Best 123 Ignition Curve for ‘69 911T (Weber Carbs)? Ian (icarp), You Out There?

[AzioAceAzio]

Hey all,

I’m setting up a 123 Ignition Bluetooth distributor on my 1969 Porsche 911T 2.0L with Weber carbs, and I want to make sure I’ve got the best possible ignition curve. I’ve gone through a bunch of threads, but I want to confirm before locking it in.

Here’s the curve I’m considering:


Questions:
1. Is this the best curve for a stock ‘69 911T with Webers?
2. Should I cap total advance at 32° instead of 34°?
3. Is there anything Weber-specific I should tweak for better idle and throttle. response?
4. Ian (or anyone familiar with icarp), does this match what you’ve found works best?

Trying to get this right the first time, so I’d appreciate any insights. Thanks!

Robbie

[AzioAceAzio]

For what it’s worth, the car also has a MSD 6AL ignition system and MSD Blaster coil set up.

[Nditiz1]

Looks pretty close to mine.

I would drop the 34 @ 6000 to 32.

My last 3 points are

29 @ 2900
32 @ 6000
32 @ 8000

Since I regularly hit above 6k I want to make sure the 123 does not do something wonky when it goes off the graph. You may want to perform the same.

[AzioAceAzio]

I'm spending way too much time obsessing over the perfect ignition curve and landed on this one (see attached image).

I fed ChatGPT more information about the car (beloved to be stock 2.0L, Weber carbs, MSD 6AL, Blaster coil, Dansk RSR muffler) and this is what it spit out.

I figured I’d run it by the experts to see if this even more revised curve makes sense?

[AzioAceAzio]

@Nditiz1 - this was for an original 2.0L?

Originally Posted by Nditiz1

Looks pretty close to mine.

I would drop the 34 @ 6000 to 32.

My last 3 points are

29 @ 2900
32 @ 6000
32 @ 8000

Since I regularly hit above 6k I want to make sure the 123 does not do something wonky when it goes off the graph. You may want to perform the same.

[Nditiz1]

Sorry mine is from a 3.2. You will want to use the below, which is close to what you have. This is per Ian for all 2.0-2.7L

[mysocal911]

Remember all the factors that contribute to detonation besides the max advance;

1. ambient temp
2. load on the engine, e.g. climbing a long up-hill grade
3. actual fuel octane, e.g. pump indicated 98, but actual was 94

Lesson: Set timing on a conservative setting. Porsche knock control didn't come until the 964.

[mysocal911]

Originally Posted by Nditiz1

Sorry mine is from a 3.2. You will want to use the below, which is close to what you have. This is per Ian for all 2.0-2.7L

This is too advanced for your 3.2, even the chip "tuners" don't advance this much. Found this;

https://www.systemsc.com/tests.htm

[Nditiz1]

Never said I used the image on my 3.2. If you follow the thread I mention that mine maxes out at 32. Robbie was looking for one for the 2.0, so i provided him the image

[Schulisco]

Consider that the 3.2 Carreras in general run leaner than the previous CIS cars. Carburetted engines run even more richer. The ignition timing is also related to the mixture: The richer the mixture the more aggressive the ignition timing can be and vice versa. In conclusion: Leaner mixture burns slower than richer mixtures.

Refer to the original ignition timing curves and slightly go sharper step by step with an AFR gauge and digital engine knocking tool on a dyno only! When you can hear a knocking noise (when standing next to the engine, not while driving, then this is almost impossible to hear!) then it's mostly too late yet! The danger of destroying the engine is real!

Thomas

[AzioAceAzio]

I think I'm going to go with something a little more conservative for now. The below does not go over the max stated advance. If anyone has experience with a similar set up please chime in. Thanks!

[AzioAceAzio]

Sunday morning bump

[AndrewCologne]

Originally Posted by Schulisco

The ignition timing is also related to the mixture: The richer the mixture the more aggressive the ignition timing can be and vice versa.

Nope, richer Mixture burns faster, therefore the ignition must not be more aggressive due to detonation risk. Have a look at the mixture/ignition maps out there: With more load the mixture goes richer and the ignition gets more retarded. With less load its vice versa, the mixture gets leaner and the timing more advanced.

Btw. you gave the conclusion by yourself:

Originally Posted by Schulisco

In conclusion: Leaner mixture burns slower than richer mixtures.

:-)

[AzioAceAzio]

I ended up using Ian’s curve for 2.0 but adjusting the max advance to 35 instead of 36

[Schulisco]

@Andrew - you're right, thanks for the correction. One day I will get it... %-)

[Old H2S]

Drop your max down to 30* to start, then get someone to drive while you do "active tuning" making adjustments for YOUR car. You must write down what you liked and turn off the car to make permenent changes to your tune, then do it again, it is very fast to make changes and upload the new tune..
Then come back and beg us for the vacuum numbers.. This is where you get 28MPG.

[dedyplay]

Looks pretty close to mine.

[eastbay]

Originally Posted by Old H2S

Drop your max down to 30* to start, then get someone to drive while you do "active tuning" making adjustments for YOUR car. You must write down what you liked and turn off the car to make permenent changes to your tune, then do it again, it is very fast to make changes and upload the new tune..
Then come back and beg us for the vacuum numbers.. This is where you get 28MPG.

I haven't gotten around to doing vacuum on mine, how about spilling the beans?

[AzioAceAzio]

After digging into some research and consulting with a few friends who have these, this is what I ultimately plotted. I tried to plot the ideal timing between the max and min acceptable advance. If anyone has experience with a similar engine configuration and has achieved better results with a different curve I'd love to test it as well.

[snbush67]

A couple of key points have been made, you need an AFR reading, and a friend to adjust the curve using Bluetooth tuning whilst rolling. You can add as little as .5 degrees using the 123.

You want to ensure your carburetors are jetted correctly, get as close as you can, the target is 12.8 AFR everywhere, you won’t get that, but that’s the target. It would be nice to get your light cruise, close to 13 or even better 13.2, but 12.5 is acceptable for decent hwy gas mileage. From the sweet spot, say 4500 rpm’s when you give full rapid throttle, the pump jets should stream fuel for a few seconds and the AFR’s should go to 10 or lower AFR without stumble, then continue up through 11-12 afr and at redline (6800- 7000 rpm’s) should finish at about 13.4 or less, you don’t want it going too lean up there at the redline.

If everything on the carbs is balanced and adjusted you may still notice small coughs or blurps here and there at light or hard throttle openings or even at cruise, this is where you can start playing with small 1 or 2 degree adjustments in the curve at the rpms where your not getting smooth running or where you think you can get your AFR’s closer to perfect.

Also as mentioned, vacuum, is a very important feature of the 123. I was able to discover a vacuum source beneath the throttle plates on PMO’S, I’m not sure if the Weber has that. If there is a way to get vacuum you can hook that up to the 123 and watch the vacuum that it pulls using the app, then you can advance the spark at load and lower rpm’s to get better results.

Every motor is different, every motor deserves its own tune. A generic curve will get you close, sometimes very close, but if you’ve been lucky enough to drive or ride in an icarp tuned car, well…then you know what perfect feels like.

Finally the truth of perfect tuning is in the spark plugs, I have learned so much from Ian, reading spark plugs is another chapter, coming soon.