In reply to a message from Jeff R sent Sat 20 Mar 2010:
Hello Jeff,
If you think you have pinging at 34 degrees, you should not be
considering increasing it to 42. There are a lot of variables in
this equation, fuel octane, coolant temp, air temp, valve timing,
actual compression, carbon, oil dilution, etc… You want to find
how much your engine can tolerate, rather than look to a book for
the answer. My experience is Hammill’s advice is too high,
especially if your engine runs hot or burns any oil.
The emission specs are sometimes counter intuitive because they
were all about meeting an artifical test. The vacuum retard was to
meet the curb idle HC test, it makes the engine run hotter and is
better off disconnected. Some of the US emission emgines went down
to 7:1 compression and the high advance was an attempt to get some
decent fuel mileage because the vacuum advance was replaced with a
retard to meet the idle test. With hotter intake air and leaner
mixtures you would expect the engine to have a lower knock limit
with the same fuel.
Mild pinging is OK, detonation is bad. My advice would be to pull
the spark plugs and inspect the insulators for aluminum flecks with
a magnifying glass. With all the plugs out, I would do a proper
compression test to see what you have. Then fill up with the
highest octane fuel you can find, test the car on a cool morning,
and see if there is a change in the noise you think is pinging. If
you can find some race gas, you will know immediately if it is
valve noise or something else. Pinging only happens under load,
immediate stops when you close the throttle, and is very
temperature sensitive. The probability of pinging is highest around
the torque peak, when VE is highest, around 4000 rpm in your
case. The noise will be quite different with a cold and hot
engine and a cold or hot day.
Paul–
The original message included these comments:
I have a US spec S2 E- Type which has its stock 9:1 compression
engine and the dual Stromberg emmisions set up.
A year or so ago a swapped out the original retard dizzi for a 123
JAG unit. The effect has been amazing - on the button starting,
faster response and a much smoother engine.
My question is that I’m not sure I have the 123 adjusted to the
correct setting. It’s presently on setting 2 which whilst fairly
aggressive at 2000 rpm maxes out at 34 degrees. On aggressive
acceleration I occasionally get a noise that sounds like a loud
metallic rattle from the valve train which I suspect to be pinging.
Could anyone advise on the best setting and if I should choose a
–
PS
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