General

Model Year Differences

>Is there a place on the net that lists the minor differences in each
>succeeding model year, particularly the S4? Thanks in advance for any help.
>
>Dick
>85 Black/tan

Phil T.'s website has a quite extensive list of changes to model years as the cars evolved. Check:

http://www.928s4vr.com/

Since your interest lies primarily in the '87 up S4's, here is
some related info from a Panorama article written by Kim Crumb.
This is from the July 1997 issue, and is of course plagiarized
(although condensed and somewhat disjointedly organized)
and submitted to the list without anyone's permission... ;^)

The following are external, visual clues for quick identification:

- 87 & 88 have "windshield impregnated" radio antennas
- 87 is the first year for 8" wide rear "forged slot" wheels
mounted with 245/45/16 rubber
- 89 & up have the sweptback roof antenna
- 89 GT's have the "one year only" forged Club Sport wheels
in 8x16 front and 9x16 rear sizes. Tire size same as 87's.
- 90 & 91 GT's return to a cast wheel in 7.5x16 and 9x16 sizes.
Wheel is "Design 90" type, visually *similar* to Club Sport.
These wheels also incorporate RDK system sensors (tire pressure
warning). Still using 225/50/16 and 245/45/16 rubber.
- 92-95 GTS models have a different rear bumper cover/taillights.
They also have the "aero" teardrop-shaped side mirrors.
Rear wheel openings are "flared" for fitment of larger tires.
- 92 & 93 GTS models have 17" wheels - 7.5x17 & 9x17 fitted
with 225/45/17 and 255/40/17 rubber. Wheel style is "C2"
type, and RDK sensors are still used.
- 94 & 95 GTS models have the same wheel/tire sizes, but wheel
style is "993/Cup" type (cast) and RDK has been discontinued.
- GTS models have larger brake discs, and the front calipers
are the Brembo "Big Black" type.

Here are *some* of the mechanical changes:

- 87 introduced a new engine management system incorporating
a knock sensor.
- 87 & up S4's have larger valve sizes than the 85/6 four cammers.
- 87-91 S4's are rated at 316-320hp (depending on source) @
6000rpm. Compression ratio is 10.0:1
Engines incorporated special oiling "squirters" directed at the
undersides of the pistons to reduce temperatures.
- 87 & up changed to a single disc style of clutch assembly
replacing the earlier twin-disc type.
- 88 introduced another change in the engine management system to
an "adaptive electronic" type.
- 89 S4 models had revised final drive gear ratio, with a "lower"
2.54:1 gearset replacing a 2.20:1 ratio
- 89 GT's had camshaft changes to yield 326-330hp @ 6200rpm, came
with standard limited slip differential in a 2.72:1 ratio
- 90 & up models have as standard equipment a limited slip
differential (PSD)
- 91 models had no new changes, and 92 models were not imported
to the US but remained available in the "Rest of World".
- 92 & up GTS models had the engine displacement increased to
5.4 liters, with 345-350hp @ 5700rpm and 369 ft-lb of torque.
Compression ratio was raised to 10.4:1
- 92 & up GTS models with manual transmissions had a special spraybar
lubrication system and an integral fluid cooler.
- 92 & up GTS models with manual transmissions had a rear transaxle
gear ratio of 2.73:1 while the automatic transmission cars used
a 2.54:1 ratio.
- 94 & 95 GTS models had a design change in both the connecting rods
and piston skirts. These were the first to use forged pistons.

This is in no way a "comprehensive and all-inclusive" list, but will
provide you with a substantial idea of *most* of the basics. As always,
I encourage anyone else to suggest additions and/or corrections to any
of the above info.
I have not even attempted to venture into the realm of the car's
"interior" changes. I'll leave that up to DR or someone else
infinitely more knowledgable.
And thank you, Mr. Crumb for a great article!
As well, a special thanks to Philip Katz who faxed me a copy of
this article back in early 1999.

Brad Orr
'78 Euro 5 speed
928 Owners Club