I have a thing for the old style Audi A8’s. I believe they call them the D2 chassis. It’s the 1997-2002 body style. It’s more square, but I like them a lot. My boss had one for a while and I would take if for a couple of days. I loved that car, V8 power with that European ride that is so good. It may have just been the wheelbase of the car that gave it that stable ride but it was awesome. I believe that his was a 98 model A8.
Anyway, ever since I’ve driven that car I’ve wanted one. It’s not like they are out of reach either, a used one can be had for around $3000. That’s an A8 though, and being the sports enthusiast that I am, I would like the S8.
I’ve often thought about purchasing an A8 and seeing what it would take to convert it to S8 specs. In my amateur mind, I thought it would be a simple intake or cam swap, maybe an ECU, and exhaust, lower it a bit and bingo, A8-S8!
That’s not really the case. In all reality, this conversion would be purely cosmetic. The performance gains that are found in the S8 platform of that era are significant and achieving them are extremely cost prohibitive. You pretty much need to swap motors! Even though they are both the 4.2L V8 40V engines, the S8 has forged rods, different intake manifold, different cams (and there are 4 of them that would need to be changed, as well as the lifters to accommodate them), and a less restrictive exhaust system. Being an Audi, you can imagine how much that exhaust alone would cost, let alone the entire conversion! Oh yeah, you would probably need to get the S8 ECU as well. I can find a used S8 of that vintage in my area for around $7500. I would be picky about mileage, but they all have a ton at this point.
Still, I would not be against performing the cosmetic / suspension conversion. The cars are pretty much identical in every way, except for some distinct differences. The S8 rides on 18” Avus wheels. These can be had for around $500 used. Of course you will need to put tires on them, the size that the S8 came with is 245-45/18. You could probably get some tires for around $400, they would be cheapies but they would be within spec.
I would upgrade the suspension as well to get as close to the S8 as possible. I would purchase the Eibach springs to lower the car, and just buy the correct shocks/struts for the S8. I believe that the only difference is that the S8 shocks were twin tube for a stiffer rebound. The car would sit a little lower on the Eibach springs but that would be fine with me.
I would also change out the front and rear sway bars, the S8 has larger front sway bars 29MM than the A8 which has 26.8MM fronts. The rear bars on the S8 were also larger, 17.3MM vs. 14mm for the A8. The cost of the front sway bars would be approximately $270, and the rears would be around $210. I may just change out the rears to obtain more bite out of the front of the car. Adding more sway bar to the rear will decrease under steer! It would also save me $270!
So if I could pick up an A8 cheap enough, $3000 or so, I could do the suspension and wheel upgrades to get it to handle more like an S8, maybe even better. That would cost about $2000 if I don’t do the front sway bar. So for $5000 I could have an A8 that looks and handles like an S8 but still would not have the power. I think I would do it depending on the car; S8’s are getting pretty rare where I live and good ones are fairly pricy. You can get an A8 pretty cheap and the car can still be in good shape. Now my wheels are turning. This might be my next project!