123 Distributor CSV vacuum line

[paults1]

I have installed a 123 distributor on my '63 230Sl. I need to know if I should still use, connect, the vacuum line/tube from the intake CSV to the port on the 123 distributor. The distributor I replaced is the Bosch 051. I know I don't need the other components of the 051, condenser etc.  I also installed the RED coil.

Regards, Paul Sorgen, Early 1963 230Sl, 2021 E Class 4 Matic

[Cees Klumper]

I am pretty sure you do need to connect the vacuum line. The 123 still needs the input for the advance etc.

[dirkbalter]

I replaced a 051 as well and you do need to connect the vacuum.

[Peter]

The vacuum needs to be connected, no capacitor and resistor.

See manual attached below.

Peter

[wwheeler]

Speaking of no resistor with a 123..... I know the 123 manual states that the distributor does not need the resistor, but what about the coil?

I have had a 123 on my W111 since 2009. That whole time I had the ballast resistor bypassed. This last year year I began having starting problems and has now been traced to a weak ignition. Tests showed that the coil was weak. In 2009, I installed the 123, a new red coil with matching resistor, new cap, rotor and plug wires. Today I replaced the coil, cap and rotor and Bam! It all works now.

I was cautioned by a mechanic that you can slowly degraded the coil by bypassing the resistor. Maybe he is right? Anybody else had a similar issue?

[Pawel66]

I did not have an issue with the coil yet. But I specifically wrote to 123 technical help - no resistor was the answer...

[wwheeler]

Because the distributor is fully electronic and does not have points, it can handle the full voltage 13V +/-. No argument there. But the coils were designed knowing that the resistor would be in-line. The question is can they handle the full voltage over long periods of time? They obviously can short term because that is what happens when the engine is cranking. The extra voltage would presumably create more heat. Is that heat damaging over time? Not sure.

Maybe the thing to do is ask 123 distributor if they have specifically tested coils long term with full voltage. I had no issues for the first 10 years with the 123 and the resistor bypassed. Problem just showed up recently.

[Chris Long]

On the original question if you are using the Bluetooth/USB programmable version I believe you can program it to ignore all vacuum inputs and just use the rpm curve.

[dirkbalter]

On the original question if you are using the Bluetooth/USB programmable version I believe you can program it to ignore all vacuum inputs and just use the rpm curve.

I agree but would ask, why wouldn’t you use the vacuum?
I believe the non usage of the vacuum line is more of an issue for the late 280‘s with emission controls and different logic on the vacuum.

[Cees Klumper]

Plus the rpm curve will lag behind the vacuum created by the driver's intent, if that makes sense?

[MarkCan]

I can not speak directly on the M127 engine yet. I’ll be there soon but for now I’m at the reassembly stage. Anyway, from my past experience on other units, in the sequence of events, change in vacuum is there before there is change in rpm. Using your vacuum line will provide for more accurate and timely response. Sure, you can use electronic curves to program it. Will you be able to achieve the same results? Highly unlikely with only 5 point curves. Not to mention the time it will take to rediscover America.

On the subject of the coil, personally I would use some resistance with your new high output coil (as manufacture suggest). If you not crazy about it, you can go as low as 1kohm.

[Nicolas Aristodemou]

On the original question if you are using the Bluetooth/USB programmable version I believe you can program it to ignore all vacuum inputs and just use the rpm curve.

I agree with above statement. Bluetooth 123 units can be programmed to ignore vacuum inputs since they can be set using the App on your mobile to provide any advance at any rpm. I have been using this setup for past seven months and some 000s of km with brilliant results.

The total advance given by an 123 unit is the sum of the vac advance plus “centrifugal” advance at any rpm. All this is done electronically by the unit based on rpm and vac inputs. So if you want say 20 deg BTDC at 2000rpm you can program 10 deg on centrifugal curve and 10 deg of vac curve for a total of 20 deg. Or simply 20 deg on centrifugal curve and 0 deg on vac curve. You must have the programmable unit though since the non programmable unit needs the vac inputs.

[stickandrudderman]

Because the distributor is fully electronic and does not have points, it can handle the full voltage 13V +/-. No argument there. But the coils were designed knowing that the resistor would be in-line. The question is can they handle the full voltage over long periods of time? They obviously can short term because that is what happens when the engine is cranking. The extra voltage would presumably create more heat. Is that heat damaging over time? Not sure.

Maybe the thing to do is ask 123 distributor if they have specifically tested coils long term with full voltage. I had no issues for the first 10 years with the 123 and the resistor bypassed. Problem just showed up recently.

!23 makers insist that only a coil of 1kohm should be used.
More resistance = more heat and therefore shorter life.