My understanding is that the Turbo motors do in fact still make Power well
past mid stroke.... but again I'd defer to Mike Lefever and Dave on this
one.... they would know better then I would.... I'm just in love with the
concept of Turbo's and EFI....wonderful stuff..... one day I'm going to
have to give it a whirl......
Keith
----------
> From: Thomas E. Bryant <saltracer@awwwsome.com>
> To: Keith Turk <kturk@ala.net>
> Cc: dad land <eaglemot@bellsouth.net>; Land-speed@autox.team.net
> Subject: Re: Nitrous 101
> Date: Wednesday, February 27, 2002 4:17 PM
>
> Keith,
>
> Lots of good info stated elegantly, as usual. One thing that I would
> question though is the expansion benefits through out the stroke. As I
> understand the combustion process, any expansion past roughly 23 degrees
> past TDC is not very effective since the piston moving down the hole
> expands the area in the cylinder faster that the gases expand.. As I
> understand it, timing advance is desired to start the combustion process
> at the proper time, dependent on the mixture quality, to reach peak
> pressure about 20 degrees ATDC.
>
> We have run nitrous with moderate success since 1989, when not many were
> doing very well with it. We carried it on the car for a few years before
> that, but had waited until we got things sorted out on the basic tune-up
> to have the courage to use it. I can tell you this, if the basic tune-up
> is not right, you will destroy parts when you hit the nitrous,
guaranteed!!
>
> Early on, I enjoyed a good relationship with Dale from NOS and gained
> some excellent info from him. We have taken a bit of a vacation from
> nitrous to pursue the gas class records, but we will be back on the
> scene in the future. It is just too much fun to hit the nitrous!
>
> Nitrous does speed up the combustion cycle and therefore needs to be
> properly retarded or detonation goes wild! I have seen the results too
> often. Just the fact that the nitrous is being introduced, even if it
> was the same oxygen content as the air we breath, still fills the
> cylinder to a level above naturally aspirated engines which increases
> heat and pressure requiring timing reduction.
>
> We also retard 2 degrees for each 50 hp as suggested by the experts. We
> us a MSD igniter with the retard function that has worked well for us.
>
> Tom, Redding CA - #216 D/GCC
>
> Keith Turk wrote:
>
> >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?
> >)
> >----------
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