After years of tweaking, this Porsche 928 is a cruise missile of a grand tourer

In 1998, George Suennen was in the market for a grand tourer. He needed a back seat to accommodate his two children, and he needed some everyday practicality, but he also had track days in mind. A 1981 Porsche 928 fit the bill quite nicely; it was affordable, so he snapped it up. Suennen drove it for two years and loved the handling. It just wasn’t quite powerful enough.

Two years later, he bought a 1990 Porsche 928 S4 that brought a lot more power to the table. It was comfortable on the highway, although it did pack on some weight compared to his earlier 928, so there were compromises that made it less suitable for typical track use. Fortunately for Suennen and his Porsche, there was a kind of racing that was well-suited for his interests and his car’s strengths. As Suennen explains, “It’s a great GT car, built to cruise the Autobahn at high speeds, which fit well with high-speed, road-rally events.”

Open road rallies like the Silver State Classic place drivers into classes based on their performance level, and the drivers aim to complete the long highway course with an average speed as close to their prescribed speed as possible. If you’re familiar with the Great Race, it’s a similar concept, on a shorter, faster scale. You’ll see lots of turn-of-the-century cars at both events, it’s just that they’ll be from a different turn of the century.

Suennen began tracking his 928 shortly after buying his S4 and it did well right off the bat. The first changes he made to the car were mostly to get it back up in top running order: a brake tune-up, timing belt replacement, new tires on stock Design 90 wheels, and a rear muffler bypass. In order to meet the safety requirements of the Silver State Classic and other open road rallies, the Porsche also needed a roll bar, five-point harness, and fire extinguisher.

“I was able to run up to the 145-mph average class with only minor modifications,” Suennen says. Those minor mods amounted to a modified driveshaft and bearings, a new in-tank fuel pump, and aftermarket shocks and suspension tuning.

That’s when the racing bug really bit Suennen, and the allure of higher and higher speed led to a methodical approach to building the car into a more capable machine.

For the 2004 Silver State Classic, Suennen added a Vortech V2-SQ S-Trim supercharger kit with an intercooler from Rennlist regular Tim Murphy, along with a set of 928 GTS “Cup” wheels. That made him competitive in the 155-mph class, but he wasn’t satisfied.

In 2006, the addition of a full roll cage, X-pipe, fuel cell, removable steering wheel, and race seats opened up the 160-mph class. It was in this configuration, while racing in the 2007 Bonneville 100, that the V-8 engine lost oil pressure at 188 mph. As he coasted and pulled off the course, the engine was making some awful racket. The V-8 was done for, but Suennen and the rest of the car certainly weren’t.

A new 5.0-liter V-8 from a 1987 928 S4 gave Suennen and his 928 another lease on racing, but it never got sorted out. For 2009, a third engine gave him a clean sheet to build an even more powerful racer using a Vortech V1 T-Trim supercharger borrowed from the second engine build with a new intake and, most importantly, a SharkTuner to program the fuel and ignition curves.

Several small changes over the next nine years honed the 928 even further, but the third engine seemed to be the charm. Suennen experimented with an aftermarket set of cams in 2014 but went back to the stock specs. Aerodynamic mods and additional cooling for the intake charge and supercharger oil were added before Suennen eventually opted for yet another supercharger, a V1 Ti this time, for even more airflow.

With each iteration, Suennen’s 928 became more and more powerful, and the suspension and aero mods made it manageable at speeds in excess of 200 mph. 

The culmination of the grand-touring Porsche 928’s transformation came earlier this year at the 2019 Silver State Classic Challenge. Suennen’s goal for his return to the 180-mph class was to improve on his 176-mph average from 2018 and up his personal record for top speed at 213 mph.

Suennen was the first in his class to hit the road, and the new supercharger had no trouble making more power and helping the engine pull harder than ever before. He was able to hit all his marks, slowing down to 160 mph or so for the long, sweeping turns on the highway and making up his average in the straights. When he flew past the last timing station he knew he’d be a contender, and when the final results were in he claimed first in class with a 179.8144-mph average over the 90-mile course, as well as fastest overall, hitting 219.0 mph along the way, a new personal record.

It wasn’t that long ago that only the most exotic of supercars could eclipse 200 mph, and Suennen’s 928, while being well-engineered from the factory, is not what pops into your head when you imaging a 219-mph car. It’s the result of Suennen’s hard-fought labor and help from a tight community of Porsche enthusiasts—the car’s achievement is a victory for everyone involved.