words: Dan Klaudt, photos: Tanner Gjersvig
Editor’s Note: This article originally ran in the Q2_2022 issue of quattro Magazine. If you would like to subscribe to quattro Magazine, please join Audi Club here.
When you speak with Ben Castle, you can tell by his voice that he is passionate about his cars and has a few cars to be passionate about. He’s had many cars over the years, and numerous Audi models, including a ‘95 S6, B5 S4, a V8-swapped Coupé quattro and his most recently completed project, a white 1995 Audi 90 quattro with vintage Treser smoked taillights.
Audi has had an influence on Ben from an early age given his parents drove them, but he doesn’t recall the actual models. This particular 90 quattro is actually Ben’s second. He had a ’93 that he credits for jump starting his mechanic skills and project passion, and that he sold locally. He later found it again in a salvage yard where he requisitioned parts like the original spoiler and Bilstein shocks. The spoiler is on his current 90 that he purchased in 2016 from a woman in Louisville CO, who used it as her daily driver. He bought it sight unseen and with some love, it eventually became the car you see here.
Originally a V6 car, Ben drove it while he was collecting parts for the swap that included a trip to Carlisle before getting down to the business of building his latest beauty. The stock engine was replaced by a fully built AAN-code 5-cylinder turbo motor from a 92 S4. In order to mount that, he sourced B3 engine mounts and welded those into the B4 frame rails.
The engine was a full build, including rods from Integrated Engineering, 7A cams, ARP head studs, 1100 cc injectors, an EFR 6258 turbo to minimize lag and increase torque, a reinforced crank pulley by Terrybullone (of the S2forum), a windage tray by Thuppu (also of the S2forum), an RS2 crank pulley and V-belt plus narrow serpentine belt configuration like the RS2 ABY code engine, an RS2 fan shroud with Audi 200 fan, a 200 catch can from Provent. Engine management comes from VEMS and tuned by Mark Swanson for E85. Exhaust exits through an RS2 evo manifold, a 3-inch downpipe and mid-pipe from Wagner, and finally a 3-inch Jetex RS2 exhaust. The car also uses a 3B cross-pipe and intercooler.
The 90’s transmission is an 01E 6-speed. Ben performed the JHM rebuild on it a few years ago and sourced an “AZC” code B5 S4 rear end with differential from Poland to keep the gear ratios matching front and rear for the push button locking rear differential. The car is currently equipped with a Southbend Stage 3 endurance clutch, JHM stainless Shifter knob including an “034” Bilzcat short shift kit including an RS2 shifter lockout.
The car’s suspension uses Bilstein struts from a C4 S4 in front, with struts from a B5 S4 in the rear. The front strut tubes were modified to fit the larger bore struts with Mance Pro-mounts using a spherical bearing design all using H&R 29867 springs. Since American B4 models came with limiting 4×108 wheel fitment, Ben also installed 5-lug swapped knuckles with all with new bearings.
For improved stopping power, he sourced 17z Porsche Cayenne calipers using 323mm A8 rotors in the front. For the rear, he chose B7 S4 calipers with 300 mm rotors. This upgrade led to a larger brake booster and master cylinder. Here again, he got creative with the Volkswagen Group parts bin, using elements from the Volkswagen Phaeton and B7 A4 for an improved booster and master cylinder setup. Finally, it rolls on 18-inch D2 A8 W12 wheels bought new from Audi Tradition.
As with most everything else on this car, Ben stuck with the OEM parts bin for body upgrades, including a late Cabriolet front bumper, RS2 headlights, those aforementioned super-rare Treser taillights, and spoiler.
Inside, the cockpit received blue-weave carbon fiber trim, a new old stock 3-spoke steering wheel, S2 auxiliary gauges, and S2 main speed gauge face.
Ben and his 90 is a fixture in the East Coast so-called “Small Chassis Audi” scene, so expect to see more of him and the 90 at events like Carlisle and other events where such unique vintage Audi models join the field.