Re: Ignition Timing Then and Now

[Simon Favre <simon@domain.elided>]

See below:

Bob McKeown wrote:

>Recently I took my trusty Duetto to the new dynamometer shop here in 
>Nashville. My car has standard (not Veloce) cams and an otherwise completely 
>stock engine with good compression. What an eye-opener! 
>
>I wasn't prepared to see that maximum flywheel output was a paltry 75 
>horsepower! The good news was that the torque curve was as flat as Kansas 
>(that's very flat).

Well, an Alfa 1600 engine isn't supposed to have a torque curve THAT flat.
I wouldn't call that good news. A decent streetable 1600 should feel like
it really comes alive at 4000 RPM. I think the peak torque should be around
5000-5500.

>The timing was set at 40 degrees BTDC, per the specifications Alfa published 
>with the car many years ago. At the suggestion of the dyno guys, we started 
>backing down the timing, and voila - there was the power I'd been missing. 
>
>With a final timing figure of 28 degrees BTDC, the power reached a much more 
>acceptable figure of 96 at the flywheel with a very broad peak around 6,000 
>rpm. Despite the published spec of 125 h.p., the dyno shop guys felt that the 
>96 h.p. number was probably reasonable for a 1.6 liter engine in 1966. 

The cams have a lot to do with it. Did you check the cam timing before going
to the dyno? If the current cams are off a bit, that might explain why you 
had to back off on the timing to get some more power. You might also have a 
distributor that's advancing too agressively. Try having the disty run on an
advance curve machine. Also, Dropping in Veloce or Euro 1600 cams was always 
worth a few HP. 

>Can anyone tell me why Alfa would publish a timing spec that was so totally 
>out of kilter? Was 40 degrees BTDC a reasonable timing setting in 1966, and 
>if so, why?

On possible reason for the 40 degrees might be the universal availability of
leaded gas in 1966. Note also that HP measurement techniques did change over
time. I believe in Europe, the DIN numbers quoted were always higher than
the SAE figures quoted here. Besides, you ever heard of a car manufacturer
that DIDN'T exaggerate claims? ;=)

Simon

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