2.0 w/ DASC... wow!

[Budget M3]

using the wiki animation and mathematics:

keep crank same
+ keep bore same (same pistons)
+ move spark plug higher
======================
volume in orange increases

I'm not saying this is something a shadetree mechanic should try at home or that Hartge doesn't change other parts as well, just pointing out that it is possible to increase displacement without changing other parts. The OP's comment about the gaskets got me thinking that could be how they got to their 2.0 measurement.

[Uber E30]

Originally Posted by Budget M3

volume in orange increases

The volume in orange is the swept area, the pistons cant just move higher because you made the HG larger. If that were the case they would be constantly slapping the head. The height that the pistons go is determined by the rotating mass on the bottom, IE the crank.

I have drawn a picture for you, the red area is the swept area. As you can see adding more above the piston w/o changing the crank does not add to swept, as the piston is already at a max height stock.

[Budget M3]

I actually looked into the Hartge conversion when I bought my ti new in 1998 in Germany. At the time, I remembered the gasket as the way they increased diisplacement without machining the block or head. I just dug up the paperwork for when I received the quote from Hartge (which BTW was $8000 USD in 1998--yikes!). It shows that they do indeed also change the crank, thereby increasing stroke. A gold star for you, sir!

[Uber E30]

Yikes what was included in the 8k? Just the engine/software or did you get fun bits like exhaust, strut bar, etc?

[Budget M3]

It did include a cat-back exhaust, ECU mods, and a Hartge-labelled valve cover but nothing else. Hartge is expensive stuff! Needless to say, I did not take advantage off their "offer". You get more punch with a DASC for less than half the price!

[Uber E30]

For sure, I LOVE hartge though. One of my previous e30's was going to be a hartge tribute. I had the wheels, aesthetic bits, and body parts which are pretty hard to find. Ended up getting a good offer on the car before I pulled the trigger on the install/paint though so it never panned out.