From: Noddy on

"Yvan" <me(a)privacy.net> wrote in message
news:5rd2hmF13k6igU1(a)mid.individual.net...

> I will first test the one I am currently working on (like the model I
> made of cardboard). If it perform good I'll stop there, if not I will
> fabricate this new one. And I will report here, you were all very
> helpfull.

We'd be interested to hear of your results, so please let us know how you
get on.

--
Regards,
Noddy.


From: Yvan on
Nedavno Noddy piše:

> It would start easily in cold weather
> (admittedly winter in Melbourne isn't anywhere near as cold as where
> you are I expect), had a smooth idle and would deliver adequate
> performance.


What is the low limit temperature for lpg cold start? I guess it depends
on system design, humidity perhaps, and some other factors, but in
general what is the lowest temperature that would not cause vaporizer
to freeze?



--
___ ____
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/ / \/ /\ \ ** Registered Linux user #291606 **
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From: Noddy on

"Yvan" <me(a)privacy.net> wrote in message
news:5rf10mF13rv4fU1(a)mid.individual.net...

> What is the low limit temperature for lpg cold start? I guess it depends
> on system design, humidity perhaps, and some other factors, but in
> general what is the lowest temperature that would not cause vaporizer
> to freeze?

Vaporiser freezing is generally caused by an insufficient flow of engine
coolant through the unit, and that has little effect on the starting of an
engine aside from the fact that it often shuts off gas flow. That might
sound funny, but what I mean by that is that I would think the low limit
temperature for a successful cold LPG start would be the lowest temperature
you could get the lpg to turn from a liquid to a gas and be drawn into the
engine.

Unlike petrol, an lpg burning engine isn't fussed about cold, and doesn't
need it's intake temperature regulated to help with atomization. As long as
gas is coming out of the vaporiser (or converter as they're commonly called
here) the engine will start regardless of the temperature and run happily
without a choke needing to be used.

Vaporiser/converter freezing is a problem mainly to do with the latent heat
of vaporisation as the lpg is changing from a liquid to a gas inside the
vaporiser itself.

LPG is stored in it's tank in a liquid state, and the boiling point of this
liquid is around -40 degrees Celsius (which is the point at which it turns
from a liquid to a gas). As it enters the vaporiser it is still in a sub
zero compressed liquid state, and the vaporiser's basic job is to provide an
expansion/pressure reduction area where it can turn from a liquid into a gas
and then be drawn into the engine and burnt. In doing so, the lpg absorbs an
enormous amount of heat (look up latent heat of vaporisation for a better
explanation), and this can cause the vaporiser to freeze up if it's not
heated in some way.

When the vaporiser freezes gas supply becomes blocked or restricted, and the
engine obviously either won't run or will run very poorly.

To guard against this the vaporiser needs to be heated, and the easiest and
most effective way to do so is to run engine coolant through it. However
even when doing this some people still have trouble as they don't do it
properly. Athol recently gave an excellent description of the do's & don'ts
as far as coolant circulation to vaporisers is concerned, but to recap very
briefly the vaporiser should be supplied with coolant that comes from a
by-pass source that's independent of the engine's thermostat & heater supply
line.

Most people who have problems in this area have their vaporisers tapped
directly into the heater hoses with T pieces, and flow to the vaporiser can
vary from barely adequate to next to nothing depending on where the heater
controls are set and what kind of fittings they use to splice into the
lines. If your car has a heated inlet manifold with an external hose for
example, then this would be a far better choice for a vaporiser coolant feed
as these hoses are normally by-passed to heat the manifold quickly
irrespective of what the rest of the cooling system is doing.

Besides, if you spend most of your time running on lpg, you won't need the
manifold heated anyway.

--
Regards,
Noddy.





From: Yvan on
Nedavno Noddy piše:

> If your car has a heated inlet manifold with an external hose for
> example, then this would be a far better choice for a vaporiser
> coolant feed as these hoses are normally by-passed to heat the
> manifold quickly irrespective of what the rest of the cooling system
> is doing.
>
> Besides, if you spend most of your time running on lpg, you won't need
> the manifold heated anyway.


Thank you for this detailed explanation.

In my reply to Athol's post I asked if I should reroute heating of
vaporizer (converter). I Currently have two T-connectors at the cabin
heater hoses, and vaporizer hoses are connected there.

You think that it would be a good idea to connect a heater coolant into
vaporizer at the part 14 (smaller diameter hose connected here is for
carburetor autochoke heater) and output at the end of the hose 15 (it
is connected to inlet manifold). Currently I have two T-connectors at
the cabin heater hoses, and vaporizer hoses are connected there.


http://www.realoem.com/bmw/showparts.do?model=1051&mospid=47249&btnr=11_0744&hg=11&fg=35


So to summarize I could start my engine at, say -15 Celsius. Standard
coolant pump pushing coolant the way I just described should do the
job?


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___ ____
/__/ / \ ** Registrovani korisnik Linuksa #291606 **
/ / \/ /\ \ ** Registered Linux user #291606 **
/__/\____/--\__\ ** http://counter.li.org/ **
From: Yvan on
Nedavno Noddy piše:

>> And do you mean just remove choke plate, or complete with stepped
>> cam, and all the other components?
>
> Whatever is the easiest.
>
> I haven't seen all your posts so I don't know what vehicle you have,
> but in my own case I have an old Ford Falcon that until very recently
> ran a duel fuel system (it's currently being converted to straight
> gas) with an automatic choke on the carburettor. It's always been a
> pain in the backside to start on gas when cold with the choke closed,
> but it never had a hope in hell of cold starting on petrol if the
> choke was removed.
>
> The solution in my case (short of throwing the carburettor in the
> nearest bin and swapping the whole intake system for a modified EFI
> manifold and throttle body which I've doing right now) was to fit a
> manual choke conversion so the choke was left open for cold lpg starts
> and could be closed for cold petrol ones.
>
> Perhaps your carburettor can easily be converted to a manual choke and
> you can do the same thing.


I just did some testing (nice sunny weather today :-). I drilled small
hole near the top of the carburetor with a thread in it, and used a bolt
to fix choke plate in opened position. I can now start and run on lpg
from cold with spud pipes setup. I will have to test this again
tomorrow morning, it was warm outside today.

So I guess that with amos ring it must be even better.



--
___ ____
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/ / \/ /\ \ ** Registered Linux user #291606 **
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