Re: Timing, revisited....

["Jeff M" <tystorm@email.msn.com>]

First and I am going to just confirm, your timing was checked with that
brown wire under the dash unhooked? If not then you will need to unplug it
to check your true base timing (not Diacom indicated which is not the same
anyways).  Base timing for the SyTy engine should be 0 degrees with that
brown wire unplugged, else have fun trying to turn to distributor to correct
(if you do not have it, you will be getting one of those odd looking 12
point closed end wrenches to get to the distributor bolt buried behind the
manifold, fun, maybe you already know).  Once your timing is set
properly/safely at 0 degree (with your 3 degree correction), then we can get
back to the other topic here.

We now need to add (and I will try to keep it from being a mini-novel ;-), a
more wide and general statement/reason for such perceived mild timing values
in the chip and on your Diacom as compare to those used in old carb'd
engines.

Old carb vehicles were great for their times (and some owners hesitate or
refuse to accept the benefits of EFI, whatever) and the carb's fuel release
quality was OK but, the actual droplets of fuel were quite non-uniform and
rather large for the most part.  Consider that fuel being in droplets this
large burn quite slowly (and the mix of droplets for each cylinder is quite
non-consistent).  To get the fuel in this state to burn in the proper time
relative to piston location (to achieve and benefit from peak controlled
combusted cylinder pressure BMEP?) you have to advance the timing quite a
bit to insure that enough of the fuel is burned in the proper time.  NOW,
the 90s and, add to your swirling heads with their ability to churn up the
mix and promote a nice controlled fast burn, a fuel deliver device (fuel
injector) with a far better atomized fuel mixing ability, heading to the
cylinder/combustion chamber, and you have a very small/fine and quite
consistent fuel droplet sizes mixed very well with the air charge.  Smaller
droplets burn faster once ignited (and why newer fuel injected cars have had
more knock tendencies and the efforts to address that relative to the carb
days) so with this faster controlled burn, you need less timing for peak
combustion to occur AND, since you can have the timing of the spark ignition
happen later/closer to when the piston is at TDC, you will make less
negative torque (?) and use more of the combustion to make positive torque.
Negative torque happens more in that old carb engine from the timing of the
spark and starting of the combustion burn being so much sooner relative to
the location of the traveling piston (more degrees before TDC than
yours/nowadays engines).  Also, now a days with all this reduced
timing/better combustion and combustion timing, your make more power, have
cleaner emissions with a fuel injected car than a comparable carb'd engine
with the same basic layout (street engine to street engine versions).

Take all this a few steps further into what technology is doing/going to be
doing and you have direct fuel injection engines (into the combustion
chamber directly) that capitalize on having very finely atomized fuel
droplets (running something like 300-400 psi fuel rail pressure) that is
injected into the engine sooner to the time it is needed/ignited, without
the physical and timing limitations of the valve train, and you can make
timing even less, have less negative torque, and if your mix is homogenous
enough (this is the tough part) burn super clean while still making power
?!! yep and YES just in case any of us are worried about  owning a 2010 car
and be getting 40 mph but be stuck with a 20 second quarter mile ;-), we
will still get hp numbers to satisfy (though not sure about all your power
junkies ;-).

One last thing here, there are others on this list that are avid to
extremely avid on the SyTy V6 chip (and a world of other areas ;-) and if
something was really amiss with your chip values, you'd of heard by now.
There is a gentleman who has done quite a bit of work and sells a 3 bar
multi stage chip (real control of fuel/timing above 15 psi and 4, 6, 8 or 10
stages from disabled/security, valet and mild to wild depending on octane).
I have installed this chip on a Syclone and was impressed, though I already
knew of the competency level of this programmer before, his chips delivered
as promised.

Anyone please feel free to expand and/or correct any of this, always
learning (and making mistakes ;-).

Jeff M



> Bruce, Jeff et al -
>
> First, I checked that I was not having another flashback, and I'm in my
> right mind.......
>
> Then, I checked the timing again, timing light vs. Diacom vs. MAX 232
> circuit -
>
> At idle, 20" Hg vac (stock, weenie cam), 800 RPM, 160°F coolant (no
advance
> there), was reading around 20° advance *at the pulley*.  Diacom said I
> should have about 23.3°, but my vibration damper is off by 3° from true
TDC
> and it is corrected; thus the discrepancy.
>
> So - we ARE reading numbers as the timing table would predict, not 2x
these
> figures (distributor RPM vs engine RPM).  40° advance would be hard to
see,
> pretty far counterclockwise around the pulley.
>
> Didn't think I could make a bonehead mistake by mixing up the 2:1 ratio,
> but ya never know.......
>
> I've got a pair of 1996 heads to be installed soon, so I was interested in
> what changes, other than the VE tables, might be affected.  That got me
> looking @ the spark table, too.
>
> Do these (1991) heads really burn *that* fast, that timing can be cut in
> half????  Doesn't seem reasonable to me.
>
> Other speed/load (RPM/MAP) points aren't as easy to read (I don't have a
> dyno...boo hoo); although, I do remember Bruce mentioning an episode about
> a VW, a timing light and clinging to a bumper awhile back......
>
> Still puzzled; can anyone shed some more light on this???
>
> Thanks - Barry - Sy#26
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