ThetaTau87

I'm shopping for a 5-speed 928 S4 or GT. Assuming the S4 is equipped with a limited slip diff what makes the GT worth roughly 25% more for the same condition and miles? Is it just the cams and exhaust that give the GT the extra 10hp and a higher value or is there more to it?

What makes the 89 GT more desirable than the 90 & 91?

Also, why is the 89 S4 more sought after than the 87 & 88?

It seems like the 89 928 is the pick of the litter and I've never been able to pin point why. Is there a definitive guide somewhere with the model year changes and equipment listed?

Hilton

The desirability of the GT comes down to the better engine (due to cams), and rarity.

87/88 S4 in the USA has 2.20 rear end - for fuel ecomony at freeway cruise.
89 S4 with 5 speed got the 2.64 rear diff ratio which all "Euro" 87-89 S4's have.
89-91 GT has shorter 2.73 - better for acceleration, but noisier on the freeway at 3k rpms

89 also got more speakers and a bit more sound deadening than the earlier S4's (at least compared to the two 87's I've owned).

89 S4/GT has the digital dash (which is nice - I prefer my 89's dash to my '87), plus predictable LSD instead of PSD (PSD works nicely for street - but you don't get to choose its behaviour on the track).

89 also doesn't have airbags (they arrived in 90) - so it takes a factory sport steering wheel and slightly lighter weight.

Wikipedia's 928 page has a good summary of changes between each model year.

ThetaTau87

Thanks Hilton. Great info!

I was aware of the digital dash change for 89 up, but not the gearing change. The rear end ratios are a big difference with the S4 87/88 vs. 89, but not a huge difference between the 89 S4 and GT. I'm considering an 89 S4 and an 89 GT. For the cars I'm looking into the GT is actually less expensive, but has a lot more miles and I prefer the color of the S4 more than the GT. 10hp and .09 shorter rear end gear isn't that big of a difference IMO. I think I'd rather have the color I like better and fewer miles than the GTs slight extra power and gearing advantage.

Jim M.

The GT has more precise pistons, smaller well between valve pockets for exact 10:1 compression, high lift and longer duration cams. The GT cams are stamped on the ends no’s are 271.01, 272.01, 273,01, 274.01 the casting numbers are 928 105 271.OR, 928 105 272.OR, 928 105 273.OR, 928 105 274.OR. Lighter and freer flowing exhaust, revised engine computer mapping, idle at 775 vs. 675, rev limit at 6800 vs. 6600, torque peak at 4100 vs. 3200, 326 hp vs. 316 hp. 8" and 9" wheels vs. 7" and 8", 17mm rear bolt-on spacers for wider track, factory rolled fender lips for clearance with wider track, 20mm shorter shift lever. (10% less travel), Limited Slip (40%) and standard Sport Shock/Spring Option, slightly different instruments, Straight Cut racing type ring and pinion. I have both, and the S4 has slightly more torque on the low end for normal drivability, however once the GT hits 4000rpm it’s a freight train and with the close-ratio 5-speed all of the up shifts hit right in the torque peak between 4100-4300. The GT likes to be driven hard and rewards you when doing so. It’s also a much stiffer ride than the S4, and is much rarer than the S4 and therefore worth more. It was a prototype for the 90-91 transition of all 5-speeds being a GT and all autos being S4’s. When you move up into the 90 GT there were slight differences, but have the same engine etc. Here is what was lost and added on the later normal 90-91 GT: 8" and 9" Club Sport forged wheels replaced with 7.5" and 9" cast Design 90. Deleted the 17mm bolt on rear spacers. Fender lips not rolled because of the narrower track. Normally cut ring and pinion gears, 40% fixed LSD replaced with computer-controlled variable PSD, dual airbags added. Oil cooler added below the lower radiator support plus an extra air slot in front spoiler. The 89 90 GT heads are a different part number to reflect a slight amount of hand porting.

mickster

I think the only attractive thing about a 1990 GT is the PSD but then you have the added weight of a full blown airbag system) The 1991 gets better soundproofing along with the PSD but also the added weight of a full blown airbag system.

ROG100

For what it is worth I have both 89S4 5 speed and an 88SE (technically a GT) - I have also driven the other variants including the GT 89, 90 and 91.
For some reason the 89S4 5 speed seems faster in acceleration 0 to 60 and is the fastest stock 928 I have driven 0 to 60 wise. The acceleration is fierce as measured by the assometer. Once the SE is here it will be interesting to see how they compare side by side.

mickster

I am sure someone here will tell you the exact weight of all the airbag components, new dash, and for 91, the soundproofing as well as weight difference of PSD vs. LSD.

IcemanG17

I haven't driven an 89GT but have driven early S4 5 speeds and 89 5 speed.....I MUCH prefer the 2.64 box......it just feels much more powerful.... My early 2.75 race 928 pulls extremely hard for such a modestly powered 928 (being 900lbs lighter than an S4 helps too)

123quattro

Huh?

Rob Edwards

I think the G28.55/57 R&P gears are Klingelnberg palloid, not straight cut.

http://www.weddleindustries.com/site...lloid_Tech.pdf

Hilton

The 89GT was a commodity version of the Clubsport and SE models (SE being the RHD clubsport).

It used the same wheels, same cams, same gearbox (G28.55) etc. found in the '88 clubsport/SE models, although it didn't get the some of the more expensive "special" bits which the clubsport/SE got.

All the stuff dropped from the 89 GT in 1990 was probably due to the cost of producing multiple different variations of what was essentially the S4.

The feel is probably the earlier torque on the S4. I've driven a local GT and it definitely pulls better with a bit of space to wind it up.

The clubsport/SE has a few advantages over the 89GT..

Factory "clubsport" engine - with the "SP" designation after the engine number on the block. They had hand-selected bits to get the best possible tolerances/balance etc.
Lighter chassis and body panels, selected off the production line for their weight
Lighter AC compressor (SE uses the 10PA20C, not the 6E171 which all other MY88-89 928's have)
No sunroof
Less sound deadening (e.g. behind rear quarter panels) to reduce weight

Tom. M

did the SE really get all that stuff that the CS got?.... I recall the SE got the smaller A/C compressor..but the lightened panels and sound deadening were a CS only thing....and the SE was the first attempt at civilizing the CS for UK consumption?...

no sunroof GT would be cool...how many SE's don't have sunroofs? all of them?

ROG100

The SE was a Clubsport with the luxury added back - all SE's were no sunroof unless one was ordered from the factory with a sunroof - I do not know if one was but for $$$ Porsche would do anything you wanted 8>).
Trust me Hilton knows his s**t.

Mine has CS on the oil pan - added at the factory - revealed when the cross member was removed.

Tom next time we meet you get to drive my SE

Hilton

hmm.. my understanding was the SE got the same lighter body bits, but I could be wrong.

The other items are all definitely correct including there being less sound deadening; I took the rear quarter panels out of my 89 and a local SE at the same time, when we were getting our windows tinted.

The SE did have a few more creature comforts than a clubsport.. like a radio, full leather interior (dash, console, quarters etc), and AC as standard.

Plenty of GT's were made with no sunroof.. just not in the USA

Here's the numbers for no-sunroof LHD GT's:

1989 88
1990 186
1991 154

The 25-years-old rule Roger is importing his '88 SE under will come into effect next year for 89GT, and so on.. so I think LHD no-sunroof cars will become a viable import to the USA (at least for Texas?)?

Tom. M

I won't forget that offer