Douglas Braun & Nadia Papakonstantinou wrote:
> I could never get my Spit to knock...
> If anybody has an earwitness report of Spit knocking, I'd like
> to hear about it...
Chances are, you have but have never identified it! My engine is a '76,
which was the only year that came from the factory with 9:1 ratio. It is
spec'ed for "95 octane", which could mean either R or M or the modern
version (R+M)/2. So I run Sunoco Ultra (94). My engine knocks under load
if I push the timing too early, or if I run lower octane gas.
> Is it extra-loud, like all the other engine noises I hear?
"Loud" is subjective, but knock is easily discernible in my engine,
particularly when running uphill in overdrive 4th or whenever I floor the
loud pedal even in 3rd. It sounds like a light random ticking as if someone
were shaking an empty tin can with a few grains of sand inside. Knock in
any engine generally happens under load at a lower-to-mid rpm. It's not
usually an issue up near readline because it is caused by the gas hitting
max burn (actually, max cyliner pressure) before the engine has turned over
TDC. At high rpm's the engine is turning so fast that the gas doesn't have
time to burn much before TDC is reached.
> Or do all the other noises tend to mask it?
No. At least not in my Spitfire or one of my previous Caravans that was
prone to knocking while cold.
But I'm still in the dark about how to set my GT6...
Jim Muller
jimmuller@pop.rcn.com
'80 Spitfire (Percy)
'70 GT6+ (Nigel)
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