On Sun, 4 Jan 2004 15:49:54 -0600, "Biker_Bry"
wrote:


"QrizB" wrote in message
...
On Sun, 4 Jan 2004 11:41:43 -0600, "Biker_Bry"
wrote:

The difficulties to overcome LPEFI are as follows...
1. Propane cannot hold a liquid state at underhood temps (207deg F)
2. Liquid must stay at the injector at all times while running (fuel
pump
nessisary)
3. Vehicle must complete a purge cycle before starting similar to a
diesel
waiting on glow plugs.
(to rid the fuel lines of vapor).

I've been wondering if any of this is really an issue. The aim, as I
see it, is to have gas injection to the cylinder rather than to the
inlet tract. Does it actually matter whether you're injecting a liquid
or a gas?


If vapor is coming out the injector, you will only supply the cylinder
1/270th of the required fuel.

Not true. Think about the phase diagram. At temperatures above the
triple point of LPG, the vapour can have the same density as the
liquid.

4. Fuel Pump must be inside the tank, so how do you pass wires through a
fuel tank and have it safe?

And call me thick, but why does the fuel pump have to be inside the
tank? ISTM the pump could be anywhere upstream of the injectors, as
works perfectly well with diesel.

If you put the pump into another container upstream, it still must meet all
the vessel safty critera that a propane tank must meet.

Why does your pump need to be in a "container"? People have been
designing high-pressure liquid / gas pumps for generations. I'll
accept that any pump will need to be suitable and approved for pumping
lpg.

Even with this, there is a problem with cavitation when the vehicle is
situated uphill, or down hill in relation to the pump vessel intake.

Not if you get your pump design right.

--
QrizB

I sound like I know what I'm talking about, but don't
be fooled.

1. Propane cannot hold a liquid state at underhood temps (207deg F)

Sorry, but we English use centigrade now... So your measurements are in
American

David


Damn, and there was me thinking we used Centigrade TIC

And I thought it was celcius!

"SimonJ" wrote in message
...
1. Propane cannot hold a liquid state at underhood temps (207deg F)

Sorry, but we English use centigrade now... So your measurements are
in
American

David


Damn, and there was me thinking we used Centigrade TIC

And I thought it was celcius!



Well I think I'm typically English and I use Celsiheit

Because there's more to the internet than hits alone, Biker_Bry
wrote:


Any temperature increase under the hood in relation to the injector, rails
and fuel lines
will create pressure in the lines, and will continue to collect heat until
the fuel goes critical,

The heat collected by anything will be limited to the temperature of
what it is in contact with - fuel lines will not 'continue to collect
heat' once a common temperature has been reached. In a common rail
system the captive pressure in the fuel lines will be limited by a
regulator on the tank return; as long as tank pressure remains less
than pumped pressure the pressure in the fuel lines will not increase.
The fuel is continually cycling back to the tank so the fuel system
effectively becomes self cooling.

4. Fuel Pump must be inside the tank, so how do you pass wires through a
fuel tank and have it safe?

I've often wondered about getting wires into the tank in order to make
an effective fuel guage sender a possibility. But in fact I don't
really think it would be an insurmountable problem. Probably quite
easy, in fact - a solid connector embedded in enough vitreous sealant
that passes through the multivalve.

Tank must still meet all safty regulations... Would this still be possible
with a passthrough?

I would have thought this was elementary engineering. Whether or not
there are regulations that prevent it is another matter.


Mixing air/fuel *before* the cylinder breeds backfires and they will
cause
serious problems.
Ask anyone tha has used an old Impco system.

Do you mean specifically in the case of *liquid* fuel injection? Why
would this be? ATM all LPG systems mix the fuel and air before the
cylinder.

Newer intake manifulds are plastic, and can contain as much as 2.0 Cubic
Meters of
air fuel mixture ( with a vapor fogging type system).
One backfire with the hood (bonnet) up and you will be picking shards of
plastic out of your
face :-) (ouch)!

First off, you don't have room for 2 cubic meters of anything under
the bonnet - not even under the hood of a yank tank.

But I'm not sure I understand your point. ALL current LPG conversions
mix fuel and air before the cylinder; how else could you do it? This
is not the cause of backfires - a weakness elsewhere is - typically in
the ignition system. Are you suggesting that liquid injection incurs
other, additional, factors that lead to backfires?




--

Stewart Hargrave

Finally visible on www.hargrave.me.uk

I run on beans - laser beans


For email, replace 'SpamOnlyToHere' with my name

Because there's more to the internet than hits alone, Peter Hill
wrote:

On Sun, 04 Jan 2004 18:53:46 +0000, Stewart
wrote:

Because there's more to the internet than hits alone, Biker_Bry


The difficulties to overcome LPEFI are as follows...
1. Propane cannot hold a liquid state at underhood temps (207deg F)

= about 97 deg C. Actually, I doubt thet it gets that hot under the
hood, though there may be hot spots where the local surface
temperature reaches that. The cooling system on my car operates at
around 80 deg C (which doesn't appear to leave much margin).

Oil temp? 120 deg C?
Cylinder head Metal temp 150+ deg C?
Exhaust manifold temp? 400+ deg C?

None of these present much of a design challenge. Don't bolt the fuel
rail to the exhaust manifold, and make sure it's not submerged in oil.
Most designers could manage that.

The only part that the fuel system needs to be in contact with is the
inlet manifold. I've never stuck a thermometer onto my inlet manifold,
but I doubt it gets near the critical temperature - it is constantly
cooled by between several hundred and several thousand litres of cold
air a minute. And in fact the reported issue at this point of contact
is injector freezing.

After switch off the temps of many parts go way above 100 deg C. The
fuel rail and injector components are attached to the inlet manifold
which is bolted to the head. Makes hot purge cycle critical. Not so
bad with plastic manifolds.

It really wouldn't take much to insulate the fuel system from all
parts likely to get hot. Some cars already keep the cooling system
active for a while after switch off. The only thing left is ambient
air temperature. And it has never seemed to me that opening the bonnet
is a similar thermal experience to taking the lid off a boiled kettle.
Of course this may be different in hot climates.



Mixing air/fuel *before* the cylinder breeds backfires and they will cause
serious problems.
Ask anyone tha has used an old Impco system.

Do you mean specifically in the case of *liquid* fuel injection? Why
would this be? ATM all LPG systems mix the fuel and air before the
cylinder.

He's taking about the old mixer valve systems - noted for ability to
backfire even in UK.

Why 'even in the UK'?

I would contend that mixer conversions were still amoungst the most
common type done. It is not the fuel/air mix that causes the backfire,
but a weakness elsewhere, typically with the ignition system. But I'd
be interested to learn of additional factors that liquid injection
brings up.


LPi (Liquid Propane Injection) is available as a factory fit item.

It is? So all these problems are already overcome, then.




--

Stewart Hargrave

Finally visible on www.hargrave.me.uk

I run on beans - laser beans


For email, replace 'SpamOnlyToHere' with my name

On Sun, 04 Jan 2004 23:10:56 GMT, (QrizB) wrote:

Not true. Think about the phase diagram. At temperatures above the
triple point of LPG, the vapour can have the same density as the
liquid.

Triple point is -190C

A quick calc suggests that the gas will compress to the same density
as the liquid at about 300bar (needs checking). Keep your pressure
above this and you would see no difference. Of course in practice if
you keep the pipe runs away from the head the heat exchange surface at
the injector will simply not transfer enough heat to cause a problem.
On stopping the gas would just occupy a small section of the injector
pipe which was above 97C.

AJH

On Mon, 05 Jan 2004 23:26:51 +0000, "Andrew Heggie"
wrote:

On Sun, 04 Jan 2004 23:10:56 GMT, (QrizB) wrote:

Not true. Think about the phase diagram. At temperatures above the
triple point of LPG, the vapour can have the same density as the
liquid.

Triple point is -190C

Apologies. I may have meant critical temperature. But you seem to have
understood what I meant (below).

A quick calc suggests that the gas will compress to the same density
as the liquid at about 300bar (needs checking). Keep your pressure
above this and you would see no difference.

.... and 300 bar isn't an unreasonable pressure for an injection
system. Many modern diesels run at roughly ten times this pressure.

--
QrizB

I sound like I know what I'm talking about, but don't
be fooled.

On Mon, 05 Jan 2004 23:26:51 +0000, "Andrew Heggie"
wrote:

On Sun, 04 Jan 2004 23:10:56 GMT, (QrizB) wrote:

Not true. Think about the phase diagram. At temperatures above the
triple point of LPG, the vapour can have the same density as the
liquid.

Triple point is -190C

That's also the melting point - liquid and solid present in
equilibrium any vapour will need to be at very low presure. At -42C
(boiling point) vapour pressure is taken as 0 psi gauge (14.7 psi
abs).

A quick calc suggests that the gas will compress to the same density
as the liquid at about 300bar (needs checking). Keep your pressure
above this and you would see no difference. Of course in practice if
you keep the pipe runs away from the head the heat exchange surface at
the injector will simply not transfer enough heat to cause a problem.
On stopping the gas would just occupy a small section of the injector
pipe which was above 97C.

AJH

I think he meant above the critical temperature when it is no longer a
gas or liquid but a supercritical fluid. The usual condition of
propane in automotive use is somewhere between it's boiling point and
the critical temp. As a supercritical fluid the density changes with
temperature just like vapour. Changes in fuel density with temprature
on normal EFi systems are taken in to account by the manifold temp
sensor or hot wire AFM, it's assumed the fuel temperature tracks
ambient. Using propane in the supercritical region would require
sensors for fuel pressure and temperature with an ECU stored map to
give the density of the fuel. Not impossible but a real pain to have
to implement yet another map with two variables for look up.

--
Peter Hill
Spamtrap reply domain as per NNTP-Posting-Host in header
Can of worms - what every fisherman wants.
Can of worms - what every PC owner gets!

On Mon, 05 Jan 2004 22:14:29 +0000, Stewart
wrote:

LPi (Liquid Propane Injection) is available as a factory fit item.

It is? So all these problems are already overcome, then.

To repeat Cummins Westport are supplying SI LPi truck and bus engines
to the USA market. They use about 40psi injection pressure and need a
tank assist pump for low temperatures.

Vialle have the technology - numerous patents in place but it appears
they will only transfer technology to car makers as a 1st tier
supplier.

Not to sure about the current status of Bi-Phase but they claim 5400
systems installed (2001-2002?).
http://www.ccities.doe.gov/conferenc...ch_biphase.pdf
Despite the name Bi-Phase is a 100% LPG liquid phase injection system
- the petrol fuel system (tank, injectors, fuel rail etc) is not
fitted. The LPG injectors are fitted in the vacant holes on the
manifold. Overall cost ex works should be not a lot more than the OEM
petrol system, injectors and ECU should be about same cost, the fuel
rail, double walled fuel line and tank are higher cost items (maybe
double) but some saving can be made by not having to fit a separate
return line, carbon canister, vapour purge system and check valves in
fuel vapour lines. As the petrol system is never fitted would it be
eligible for a power shift grant?

When it comes to LPG North America leads the way technically through
commercial use, even though they have not had any nice big duty cuts,
grants or car tax breaks to encourage development. UK and NL have
been concerned with developing a user base for duty paid forecourt
supplies and not a viable technology base for OEM supply of LPG fueled
vehicles. As the UK infrastructure is in place now is the time to
move to 100% LPG fueled vehicles with OEM optimised engines and do
away with the dual fuel conversions.

--
Peter Hill
Spamtrap reply domain as per NNTP-Posting-Host in header
Can of worms - what every fisherman wants.
Can of worms - what every PC owner gets!

"Peter Hill" wrote in message


Not to sure about the current status of Bi-Phase but they claim 5400
systems installed (2001-2002?).
http://www.ccities.doe.gov/conferenc...ch_biphase.pdf
Despite the name Bi-Phase is a 100% LPG liquid phase injection system
- the petrol fuel system (tank, injectors, fuel rail etc) is not
fitted. The LPG injectors are fitted in the vacant holes on the
manifold. Overall cost ex works should be not a lot more than the OEM
petrol system, injectors and ECU should be about same cost, the fuel
rail, double walled fuel line and tank are higher cost items (maybe
double) but some saving can be made by not having to fit a separate
return line, carbon canister, vapour purge system and check valves in
fuel vapour lines. As the petrol system is never fitted would it be
eligible for a power shift grant?

Bi-Phase has approximatly 3000 1999-2003 fuel injected Schwan's trucks
running around America. (GMC 7.4L and 8.1L) and many Ford V10's running
around in Mexico.
Bi-Phase uses a refrigerated fuel injector and fuel line (hose within a
hose) to
keep the injector from getting too hot. They also have a composite injector
body to insulate them.
The tank is custom built and extreamly expensive. It has an internal fuel
pump
with baffels. There is an "LPDM" liquid propane delivery module with
electric solenoids for fuel feed-return in the loop that bolts onto the end
of the tank (like an man hole cover).
When the system stops, the liquid is driven back to the tank by engine
heat, so
the vehicle must run a purge cycle evey time the unit is shut off for any
length of time.
If the system does not purge, the vehicle will not start, as it only has
1/270th of the fuel
nessisary to run (I know this from experiance).
The hose within a hose idea has liquid propane supplied by a fuel pump in
the tank
running through the center hose. The injector has a restriction, and
pressure differential
at the injector itself. The liquid is injected, and the remainder is
returned to the tank
to a condenser unit. The pressure differance at the injector cools the
injector, and the
liquid coming to the injector.
The cool thing about it, is the system runs off of the stock PCM. No
reflash is needed
after the system is installed. The long term fuel trim runs happily
about -18 or so.
The only mod to the sensors, is a coolant sensor that reads a little warm
in cold days.
This keeps the system from flooding the engine, as propane doesn't need the
same
enrichment as gasoline (petrol)...

Or so I've heard...

Biker_Bry