Propane FI way to the future

[Angus Mackinnon]

Hi all,

I have been lurking here for a few months just milking other people's
ideas but being a LPG fan myself could not resist replying to Darrell's
post. 

There is a company down here in Australia ( actually in South Australia,
not where I am ) that is in the process of making an injected LPG
(propane/butane) system available. Due to my grease monkey friends and
my own interest we read a couple of articles on the system and rang the
company up. 

They were reluctant to part with very much information as they were
still really prototyping. I will impart what little (mis)information I
can remember and will try to find the article(s) later.


>4. propane carburetion systems are for the most part antiques - the design
>   of the carburetor and vaporizer hasn't changed for thirty years.  Generally
>   the systems currently available are dismally inefficient and oversimplified
>   to the point where it is difficult to impossible to tune the thing properly.

Don't give up here either. I run a locally designed and manufactured
LPG carb, not a mixer, but a fully metered carb in a LPG only setup and
it can be tuned as nicely as you want it.

>injector would have to be accurate with very small volumes of liquid fuel in
>order to meter the correct amount for a given air fuel ratio, especially at 
>idle.  Unfortunately you can't simply regulate the fuel pressure down to a
>more manageable pressure, at least not by any means I am aware of, since
>there is nowhere for the unused fuel to go.  You can't simply plumb it back
>to the tank as with gasoline EFI systems, since the tank is at a higher 
>pressure than the returning fuel.  Pumping it back would kinda defeat the 
>purpose, since not having to have a pump in the first place is a bonus.

I am sure they use an in tank pump to boost fuel pressure so a tank
return is possible. I think from memory that the tank pressure is lower
than the figure you are quoting and the fuel rail pressure is about what
you suggest. 

>The volume problem is a bit less severe in that you could possibly use a
>single direct port injector in the throttle body injection system, since
>they are made to meter much lower volumes than a TBI injector.

The system this company has designed as a prototype is on a port fuel
injected inline six. They use a local after market fuel injection computer to
control the injectors. The duty cycles were very different to the
gasoline injectors. I will have to look up the article to find out what
the injectors were like; modified or exotic I can't remember.

The final thing was the development time seemed to be quite
long: 3 years but I think that this may have been due to lack of
experience in the area. You don't want to know about the cost
though this would come down if they make it into full production. 

>paid for itself twice over in fuel savings alone.  The tank is by far the most
>expensive part of the system, it alone was about $1200.  I run a relatively 

$1200 and I thought that $AUS300 was steep for mine! 

>with some decent fuel metering and a modified ignition system.  I plan on
>using an HC11 as an ECM core, firstly doing a timing control system, and

Likewise, I had my dizzy recurved but I am not happy so I am toying with
the same idea; HC11 spark control.

>gradually adding the EFI to it.  If anybody out there has any ideas on how
>to solve the injector problem, LET ME KNOW!!!.  

Just enough info to tease you ;-);


Angus 

--

Angus Mackinnon 
Phd student and motor head
Monash University Clayton
Melbourne  Victoria Australia

angus at rdt.monash.edu.au