123 ignition for 504 XN1

[Blue_Peugeot_504]

Hi all,

My car: 1980 504 A11, Petrol, Sedan, Solex

My 504 has a Ducellier M78E electronic distributor which perhaps came from a 505 SR. Trying to find a cap and rotor for this distributor is getting harder all the time.

M78 corresponds to the advance curve which I understand is suitable for XN1 engines like mine.

My question is: Has anyone experimented with other advance curves for the XN1 engine, such as perhaps 123 ignition curve A (corresponding to M78) and compared this to a different curve suitable with low octane fuel for example?

 

[GRAHAM WALLIS]

All the SR distributors I've had have been worn out. I find the original M48 Ducelliers to be the best but a pain to have to keep the points adjusted, the 123 is good in that respect as no moving parts except for the rotor button.

 

[GRAHAM WALLIS]

A lot of the early curves are also designed for 7 to 1 compression.

 

[ThanosK]

The programmable one is a good option, best to program it on a dyno. It may seem overkill for a road car, but you will get better power, and fuel economy that will offset the cost to the dyno tune. Like Graham said, nearly all the original ones are worn out.

 

[GRAHAM WALLIS]

The programmable one is a good option, best to program it on a dyno. It may seem overkill for a road car, but you will get better power, and fuel economy that will offset the cost to the dyno tune. Like Graham said, nearly all the original ones are worn out.

One above is the normal one with the range of standard curves. If you pay a bit more for the programmable one you can adjust it but yes would need to go a dyno at a cost. I would probably get the normal 123 and set to M48. New points distributors seem to be Chinese these days, I bought two at a good price not realising, I most likely won't be using them except for emergency, have heard some really bad things about them.

 

[Blue_Peugeot_504]

Thanks Graham. I notice M48 is slightly more aggressive at 29 versus 26 degrees. Did cars using M48 historically not have vacuum advance.

 

[Blue_Peugeot_504]

Am I right that earlier XN1 engines

• Early XN1 (8.35:1 compression): Used Curve 6 - M48
• Late XN1 (7.6:1 compression): Used Curve A - M78

 

[GRAHAM WALLIS]

Thanks Graham. I notice M48 is slightly more aggressive at 29 versus 26 degrees. Did cars using M48 historically not have vacuum advance.

They all did.

Am I right that earlier XN1 engines

• Early XN1 (8.35:1 compression): Used Curve 6 - M48
• Late XN1 (7.6:1 compression): Used Curve A - M78

Later XN1s had 8.8. 7.6 for XC7 and XM7 which were detuned 1.6 and 1.8.