Date:         Thu, 2 May 2002 16:18:30 -0400
Reply-To:     "G. Matthew Bulley" <gmbulley@BULLEY-HEWLETT.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "G. Matthew Bulley" <gmbulley@BULLEY-HEWLETT.COM>
Organization: Bulley-Hewlett
Subject:      Advancing timing for more power, was: Boston Bob's web site
In-Reply-To:  <B8F6E2AD.82DC%eric@seniornet.org>
Content-Type: text/plain; charset="US-ASCII"

First off, advancing your timing outside of spec isn't a very swell
idea. BTDT....

Here's the basics of how it works though...

Your ignition timing is set at a specific point of the combustion cycle
to present a nearly complete burn of the fuel products within the
combustion chamber. Believe it or not, it takes a long time for the
flame front to reach all fuel mixture in the cylinder, even with
advanced VW head designs that create great squish and swirl in the
combustion space.

Consequently, *some* of the fuel mixture goes unburned before the
exhaust valve opens and pressure is lost in the cylinder. If you lit the
spark later, (retarded timing) even more of the fuel products would go
unburned, and even more potential energy would go out your exhaust
system.

If you lit it a bit earlier, you stand the chance of burning more fuel
in the combustion space, since the flame front would have time enough to
reach more of the fuel product before the exhaust valve opens; more fuel
burned before the exhaust valve opens means more expansion of gasses
inside the closed combustion space, and, Viola! A little more power.

Sadly though, if you advance it past a certain point (a point that
roughly corresponds with the factory setting), two things happen. Too
much heat builds up in the cylinder area because of the longer flame
duration in the cylinder; more heat than the metal and the cooling
system are designed to wick away means things (literally) start to melt.
Pistons get holes in them. Valve heads become crescent shaped, rather
than round. Cylinders crack. Valve seats sink into the head. It is
pretty sucky.

The other thing that happens as a result of this extra heat, is multiple
flame fronts can erupt uncontrollably inside the cylinder, since there
are hot spots of glowing metal in the combustion space, and these
fire-off the fuel mixture as it is being compressed.

As a result, you hear knocking, or pinging, as the flame fronts collide
inside the combustion space. So you run down to the local petrol/gas
station and fill up with their fancy pansy 93 octane super blend, and if
you haven't burned a hole in your pistons or scorched a valve on the
way, your motor runs somewhat nicely again.

But you are paying a shitload of money ($3++ per tankful) for a
teeny-tiny increase in performance. If you took that $$ for your weekly
tankful, and invested wisely for a couple years you could slap in a
really phat motor that blows the sliding door off the track, and picks
the front end of your van off the ground. Okay, maybe not THAT phat, but
you could buy something nice.

Needless to say, until one of the wise-guys on the list modifies VW's
anti-knock ignition control for use on our Vanagons, twisting the dizzy
is lame way to get more ponies; ifn you asked me.

Developing business and guiding change since 1996,

G. Matthew Bulley
Bulley-Hewlett
Corporate Communications
Business: www.bulley-hewlett.com
Alliance: www.ntara.com
Phone: +1.919.658.1278


-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf
Of Eric Spletzer
Sent: Thursday, May 02, 2002 3:34 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Boston Bob's web site

Forgive my newbieness, but what exactly do you mean by advancing the
engine
to get extra power?

My van could sure use it.

-eric
'85 Vanagon


On 5/2/02 12:29 PM, "gary hradek" <hradek@YAHOO.COM> wrote:

> Bill,
>   Now I do not recall boston bob say anything about
> the world being flat, yet.   Most engine rebuilders
> see the worst of what we do to our engines.   I agree
> that 87 octane will work well with our vanagon,
> however if you advance the engine to get that extra
> power you should take boston bob's advise and use the
> higher octane.   It may prevent boston bob from seeing
> your engine quite so soon.   gary
> Date:    Thu, 2 May 2002 12:44:09 -0400
> From:    wb6otg <wb6otg@INTREX.NET>
> Subject: Re: What Octane Fuel
>
> A stock Vanagon will run fine on regular gas.  Some of
> the information
> on Boston Bob's web site is just plain wrong.
>
> I think its time to pull this out of the archives and
> dust it off:
>
>
> Here's the story on octane:  At one time (up til the
> early '70s?),
> there
> were two ways to measure octane, research octane
> (based on lab work
> with
> the fuel) and another system (I forget the name)
> based on tests in an
> actual engine.  The two systems usually give somewhat
> different
> numbers.  Most car makers (including VW) specified
> research octane,
> often
> listed as R.O.N. (Research Octane Number?).  The US
> government, in its
> usual wisdom, decided that since people couldn't
> agree on a method,
> they
> should invent a third one!  So, when the government
> started requiring
> that octane be marked on the gas pump, it was
> required that the two
> existing methods be averaged to come up with a number
> (the fine print
> on
> the sticker even reads (R+M)/2.
>
> So, when VW calls out 91 R.O.N., as the gas flap
> sticker on my Jetta
> and
> the owner's manual for my Vanagon both do, that is
> the same (more or
> less) as the US gas pump number of 87, which is the
> usual number for
> regular in most areas.
>
> Bill
>
>
>
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