Twin Spark heads

[C M Smith <cmsmith@domain.elided>]

I thought the main advantage of twin spark heads was the ability to operate 
with higher compression without detonation. With single spark heads the end 
gas preignites if the compression ratio is too high. This results from the 
expanding flame front further compressing the mixture before it has time to 
ignite. The second plug ignites the end gas in a controlled fashion 
preventing this source of detonation.

I also thought this technique had been refined to increase fuel efficiency 
and reduce emissions by delaying the second spark a little. It would still 
produce more power, but also burn cleaner and cooler.

BTW, high octane gas has less energy per unit volume due to anti knock 
additives reducing the volume of actual gasoline. Variable octane engines 
like my SAAB turbos actually get slightly better fuel mileage with the 
lower octane fuels for this reason.

Cheers

Michael


C M Smith
(403) 282 9740
(403)234 7779 (Office)
(403)263 7897 (Fax)
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided