123 Tune+ ignition curve for 2.0S

[prea]

Hello,

I have a 123 Tune+ distributor and I'm about to install it to my car. I do have a 002 on it now and it works well - that's the main reason I have been postponing the installation of 123. However, I think it could provide better starting and smoother transitions when tuned properly and most importantly no hassle with the points.

I did a first version of the curve (see below) and would like get second opinion and/or any recommendations regarding it. 123 uses crankshaft rpm and degrees.

Br,
Aki

[NorthernThrux]

What year is the car? Have you added vacuum advance or are you running as stock?

Ravi

[prea]

Car is '68, as it is ROW model the engine spec is the same as in '67 S. No vacuum advance, aftermarket stainless exhaust system which might or might not flow slightly better.

Br,
Aki

What year is the car? Have you added vacuum advance or are you running as stock?

Ravi

[prea]

Just a note regarding static advance in pic: It does no affect to tune, it is just calculated to readings in the app. So it needs to be set in mechanically or needs to be taken account in the curve. Might be less hassle to have all in taken account in the curve.

Br,
Aki

[NorthernThrux]

OK, so a 1967 911S according to the shop manual should have a total advance of 30 degrees BTDC at 6000 rpm . So your static advance plus your distributor curve advance should not exceed 30 degrees. I assume the distributor curve you have shown is just the advance curve, and needs to be added to the static advance. At idle, you should have something around 6-8 deg BTDC (which isn't marked - you'll have to calculate it and mark it using the Z1 and the 1st of the two timing marks to the right of it (30 deg)), Or the shop manual calculates it for you. 5 mm to the right along the circumference of the pulley from the Z1 mark (my math says 6 mm, but close enough).

You can just add the static advance in your curve. Not sure how the 123ignition interpolation software treats this as it creates the full curve, but its probably a simple offset and should work.

This is what the stock curve looks like. This is for distributor shaft speed. Multiply the numbers by two for in-car wrt engine speed and advance. This is what your initial advance curve should look like. Then add 5 deg of static timing advance when you install it.

Remember crankshaft rpm = x2 distributor rpm and crankshaft degrees is x2 distributor degrees.

I recently installed a 123ignition distributor (the simple switched version - anything else is overkill for our cars). It definitely improves starting and smooths out the engine. You should use a synchrometer to verify all your velocity stacks are sucking the same amount of air and get your idle set properly.

cheers,
Ravi




EDIT: BTW, curve 2 is what they use in the switched version. You need to add the static timing to these numbers. So at most 8 degrees. You could also add the vacuum advance if you wanted to.

[prea]

Thank you Ravi for your comments. I updated my initial curve to contain 8 degrees of static advance (factory setting for 2.0S) so I can set everything to TDC. Carbs have been synched and ituned with colorsynch method, I'll repeat that once new distributor is in just to see everything is good.

OK, so a 1967 911S according to the shop manual should have a total advance of 30 degrees BTDC at 6000 rpm . So your static advance plus your distributor curve advance should not exceed 30 degrees. I assume the distributor curve you have shown is just the advance curve, and needs to be added to the static advance. At idle, you should have something around 6-8 deg BTDC (which isn't marked - you'll have to calculate it and mark it using the Z1 and the 1st of the two timing marks to the right of it (30 deg)), Or the shop manual calculates it for you. 5 mm to the right along the circumference of the pulley from the Z1 mark (my math says 6 mm, but close enough).

You can just add the static advance in your curve. Not sure how the 123ignition interpolation software treats this as it creates the full curve, but its probably a simple offset and should work.

This is what the stock curve looks like. This is for distributor shaft speed. Multiply the numbers by two for in-car wrt engine speed and advance. This is what your initial advance curve should look like. Then add 5 deg of static timing advance when you install it.

Remember crankshaft rpm = x2 distributor rpm and crankshaft degrees is x2 distributor degrees.

I recently installed a 123ignition distributor (the simple switched version - anything else is overkill for our cars). It definitely improves starting and smooths out the engine. You should use a synchrometer to verify all your velocity stacks are sucking the same amount of air and get your idle set properly.

cheers,
Ravi




EDIT: BTW, curve 2 is what they use in the switched version. You need to add the static timing to these numbers. So at most 8 degrees. You could also add the vacuum advance if you wanted to.

[Richy]

As per the factory workshop manuel , the timing for a 911S is 0 degrees at idle , so where is the 6-8 degree spec ?

[prea]

Hi Richy,

I’m referring to owners manual and it says 8 BTDC static and 30-31 segrees @6000 rpm. So 0 at idle is about in the range given the idle is in correct level?

As per the factory workshop manuel , the timing for a 911S is 0 degrees at idle , so where is the 6-8 degree spec ?

[prea]

My first test run was with the curve shown below. Seems to be working good and engine pulls strongly. I'll be trying out some changes in the future, but in case someone else is looking for a curve for 2.0S this could be used as basis.

Br,
Aki

[NorthernThrux]

From http://www.sparkingplugs.com/9.html
My service manual and everything I have read says advance at idle (static) should be 5-10 degrees so that total advance at 6800 rpm is under 35 degrees.