Date: Sat, 01 Nov 1997 09:04:55 -0800
From: Robert Harris 
Subject: EFI questions and thoughts
To: 'Dave Williams' 

Ruled out three BI fuels for the RV:
A. CNG - very high octane, cheap, subsidized, readily available in So. Cal. BUT
equipment is bulky, expensive and CNG is not readily available outside of big
cities
B. M85 - high octane, cheap, subsidized, readily available in most big cities,
high latent heat of evaporation, good for "boost" fuel - i.e. engine under
medium to heavy load - BUT equipment is expensive, limited rural availability,
part throttle operation sucks and is prone to wild pre-ignition if not run
rich.
C. Ethanol - not in Iowa, so not available.  Never even considered it.

What is available is what I have to have anyway, a humongous tank of LPG,
another honker tank of water, and a big fuel tank.  Diesel would be nice, and
used trucks with everything I need are not out of reach - but - you get bent
over at truck repair places so bad that you need to do deep squats on a
fireplug to prepare yourself.   This leaves gasocrap as the default fuel - just
the way the oil companies and tax authorities want.

Now on to questions about the GM TPI unit:

A. First use of LPG:  Liquid propane.  Treat it like Nitrous Injection.  At
some medium - high load, turn it on by a simple solenoid and vent it thru a
fixed orifice into the intake manifold plenum. Possibly stage it in several
steps.  This raises the octane of the total fuel air mixture considerably.  It
should result in significant charge cooling because of evaporating the liquid
LPG (even Butane has a very high latent heat of evaporation compared to
gasoline) in the charge rather than in an evaporator.  Looking at spark advance
curves, propane at medium RPM or medium load burns faster than gasoline,
requiring less advance, so a retarded curve to accommodate cheap gas in a high
compression engine would be close to what an LPG/Gasoline full power curve
should be - letting the knock fine adjust.  Would simply lying to the computer
and never letting it know by TPS switch that WOT had occurred, keep the
computer in the mode where it monitored EGO and adjusted fuel flow - even if
the MAF had maxed out?  Reason is simple.  Cars blip to WOT and stay short time
under high performance demands. RV's go WOT on the Grapevine for a half hour -
some grades even longer.  If it can be lied to and stay in EGO feedback, then
using liquid LPG as boost fuel for higher octane and charge cooling under heavy
load is simple enuff for a politician to understand.  Turn it on, and the
computer adjusts very quickly to it.  Small delay while liquid is purging gas
and initial boiling in line simply means that the liquid LPG is soft staged
giving the computer EGO even more time to adjust the mixture.   Side benefit of
fixed orifices - the hotter the air temp, the more need for charge cooling and
increased octane, the greater the LPG tank pressure is and voilla  the greater
the flow to the engine - hopefully self compensating - approximately.
B. Can the Spark advance be programmed for an initial starting retard, then a
very high (16 to 20 degree) initial advance and a short steep curve of total
advance out to say 32 to 34 degrees?  Had a Honda Accord engine in a Civic
wagon. When I changed the early model distributor to a late model one that had
very high static advance and modest centrifugal and somewhat reduced vacuum, I
noticed that acceleration, power (measured by top speed up a difficult grade)
and fuel economy increased - leaving me a firm believer in as much initial
advance as the engine will accept.
C. How sensitive is it to engine temp, and can the set point temp be adjusted
D. How available is reprogramming stuff that can be done by the user, reducing
dependence on gurus?

Side item, noticed that you no longer publicly support de-stroked 370's - must
be building one for some-one.  Hate the competition.   Been watching the World
of Outlaws sprint cars.  Makes me homesick for the long gone Ascot track.
Noticed no Fords - nothing but chevies with a token Mopar or two.  Great late
night satellite TV

You mentioned a book on resonance tuning earlier.  Where can I get it, is it
any good and what's its full title and ISBN and aprox cost??   Have a whole
bunch of funky tuning ideas I need to expose to the light of hard math and
theory.



Date: Sat, 03 Oct 1998 07:46:00 -0500
From: dave.williams@chaos.lrk.ar.us (Dave Williams)

-> to: bob@bobthecomputerguy.com (Robert Harris)
-> subject: hot gas
->
-> Say we're running gasoline or gasocrap and want to play with heated
-> fuel, a'la Pogue or Honda F1.  We mainly want to heat the fuel to
-> encourage it to break into smaller droplets; any increase in chemical
-> activity would be nice, but we won't worry about that yet.
->
-> Since we don't have any way to determine the droplet size (? do we?
-> Have any of your references mentioned how they do it?) we could
-> simply heat the fuel up to somewhere near its flash point and
-> encourage flash to vapor instead of going to droplets.  Let's say
-> somewhere between 200 and 300F, depending on the fuel.  The vaporized
-> fuel would displace some air, but for a first approximation we can
-> ignore that - it doesn't seem to be a problem for propane - and
-> concentrate on thermal effects.  Let's say we have an intake charge
-> temp of 100F and we inject fuel at 200F. The mass ratio of air/fuel
-> is about 14.7:1, or around 7% of the air would be displaced by fuel
-> (actually less, since even droplets took up volume before) and the
-> thermal gradient would be 93/100 / 7/200, which would factor out as
-> 93/100 / 3.5/100; charge temp would not be affected much.
->
-> With a circulating rail setup and solenoid injectors it would be easy
-> to control fuel temp, and it'd be right there on the pressure side.
-> Lots of cars go through all kinds of contortions to prevent boiling
-> in the rail under heat soak conditions.  This is apparently since the
-> injectors would be squirting vapor on restart, and they'd be way
-> lean, since the pulsewidth would be set for liquid fuel.
->
-> If you watched the fuel rail temp and O2, you could make a fair guess
-> as to whether you were injecting liquid or vapor, and deliberately
-> crank the rail temperature up as high as you liked to ensure
-> vaporization. The funky part would be the transition zone where you'd
-> have some liquid, some vapor.  This would require watching the O2
-> sensor to see if the AFR went crazy.  For a drive-to-work car it
-> would probably be hard to ensure smooth operation, but for a long
-> haul vehicle it might not be an issue.

Low Fangled Auto Tech
---------------------

Date: Sun, 04 Oct 1998 11:13:00 -0500
From: dave.williams@chaos.lrk.ar.us (Dave Williams)
Subject: FI question


-> Has anyone had any experience with using very hot fuel on a street
-> injection system?

This is the basis of the (in)famous Pogue carburetor.  You could jacket
the fuel rails with engine coolant to get 180-210F easily enough, but
for faster warmup and higher temps - and better temp control - you could
use one of the electrically operated EGR valves and route exhaust
through the jackets.

Main apparent problem with heated fuel rails is boiling/vapor on
shutdown.  Most new design EFI systems jack up the fuel pressure on
start to reduce this tendency, as metering vapor instead of liquid would
make the engine run very lean.  With the exhaust-jacketed fuel rail, you
could use an electric smog pump off a late Corvette or Camaro and a
thermistor, and blow cool air on the rail until the temp drops to
whatever is needed to prevent boiling, say 175F, given typical underhood
temperatures.  The neat thing about this setup is you can use cheap,
easily available "smog control" components that might even already be on
the car.

The early heated carbs were intended to vaporize the fuel so it could
make it through the manifolding without puddling.  Port injection
reduces that tendency, but solenoid injectors do a very poor job of
atomizing the fuel compared to a carb.  If the fuel was heated it would
help.  Also, back to the "gasocrap" idea of extending mileage by
injecting anything that's handy that's flammable, adding heat certainly
wouldn't hurt.


-> What is under discussion is bypassing or running a separate injection
-> system for a small amount of fuel, passing it through a heat
-> exchanger and injecting the hot fuel at idle through cruise,
-> reverting to cold fuel as the power demand increases.

I'm not sure it would be necessary or desirable.  If you're heating the
fuel to enhance vaporization, going back to cold fuel would increase the
droplet size, so you'd probably have to go back to rich again.

Would, say, 200F fuel affect volumetric efficiency?  Some, but run some
numbers.  Say AFR of 15:1.  Inlet air temp is 100F.  Your ratio looks
like 15/100 by 1/200, reduce to 15/100 by 2/100.  But your fuel temp
would be on the order of 150F anyway once the engine is thoroughly
warmed up, so the change in air temp would only be a quarter of that.


-> Looking for ideas on how to implement.  Leaning to a separate
-> injection system using CIS nozzles.  Heat exchanger would be either
-> coolant or valley cover air or ????

I'd love to be able to do it with CIS nozzles, but it looks more suited
to a conventional rail and solenoid arrangement.  Hmm... I wonder what
the thread is on the end of the Bosch nozzles; it might be possible to
make some heater adapters.  And you wouldn't care if the fuel flashed to
vapor in the nozzle since the flow would always be the same, as it's
pushed in through the hose, rather than metered by pulsewidth.  Hmm...

Low Fangled Auto Tech
---------------------


Date: Tue, 06 Jul 1999 14:51:19 +0000 (GMT)
From: bob@bobthecomputerguy.com (Robert Harris)
Subject: Another Harris Heresey - bugger your mind
To: dave.williams@chaos.lrk.ar.us (Dave Williams)

It takes work to compress air.  Much of the work used to compress air on a
less than 100% efficient compressor shows up as excess heat.  This excess heat
and some of the heat of compression is rejected to an external heat sink with
conventional aftercooling.

For chemical aftercooling - all of the excess work is recovered as heat and
added to the combustion process - thus we have very high compression
efficiency of the SYSTEM.   Don't let the dweebshit hang you up on the spot
efficiency of just the compressor.

Now back to the combustion effect of some alcohol.  The problem of long chain
hydrocarbons is that they isomerize - make longer chain molecules than they
start with and this leads to runaway temperatures and pressures.  Quote
Glassman

"It has been suggested that the greater tendency for long chain molecules to
knock as compared to smaller and branched chain molecules may be a result of
this internal, isomerization branching mechanism."

Now the addition of methanal simply adds two hydrogen hungry radicals early in
combustion that speed the destruction of the fuel molecule.   CH3 and OH.   It
may well be worth considering adding some alcohol - either methanal or iso
propanol to gasocrap - not to raise octane - but to enhance combustion by more
completely consuming the long chain kerosine / diesel fuel molecules.

It is critical for the radical pool to form that the ignition phase provide
free hydrogen.  This H radical then develops a radical pool of OH, H and O.

Hydrazine is trick shit.  It not only decomposes into H radicals very easily
but the N bond splitting releases large amounts of energy so small amounts of
H2N-NH2 seed the radical formation process and jump start it with lots of
energy.  And its virtually undetectable in small quantities.

Acetone - CH3-CO-CH3  is good.  Note the hydrogen hungry CH3 attack radicals
that will probably evolve into Ethane ==> Acetylene.  Note the drop out CO
molecule for instant molar product.    Nice stuff.

Boron - some premium gasoline had boron additives into the sixties.  Rumored
to have been added to joy juice blends - anytime you see green tips in flame,
almost certain to have been boronated.  Wad da puck?   Boron has almost twice
the energy of carbon.  Replacing some carbon in fuel with Boron could raise
the energy density - read power - significantly without increasing the amount
of fuel and oxygen consumed.  Very little literature except as relating to
rocket engines.   Kelly Johnson used it as lighter fluid for the fuel in the
SR-71.  Wonder how to get some boron into joy juice.

Chain branching reaction ends with wall impact.  Runaway chain branching leads
to knock.   Lead works at mid temperatures apparently by providing large
"cool" molecules to function effectively as walls and terminate chain
branching.  Surface area effect.  Maybe - but seems to be consensus.

Enter Ferrocene.   Same mechanism.  Same effect - but requires more metal.
Down side - iron particles after combustion.  Solution - bring it on under
boost only.   Use a magnet in the oil pan to scavenge oil borne particles -
count on the water to steam clean the cylinders anyhow so all particles exit.

The dampening of the end reactions means that we can crank up the early
reactions without runaway chain branching in the middle stage - read more
hydrazine - more better power.

And this alcohol thing - its the reason Hamilton simply calls it preburned
fuel and lets it go.  Can you see the wild anally extracted horse puckey that
would flow on REC.AUTO.TECH if he tried to explain what really happens?

The absolute venom that would flow from those who don't know?  Would make Gar
Puss positively pleasant to be around.