8o I must say that's probably the most complete breakdown on the co=
mbustion cycle of gasoline I've read in a long time if ever! One of the rea=
sons I love this place is because of the wealth of information which exists=
with the members here, which is why I posted this question here to begin w=
ith. I actually plan to move the battery tray and install the micro gen the=
re, which will solve any ventilation issues related to combustion. yes it i=
s the easy way out, but I posed the question just the same. However I =
want to take just a little issue with the consumed oxygen level if indoor a=
ir were used, this is assuming a completely sealed fuselage in which no new=
air would be drawn in to replace the exhausted air, and thus depleting the=
amount of breathable O2. However this is hardly the situation with a GMC w=
hich in my case has open vents above the fridge and stove as well as 2 poor=
ly sealing roof vents, and main door seal. (yes I still have some items to =
fix on my rig) so even if the relatively small 76cc engine were run inside=
, assuming a completely sealed exhaust path outdoors, the negative pressure=
differential created inside the coach would invite a current of air to flo=
w in from the afire mentioned sources of ventilation. something probably no=
t really wanted on a cold evening. I simply wanted to pose the questi=
on could it be safely done, I believe if a sealed compartment were construc=
ted with powered ventilation and ducting for both drawing in outside air, a=
nd drawing out exhaust with bilge fans, it would be a moot point, since nei=
ther indoor air would be used nor would exhaust be an issue with a constant=
flow of air moving through the sealed chamber with no chance for any exha=
ust to enter the living space.I have arrived at the conclusion that putting=
the gen in the engine compartment and moving the battery would simply be e=
asier and it would be protected from the elements just as well with much le=
ss hassle or hazard. To Dr Lincoln, I want to thank you for taking =
your lunch time to write that up, as a Doctor I know your time is very valu=
able, and when one is busy, getting time to eat even more so. Just for the =
record its not the first time I've been told "if you do that you're gonna k=
ill yourself!" I like to push the envelope a bit, so if I do wind up in the=
obit section someday, I can assure you it won be for something as embarras=
sing as that. I take pride in being a little bit out there and non conventi=
anuary 2011 13:07 > Lunch break time=C2=85. > > There was a questio=
n of oxygen starvation raised. As a pulmonary physician, I couldn't let th=
at go without trying to figure out if it was likely to be true or not. =
> > 1. Combustion calculation: > > 1. Gasoline is a mixture of=
hydrocarbons, nominally about C8 H18 (isooctane), specific gravity 114.23 =
gm/mole > > 2. Stoichiometric complete combustion of hydrocarbons=
: > > CxHy + (x + y/4)O2 --> xCO2 + (y/2)H2O > 4. Substituting=
into the equation: C8H18 +(8 + 4.5) O2 =C3=A08CO2 +9H2O > > 5. T=
hus every molecule of isooctane completely combusted will yield 8 CO2 and 9=
water molecules and consume 12.5 oxygen molecules > > > > 2. =
Determine how much isooctane is in a gallon of gas > > 1. Isoocta=
ne specific gravity 688 kg/m^3 liquid state > > 2. 1 m^3 1,000=
liters 264.172 gallons, so one gallon contains 2.60 kg of isooctane =
> > 3. 2,600 gms of gasoline / 114.23 gm/mole 22.76 moles of iso=
octane. > > > > 3. Determine the waste products resulting fro=
m burning a gallon of gas completely (assuming no CO, NO2, etc here=C2=
=85complete combustion into water and CO2) All this goes out the exhaust p=
ipe (Shan hopes!) > > 1. 22.76 moles burned x 9 204.84 moles w=
ater produced =C2=85at 18 gms/mole that=C2=92s 18 * 204.84 3684.12 gram=
s of water (almost a gallon) > > 2. 22.76 moles burned x 8 182=
.08 moles of CO2 produced=C2=85at 44.01 gm/mole that=C2=92s 8013.34 grams o=
f CO2 produced. CO2 weighs (at standard temp and pressure dry) 1.977 gm/li=
ter, so that=C2=92s ca. 4000 liters of CO2 produced (Global warming!) > =
> > > 4. Determine the oxygen consumed from burning a gallon of =
gas completely > > 1. 22.76 moles burned x 12.5 moles oxygen consu=
med/mole of gas burned 284.5 moles of oxygen consumed. > > 2. =
With oxygen at 16 gm/mole, that=C2=92s 4552 gms of oxygen consumed when a g=
allon of gas is burned. Oxygen=C2=92s density (100% oxygen) is 1.429 gm/li=
ter at zero centigrade (ok, you=C2=92re living in a cold coach). In room a=
tmosphere at sea level, with 21% oxygen, that=C2=92s ca. 0.30 gms oxygen/li=
ter of room air. > > 3. If 4552 grams of oxygen are consumed, ca, =
4552 / 0.30 15,173 liters of room atmosphere are going to be pumped th=
rough the engine. That=C2=92s ca. 536 cubic feet of atmosphere. If the co=
ach is 7.5 x 6 x 26 feet inside, the total volume of the coach is ca. 1200 =
cubic feet. > > > > Conclusion: A catalytic heater (whic=
h exhausts inside) doesn=C2=92t create a negative pressure in the coach by =
dint of producing 8 CO2 and 9 H2O molecules that take the place of every 12=
.5 molecules of oxygen consumed. I'd say that a catalytic heater can surel=
y deplete oxygen concentrations if you burn enough fuel. If you could real=
ly use up 536 cubic feet of atmosphere by running through a gallon of gas (=
or equivalent molar weight of propane), using a catalytic heater, that'd be=
serious, and not just from oxygen starvation but from CO2 acidosis. I sug=
gest that nobody run a catalytic heater without several windows open! On t=
he other hand, an internal combustion engine is a volume air pump and it ex=
hausts all the air it takes in. It thus creates a negative pressure that w=
ill be supplied by leaks inward to the coach from the surrounding air. So =
I don=C2=92t think Shan=C2=92s arrangement would necessarily cause oxygen s=
tarvation because as 21% oxygen room air is consumed and pumped out more 21=
% oxygen atmosphere will leak into the coach. I think one can practically =
guarantee that a 35 year old coach _won't_ develop a subatmospheric pressur=
e, even with the windows closed: a multitude of small leaks will suffice t=
o let in all the air pumped out
. > > HOWEVER, I still have =
a dire concern that Shan will kill himself, German engineering genes and al=
l, from incompletely exhausted carbon monoxide. Shan, think of how your ob=
it might look: do you really want even a small chance of that? Then there=
'd be the humiliating post-mortem endowment, in your name, to the local fir=
efighters. For the next 50 years they'll to go to the elementary and high =
schools to warn kids about the dangers of carbon monoxide poisoning, all in=
your name (imagine a flower-wreathed picture on an easel in the gymnasium,=
standing to the firefighter's podium, and the bored kids texting each othe=
r about what a turkey you must have been to have engendered a perpetually e=
ndowed safety assembly in your name). I know that such an ignoble end woul=
d be too embarrassing for me by far. > > Run the generator outs=
ide! > > > Now it is time to return to work! > > Mike Lin=
coln > > > > > > On Jan 26, 2011, at 12:59 PM, Shan Rose=
wrote: > > > > > > > My Onan runs like a top, the reason for th=
e smaller gen is 4 fold, one is the fact that it uses about .1 gal an hour =
at 1/4 load the onan with almost no load burns about .4 gallons an hour. Se=
cond is noise, unless running the roof AC, water heater, or some other elec=
trical appliance which demands heavy current, the onan is overkill. Third i=
s portability, I can take the smaller gen with me anywhere without having t=
o drive the coach there. 4th is to reduce wear and tear on the onan, since =
mantainance costs are significantly more ofor the onan (last oil change for=
the onan was about $40, compared to just $6 for the yahmaha) the onan is a=
great genset, once I worked out the bugs, mine has provided me with severa=
l hundred hours or reliable service, and by splitting the load with another=
APU I can make the onan last even longer before a major overhaul will be r=
equired, so now I will only need onan under severe usage conditions and not=
just to nuke something or watch a little TV whe > > n im in my rig... =
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