Hi John,
You wrote:
> Spec for timing of Triumph four bangers is 4 degrees before true dead
>center. But this was written with 96 octane gas in mind and required. Is
>anyone retarding spark to two or zero degrees as a matter of course in
>order to deal with the the 92 octane gas that is the best grade available?
>This was recommended to me.
Be aware that the measurement method for octane changed between the time
that spec was writtne and now (also between Britain and the US, I believe).
In the old days (and maybe still in England), they just used "research"
octane numbers, now they use an average of "research" and "motor" octane
ratings - these are two different test methods. The upshot of that is
that the same gasoline dropped about 5 octane points. In other words,
the old 96 octane is the same stuff as what's now rated at 92 octane!
So, my advice is to not retard the timing unless you're having trouble
with pinging.
>BTW, I toy with the idea of using a mixture of 92 octane and 100 octane
>Aviation gasoline.
Unless you've raised the compression significantly above stock, there's
no advantage to this - you'd just be wasting your money. Of course, I
tend to run 115 octane Cam2 race gas in my TR-4, but its got a compression
ratio of 12.75 to 1!
Malcolm, this might be something to add to the FAQ since it seems to come
up about once a year or so.
later,
John Lye
'59 TR-3A, '62 TR-4, '70 GT-6+
email: rjl6n@virginia.edu
homepage: http://avery.med.virginia.edu/~rjl6n/homepage.htm
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