From: Yvan on
Nedavno Noddy piše:

> Does the new carburettor have an auto choke?
>
> If it does, you need to have it removed.


And do what when it's very cold, and I need to start on petrol? I never
heard before that you need to remove choke to be able to start / run on
lpg when the engine is cold.

And do you mean just remove choke plate, or complete with stepped cam,
and all the other components?


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From: Noddy on

"Yvan" <me(a)privacy.net> wrote in message
news:5qoasbFvd0dpU1(a)mid.individual.net...

> And do what when it's very cold, and I need to start on petrol? I never
> heard before that you need to remove choke to be able to start / run on
> lpg when the engine is cold.

Cold engines are a lot harder to start on petrol as the fuel is harder to
atomize, and the purpose of a choke on a petrol engine is to restrict the
airflow into the engine thus richening the mixture. If your engine starts on
lpg the fuel coming in is already in a gaseous state and doesn't need to be
atomized. If your lpg is being delivered through the top of the carburettor
through a mixer ring of some type, then having a closed choke between the
gas entry point and the engine is starving the engine of fuel and making it
hard to start.

> 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.

--
Regards,
Noddy.


From: Yvan on
Nedavno Noddy piše:

> Cold engines are a lot harder to start on petrol as the fuel is harder
> to atomize, and the purpose of a choke on a petrol engine is to
> restrict the airflow into the engine thus richening the mixture. If
> your engine starts on lpg the fuel coming in is already in a gaseous
> state and doesn't need to be atomized. If your lpg is being delivered
> through the top of the carburettor through a mixer ring of some type,
> then having a closed choke between the gas entry point and the engine
> is starving the engine of fuel and making it hard to start.


LPG is not delivered trough the top of the carburetor, I have a spud
pipe just below the narrowest part of the venturi.

I have no problem with starting on petrol, and I have to, because it can
get very cold here so vaporizer can freeze if I start on lpg.


> Perhaps your carburettor can easily be converted to a manual choke and
> you can do the same thing.


I just replaced original Pierburg 1B2 with Weber 32 ADF ('87 BMW 316). I
had no problems starting on lpg with the old carburetor.

I also have a problem with tuning the second barrel on lpg, so I suspect
that there may be something wrong with my vaporizer. Since it has only
adjuster for idle, and nothing else I am gong to a shop that did the
conversion to check it on Monday.

Unless someone here (it seems that Athol is an lpg expert) has any other
suggestion I can try. There is a link in one of my earlier posts to a
webpage with photos of my current setup.


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From: Noddy on

"Yvan" <me(a)privacy.net> wrote in message
news:5qpu46F112pipU1(a)mid.individual.net...

> LPG is not delivered trough the top of the carburetor, I have a spud
> pipe just below the narrowest part of the venturi.

Any particular reason why?

spuds pipes are generally next to useless.

> I have no problem with starting on petrol, and I have to, because it can
> get very cold here so vaporizer can freeze if I start on lpg.

Fair enough.

> I just replaced original Pierburg 1B2 with Weber 32 ADF ('87 BMW 316). I
> had no problems starting on lpg with the old carburetor.

Can I asked why you changed it?

> I also have a problem with tuning the second barrel on lpg, so I suspect
> that there may be something wrong with my vaporizer. Since it has only
> adjuster for idle, and nothing else I am gong to a shop that did the
> conversion to check it on Monday.
>
> Unless someone here (it seems that Athol is an lpg expert) has any other
> suggestion I can try. There is a link in one of my earlier posts to a
> webpage with photos of my current setup.

I don't see all the posts in this group sometimes, so I've missed those.

Athol is indeed a *very* knowledgeable person (both on lpg and in general),
and I'm sure he'll offer you some great advice when he gets a chance.

I don't know what your secondary problems are, but for my money I'd do
whatever I could to get rid of the spud pipe as they're an extremely
unsatisfactory method of getting gas into the engine. If you don't have an
automatic mixture control device in the gas feed line between the vaporiser
and the spud pipe then the best you can ever do is tune the manual adjuster
for the best performance with both barrels of the carb open and put up with
the over rich mixture when they aren't.

Did the car perform okay on lpg before you changed the carburettor, and have
you made any other changes beside the new carb?

--
Regards,
Noddy.



From: Yvan on
Nedavno Noddy piše:

>> LPG is not delivered trough the top of the carburetor, I have a spud
>> pipe just below the narrowest part of the venturi.
>
> Any particular reason why?

Yes. There was no room to fit mixer plate on top of the carburetor. And
I can't lift airbox up as it would hit the bonnet.

> spuds pipes are generally next to useless.

:-(


>> I just replaced original Pierburg 1B2 with Weber 32 ADF ('87 BMW
>> 316). I had no problems starting on lpg with the old carburetor.
>
> Can I asked why you changed it?

Because I could not tune it to function properly. I had very poor
running on both petrol and lpg when engine is cold / warming up.

So I asked on few newsgroups, and all suggested I should bin Pierburg,
and get a Weber. So I did. First I fitted two double sidedrafts, but
these would not run on lpg at all (something about air moving at low
speed) and idled poorly.

So now I bought Weber 32 ADF that is suppose to be exact replacement. I
got it running nicely on petrol, but I now have problems on lpg.

Perhaps I had some petrol related problem with my old carburetor, and
separate vaporizer problem. So when I changed carburetors, petrol
problem is gone, but lpg related is still here.

> Athol is indeed a *very* knowledgeable person (both on lpg and in
> general), and I'm sure he'll offer you some great advice when he gets
> a chance.

I think that he was the one that was trying to help me with my
sidedrafts a year or so ago.


> I don't know what your secondary problems are, but for my money I'd do
> whatever I could to get rid of the spud pipe as they're an extremely
> unsatisfactory method of getting gas into the engine. If you don't
> have an automatic mixture control device in the gas feed line between
> the vaporiser and the spud pipe then the best you can ever do is tune
> the manual adjuster for the best performance with both barrels of the
> carb open and put up with the over rich mixture when they aren't.

I have separate adjuster for each barrel on the Y piece.


> Did the car perform okay on lpg before you changed the carburettor,
> and have you made any other changes beside the new carb?

It performed OK when warm, but I could start easily on lpg, and engine
would not die if I was quick with my foot on the accelerator. Now I can
not start on lpg, and engine will die if I switch to lpg before it
warms up more than 1/4 of a normal operating temperature, and will
stall at idle before temp needle passes 1/2.

And I did not change anything else, just the carburetor.


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