An Introduction to Turbo Diesel Special Tuning

AllardALLARDS 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.

Allard Aluminium ProductsBecause 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.

Allard Aluminium ProductsOn 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.

Allard Aluminium ProductsIncreasing 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.

Allard Aluminium ProductsDiesel 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.