On Wed, 14 Apr 2004 08:50:59 -0500, "L.D."
wrote:

wrote:

On Tue, 13 Apr 2004 15:47:18 -0500, "L.D."
wrote:



Orval Fairbairn wrote:



In article . net,
UltraJohn wrote:





I double checked and it was Exxon and it is quite pricey. . .
regular 93 octane here is about 195 and this 110 leaded was 4.25 a gallon!
but hey if your running 12.5 to 13.0 to 1 compression you have to pay the
price. .;-)
John





Actually, you can get an extra boost if you mix 1:4 ratio 100LL and
premium unleaded. Low concentrations of TEL yield large octane boosting.




Orval,
When you say "extra boost", what do you mean? If you mean power, you are
wrong. Higher octane is less explosive, harder to set off, less power,
that is the reason you don't get preignition. It won't ignite from high
compression, a glowing piece of carbon or early timing, etc as lower
octane will. To get the most power use the lowest octane you can with
out ignition knock.
L.D.



No, better to tune the engine to make use of the extra octane. Higher
CR, more advance, or better intake/exhaust can allow the engine to use
the extra octane and produce significantly higher power. High octane
fuel does not necessarily burn slower, it is just less prone to
auto-ignition.
Propane burns faster than gasoline and is 150 octane, on average.

I have had several vehicles over the years that produced enough extra
power (and therefore economy) on hightest to MORE than pay the
difference in cost. Being computer controlled engines, knock was never
an issue - I could likely have run the thing on Kerosene after it was
warmed up.



Oh yes, I agree to tune the engine, higher cr, more advance and so on,
but that aggravates pre ignition. Then you may have to use higher
octane. I didn't mean to use lower octane instead of good tune. When you
do tune correctly and you still don't have pre ignition, then no need to
use higher octane. In fact it is counter productive. You said propane
has about 150 octane. I new it was very high although I didn't know the
exact #. That is my point, I have run propane in trucks and tractors
and it doesn't have as much power and it uses more fuel. So again my
belief is octane rating is not a power rating. If it was, burning
propane would give more power.
L.D.

You are missing the point.
An engine TUNED for high octane fuel will produce more power from each
gallon of that high octane gas, still below the "detonation" point,
than an engine properly tuned for low octane will on low octane.

It is also obvious you have never converted IC engines for propane in
a serious way. Propane has a lower energy content per lb than
gasoline, but if properly set up to take advantage of the octane
available in propane, the engine WILL produce significantly more power
than the original engine running on gasoline. Proper conversion of a
carbureted engine required cold manifolding, different plugs, modified
timing, among other things.

You WILL use more fuel.
Octane is NOT a power rating, but high octain fuel, while not CAUSING
an engine to produce more power, definitely ALLOWS it to.