Has anyone a recommendation for such a product? Since swapping over ECUs
in one of the diesel Land Rovers, the engine has been noticeably noisier
which I put down to a touch of pinking. Ideally I'd get the software
tweaked in the new ECU but that's not poss right now I just need a
temporary fix until such time as I can get it hooked up to a compatible
interface. Any suggestions?
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Injection timing is quite critical. The fuel is supposed to burn as its
injected into the hot compressed air.
If it's early the compression won't have increased cylinder air temp to
ignition point. Then you have a lot of fuel in the cylinder just waiting
for the air temp to rise which is delayed by the fuel cooling it. Kaboom!
If it's late the peak cylinder pressure will be reduced and there may be
fire out of the exhaust ports.
Either way power is reduced.
A homogeneous charge engine that induces and air and fuel mixture is the
Otto engine and has spark ignition.
The Diesel has no throttle it always induces a full charge of air. Fuel
is delivered near TDC in a quantity set by the accelerator pedal.
All automotive Diesels I know of are direct injection. Some had a
separate ball shaped combustion chamber ported of the head. The
injection pump and injectors made Diesels very expensive compared to
carburetors fuel system and points ignition of the petrol Otto engine.
The mechanical injection pump and injectors have been supplanted in the
last 30 years by ECU controlled common rail injection.
Direct injection on petrol of cars is also quite recent. There was a
period of about 20 years (1980-2000) where port injection replaced
carburetors, injection could be 85-90% of the whole cycle at high load.
Direct injection on petrol engines works in 2 modes. One mode it injects
like a diesel late in the compression and the fuel self ignites, this is
used at low power and moderate cruise. The high load mode injection of
fuel will start on induction stroke after the exhaust valve has shut and
continue for most of compression when it's ignited by a spark.
I think all diesel engines of a reasonable size compress air only, and
inject fuel either directly into the cylinder, or indirectly into a
pre-combustion chamber operating at the same pressure. These are
essentially two systems for mixing the fuel and air as it burns.
Ignition timing is controlled by the injection pump. This as well as
the more robust construction (necessitated by the higher compression
ratio compared with petrol engines) is the primary manufacturing expense.
By comparison, diesel engines for model aircraft are built with only a
few cc capacity and rely purely on compression ignition of a fuel-air
mixture. They are therefore simper than a comparable petrol engine.
There are "petrol" engines of similar size, usually fuelled with a
mixture of methanol and nitromethane, which use a glow plug for
ignition. This is pre-heated electrically and is generally contructed
using platinum. Ongoing combustion maintains its temperature and the
platinum is a catalyst enabling combustion. Timing is controlled by the
air/fuel mixture, and the ratio of methanol to nitromethane.
These designs are 2-stroke, so have no camshaft or valves; and the
eletrical supply is only required for starting so is not carried on the
aircraft or whatever. For capacities above about 30cc it becomes
possible to include valvegear and spark ignition so this is typical for
chainsaws, lawn mowers, or motorbikes.
Petrol engines can still be injected, either by injection into the inlet
manifold or directly into the combustion chamber; but this is to manage
proper air/fuel mixing and fuel metering. It is also independent of
gravity so ideal for use in aircraft where a float chamber to control
fuel flow would give problems, though there were compromise carburettor
designs during WW2 used to mitigate the problem.
That is a little surprising for the time- there wouldn't have been many
women engineers. (I'm not suggesting women don't make good engineers -
just recognising the way things were. ) Do you know her name please, a
useful example to have.
Always smile when walking, you never know where there is a camera ;-)
Just in case Mr Cheerful is otherwise engaged I think he may have in mind:
I knew in the 60s a former Spitfire pilot who'd met her when his plane
was done and sang her praises.
reply-to address is (intended to be) valid
Miss Shilling's Orifice. A restriction in the fuel line that limited
fuel flow to max power fuel. 109's had fuel injection and were getting
away by diving sharply. The negative G caused the float system in the
Merlin's carb to flood the carb. As the sharp dive would be in pursuit
it would be at full throttle so max throttle fuel flow was needed and
excess fuel from a flooded carb would make the engine splutter and cut
out. She also supervised the teams of fitters that went out on squadron
to fit the mod.
Before that British fighters had to do a roll into the dive to keep
positive G on the float system but that still slowed them up, though not
as badly as having the engine cut out. There was scene in "The Battle of
Britain" where the the roll into a dive was explained.
Miss "Tilly" Shilling.
Holder of a Brooklands Gold Star for lapping Brooklands at over 100 mph.
Told her fiance that he had to get one too as she wasn't going to marry
anyone that wasn't her equal. Disconcerted friends by having dismembered
Norton's in the kitchen.
The Daimler-Benz DB601 in the Bf 109 (not Me!) had direct fuel injection.
Miss Shilling's Orifice was only used on the Merin until an anti-G
version of the SU carburettor was designed. This was later replaced by
the pressure diaphragm Bendix carburettor. There was also a Stromberg type.
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