[Shotimes] Gas

[Ron Porter]

Oh boy, I'm off the list less than a day, and "this" topic comes up again!!

I randomly picked one of Zack's emails for response, and I'll dump here!!

Anyway, here is the Pat Bedard C&D article on the SHO octane issue from June
1989. Read it carefully, and note that it actually mentions a real, live,
Ford engineer who worked on the program:

http://www.v8sho.com/SHO/Savemoney.htm

Keep in mind a few things. In 1989, this seemed like a high compression
engine, but nowadays there are Hondas with 11:1 CRs that specify 87 octane.
By today's standards, the SHO engines are low compression. Note that in the
article, they speak of "adverse conditions". I do what Don does, I ran 87
all year, then I would go to 93 for the Convention with it's high temps,
road course, and dragstrip use. Other than towing a trailer across Death
Valley in summer with four passengers, you won't get into many "adverse
conditions".

OHC, central-plug engines are not as timing-sensitive as old OHV engines.
Total timing is not that high (36?), and the knock sensor only briefly pulls
out around 4 degrees, IIRC. There are no bolt-on mods that should alter your
octane needs, until you get into blowers, turbos, nitrous, or have bumped
your CR like John Hrinsin. If you are getting pinging on octane below 91,
you have some tuning issues. We can also argue all we want, but I don't
believe in the "silent pinging" theory that has come up just in the past few
years. I believe it's a rumor started by gas companies to sell more premium
gas. See the Ford guy's comments in the article above.

As was mentioned, octane is only used to control pinging and detonation, it
adds nothing to the power output. Straight gas has a very high BTU content,
and anything added to it (octane boosters, detergents, alky) drop the BTU
number. It's the BTUs that give you power and fuel economy. In living in RFG
gas areas (Chicago and Louisville) for a number of years, the car never
pinged, but power and economy were down. Gassing up out of town immediately
helped. Alky (ethanol/methanol helps out the octane, but drops the BTUs).

Running higher octane also has the minor effect of retarding the timing, as
the fuel does not light off as readily. There have been tests, as well as
personal experiences, where lower octane makes the car perform better.

Also remember that the knock sensor is not a "magic" device. It works in a
very hostile loud, vibrating environment, and it is kind of a "dumb" device,
in that it only looks for a certain frequency that has been associated with
pinging. At least one person (Ransom?) has hooked a light up to the sensor,
and the sensor goes off with some regularity, as their sounds/vibrations
most likely are crossing it's frequency (much like burglar alarms set off
radar detectors because they share a frequency).

Doesn't matter whether the car is a Gen 1 or 2 or 3, ATX or MTX, they don't
need 91 or higher octane for 95%+ of about everyone's driving. Part of the
trick is to get "good" 87, with no alky. Granted, this is impossible in some
parts of the country. This is part of the reason that we do our Lapeer Days
in early May and October, as the Detroit area goes to Summer Gas (a type of
RFG) from June through mid-September.

As the cars get older, I can see where some may need maybe 89 octane due to
conditions experienced over the car's life. At any rate, run the lowest
octane that doesn't ping, don't lug your engines below 2k (I have followed
the "2K Rule" for many years....that is, stay in a gear that always keeps
the rpm above 2K). And buy good gas.

Ron Porter

-----Original Message-----
From: shotimes-admin@autox.team.net [mailto:shotimes-admin@autox.team.net]
On Behalf Of Zach Leahy
Sent: Friday, April 08, 2005 11:27 AM
To: Dave Garber
Cc: shotimes@autox.team.net
Subject: Re: [Shotimes] Gas

I find that the fuel choice can be directly dictated by how you plan
to drive.  The "new" 92 get mid-grade at best when I fill up, but the
93, with the engine being modified takes significant drop in power
even when bumping down from 92/93 to 89.  If you think I am crazy,
yall can come and pay for a few tanks of gas and try it out.  Now, the
93 is not stock by any means, and i think that has a lot to do with
it.  I demand a lot from that car as well, so given the sum of all of
that... the 93 gets premium almost always.  the exception to this is
if I know I will be driving hundreds of highway miles with that car.

The stock 92 though runs fine on 87, and will probably be run on that
regularly since it is just my commuter now.  It gets run through the
RPMS sometimes, but not too often.  It seems perfectly happy with
normal gas.  Pretty much if you have a car that has been modified to
the point that lower octane gas does not give the required
performance, youwould know that already.

Z