It seems there is some interest in fitting alternative turbochargers, either to deliver more power (often at the expense of reliability), or as a result of a failure of the original Garrett T2. I have some experience in matching turbochargers to engines, so I thought it would be nice to create this thread for those who wish to discuss this topic. Let me say from the outset that I am not in favour of fitting large turbochargers in an effort to extract large amounts of power from small engines. I am however in favour of more reliable and more efficient technology.
For those not familiar with the principle of operation of a turbocharger I would recommend that you download a Garrett turbocharger catalog here: http://www.turbobygarrett.com/turbobygarrett/products/catalog.html which includes a basic explanation of how a turbocharger works, and how to select a turbocharger to match your engine. Garrett are the only company I am aware of that make their turbocharger compressor and turbine data freely available over the internet, which is why I prefer their products. Also note that Garrett do not supply data for their old T-series turbochargers (T2, T3 etc ...) over the internet, which have been copied adinifinitum by other manufacturers. They only supply data for their GT-series, which are vastly superior in my opinion.
If you want an old T2 or T3 (designed in the 1940's) then they still work fine, but chances are you may be buying a unit made in a less reputable country/factory, so check the manufacturers markings before you take delivery - I mean this :!: These low quality units do not perform according to the compressor and turbine data downloadable from other sources, so matching these units to your engine is generally impossible. Buyer be warned.
Having read the first few pages of the Garrett catalog and you are still serious about fitting a new turbocharger then I would recommend you purchase the book "Forced Induction Performance Tuning" by A. Graham Bell, published by Haynes in the UK, see http://www.haynes.co.uk/webapp/wcs/...10001&storeId=10001&productId=11153&langId=-1. The R5turbo engine and the infamous "Dispositif Prerotation Variable" turbo (pioneered by Jean Pierre Boudy and used to great effect on the Maxi) is discussed briefly under the heading of "Rally Engine Development". This device employs a set of adjustable vanes positioned at the inlet to a T31 compressor in order to effectively adjust the compressor inlet area and the direction at which the airflow hits the compressor wheel. The position of the vanes was controlled via the throttle linkage. So far as I am aware the Maxi employed a T04 turbine.
Another good book, although slightly less holistic in my opinion, is Corky Bell's "Maximum Boost: Designing Testing and Installing Turbocharger Systems", published by Bentley Books in the UK, see http://www.bentleypublishers.com/product.htm?code=GTUR. This book does however include a detailed explanation of the Variable Area Turbine Nozzle (VATN) turbocharger, which is similar in principle to Boudy's design, but has the variable vanes positioned around the turbine wheel, instead of adjacent to the compressor wheel (the former being a lot more tricky when you consider the temperatures involved).
For those seeking a modern VATN turbo the VAT25 (as used on the 1992 Peugeot 405 T16) can still be purchased from Garrett (I don't think it's in the catalog), and is an ideal candidate (provided you are prepared to tackle the task of operating the vanes) for the R5T 1397cc engine.
For those who have a preference, most of the calculations in "Forced Induction Performance Tuning" are in Metric units, while those in "Maximum Boost" are in Imperial units.
Comments, questions and ideas welcome.
For those not familiar with the principle of operation of a turbocharger I would recommend that you download a Garrett turbocharger catalog here: http://www.turbobygarrett.com/turbobygarrett/products/catalog.html which includes a basic explanation of how a turbocharger works, and how to select a turbocharger to match your engine. Garrett are the only company I am aware of that make their turbocharger compressor and turbine data freely available over the internet, which is why I prefer their products. Also note that Garrett do not supply data for their old T-series turbochargers (T2, T3 etc ...) over the internet, which have been copied adinifinitum by other manufacturers. They only supply data for their GT-series, which are vastly superior in my opinion.
If you want an old T2 or T3 (designed in the 1940's) then they still work fine, but chances are you may be buying a unit made in a less reputable country/factory, so check the manufacturers markings before you take delivery - I mean this :!: These low quality units do not perform according to the compressor and turbine data downloadable from other sources, so matching these units to your engine is generally impossible. Buyer be warned.
Having read the first few pages of the Garrett catalog and you are still serious about fitting a new turbocharger then I would recommend you purchase the book "Forced Induction Performance Tuning" by A. Graham Bell, published by Haynes in the UK, see http://www.haynes.co.uk/webapp/wcs/...10001&storeId=10001&productId=11153&langId=-1. The R5turbo engine and the infamous "Dispositif Prerotation Variable" turbo (pioneered by Jean Pierre Boudy and used to great effect on the Maxi) is discussed briefly under the heading of "Rally Engine Development". This device employs a set of adjustable vanes positioned at the inlet to a T31 compressor in order to effectively adjust the compressor inlet area and the direction at which the airflow hits the compressor wheel. The position of the vanes was controlled via the throttle linkage. So far as I am aware the Maxi employed a T04 turbine.
Another good book, although slightly less holistic in my opinion, is Corky Bell's "Maximum Boost: Designing Testing and Installing Turbocharger Systems", published by Bentley Books in the UK, see http://www.bentleypublishers.com/product.htm?code=GTUR. This book does however include a detailed explanation of the Variable Area Turbine Nozzle (VATN) turbocharger, which is similar in principle to Boudy's design, but has the variable vanes positioned around the turbine wheel, instead of adjacent to the compressor wheel (the former being a lot more tricky when you consider the temperatures involved).
For those seeking a modern VATN turbo the VAT25 (as used on the 1992 Peugeot 405 T16) can still be purchased from Garrett (I don't think it's in the catalog), and is an ideal candidate (provided you are prepared to tackle the task of operating the vanes) for the R5T 1397cc engine.
For those who have a preference, most of the calculations in "Forced Induction Performance Tuning" are in Metric units, while those in "Maximum Boost" are in Imperial units.
Comments, questions and ideas welcome.