Re: 98 Octane?

["David R Johnson" <johnsnd@domain.elided>]

On Mar 31,  9:23am, Jorge wrote:

> has experience with some boost of power for street or race with the
> VP racing fuels?  Their brochure lists "Performance Unleaded suitable for
> high perf. street, Octane R+M/2: 100; and "Motorsport 103" also for high
> perf. street cars R+M: 103, Motor Octane 99, as well as other pure racing
> fuels.

<snip>

> Aside from the needed timing adjustments, is =
> is
> at all advisable, even mixing race/premium fuels?
> just want to extract a few more horses from my Milano (75)

I am not familiar with the engine management system on the Milano (is it
similar to my GTV6?), but generally very few vehicles will obtain greater power
from running fuels with octane higher than the owners manual recommendation.
 Octane is not a measure of energy, but of resistance to burning.  The reason
that performance street or racing engines often use higher octane fuel is to
provide resistance to detonation.  This allows you to run higher compression
ratios or more timing without blowing holes in your pistons.

If the Milano has a knock sensor and a timing retard feature (i.e. it retards
the timing when knock is detected to prevent damage), then it is possible that
you will get more power with a higher octane fuel.  However, this is only the
case if you are experiencing detonation with regular street fuel (hard to tell
without a diagnostic tool for the computer, unless you can hear it in which
case the motor won't last too long!).

Usually the motor is designed to run without knock on ordinary street gas, and
the knock sensor is there to protect the engine if you get a bad tank of gas.
 Thus running race gas on a stock motor would result in no power gain, unless
there is another problem resulting in knock.  If this is the case you should
definitely fix it instead of relying on race gas, a band-aid solution IMO.

If OTOH your motor or engine computer programming has been modified, then you
may get a benefit from higher octane.  In this case however, you will need to
always run the higher octane to avoid risk of engine damage (assuming you don't
run a fancy aftermarket computer which can switch between street and race
timing maps).  This can get expensive and impractical if the car is used much
on the street.

Hope this helps,

Dave J.
1982 GTV6

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