Six hundred. Seventy-four. Horsepower. At the wheels-all four of them. At a 5,500-foot elevation. Chew on that for a moment... spit out the gristle of correction factors, dyno type, yada yada yada, and digest five inline cylinders of 20-valve turbocharged goodness. And the aperitif of 599 lb-ft of torque-also at the wheels-is simply delicious. This is an absurd portion of power, however you opt to cut it.

Purchased new in 1993, Hap Maguire's been playing with his Ur-S4 for nearly two decades and has spent thousands of dollars in trial and error. His latest lunacy has manifested itself in a 2.5-liter stroker whose output summarily eclipses that of even the stalwart Sport Quattro S1's mere 591 hp. Collaboratively masterminded by the apparently deviant and diabolical minds of Dave Jones of S-Line Motorsport in Denver, Colo., Brendan Rudak of Apikol in Boulder, and Javad Shadzi of 034 Motorsport of Freemont, Calif., Hap's build paddles its own canoe with Paul Bunyan's hands.

The build stats are not for the squeamish: an E85-fed, titanium valve, ported, polished, and Swain-coated and flowed head with solid lifters, HD springs, and titanium retainers is supplied with a biiiiig SX Performance 18203 external fuel pump and before/after Fuelab inline filters. Injector Dynamics 2,000cc injectors accompany a polished Wagner port-matched intake manifold and an 034 Motorsports fuel rail and 70mm throttle body to ensure enough mojo is sent to Wiseco 83mm pistons atop titanium Carrillo rods with ARP bolts.

A practically erotic S-Line Motorsport equal-length and firing-order-sequenced stainless exhaust manifold powers an Innovative Turbo Systems F272 triple-ceramic ball-bearing turbo and Tial Sport V44 wastegate that's good for 825 hp. It's also about the size of my feeble cranium. The 105mm turbo intake with AEM air filter blows through a 24x10.5x4-inch front-mount Garrett intercooler with Apikol polished end tanks and 3-inch polished aluminum plumbing from turbo to throttle body, with a hard mounted Tial blow-off valve. A NOS spray-bar activated at WOT and/or on-demand is wound across the FMIC's face. The custom 3.5-inch downpipe breathes out a Magnaflow exhaust that splits into twin 3-inch (in) Magnaflow boxes with dual 2.5-inch (out) tips whose install required "maneuvering" the spare tire well. Synthesizing the synapses is 034 Motorsport stand-alone software, capping the fun at 33 psi with gear-dependent mapping.

Suffering stat overload, it's time to WOT this mofo.

Firing up such a complex creation is surprisingly simple-a brief kick of the starter summons the iconic five-cyl to a cam-tastic high idle of 1250 rpm. E85 wafts across your nostrils with a near exotic and addictive allure. The bespoke Southbend race/street clutch and lighter (by 17 pounds) 034 flywheel don't have my left calf palpitating nearly to the degree I expect to cope with this level of power, and uptake comes with deft ease and a satisfying, subtle grab. Testament to Audi is the Kluge-rebuilt OEM six-speed ready to repeatedly withstand in earnest what I'm about to dole out, while the Stasis-tweaked center Torsen differential ensures optimal torque split.

Petering about town, it's much like my old S6 or one of the dozens of other modded Ur-Ss I've piloted-tame, tractable, docile even. Folks often deride and chortle in turbo-lag mockery when peak horses and turbo sizes of this magnitude are uttered. A quick perusal of the dyno plot reveals an entirely vast expanse of area "under the curve." Maguire is putting down more power at 4000 than most chipped Ur-Ss are making at peak. Then consider that area under the curve is exploited by a 6-gang 'box coupled with an 8000-rpm redline, and pundits are enlightened. Precision shifts are delivered through the Apikol short-shifter combined with a lead-filled shaft and shortened lever, as operating temps are monitored through myriad mission control gauges: boost, EGT, AFR, oil pressure and temp, coolant temp, voltage, fuel.

And speaking of gauges, I see the temps are up-it's time to explore the deeper regions of the 8k tach. Revs build with eager smoothness to 4800, when full fury explodes onto the helpless pavement. A raucous WRC orchestra erupts and I'm suddenly possessed by Walter Rohrl clawing at Pike's Peak. While the cabin soundtrack is aural nirvana, it is trounced with WOT blowby; the sounds emitted on approach are saturated with the whistle/whine/whoosh of a thousand phone books shredded in unison. The approach onslaught is frightfully vanquished by the cacophony of a futuristically-tuned Rally Acropolis exhaust bellow upon its exit from your view, leaving you quivering in a babbling, nonsensical, does-not-compute disbelief of how and why a near-4,000-pound old-man sedan just defied physics, reality, normalcy.

Rev-limiter a must, but not a pedestrian limiter here, no. Rudak's programmed in a "soft limiter," cutting a cylinder out at a time per rpm increment so as to avoid the ungainly brick-wall party foul. Overtly evident is the State of Tune that Jones of S-Line, Rudak of Apikol, and Shadzi of 034 have endowed in symbiotic synergy. We're talking OEM smooth, refined, willing, capable. With these extreme thresholds exploited in excess I keep expecting a hiccup or sputter in protest... there aren't.

Feedback through the perforated leather wheel is achieved by a corner-weighted alignment with 2.5 front camber made possible by Dave Stone coilovers and spherical bearing camber/caster plates. The geometry is also atypical of a C4-chassis Audi, whose excuse for geometry is more stagecoach than sport sedan. Custom-valved Koni dual adjustable shocks fill Hyper Coil springs, and turn-in is assured by a 28mm S6 Plus front antiroll bar and a custom 28mm three-way-adjustable custom rear bar. The ensemble is shockingly comfortable, impressive considering its performance envelope.

Feeding in a full size-ten of middle pedal, the leather/Alcantara Sparco Milanos hold me firmly yet comfortably and Cayenne Turbo front calipers arrest my debauchery with 355mm two-piece rotors and Apikol hats and brackets. Dance partners for the big yellow fronts are 993 Turbo rear calipers on 314mm rotors, a major C4-chassis feat considering the rear calipers double as the E-brake. The best part of the equation is the brake dive that isn't, a trait of all modded Ur-Ss I've heretofore driven.

Control being nothing without vision, Euro headlight lenses and xenon lows are accompanied by 100W highs, clear corners, and an alluring full Euro array in the rear. The levels of power quickly overwhelm Kosei K3 18s wheels shod with Bridgestone RE11s. To the obvious inquiry, Maguire is quick to retort with two words: "wide-body." As it sits, wider rubber simply doesn't fit.

In spite of the potential lack of traction, Apikol has even bestowed upon it Launch Control. An oxymoron of sorts-Launch Control is anything but. Retarding ignition timing and allowing for all of the 33psi to build at redline-at a standstill...

Save a seat at the asylum for Hap; it appears he's been living in and around the oxygen-challenged Mile High City entirely too long.

1993 Audi S4

Layout
Longitudinal front engine, all-wheel drive

Engine
2.5-liter I5, dohc, 20-valve. Wiseco pistons, Carrillo rods, ported head, titanium valves and retainers, heavy duty springs, port-matched intake manifold, S-Line Motorsport custom camshafts and tubular exhaust manifold, 034 adjustable cam pulley and engine mounts, Innovative F272 "triple ceramic" BB turbo, SX external fuel pump with Fuelab adjustable regulator and 2,000cc injectors, Tial wastegate, Garrett intercooler with Apikol end tanks and Tial BOV, NOS serpentine FMIC spray bar, custom aluminum radiator, Earl's oil cooler, Magnaflow exhaust, 034 standalone engine management and Stage II ECU

Transmission
CRB six-speed manual. 034 mounts and flywheel, Apikol shift kit, Southbend custom clutch, Stasis Torsen center diff

Suspension
Dave Stone coilovers with Hyperco springs and custom Koni dual-adjustable dampers, Stone camber/caster plates, 28mm front antiroll bar, 28mm adjustable antiroll bar

Brakes
OEM Porsche Cayenne Turbo calipers, 355mm cross-drilled rotors, custom hats and brackets (f), OEM Porsche 993 Turbo calipers, 314mm cross-drilled rotors, custom hats and brackets (r), braided stainless lines, Textar pads

Wheels and Tires
Kosei K3, 8.5x18
Bridgestone RE11, 255/35

Exterior
Kamei grille with RS2 rings, European head- and taillights

Interior
Sparco Milano seats, Sparco harnesses and pedals, Audi Sport steering wheel, European shift knob, Innovative wideband air/fuel meter, Autometer EGT and boost/vacuum A-pillar meters

Performance*
Peak Power: 674 hp
Peak Torque: 591 hp
*Owner data, claimed at wheels

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By Paul Krasusky
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