What I was going to say about Cylinder pressure is this.... within a give
cycle an internal combustion engine operating at 100% volumetric efficiency
can produce X amount of HP. We can aid the combustion process by several
artificial means. lets take a sec and look at what is mechanically
happening to each of these and experiment with my understanding of
each..... as it relates to the cylinder pressure and the Manner in which
it's formed.
I'm sure there is a fancier way of saying here's your choices... Naturally
aspirated....Turbo/Blower ... Fuel/Nitrous....
In a naturally aspirated situation the fuel is ignited and the flame
propagation is directly proportional to the fuels octane... the amount put
in is virtually equal to the size of the bore and stroke of the
cylinder.... ( assuming your at 100% VE and not over or under it ).... As
the gases are ignited they start to expand and put a force on all
components off the combustion chamber... ( yep the head gets the same
force) The Piston then is Forced to start it's travel down the cylinder
bore.... the gases continue to expand as the combustion process takes place
and force is produced throughout the stroke... ( for the most part ) we
fire that spark plug early to give this flame front time to advance to the
point it will excerpt Maximum force.
In a Turbo or Blower application we increase the Pressure of the intake
charge and thereby allow us to install more air/fuel during each combustion
cycle..... so what happens is that the Volumetric efficiency is that it is
Radically increased in direct proportion to the amount of Boost and Fuel
added. ( up to a Point of diminishing returns ) Now when we fire this
fuel/air charge it's combustion process is greatly aided by the added fuel
and air... and it then increases not only the force down the stroke but
continues to expand for the FULL stroke of the motor.... somewhere in here
ya gotta know it's producing HUGE amounts of Pressure on the crank at 90
degrees or mid stroke and gob's of Torque are created as a result ... the
second key is the continued expansion to the bottom of the stroke.... so
it's making Mass hp.
Okay now on to the only Fuel that I know about .... well I might expand on
my limited knowledge of Nitro but I would really rather someone with a clue
do that.
Nitrous oxide is nothing more then a Oxygen rich air.... 33% oxygen by
content as opposed to around 23% in the ambient air...... N2O + two Parts
Nitrogen one part Oxygen........ hmmm this is making sense so far....
scary.... okay... what we are doing is introducing more Oxygen when the
Valve opens so the intake charge carries more capability to accept Fuel....
and it is the FUEL that makes the cylinder pressure..... what does happen
thou is that this Oxygen rich mixture is that it burns FASTER so the actual
flame propagation within the cylinder is happening quicker and the
combustion process is almost taken to the point of being a Explosion
process..... what that means to us the casual observer is that the Flame
front travels much faster and the actual Fuel air charge is used up more
quickly..... so to is the power making capacity fuel/air charge..... think
of this as a tortise and the Hare..... story..... Nitrous charges hard up
front but by mid stroke it's about spent.....( that maybe exaggerated but
not much ).....
So anyway it's got great pressure making ability BUT it's also going to
impart high degrees of cylinder pressure in the early stages of combustion
through Mid Stroke..... When you look at these high degrees of cylinder
pressure you have to understand that it's going to do some damage to any
component in the process that isn't up to the task.... It also makes sense
that you would want to start this process a bit later in the combustion
cycle hence the retarded timing...
Whew.... Now I'm sitting back looking at all those sentences run together
thinking Dave Freiburger could edit this into usable information.... but so
could my second grade teacher.... only difference is He would have a clue
was I was trying to say.
Keith ( Okay Dahlgren.... did I listen or did I miss the class altogether?
)
----------
> From: Keith Turk <kturk@ala.net>
> To: dad land <eaglemot@bellsouth.net>; Land-speed@autox.team.net
> Subject: Nitrous
> Date: Wednesday, February 27, 2002 11:43 AM
>
> Port systems are just infinitely more tunable then a plate and they are a
> very direct path to the intake port.
>
> we're taking out 2 degree's of timing for every 50hp of Nitrous.
>
> I had all the stuff to install a high speed timing retard for the top
end
> of the course but we chose not to. I have read about many folks who have
> been successful using a High speed retard it's just not part of our tune
> up.
>
> K ( I was trying to write an inclusive bit on Cylinder pressure and how
> it's manifested with all the different type of Power enriching systems...
> LOL but you got impatient .... I guess I'll continue on writing that thou
> cause it's kinda interesting. )
> ----------
> > From: dad land <eaglemot@bellsouth.net>
> > To: Keith Turk <kturk@ala.net>; Land-speed@autox.team.net
> > Subject: Re: Tech Questions
> > Date: Wednesday, February 27, 2002 9:10 AM
> >
> > yes, keih...........if you were to use nitrous on a gas
> motor..........what
> > are the pro's and cons of a plate system versus direct port injection
> with
> > an injecter for each cylinder? and next, when you activate the
> > system.......and i could retard the timing, how much (in degrees)would
> you
> > retard it? next if you were just running gas, on top end, and you could
> > retard the timing to make more power up there. at what RPM would you
> retard
> > the timing? and how much?????? thank you! as i don't know it all but
i
> do
> > know enough to know that i don't know it all.....ol'dad
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