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Source: www.europartsinc.com File Size: 76.62 KB Category: Automotive Last Download : 8 days 6 hours 33 minutes ago Share this info: Short Description: turbocharger evolution for the Volkswagen. The IHI turbos offered great ... The design philosophy behind the phase three-turbo installation was many fold. ... Content Inside: 1987 VW 16 VALVE TURBOCHARGER DESIGN PHILOSOPHY By Talbot Hack Callaway Engineering Department This project for VW is the third generation of systems for the water-cooled platform. Our first attempts were for the early Rabbit style. It incorporated the same basic engine as today but with a different configuration. We had the intercooler mounted far from the engine with a great deal of extra plumbing. A big Rotomaster turbo was used in this application with a cast iron manifold and our microfueler system. The cars ran very well but generated their power at a very high engine RPM and had poor low-end response. They were the classic "rubber band" kind of turbo cars. They were exciting to drive. No accurate dyno runs were made with this particular combination, but early on testing was done, and 250 hp had been obtained with a specially prepared engine. This was obtained, however, with big valve heads, with a VERY large turbo with poor response, a big intercooler, and a large microfueler nozzle. Many other minor changes were made in the search for additional power including high boost. The second generation we worked on was based on an IHI turbo, which is a much smaller turbo with good response. It has, however, high backpressure, which limits top end power. It is a "low end" kind of turbo. We started using this particular turbo at a time when people were unsatisfied with the response of a turbo engine. We felt that the correct move was for a smaller turbo with good response in the low end, which would ultimately augment the torque and horsepower curves as low as possible in the RPM range. In this application we were not as concerned with the top end power as much as its overall versatility. This was done in the 1985 and 1986 model GTI autos based on the Golf platform. Because of other restraints we decided to place the intercooler as close to the engine as possible. This helps performance considerably in the area of response, it eliminated a lot of plumbing, and it made the kit less complicated. The only hassle to the kit buyer was the fact that he needed to put a hood scoop on the car in order to get air to move across the intercooler. Negative points of the earlier systems included the need to have a great deal of plumbing. We then decided to rethink our successful configuration to advance to the next step in turbocharger evolution for the Volkswagen. The IHI turbos offered great response on the low end, but it was thought that this was a limiting factor in creating additional top end performance. Did this new 16 valve technology mean that we could increase the turbo size and get better top end response while retaining excellent mid range performance? Rotomaster felt that they had a turbo, which would meet our requirements. Another area of concern was the oil drain location, which we have used, in past kits. A return hole was drilled into the base of the cylinder block between the number three and four journals and fitted with a special 45� fitting in order to accept an oil return fitting from the turbo. A continuous downhill slope of no less than 15� was necessary in order to prevent a lack of return oil feeding in all conditions. In this configuration the turbo was mounted very low in the chassis, which required pounding holes in the firewall due to its 1987 VW 16 VALVE CALLAWAY TURBOCHARGER DEVELOPMENT PROGRAM 1