ALLARDS have been associated with superchargers and turbocharging
for more than 25 years and in that time has developed and fitted an
extensive range of special tuning conversions and built up a considerable
amount of technical expertise in this field. More recently we have turned
our attention more to turbo diesels, with the emphasis on the improvement of
performance with optimum economy.
Because of the way turbo diesels are set up at the factory to suit the
average driver and urban driving conditions, many vehicles can have their
performance improved by up to 25% with only a small increase in fuel
consumption and a mild increase in maximum boost pressure. Our PHASE. 1
tuning system can normally produce the unique combination of up to 10-15%
increase in power and torque and in economy mode, up to 15% improvement in
fuel consumption. An increasing number of turbo diesels are now equipped
with an electronically controlled fuel pump, on these vehicles up to 25%
improvement is possible when uprated ECU is used in conjunction with one of
our uprated intercoolers.
On a turbo diesel engine the fuelling curve relative to airflow into the
cylinders is the critical factor. Too much fuel without sufficient airflow
will produce an over rich fuel air ratio leading to smoke. It is important
to have good boost available at low rpm to create sufficient airflow, but
actually, boost pressure and the maximum boost are very much less important,
provided sufficient cooled airflow is achieved.
Increasing boost at lower rpm can be very beneficial, but in many cases just
increasing maximum boost even if fuelling can be matched to it, will not
necessarily increase power very much. There can be many reasons for this.
One of the most significant is that modem turbochargers are of the low match
type with relatively small compressor wheels working at very high speed. An
increase in boost will increase the speed of the turbocharger, which can
increase the air delivery, but air temperature rises more rapidly and the
compressor runs out of its speed vs boost efficiency envelope. The rise in
air temperature quickly offsets most of the increase in mass airflow,
resulting in minimal increase in power and increased thermal and mechanical
loads on the engine. The introduction of (VGT) Variable Geometry
Turbochargers will improve volumetric efficiency over a wide rpm range, but
the importance of an effective intercooling system will still be essential
to increase flow, reduce thermal loads on the engine to minimise exhaust
smoke: and to improve specific fuel consumption.
Diesel engines will always be limited in their rev range as compared to a
petrol engine and although they can be tuned in a similar way, e.g. with
cylinder head modifications, change of camshaft etc., these methods are not
particularly cost effective due to the amount of labour entailed and the
renowned longevity of the diesel engine can be considerably reduced by this
type of modification. This is why we concentrate on intercooling (charge
cooling) and optimisation of the air/fuel ratio. Intercooling provides the
most cost effective way of substantially increasing performance from
tick over to maximum rpm, at the same time as having the potential to improve
fuel consumption, reduce the thermal load on the engine and reduce smoke
emissions. We have developed a range of complete intercooler conversions or
an uprated intercooler, when one is already fitted as standard for many
turbo diesels. Further installations are continually being added and we are
pleased to quote for and the manufacture for any vehicle which we do not
already have an intercooler.
We also manufacture charge air to water (intercooler) charge coolers, which
have a very high thermal efficiency at higher temperatures. They can be more
easily installed where space is limited but more components are required for
the installation so costs are higher. |
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