Re: [DML] Re: DMC to LPG CONVERSION

["Tom Niemczewski" <dmctom@xxxxxxxxx>]

David,

I have to post a reply, because I have a feeling that you're getting the CNG 
and LPG mixed up.

> With the proper equipment backfires are a thing of the past. Used to
> happen with the "choke" or the additional priming fuel to start cold.

With liquid gas injection there are no backfires. With regular mixer that 
mixes gas with air it does happen. LPG injection is expensive so most go 
with the old style system. There are a lot of cars running on LPG in Poland 
and we have lots of filling stations everywhere. Severe backfires are also 
very common. Believe me, I've heard it many many many times.


> The cold problem is getting proper atomization on a cold engine when
> the vaporizer has not reached operating temperature and in extreme
> cold the low pressure from the fuel tank.
The temperatures in Poland dropped last winter to -30C (-22F) and when all 
diesel powered cars, trucks and even buses were all frozen solid, the LPG 
fueled cars were still running just fine with no bypass valves of any sort 
and no problem with low pressure in the tank. LPG boils at -45C (-49F). At 
temperatures above -35C the pressure is of no concern. If the temperatures 
in your area drops below that then.... you should move south ;)

> The
> octane IS lower, it can't be calculated like liquid gasolne, has the
> effect of leaning out under certain conditions, another reason for the
> lowered gas mileage (besides the retarded ignition). Another problem
> is refill times. On a regular car you can refill in minutes. For LPG
> it takes longer and in many places they want you to remove the tank
> before they will fill it so it can be weighed as it is filled so it
> can't get overfilled.

Filling takes about the same time as to fill up with gasoline and you DO NOT 
need to remove the tank.
Again, you are either thinking about pure propane or CNG. LPG is at constant 
pressure and filling is done by pumping liquid into the tank. Just like 
gasoline but the connection is sealed and under pressure. The pressure in 
the tank changes very little if the tank is almost empty or full.

To answer the octane rating problem...
http://en.wikipedia.org/wiki/Autogas
and
http://en.wikipedia.org/wiki/Octane_rating
Here you will find the following information:
Liquified Petroleum Gas (LPG) typically have octane ratings of 110.
You will also find information as to why the gas milage is lower. It has 
nothing to do with retarded ignition or octane rating but with energy 
content which is lower than that of gasoline.


> Another big drawback is the lack of a
> conventional fuel gauge. You have to keep track of consumption by
> hours run or miles travelled to know what is left.
This is true, there is no fuel gauge. The good thing is that you do have a 
"low fuel" or "reserve" light.


> IMHO it isn't worth
> it unless you have a daily driver and you can beat the raod tax.
In my opinion it makes no sense for a DeLorean. Fleet cars, cars that drive 
many many miles in a year - big YES. Sports cars, 'weekend' cars, and cars 
that get less than 50k km a year (30k miles) should stay with gasoline.


Hope this clears things up a bit

Tom Niemczewski
vin 6149 (in Poland!)
Google earth: 52°25'17.30"N 21° 1'58.00"E
dmctom@xxxxxxxxx
www.deloreana.com



> --- In dmcnews@xxxxxxxxxxxxxxx, "Tom Niemczewski" <dmctom@...> wrote:
>>
>> Hello
>>
>> David, the octane rating is HIGHER. For LPG it is something around
> 105. CNG
>> is around 120.  You are correct about mileage. An engine requires
> about 20%
>> more (properly tuned) LPG than gasoline. Low temperatures do not
> affect LPG.
>> It's diesel that freezes, not LPG.
> [moderator snip]
>
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