Optima Ultimate Street Car Invitational

Are you kidding? There's no rulebook to the Optima Ultimate Street Car Invitational.

Rules would mean this is serious motorsport. The competition guidelines are listed on five sheets of A4 paper.

To make it really easy, everything here wears a number plate, rolls on street radials and the organisers add: "We stress safety, fun, organisation and friendly competition."

No Bernie Ecclestone types welcomed. This is motorsport uncomplicated, light on rules and heavy on horsepower. The crop of more than 90 street cars that arrived in Las Vegas last week earned a spot in OUSCI by competing in one of nine Ultimate Street Car Association qualifying events throughout the country.

A wildcard entry is the other way to earn an invitation. About 15 cars, selected off the show floor at SEMA, received a special 'come play' invite from the promoter with instructions to arrive at Las Vegas Speedway on Saturday morning and don't expect to leave until Sunday night.

The Invitational was conceived about nine years ago by a group with the idea of showcasing modified street cars that really did what they were modified to do. No coincidence that the event is now supported by sponsors like Wilwood, RideTech, Lingenfelter and Detroit Speed.

Arriving from Detroit, Mark Stielow's yellow 1969 Camaro is the perfect example of cars that do what they were modified to do. He's been here and won before in 2010 with Red Devil, a 1969 Camaro, and in 2012 with Mayhem, a 1967 Camaro. Last year he finished in the top 20 with yet another 1969 Camaro called Hellfire.

He traded Hellfire for this Camaro and started tinkering. It is a brilliant mix of classic Camaro blended with modern high technology. The supercharged LS7-based V8 as Stielow says, "was a science project."

He's running 14.2psi boost on E85 fuel. The outcome is 723kW and he modestly holds it to a 6800rpm rev limit. Why E85? "It is $1.95 a gallon a block from my home," he answered.

Engine, suspension, brakes – to do well here, you need all three. Stielow's Camaro stops like it is chained to a pole. The carbon fibre discs and big callipers are current-generation C7 Corvette and controlled by a Bosch Motorsport standalone ABS system.

The final component in this very competitive package is Stielow himself. He can flat-out steer. But the big chunky Camaro is way off the pace of Danny Popp's incredibly quick 2003 C5 Corvette ZO6 and a pair of well-prepared 2006 Mitsubishi Evo IXs.

The winner is the car/driver earning the most points through five events: a cruise in town that includes a jaunt through a shopping centre with speed bumps, design and engineering inspection, autocross, speed-stop time trial that includes a high-bank left turn for amusement, and an all-out fast lap around a 3.5km circuit.

Popp from Ohio driving his C5 Corvette ZO6 was lapping in 1min 39sec and setting best lap times. Brandon Ranvek in an Evo IX RS is lapping in the 1min 43sec range. Andy Smedegard in another Evo IX is lapping within tenths of Ranvek.

Ranvek and Popp went head-to-head last year for the overall crown, and this year it again looks too close to call after the first day.

"You need to win day one – specifically the autocross – to win the competition," said Ranvek, if the Evos have any chance of dethroning the two-time Invitational champion Popp and placing the imports atop the podium.

Ranvek wins the autocross. But, it is Smedegard who puts together an impressive first day with second overall best times in the autocross and speed-stop. Popp follows in third in both events.

Giving away as much as 500kW to the competition, Bob Boileau from Colorado hustling his 1966 Datsun ute was lapping a few seconds under 2 minutes. Why do the guys with the least horsepower wear the biggest smiles? Tucked under the little Datsun's standard sheet metal is a Mazda MX-5 1.6-litre drivetrain, rack and pinion steering, power-assisted brakes and compact independent rear suspension. Bob has a cool day job as owner and president of Pikes Peak International Raceway.

Looking like a lost UPS delivery van, Martin Pond's weapon of choice is a brown 1980 Mercury Zephyr wagon. Lapping in the mid 1min 50s the Zephyr is a real sleeper and obviously had something to hide. Pond picked the Zephyr because it is built on the same Fox platform as the Mustang and with a 102mm longer wheelbase. The Zephyr is now a lot less Mercury and a lot more Mustang. A SVO front subframe and a 2004 Mustang Cobra IRS found on Craigslist bolted up. You may laugh along with everyone watching, but with a Ford Motorsport 7.0-litre Windsor crate engine making 400kW, the Turdster had no problem pushing the Porsches down the straights.

This was supposed to be the year of the Mustang. Two 2015 Mustangs along with six earlier generations arrived to take on the 18 Camaros. Mustang has historically struggled to match the speed and handling of the Camaros, but Ford's new and improved Mustang with IRS and the high revving 5.0-litre Coyote gave hope. It was not to be. The Mustangs never threatened.

On the other hand, the 1966 red Mustang being shuffled by Californian Mike Hamrick caught everyone's eye. Built as a daily driver and as sexy as a Vegas showgirl, the vintage Mustang carried the new Mustang's 313kW V8 within a TCI front subframe, a set of big Wilwood brakes and a spotless interior.

Local Vegas-sider Thomas Smith drives his Subaru STi daily. The odometer is showing 130,000 miles, but he pushed the STi to stay on pace with the smaller, lighter Evos during Saturday's autocross and speed-stop time trial. The STi is heavy; that's the basic problem, and it stubbornly won't change direction as quickly as the Evos. Despite Smith's claims of around 350kW, the STi drops time against the Evo IXs around the 3.5km circuit. Smith's best of 1:45 isn't a match for the Evos, turning 1:43s.

Popp is too bloody quick for everyone. Popp has been driving competitively for more than 20 years and he's acquired seven SCCA national autocross championships and five NASA national championships. He bought the Corvette ZO6 new in 2003 and its 43,000 miles were almost all clocked in competition. He's won here in 2011 and 2014.

The Lingenfelter-built LS7 would normally displace 7.0 litres (427ci), but they de-stroked it to displace 388ci (6.4 litres) to pull out low-end torque to make better top-end power and rev a lot harder. Popp spins it to 7800rpm and it pushes 429kW to the fat rear rubber.

"It is incredibly fun to drive on the circuit," said Popp, whose driving style can be described as clean in and quick out.

As expected, Popp and the Corvette win the hot lap followed by Hugh Bate a 2013 Nissan GTR, with Smedegard and the Evo in third.

Popp's best lap time reaches into the 1:39s and gives him the needed points to win overall, if barely, over the Evo IXs of Smedegard and Ranvek.

Before heading back home to Wisconsin and Minnesota, Smedegard and Ranvek are heading west to California to race in a sprint event and enjoy the warm weather.

Once home Smedegard says he'll park the Mitsubishi and step into his Honda. "During the winter, I race a Honda S2000 on ice."

You can expect the Evos will return next year, and Popp and the Corvette will be waiting.