[Diy_efi] Evaporative fuel injection (evolution of the evap carby)
benof1987 at hotmail.com
Fri Nov 24 03:06:58 CST 2006
It appears I was a little off the temperature mark... So in the example you
described, the vapour is made in a seperate canister using a heating element
that draws near on 100 amps (at 12 volts) in conjunction with the exhaust
heat to completely vaporise the fuel. There is also a second reservoir, and
a set of injectors. Is this correct?
>From what I can see the gas production works much like a carburettor
accellerator pump circuit... The gas is produced/boiled/whatever in the heat
exchanger until it reaches a certain level/pressure (like a float), from
which it is moved into the 1L reservoir (much like an accell pump). When it
is needed it then flows through the injectors and into the intake (like the
pump when it is working).
This seems like a good system to me, and in operation, I cannot see much of
a difference between that idea and my own (parts list is completely
different, and the way it works is too, but the end result of hot fuel vapor
being injected in a multipoint configuration is the same.
Yes I can see your concerns about the heavier parts of the fuel condensing
again, but given the short length of port between injector and inlet valve,
the fuel condensing could not possibly be any worse than a normal injector.
Also injecting fuel as a gas, the gas can be far more directional (fuel has
to be sprayed, and as we already have a vapour in this idea we can point it
in one direction and straight into the combustion chamber, the vapour does
not have to come near a port wall if the ports are straight enough. Yes its
possible, but it shouldnt happen in most situations and the amount it
happens would be negligible (and hence its effects would be too).
And my calculations for the horsepower loss were based on 100% air in the
intake, with no fuel going in (like a direct injection setup), and the
percentage of air in the mix with gaseous fuels (ie my idea), at a rich
mixture of 12:1. So the same numbers would apply to the port fuel injection
(a 7.5% loss due to displaced air).
Also, with the change in throttle problem, the idea was to run the engine at
14.7:1, which isn't rediculously lean (however lean running would be
possible). Maybe the blocks could have an accellerator pump of their own (ie
a surge of power/heat) to cope with the sudden fuel loads it will get.
However it may be neccessary to have a normal injector at the throttle body
to cover extreme conditions.
Maybe water injection is the solution to the high combustion temps
associated with lean burning. Admittedly it means more things to fill, but
all joe blogs needs is a great big light to say there isn't much water left.
We all know he is already capable of putting a bottle of valve saver/octane
injector/miracle juice into his tank, so opening his bonnet and pouring it
in there shouldnt be a problem. A failsafe (reverting to stiochimetric
afr's) could also be introduced if someone forgets.
Maybe a rethink of the blocks is in order, maybe this idea needs a spray
onto a hot block to work more efficiently...
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