible that still allows you to return to normal idle, you may be able to pull this off @1000 rpm given the dizzy has no moving parts, but if that causes idle run up then try 1100, then 1200.
then:
1500 RPM 17deg
2000 RPM 20deg
2900 RPM+ 27degrees


That will give you the most responsive curve while still being within factory specs.

You can tweak this and add additional points that round up the curve a bit but as you really shouldn't be under heavy load below 2900 RPM anyways you probably wont notice much from the effort other than a slightly snappier throttle.

[JamesM]

Also worth noting, it looks like your idle is currently set to 0 advance.

IF you can keep the idle speed under control you will most likely get a stronger idle by increasing advance at idle a bit. All type 4s I have seen have produced best idle vacuum/strongest idle somewhere between 8-12 degrees advance at idle. However with a stock d-jet setup this will be dependent on if you are able to adjust the idle speed properly still with the stronger vacuum.

[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.

[914_teener]

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.

My quess in lean on part load...which begs the question: When it was tuned with the wide band was it tuned on part load...meaning under load?


Good Luck.

[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.

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.

The pinging was just your motor begging for an aftermarket/programable ECU (IMG:style_emoticons/default/biggrin.gif)

[Lockwodo]

@jhynesrockmtn , it would be good to have some advance at idle if you can do so and have the idle speed you want. You'll have better throttle response coming off idle that way.

Also, I noticed on your 123 dashboard that voltage is ~12.5. It should at least 13.6 to 14.2 at idle. You might want to check on that.

[emerygt350]

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.

Just curious, are you using the vacuum advance or did you when it was pre Bluetooth?

[jhynesrockmtn]

@jhynesrockmtn , it would be good to have some advance at idle if you can do so and have the idle speed you want. You'll have better throttle response coming off idle that way.

Also, I noticed on your 123 dashboard that voltage is ~12.5. It should at least 13.6 to 14.2 at idle. You might want to check on that.

I did add some advance at idle and will continue to drive it and play around with the values. Idle settles in at a steady 900. So far really pleased with how it is running. I'll put some miles on and pull the plugs to see how they are doing.

I'll check on the voltage. Thanks for pointing that out.

[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.

My quess in lean on part load...which begs the question: When it was tuned with the wide band was it tuned on part load...meaning under load?


Good Luck.

Not at all lean, using Tangerine Racing MPS tuning kit and I’ve swopped fuel injectors for new aftermarket 2.0 L which seem to run rich out of the box.
Competed in 2 TDS rallyes this past weekend, 400+ miles through Mojave, oil temp never topped 210*F, wicked fun, 1 an SCCA national event the other a SMSCC event.

[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.

Just curious, are you using the vacuum advance or did you when it was pre Bluetooth?

No vacuum advance with the 123 B curve, only vacuum retard. The 123 only has a single port that can be advance or retard depending on the curve being used.
It is dependent on the throttle body ports, I think ‘73 has 2 ports, ‘74 and up 1 port?

[Lockwodo]

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.

Just curious, are you using the vacuum advance or did you when it was pre Bluetooth?

No vacuum advance with the 123 B curve, only vacuum retard. The 123 only has a single port that can be advance or retard depending on the curve being used.
It is dependent on the throttle body ports, I think ‘73 has 2 ports, ‘74 and up 1 port?

'74 just one TB port.