Back in 2008, I brought my radar gun to Petit Le Mans and captured trap speeds at three corners to document the unbelievable performance capabilities of the American Le Mans Series LMP1 and LMP2 prototypes, along with the GT1 and GT2 cars of the day.

With the help of a few IMSA WeatherTech SportsCar Championship teams — under the condition of anonymity — representing the Prototype, GT Le Mans, and GT Daytona classes, RACER can bring you a unique speed comparison of how the ALMS cars of 2008 and IMSA machines of 2018 generated speed around the 2.5-mile circuit.

Before cars get to Turn 1 at Road Atlanta they plummet down the steep Turn 12 approach, turn right at unabated speed and fly down the front straight at breakneck speeds before making a sharp right into the downhill compression at Turn 1. Once they track out to the corner exit, it’s a battle against lateral and vertical g-forces as they climb the hill and carry that crazy momentum to the crest of Turns 2 and 3.

In 2008, the last year of the American Le Mans Series’ golden era, I went out to record the truly alarming LMP1 and LMP2 speeds at the apex of Turn 1 — the fastest of them all, the modest speeds at the apex of Turn 7 heading onto the long back straight, and the wicked top speeds entering the downhill braking zone for Turn 10. It created an interesting portrait of the times and technology on hand.

In 2008, free thinking, friendly technical regulations, and prodigious budgets inspired the creation of legendary machines that left fans and drivers in awe of their raw capabilities. Within the LMP1 factory efforts, it was Audi’s hushed intensity with its twin-turbodiesel V12-powered R10 TDi, and Peugeot’s hulking 908 HDi FAP using its own twin-turbodiesel V12 monstrosity in the engine bay. LMP1 privateers were represented by twin-turbo V8 AER-powered Lolas, and naturally-aspirated Zyteks and Creations with V8 or V10 power.

In LMP2, it was a fleet of Acura ARX-01bs, a cadre of Porsche RS Spyders, and a new Lola coupe with a Mazda turbo-four in the back that made it through practice before a crash forced its withdrawal from the race. Lighter and less powerful than the LMP1s while packing more downforce, the LMP2s lost the wars on the straights but humbled their bigger brothers in the twisty bits. There were even rumors of a few LMP2 drivers taking Turn 1 flat in testing as the laws of physics were stretched.

Jump to the LMP2-based Daytona Prototype internationals and the spec LMP2s found this week with IMSA at Road Atlanta, and there’s not much linking 2008 to 2018 in terms of rules, aerodynamics, or tires.

Power levels are somewhat close across the LMP2 eras, but not so with the former LMP1 category. Obscene torque figures and hundreds of extra horsepower made the LMP1 factory cars truly untouchable around Road America.

On the GT side, Corvette Racing was in the final year of internecine fight within the GT1 category using its glorious C6.R. And in GT2, all manner of factory and privateer models — from Ford GT-Rs to Panoz Esperantes to Porsche 997s to Ferrari F430s — ensured the prototypes had plenty of cars to dodge at warp speed.

Unlike today’s GTLM and GTD cars that sport giant splitters and diffusers and use downforce as a serious performance aid, the ALMS GT1 and GT2 fields weren’t aero-driven, which made for different approaches to traversing the speedier corners.

Here, using a fresh blend of words and radar data from 2008 plus onboard data supplied from Thursday’s practice sessions for the WeatherTech Championship finale, we have our comparo:

Turn 1 is rather bumpy and can disturb a chassis with little effort. In shooting the 2008 trap speeds and observing the handling behaviors of the field, I was most impressed with the four Acura ARX-01bs as they absorbed the bumps — slightly bounding over them — and were less visibly disturbed than the rest of the prototypes. The ARX-01b’s also claimed four of the five fastest speeds at this corner.

Marco Andretti’s No. 26 Andretti-Green Racing Acura was fastest of all entries at a staggering 143.4mph at Turn 1’s apex, followed by Timo Bernhard at 141.2mph in the No. 7 Penske Racing Porsche RS Spyder. A motivated Simon Pagenaud — years before he’d make an open-wheel return — was third in his No. 66 de Ferran Motorsports Acura at 140.7mph. Acuras took fourth fastest at 140.3mph with the Patron Highcroft Racing ARX-01b piloted by Scott Sharp and fifth with Michel Jourdain in the Lowe’s Fernandez Racing Acura at 139.8mph.

Despite the brutal straight-line speeds generated by the turbodiesel LMP1s, the No. 07 Peugeot 908 could do no better than sixth at 138.5mph. The Audi R10 TDIs were even slower in the one session I captured, with the No. 1 and No. 2 R10I’s at 133.7mph and 133.2mph, respectively. Both were clearly faster in Turn 1 during subsequent sessions, leading me to believe that by race day, there was little difference between the French and German cars.

Although the LMP2s arrived at Turn 1 with less top speed than the LMP1s, their lighter weight and impressive downforce meant less speed was surrendered as they carried big momentum through the rocket-fast bend. All of the fastest prototypes from 2008 used non-spec Michelin tires; in 2018, Continental provides a spec tire for all WeatherTech Championship prototypes.

Using data from two leading IMSA Prototype teams — one DPi and one LMP2 — we see their pace at the apex of Turn 1 is well below the LMP2 speeds from 2008, but considering the difference in tire vendors and reduced downforce at their disposal compared to the 2008 LMP2s, it shouldn’t be a surprise. One Prototype team reported a best of 130.5mph on Thursday, which is 12.9mph down from Andretti’s peak in 2008.

The timing of the radar gun use and lapping for the GT1 Corvettes did not allow speeds to be recorded in Turn 1, but among the GT2 cars, Risi Competizione’s Ferrari F430 and the No. 71 Tafel Racing Ferrari F430 were on rails through the corner. Risi’s Jaime Melo achieved 113.5mph at the apex of Turn 1, which edged the 113.2mph set by Tafel’s Dirk Muller.

A leading GTLM team reported its Turn 1 apex peak was 114.5mph, or 1.0mph above Melo’s GT2 Ferrari. Both were set on non-spec Michelins. A leading GTD team, with its GT3 cars on spec Continentals, said its best was 105.0mph.

Moving away from Turn 1, using the radar gun at Turn 7 provided a window into the baseline figures needed to determine the speed differentials for peak velocities into Turn 10.

ALMS LMP2 cars were fastest again at this painfully slow corner in 2008, with Marino Franchitti’s No. 20 Dyson Racing Porsche RS Spyder setting a best of 49.2mph. The No. 7 Penske Porsche RS Spyder was second at 48.9mph, and Franchitti’s sister car, the No. 16 RS Spyder of Guy Smith, was third at 48.8mph to give Porsche a sweep of the top three.

Representing LMP1, Peugeot’s No. 07 908 and the No. 50 Team LNT Zytek 07S-Zytek were next and tied at 48.7mph. The No. 2 Audi R10 was just a tick behind at 48.6mph.

Advancements in suspension technology could explain the impressive number put up this week in Prototype as 53.5mph — up 4.3mph over 2008’s best — was recorded.

ALMS GT honors went to both Dirk Werner in the No. 87 Farnbacher-Loles Porsche 997 from GT2 and Jan Magnussen from GT1 in the No. 3 Corvette C6.R as they produced the same speed of 44.5mph.

Like IMSA’s Prototype speed at Turn 7, numbers went up appreciably in GTLM with a 52.5mph, and a 51.3mph in GTD, which speaks to the general gains and improvements in GT technology over the last decade.

Looking at all four ALMS classes, the split between fastest and slowest cars in Turn 7 was just 7.9mph, compared to 31.1mph in Turn 1. In IMSA, the Turn 7 range was a scant 2.2mph from GTD to Prototype, and at Turn 1, it was 25.5mph.

The most fun comes from Turn 10 and calculating the speed gained by the end of the straight.

Peugeot topped all ALMS comers at 200.2mph with the No. 07 908 LMP1 — a gain of 151.8mph between corners! The second fastest top speed went not to an Audi, but the No. 37 Intersport Racing Lola B06/1-AER LMP1 of Clint Field at 195.5mph. Allan McNish was third in the No. 1 Audi R10 at 192.5mph, gaining 144.3mph down the long straight. The No. 2 Audi R10 hit 191.9mph for a gain of 142.9mph.

Two privateer LMP1 entries from England were next with the No. 50 LNT Zytek at 190.0mph for a gain of 141.2mph, and the No. 888 Creation CA07-AIM set an appropriate top speed of 188.0mph, picking up 140.5mph from Turn 7.

The No. 3 Corvette C6.R GT1 was faster than all but two LMP2 cars. Penske’s No. 7 Porsche RS Spyder hit 183.7mph, B-K Motorsports’ Lola-Mazda climbed to 179.9mph, and behind them, the Corvette wasn’t far off at 177.7mph. After the C6.R, Gil de Ferran’s Acura LMP2 followed at 175.9mph.

In our IMSA Prototype time warp, the best top speed was 178.6mph, which was reached after that 53.5mph start, giving us a 125.1mph differential. Compared to the differential of 134.8mph for the No. 7 Porsche RS Spyder 10 years ago, the gap between LMP2 eras is surprisingly small.

Drop in the 151.8mph differential for Peugeot’s LMP1 dragster, though, and the lack of modern firepower is revealed.

Finally, Dirk Muller’s Tafel Racing Ferrari F430 owned the leading GT2 top speed at 169.3mph — a gain of 125.9 from Turn 7. He was shadowed by Dirk Muller’s Farnbacher-Loles Porsche 997 at 168.5mph, for a 124.0mph increase. Black Swan Racing No. 54 Ford GT-R was in the same ballpark at 167.7, picking up 126.8mph on the straight.

By sheer coincidence, our anonymous GTLM data was identical to Muller’s speed, coming in at 169.3mph. Its differential of 116.8 is lower, however, due to the higher speed entering the straight. In GTD, our peak was 161.4mph, giving us a 110.1mph increase from Turn 7.

Minus the giant outlier of the LMP1 class, today’s LMP2-based prototypes aren’t completely outclassed by their predecessors in the beloved ALMS LMP2 category. The ALMS RS Spyders and ARX-01bs can’t be touched by IMSA’s DPis or spec LMP2s in the fastest corners, but in the slower sections at Road Atlanta, and on the straights, the margins are either similar or fall in their favor.

The current GT cars tell a familiar tale. Remove the wild GT1 cars from the equation, and the figures for GTLM, more than GTD, align with the old GT2 performance levels. With GTLM, a modest speed increase at Turn 1, large gain at Turn 7, and identical top speed into Turn 10 suggest IMSA’s efforts to tightly control today’s factory cars has kept a lid on their true potential. That sentiment was not found with 2008’s GT2 cars.