Re: Octane and engine health

["Jorge & Ani Mazlumian" <jorge.ana@domain.elided>]

Thanks to Eric S., John F., Alan L. and Greg H. for their responses.
To recap, I asked: "I understand that higher octane than recommended in a
street engine will not
add horsepower.  But will it protect the engine from knocking under more
extreme driving, such as time trials?"
May be I should have said pinging instead.  It is (I hope) common knowledge
that higher octane will NOT increase horsepower, speed, performance, etc, on
an engine not prepared for high octane gas.

I asked the question because during practice for time trials with a stock
(well, S-cams) 3L V6 engined Verde, the engine suddenly lost power, oil
pressure went to Zero, and the temp went very high (red light), and by the
time I heard the engine noise through my helmet, it was too late.  Now I was
told before this happened, that in order to "protect" the engine from
pinging under extreme conditions (such as this), adding some high octane gas
would act as an octane booster, without loosing (or gaining) any power.

For the record, car has 270,000 miles, engine rebuilt about 120,000 miles
ago, consumed about a quart every 600-700 miles.  Had a fresh oil change (a
week prior), with Kendal 10-40 (there we go again), and I always checked all
the fluids including oil before every run.

Eric responded:
"I have no real application of running an engine under high loads, but some
side dyno data does suggest that one may need higher octane after extended
high load applications.  This would be mainly due to heat being stored up in
various parts in the head, and this would be especially true if you are
using the hot range spark plugs.  Even if your engine is not over heating on
the track, it's still possible to get local hot spots.
Even without the above rationalization, I look at it as cheap insurance, as
we do this to our GTV."

While John F. in South Africa said:
"A pointer to how octane affects HP.  My Alfetta 2L motor with 12:1 CR
delivered approx.
140kW (225HP) on the dyno with 97 octane fuel.  Changing to 102 octane the
power dropped
off nearly 30%, because I was unable to reset the timing in the ECU.
Detonation is a function of combustion chamber temperature.  If the
temperature exceeds a
safe temperature the detonation starts all over again.  Dumping some higher
octane fuel
into the system would reduce the overall temperature and reduce the
detonation.  It is a
complex subject!"

Sounds like a low percentage (10-30%) of higher octane gas in the tank
probably would not hurt, and perhaps, only perhaps, protect the engine under
extreme performance conditions.  And a lot of praying...

Jorge Mazlumian
73 GTV in the remaking
89 Milano with a dead engine (in the transplant waiting list)
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