wow have been tied up the last couple of days but here is my take on this thread
Jon
Maybe the expert tune up does work fine for what they have tested, about 1/4
mile..It probably makes the most power for that distance and runs the best for
that distance but if you change the distance or time on I think you need to
change the tune-up some too. Kind of like running nitro 100% might be fine for
1/4 mile or less but for 5 miles might be pretty hard to make it to the other
end. If your wrong tune up involves running slightly less timing and slightly
more fuel then that wrong tune up is probably the safer one in my mind. I can't
remember if it was last year or the year before we talked a while about your
tune
up, I had suggested starting back at a lower setting and working your way back
up
in power levels plus at the time you were running a lot of ignition timing with
the nitrous if you compared the original output of the engine compared to the
size of the hit. Are you now running a lot less advance than you were? If you
don't want to reply to this on list I understand but am a little curious if that
is the case. The whole nitrous tune up is relative to the state of tune of the
engine before the nitrous, if you have 14/1 compression and on the edge of
detonation with the ignition advance and everything is optimized for running at
100 deg F and 4500 feet. then the changes you will have to make to run a big
load
of nitrous are a lot more drastic than a 9/1 engine setup to run at 70 degrees
and sea level. Also if I add 100 hp to a 100 hp engine then if you think taking
4
degrees of ignition advance is going to work you are sadly mistaken. I would
take
out at least 1/2 of the total timing to start. If you add 100 hp to a large
engine that is very inefficient
then taking out 4 degrees makes sense.
The only other question I might ask with your 'unusual tune up' is what is the
bottle pressure during the run?? Are you chasing the bottle pressure down the
track.
Tom you are only giving us about 10 degrees at best to extract the power out of
the gasoline(or alky or nitro..) does that make sense to you? With your numbers
peak pressure is at 20 degrees ATDC and it is over at 23.. Might have to spin
that one real high and need a lot of fuel to even make it run..
Keith where do I start LOL...
at the beginning I guess..
Ve is interesting but there is mechanical, combustion, thermal to consider too.
They all have to be good. You can pump lots of air and make no power I have done
it and it is easy to fall into that trap.
With any engine you have to start the combustion so that peak pressure is about
17 degrees ATDC. Before this point you are actually starting to fight to a
certain degree the expansion of the gases. That is just the best compromise that
makes the most torque(which is what we are trying to do make torque hp is merely
a mathematical manipulation to express it in a different way for other
comparisons). To take that to a different viewpoint you are oxidizing a fuel to
make heat that will cause expansion by heating up the inert gases and making
them
expand. If you have no inert gases then you have less expansion. That is why
nitrous is a case of diminishing returns in the first place. You have a lot of
heat and nothing to expand, so things melt, the heat has to go somewhere. If you
insulate and coat everything it might make it out the tailpipe else something
will get too hot and fail.
Turbos and blowers..
Air pressure has nothing to do with anything at all in this...
It is all about air density. A supercharged engine is no more than a naturally
aspirated engine running at a different altitude period... It is all about air
density, the Ve of the engine does not change one bit you are just pumping
denser
air. It has more weight per cubic foot. Same as when you go up in altitude you
have less and make less torque. Well supercharging is going down in altitude you
have more per cubic foot that is pumped. If you have more mass then it takes
longer to burn so the power stroke is longer. Also you have more gases to expand
so that takes longer as well and will extract more energy from the combustion.
Further for your theory of air pressure to work inter coolers would be both
un-necessary and actually cost power. They convert hot compressed air to cooler
air at a lower pressure. In this process they increase the density. The cooler
the air and the denser the air the better. As an aside to this as the charge air
density goes up the speed of the combustion process also speeds up, that is the
reason you run less timing with a supercharged engine as well as to a certain
degree a nitrous engine( this is why the size of the engine run on nitrous has
an
effect on timing irregardless of the size of the hit). To carry that to an
extreme put a 50 hp hit on a 1100 ci engine and what are you going to do with
the
tune up? Probably nothing, ok now put it on your lawn mower...
90 degrees ATDC...
Nothing special about this number other than it is about 18 degrees past peak,
the best mechanical advantage is about 70 to 76 degrees ATDC with 72 being most
typical. It is a relationship of stroke and rod length. Next time you have the
pan off and are degreeing a cam or have a degreed damper turn the engine till
the
rod on #1 cylinder is 90 degrees to the crank pin. Ought to be around 70 to 76
degrees ATDC.
Nitrous is easy to explain
All bang no push. Reason being it has a lot of oxidizer and fuel. But it has
less
gas to expand, so it gets done sooner. Having a more dense fuel/oxidizer mix it
requires less advance because it burns faster, plus it is potentially cooler
further increasing density..
It is all about air density, pressure recovery and thermal efficiency....
Ok class dismissed.................
Oh as for Dave Freiburger and Hot Rod Magazine
Copyright 2002 Engine Management Systems . All rights reserved.
Dave Dahlgren
(The 'Flame suit' is on now) LOL
Jonathan Amo wrote:
> Tom,
>
> Well thats funny on the NOS experts, we ran their tune-up and acquired
> several paper weights. We saved more parts running our own tune up
> instead of their recommended settings. But then again that was on a
> motorcycle and not a car. past years said by the engineers at NOS say
> our bike would not live with our setup.
>
> on another note, could a bad tune-up actually save your engine on nitrous?
>
> has bonneville proved engineers wrong what they say has not worked, and
> what they say won't work will?
>
> Jonathan
>
> Thomas E. Bryant wrote:
>
> > 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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