[CWPASADENA]

Originally Posted by krswen

Hi Marc ....

This may sound strange coming from an engineer, but as slowly as things happen with a Model A (most of the time), and given the fact that you can adjust the spark lever without taking your eyes off the road, I wonder if an experienced A driver who is sensitive to his engine sounds couldn't do just as good a job as we did in "mapping" engines. With just centrifugal and vacuum advance we still were compromising (compared to today's extensive maps).

At 2000 rpm you don't need twice as much advance as at 1000 rpm since turbulence is increasing (thus flame speed increases), but to predict the optimum spark timing was sufficiently difficult that we always developed the curves with dyno time. We still "validate" predicted maps on the dyno.

Ken

This may also sound strange coming from an Engineer but a Model A Ford is a simple car and I like to not make things all complicated.

Yes, theroletically, you can improve performance and fuel economy by always keeping the spark advance adjusted exactly for optimum engine operation, HOWEVER, any improvement you may experience when driving a Model A will be off set by constantly having to change the timing and also wearing out the spark advance mechanism.

I am a Mechanical Engineer having spent years in engine development and many many hours in the Dynamometer Cell. I am also a Race Car driver and feel I have a farily good ear when it comes to engine performance. I drive my Model As with the spark lever set as I have outlined in my previous post. I taylor the advance curves on my Race Engines for what I feel is optimum engine performance.

If someone wants to try to optimize the operation of their Model A by constantly adjusting the spark, that is fine with me BUT I think he is missing the enjoyment and simplisity of driving a car that has been around for more then three quarters of a century.

By the way, WHO SAID an engine should have twice the advance at 2000 RPM then 1000 RPM? Anyone with basic knowledge of spark ignition internal combustion engines would know this is not the case.

A Model A is a very simple and straight forward machine, Lets keep it and its operation that way.

Chris