[Diy_efi] Re: Diy_efi digest, Vol 1 #366 - 13 msgs

Fri Nov 22 14:49:53 GMT 2002

Greg,
    I do stand corrected, you are absolutely right about 'Sublimation' - 
wrong word choice on my part - I do that occasionally - or more than 
occasionally!
Re- Injectors 'freezing' I did not mention Ice ( see my later post below ).
    For an Idea of the dimensional changes in metal with low temperatures:
A friend of mine needed to replace the Ring Gear on the flywheel of his 
MG midget - The normal method is to heat the ring gear until it has 
expanded enough to slip over the fly wheel. He did not have the 
equipment to heat the ring gear, but thinking laterally (he worked at 
the time in a university physics department and had access to liquid 
nitrogen) he poured liquid nitrogen over the flywheel until it 
contracted sufficiently, dropped the ring gear on and then waited for it 
all to return to room temperature.
    From other posts it appears that whatever problems existed have been 
solved, so it really only remains for Glynne to make contact with the 
'right people' to get the latest information. Finding those 'right 
people' can however be a challenge!
Regards
Bill


>Message: 5
>To: diy_efi at diy-efi.org
From: bearbvd at mindspring.com (Greg Hermann)
>Subject: Re: [Diy_efi] LPG injection
>Date: Mon, 18 Nov 2002 10:33:52 -0500
>Reply-To: diy_efi at diy-efi.org
>
>At 9:58 PM 11/17/02, sy2th wrote:
>
>Several urban legends to de-bunk here--
>
>First-- "SUBLIME" means a phase change from SOLID directly to GASEOUS
>state. NOTHING to do with liquid state !! As when snow evaporates directly
>into the air or dry ice (frozen CO2) changes directly to a gasseous state
>without becoming a liquid first.
>
>Second-- While it's entirely possible that injecting liquid propane could
>cause THROTTLE icing under properly conducive atmospheric conditions (high
>humidity), the injectors would NOT be at all likely to ice.
>The source of the water ought to be obvious from the "high humidity" part
>of the above !
>
>Third-- Conventional propane carburetor systems absolutely do NOT draw gas
>off of the top of the tank !! They use a dip tube and draw LIQUID off of
>the bottom of the tank. The liquid then goes through the "vaporizer"--which
>uses warm engine coolant to vaporize the liquid before it goes to the
>carburetor. The tank would turn into an ice ball (again, from atmospheric
>humidity) if one even TRIED to draw the quantity of gas off of it that even
>a small engine uses under load !! ) (Not to mention that you simply would
>NOT get ENOUGH gas out of the tank to let the engine run !!
>
>Greg
>
>  
>
>>Well, maybe I need correcting also, but that makes absolutely NO sense to
>>me.  "Freeze" meaning ices up?  Where does the water come from?  It would
>>have to be in the gas for that to happen, and lots of it.  Nitrous comes
>>out of the nozzle every bit as cold as propane, never heard of any
>>'freezing' problems.  The LPG systems I've seen draw vapor from the top of
>>the cylinder, not liquid from the bottom as nitrous systems do, so what
>>gets cold is mainly the tank & the delivery line.  Remove the nozzle from a
>>propane torch & open it, aimed @ your hand - not real cold at all, but the
>>tank chills.  Now, invert the tank, so's liquid comes out - - bit of a
>>different situation, no?  Somehow, I don't think so, Al.....
>>
>>Barry - Sy#26  -  (but, hey, I'm no expert.....)
>>Bangor, MI
>>
>>At 10:19 AM 11/18/02 +1100, you wrote:
>>    
>>
>>>Glynne,
>>>        I stand to be corrected, but from what I understand there is one
>>>major hurdle which has dogged the concept of LPG injection. And that is
>>>the "Latent Heat of Vaporisation" of the LPG. The reason is that liquid
>>>fuels are injected as microfine droplets, but still a liquid however when
>>>you try to inject LPG it submilates, IE it turns directly from a liquid
>>>to a gas. To do this it absorbs heat from the surounding structure(metal,
>>>air, etc) - large amounts of heat - much more localised cooling than the
>>>waste heat into the area from the combustion chambers - and tends to
>>>freeze the injector - literally freeze it solid (either open or closed!)
>>>- thus end of control, BIG problems! This problem may have been solved,
>>>but to my knowledge has not yet been. This is obviously a much more
>>>fundamental issue to resolve before considering an ECU!
>>>Regards
>>>Bill W
>>>      
>>>
>Date: Wed, 20 Nov 2002 10:59:57 +1100
From: Bill Washington <bill.washington at nec.com.au>
>To: diy_efi at diy-efi.org
>Subject: [Diy_efi] Re: Diy_efi digest, Vol 1 #363 - 9 msgs
>Reply-To: diy_efi at diy-efi.org
>
>Gents,
>    I have not tried it, but am only relating what was said by some fuel 
>injection professionals during a presentation at our car club.
>I suspect that since injectors are designed to work at ambient temp and 
>upwards, the variety of materials used in the injectors are such that 
>the differential rates of thermal expansion/contraction are designed for 
>that temperature range, not for the -20 to -40Deg Celcius that would be 
>experienced in injecting LPG, when there may be mechanical seizure due 
>to differential contraction.
>    1. Remember that these are precision devices, therefore the 
>tolerances are very close, so only a very small differential contraction 
>in the wrong direction would be necessary to seize up the injector.
>    2. In injecting LPG it MUST be injected as a liquid to achieve any 
>consistency in metering with existing injectors which are all designed 
>to meter liquids.
>To inject it as a gas I suspect that the injector would have to be a 
>radically different design.With a liquid a slight change in feed 
>pressure will affect only the flow rate, whereas with a gas a slight 
>change in pressure affects density and flow rate, the pressure becomes 
>much more critical in trying to achieve a known metered volume of fuel!
>
>Message: 7
>Date: Sun, 17 Nov 2002 21:58:52 -0500
>To: diy_efi at diy-efi.org
From: sy2th <sy2th at direcway.com>
>Subject: Re: [Diy_efi] LPG injection
>Reply-To: diy_efi at diy-efi.org
>
>Well, maybe I need correcting also, but that makes absolutely NO sense to 
>me.  "Freeze" meaning ices up?  Where does the water come from?  It would 
>have to be in the gas for that to happen, and lots of it.  Nitrous comes 
>out of the nozzle every bit as cold as propane, never heard of any 
>'freezing' problems.  The LPG systems I've seen draw vapor from the top of 
>the cylinder, not liquid from the bottom as nitrous systems do, so what 
>gets cold is mainly the tank & the delivery line.  Remove the nozzle from a 
>propane torch & open it, aimed @ your hand - not real cold at all, but the 
>tank chills.  Now, invert the tank, so's liquid comes out - - bit of a 
>different situation, no?  Somehow, I don't think so, Al.....
>
>Barry - Sy#26  -  (but, hey, I'm no expert.....)
>Bangor, MI
>
>  
>


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