gjw@floyd.UUCP (Greg Wroclawski) (12/02/83)
The Porche 944 does indeed have an aluminum engine block. There are many cars that use aluminum engine blocks. Alfa Romeos, Renaults, Rover and Cadillac are a few that come mind. All of these cars have steel liners for the cylinder bores, so they enjoy the lightness advantage without sacrificing longevity. Thr 944 however uses an engine block made of Reynolds 390 aluminum silicon alloy. This material was originally developed for Chevrolet and was used in the Vega. I think we all remember those oil stoves. Porche has used this material since 1978 in their 928 so they are not newcomers to this material. The idea is that the aluminum alloy block has a high silicon content, something like 17%. Instead of using steel liners after the bores are finished the very surface of the aluminum is electrically etched away leaving only the granules of silicon for the pistons and rings to ride on. The main disadvantage of this process is that the block cannot be overbored. This is so apparently because the etching process requires some exotic equipement that is to costly for rebuild shops. This technology got a bad name after introduction in the Vega. However, from what I understand the oil consumption problem was also due to wearing of the piston rings due to poor materials and the fact that the Vega block had poor cooling and the engine oil ran very hot. Perhaps the sand finished bores require some unusual materials for the rings. GM's excuse for using this approach to an aluminum block is that it was cheaper to build than the conventional aluminum block with liners. What's Porches excuse for using this technology on $24,000 and $42,000 cars?
seifert@ihuxl.UUCP (D.A. Seifert) (12/06/83)
GM doesn't exactly have the greatest track record in the world for successfully introducing new technology. They tried to build a rotary engine and failed. They tried to build a rear-engine car and made Ralph Nader a household word. They *still* haven't figured out how to build brakes that will stop a car without putting it into a spin. They tried to build a car with an aluminum block and blew it. Porsche's designers thankfully don't have the same track record. motoring around with a cast-iron block designed 20 years ago that just took the F1 championship (wonder how much they want for the 4 valve-per- cyl head and the turbos?), Snoopy Madeira 320i autocrossing -- ) ( ) from the mildly opinionated keyboard of _)__________________ |OOOOOOOOOOOOOOOOOO| Dave Seifert |OOOOOOOOOOOOOOOOOO| ihnp4!ihuxl!seifert |OOOOOOOOOOOOOOOOOO| |------------------|