Description of technology
Conversion of the Nissan diesel engine, as fitted
by London Taxi International, in the Fairway and TXI
taxis, to dedicated LPG fuelling.
From the outset Jaymic’s concept of the technology
to convert black cabs to a cleaner fuel has been to
be ecologically sound as well as saving valuable energy
resources. In using as much of the existing Nissan
engine and ancillaries as possible this economy of
resources can be achieved. Rather than removing a
mechanically sound diesel engine scrapping it and
replacing it with a brand new engine that, in itself,
has used a significant amount of energy to manufacture,
our technology allows the ongoing use of the most
basic components of the original engine and ancillaries
and forms the basis of our ecological conversion concept
that has been followed throughout our research, development
work, prototype and production stages.
Our technology recycles
the existing Nissan TD27 diesel engine in the
LTI taxis, as installed by LTI between January
1989 and January 2002, converting the engine
from a compression ignition diesel to a spark
ignition engine with dedicated LPG fuelling.
The only original parts of the LTI taxi that
are scrapped are the diesel tank, exhaust down
pipe and diesel fuel system. |
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By having dedicated LPG as
the fuel we can take advantage of the higher
octane rating of LPG, compared to petrol, by
optimising the compression ratio and ignition
timing to run more efficiently. An engine that
runs on either petrol or LPG has to be optimised
for the lowest quality fuel, which is petrol.
Both the higher compression ratio and optimised
ignition map increase the efficiency of our
dedicated LPG engine and give large reductions
in NOx and PM emissions.
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Engine conversion
procedure
Fairway and TXI - the original
Nissan TD27 diesel engine is removed and stripped
to component form and inspected for wear. Depending
on the tolerances found, the cylinder liners
and pistons are replaced, or the pistons only
replaced. The rest of the bottom half of the
engine is rebuilt using new bearings, oil pump,
seals, gaskets, etc.
A Jaymic-designed and modified
cylinder head is installed on the engine. The
old diesel cylinder head being remanufactured
to be used with LPG, including suitable valves
and seats for gaseous fuels.
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The original air filter housing,
inlet and exhaust manifolds are used in the conversion.
The end result is not only a taxi that is converted
to run on LPG, but with a fully reconditioned engine
without having to replace the existing engine.
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In the boot of the Fairway
model taxi is a 110 litre LPG tank on a purpose
made mounting frame. TXI models have a 105 litre
tank The LPG tank frame has provisions for mounting
the vehicle jack, wheel chair ramps and passenger
step. The LPG filler is mounted in the original
position of the diesel filling point. The original
fuel gauge in the vehicle monitors the level
of the LPG in the fuel tank.
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The LPG fuel system on both
the Fairway and TXI models is a single point
gaseous phase induction system producing emissions
control performance between Euro III and Euro
IV levels on the Fairway and TXI taxis. An ignition/fuel
management system is combined in the same ECU.
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Exhaust system
The taxi is fitted with a new exhaust down-pipe that
includes, oxygen sensor and catalytic converter.
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