Technical RPM & Timing & Generator Light

[bellucci]

Hi everyone,

I have a Fiat 500L with a 126A (595cc) engine. It's using the 28 IMB carburetor and a contact point distributor. I noticed that my engine was idling at 1100 RPMs. At 1100 RPMs, the Generator light in the dashboard remained off. This is after the engine was warmed up, and the choke lever was fully pressed down.

I also noticed that my ignition timing was at around 18 deg at idle (total timing from TDC arrow) at 1100 RPMs. Several Fiat manuals say that my RPM should be at around 850-900 at idle and my timing should be at 10 degrees BTDC and 18 degrees at 3000 RPMs. So, I ended up retarding the timing, and now my RPM is 900 and timing is set at 10 deg. Except now, the Generator light in the dash stays on since there isn't enough rotation by the dynamo to charge the battery. When I rev the engine, however the light turns off. The belt on the pulley is not slipping to my knowledge.

Is this normal? Are there any Fiat owners out there that have a low RPM with the G light on at idle at around 900 RPMs?

In case you're wondering why I retarded the timing is because I've been reading that having an over-advanced timing could affect the overall performance of the engine at higher RPMs and while it delivers a solid idle, the premature ignition timing caps the performance of the car. I'm experiencing a cap at 37 MPH and can't get more RPMs to shift into 4 without losing power. My goal is to hit 55 MPH and believe it can be done on a 595cc engine.

Please correct me if I'm wrong with any of my findings.

Thank you.

 

[fiat500]

Your setup is just about right, 10 degrees is correct at idle, and the generator light is likely to show at the correct idle speed. You can get past 55mph with the 595 when it's set up correctly.
You add the 18 degrees to the 10 degrees to give 28 degrees dynamic advance at higher rpm.
Most important is to have the dynamic advance correct, and then accept the idle advance for what it is. Various things, such as points gap or distributor wear might be affecting the perfection of the arrangement.
Many people recommend using the factory settings as a starting point, and then to adjust by experiment to suit.

 

[bellucci]

Your setup is just about right, 10 degrees is correct at idle, and the generator light is likely to show at the correct idle speed. You can get past 55mph with the 595 when it's set up correctly.
You add the 18 degrees to the 10 degrees to give 28 degrees dynamic advance at higher rpm.
Most important is to have the dynamic advance correct, and then accept the idle advance for what it is. Various things, such as points gap or distributor wear might be affecting the perfection of the arrangement.
Many people recommend using the factory settings as a starting point, and then to adjust by experiment to suit.

Thanks, Peter! I have set my points gap to 0.45mm when fully open. Appreciate the confirmation on the generator light. Makes me feel better.

 

[Toshi 975]

Peter has mentioned distributor wear already, it is worth checking the distributor Bob weight springs that can stretch or even break in which case the timing will advance as soon as the engine starts instead of the gradual increase up to 3000 rpm