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Gentlemen,
i may be chiming in a bit late here - but there may some helpful additionals here..
Actually, there are several small but significant differences between the Euro and U.S. 3.0l engines. Starting with
the transmission, 2nd gear is shorter/numerically taller (i.e. better
acceleration) that was used on only the 1978 vintage SC.
The USA 'SCs from 78-79 had 95mm pistons and a
8.5:1 compression ratio and 39 & 34mm intake and exhaust ports. They also had a smog pump in california
along with a restrictive catalyst exhauast.
The CIS system is also less agressive in that the fuel distributor is
smog-friendly (I believe it offers less potential volume) where as the Euro unit is idential to that of the MBZ 450SEL and 911Turbo fuel distributor and can be set to run a little meaner =i.e. rich. The USA cars are inherently lean on the top-end, particularly on post-1980 vintages. Finally, the USA car has not only a less-agressive advance curve in the ignition distributor, but it also has a vacum-retard unit whereas the Euro has only vacum advance.
In 1980 the USA cars received an increase in the compression ratio to 9.3:1 and retained the 95mm pistons. They also introduced a Llamda/Oxygen sensor for the catalytic-converter which enabled Porsche to do away with the smog
pump. However, in the interest of smog compliance and maintaining an acceptable Corporate Average Fuel Economy -as
the required by our Federal Goverernment (or pay bigass penalties) Porsche elected to REDUCE the port size to 35mm intake and 34mm exhaust.
The horsepower was rated the same at 180hp.
The Euro motor enjoyed 98mm pistons with a 9.8:1 compression ratio, more aggressive fuel and ignition distributors,
larger intake runners, and a more aggressive 2nd gear. They were also a tad lighter since they didn't have to
meet the USA safety requirements. Most of the
grey-market imported cars skimped by on paper but did not have the proper safety cross-member bars in
the doors, in addition to the USA's nasty 5mph bumpers.
Otherwise, there is no difference...
Maurice Perkins
1980 SC Coupe
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