Wavey

Hi All,
I have a decision to make between 2 S4s
A MY 1988 and a MY1990.

@Hilton @928cs has informed me that 1990 most likely has higher compression 10:1 as opposed to 9.3:1.
They both have the same HP and 0-60 on paper.

Does the higher compression add much to real work acceleration and performance?

I just noticed the final drive ratio went from 2.2 to 2.5 in this period also and 0-60 reduced by 0.3seconds. Is this noticeable in a 30 year old car?



Many thanks,
Robert.

puyi

No!

Higher compression ratio may increase fioul efficiency, but torque is the same between MY, so "road" efficiency are the same

Hilton

Having both types of S4, the difference isn't huge - both are rated same hp from factory too. I do notice the 87's feel a little different pulling from low rpm's - I originally just figured it was just a feel between my first 87 and my 89, however when I sold that 87 (couldn't live with the sunroof) and got another 87, found the same characteristic. I haven't had my 87's on a dyno to compare figures, but the difference is marginal, and the odds of getting both my 928's to a dyno at the same time are slim to none, plus the 89 is not completely stock anymore (the 87 is.. including the air pump, factory exhaust, etc.).

Having said which - I wouldn't dwell on it.. out of the list of things to look for, its not a consideration to be honest.

Be more concerned with interior originality and condition, mileage, option codes (leather interior upgrades, any exclusive options, special colours, LSD (if pre-PSD years) etc.), paint condition, mechanical originality and then service/maintenance history. If you find two cars which tick all those boxes at your price, then sure, worry about compression, but for now, just choose the better car, and enjoy it

Wavey

Thank you Hilton for further help - I did not realize you had both cars. Below are my 2 finalists.
https://www.autowereld.nl/porsche/92...4/details.html
https://www.autowereld.nl/porsche/92...1/details.html

The 87 is €3k more expensive. Is a dealer sale. Perfect body and nice wheels.
The 90 is a private sale with slight body scratches that may need a re-spray. I dont like the older flat alloys and will change them at cost of €2k. Transmission has been overhauled.
Both will ship with TB & WP and a 90% complete service history.

I'm not afraid of DIY work on the interior but I wont touch an exterior.
The compression question has weighed on my mind as acceleration is my number 1 priority and the reason I am moving from my current 83S.
I see an X-pipe and Porken chip in the near future!


Always happy to hear opinions if you have any.

Does the change in final drive ratio make any difference?

Robert.

928cs

All automatic Euro S4s have the same final drive ratio.
But if your goal is the feeling of the acceleration, I advise you to test a S4 before buying one.
A Euro S in good condition delivers a good deal of sensations, more than an average S4.

Speedtoys

I mean, its ok to have your reasons, but "accel from a stop" really isn't in the wheelhouse for any non-stroker/charged 928. It's geared the other end of the spectrum from drivelines that do well here.

You can out the 2.7x rear end in the automatic, and a similar "low" gearing in a 5spd I think...that helps some..

I beat nothing 'fast' off the line, but if we have room to get to 3rd gear, is falls apart fast for the other car and I'm gone...because then my high gearing is in my favor and all they're doing is shifting..shifting..and shifting...

Honestly, I think my Porken chipped 85 (Daugters car) is a more fun light to light car than my heavier S4, even with the higher torque.

Hilton

Both the cars you linked have full leather interior (which is a good thing). The quality of the factory leather interior is excellent and its very expensive to replicate for repairs/replacement, so I rate the condition importance high still.

For the body scratches - 928's factory paint is exceptional too, very good quality and thick, and will respond very well to a good cut and polish, so it may still be saveable/acceptable (unless the clear coat has started to die from extreme UV damage - rare in Europe).

For the final drive, I've driven auto S4's and they felt fairly similar to my cars - both mine are manual with the 2.64 final drive G28.12 gearbox. The GT gearbox does feel slightly faster - but that could have been the noise

Note that non-USA Auto S4's have a 2.54 final drive ratio from memory - the US ones have a very long-legged 2.20 for fuel efficiency reasons (which also gives high powered ones a very high top-speed potential). Certainly locals with the 2.5x Auto one can spin their wheels easily starting in first.

The 928 is a relatively heavy car (expecially for the era) and these days is easily beaten by many production cars.. I don't drive them for the sprint as even my X5 is faster off the line, I drive them for the touring and overall smiles.

Speedtoys

"Certainly locals with the 2.5x Auto one can spin their wheels easily starting in first."

I dyno fairly strong, and with the 2.7x LSD auto rear, and a healthy AF transmission, I cant.

Maybe if I put a 16" wheel back on, I might get a revolution..

Wavey

Thank guys.

To be clear, my goal was not to buy a 928 because a want the fastest accelerating car I can get of that era.
But instead to find the fastest accelerating 928 I can in my budget.
My budget limits me to auto S4.

Hope that makes more sense!

The Forgotten On

Either way. get a later one. They 88 and 87 have weaker head bosses that crack. That was fixed in the 89 model year (88 in some countries as they count the year it was registered as the model year) among a litany of other...refinements.

The digital gauge cluster being the most notable.

I have an 89 and it feels decently quick off the line in second. Mash it and 1st will really get you moving.

I do think however that my 85 with factory sized 16 wheels is quicker off the line, but that is probably due to it having less than1/5th the miles my 89 has. The 89 really comes alive above 4k rpm on the highway though...