[Diy_efi] Evaporative fuel injection (evolution of the evap carby)

[Ben P]

If you could elaborate on why you think each of those things would happen it 
would be better... But I'll give my point of view on what I think your 
arguments are based on.

First up I am assuming that your claims of huge detonation, pre-ignition, 
and (most of the) lack of power centre around intake temperatures. I do not 
think that the intake temperatures would rise much.
*Note: For this I am assuming that both air and evaporated fuel have the 
same specific heat and mass (per litre at STP) which is incorrect, but they 
should be close enough to eachother to get similar numbers I have*
If you have an air-fuel ratio of 14.7:1 (by mass, but given the previous 
assumptions, this also becomes volume), you then have 14.7 litres (or kg) of 
air at 30 degrees celcius, and 1 litre (or kg) of fuel at 300 degrees. When 
you multiply the volume of air by its absolute temperature (kelvin) you get 
4456.3 degrees/litre (I am unsure what to call this measurement, but all we 
are doing is calculating an average), and when you do the same to the fuel, 
you get 573.15 degrees/litre. add them together and you get 5029.5 
degrees/litre. Divide this by litres (15.7 total volume) and you get  320.3 
degrees K, or 47.1 degrees celcius. Not that much of an increase, and 
certainly no worse than most cars in a hot environment. Granted that once 
you have already boiled a fuel and introduce it to the intake it has no 
evaporative cooling effect, the difference in intake temps at the valve is 
likely to be the 17 degrees implied here, it still wont be that dramatic.

As for the fuel condensing on the walls of the intake manifold, this should 
not be a problem with my idea. As the fuel would all eventually evaporate if 
left alone anyway, the only way fuel could condense back to a liquid is if 
the walls of the manifold were very cold, which wouldnt happen outside lab 
conditions anyway (bar extreme climates). Under these conditions not a huge 
amount of fuel systems would work at all anyway. The fuel is simply too hot 
to condense under atmospheric pressure. I believe that the condensing you 
are reffering to is from very fine droplets of fuel that have not evaporated 
fully (ie what carburettors do) hitting the walls of the manifold and 
sticking to it. Gases dont have the problem of sticking to anything...

I am wearing the second low power argument for now (fuels displacing intake 
air), but even at a 12:1 AFR, the fuel would only take just over 7.5% of the 
volume, for the same 7.5% power loss (plus the losses due to heat though, so 
maybe 10-12% overall).

And what on earth do you mean by "an inability to fuel appropriately for 
large values of delta alpha", I can't understand it.

again, explain your theories. Any ignorant person can say things like 'it 
wont work', but not a huge amount of people explain why.

cya
Ben

*I checked out the Smokey Yunick thing and couldnt make sense of any 
information. I get its claims, but no data on its workings.

>From: Adam Wade <espresso_doppio at yahoo.com>
>Reply-To: diy_efi at diy-efi.org
>To: diy_efi at diy-efi.org
>Subject: Re: [Diy_efi] Evaporative fuel injection (evolution of the evap 
>carby)
>Date: Wed, 22 Nov 2006 02:43:33 -0800 (PST)
>
>--- Ben P <benof1987 at hotmail.com> wrote:
>
> > thoughts people?
>
>Pre-ignition, destroying the engine in short order,
>even with a painfully low compression ratio; an
>inability to fuel appropriately for large values of
>delta alpha; reduced power output for a given size
>engine (lower CR, plus less total air mass inside the
>combustion chamber due to it being heated so much);
>vapors condensing back to liquid form in the manifold
>and causing a lean condition that would increase the
>propensity for pre-ignition and detonation.
>
>I'd be interested to see actualy data of how it
>compared to the same engine fueled by a regular
>injection system, but I predict it is going to fare
>very poorly when a head-to-head is done.
>
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>
>
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