Because there's more to the internet than hits alone, Peter Hill
wrote:
On Sun, 04 Jan 2004 18:53:46 +0000, Stewart
wrote:
Because there's more to the internet than hits alone, Biker_Bry
The difficulties to overcome LPEFI are as follows...
1. Propane cannot hold a liquid state at underhood temps (207deg F)
= about 97 deg C. Actually, I doubt thet it gets that hot under the
hood, though there may be hot spots where the local surface
temperature reaches that. The cooling system on my car operates at
around 80 deg C (which doesn't appear to leave much margin).
Oil temp? 120 deg C?
Cylinder head Metal temp 150+ deg C?
Exhaust manifold temp? 400+ deg C?
None of these present much of a design challenge. Don't bolt the fuel
rail to the exhaust manifold, and make sure it's not submerged in oil.
Most designers could manage that.
The only part that the fuel system needs to be in contact with is the
inlet manifold. I've never stuck a thermometer onto my inlet manifold,
but I doubt it gets near the critical temperature - it is constantly
cooled by between several hundred and several thousand litres of cold
air a minute. And in fact the reported issue at this point of contact
is injector freezing.
After switch off the temps of many parts go way above 100 deg C. The
fuel rail and injector components are attached to the inlet manifold
which is bolted to the head. Makes hot purge cycle critical. Not so
bad with plastic manifolds.
It really wouldn't take much to insulate the fuel system from all
parts likely to get hot. Some cars already keep the cooling system
active for a while after switch off. The only thing left is ambient
air temperature. And it has never seemed to me that opening the bonnet
is a similar thermal experience to taking the lid off a boiled kettle.
Of course this may be different in hot climates.
Mixing air/fuel *before* the cylinder breeds backfires and they will cause
serious problems.
Ask anyone tha has used an old Impco system.
Do you mean specifically in the case of *liquid* fuel injection? Why
would this be? ATM all LPG systems mix the fuel and air before the
cylinder.
He's taking about the old mixer valve systems - noted for ability to
backfire even in UK.
Why 'even in the UK'?
I would contend that mixer conversions were still amoungst the most
common type done. It is not the fuel/air mix that causes the backfire,
but a weakness elsewhere, typically with the ignition system. But I'd
be interested to learn of additional factors that liquid injection
brings up.
LPi (Liquid Propane Injection) is available as a factory fit item.
It is? So all these problems are already overcome, then.
--
Stewart Hargrave
Finally visible on
www.hargrave.me.uk
I run on beans - laser beans
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