The replacement for the DFS is known as the X series, and its first member launched in 1992 under the XB moniker. Come 1996, the XD entered the scene with approximately 850 horsepower on methanol and a top end of 14,700 revolutions per minute. This engine is believed to belt out in the ballpark of 600 ponies on pump gas with the turbocharger yanked out.
Early-spec engines use dual round exhaust ports, whereas later XDs adopted squished ovals. Capable of well over 300 hp per liter of displacement, the XD rocks a wet-lined alloy block with Nikasil aluminum liners. Introduced by Mahle in 1967, this coating was developed to allow the Wankel engine’s apex seals to work against the aluminum housing with very low friction.
Gifted with a Hall effect sensor, the XD features 16 fuel injectors developed by the motorsport division of Bosch. The heads are aluminum, the crankshaft is billet steel, and the connecting rods are made from titanium.
Michael Andretti racked up five victories in the XD’s first year of production, which is an impressive feat in and of itself. Also impressive is the XD offered by Collecting Cars, a display piece that comes with carbon-fiber velocity stacks, custom billet stands, a glass top, and glass brackets.
Located in Huntingdon Valley, PA, this bad boy is offered at auction with four days of bidding left at press time. The current bid is $750.