Youve probably heard of GT2 and GT3, not the least because of the hot Porsche 911 road cars that celebrate these legendary international sports car racing categories. But GT4? OK, quick back story: GT4 was introduced in Europe in 2007 as an FIA-sanctioned series for amateur drivers, with cars that were neither as fast nor as expensive as the pro-focused GT2 or GT3 machinery. Its proven a pretty popular support act, with GT4 versions of dozens of cars, including Ford Mustang , Chevy Camaro , Porsche Cayman, BMW M4 , Aston Martin Vantage , Jaguar F-Type , and McLaren 570S now homologated to compete. The 2020 Mercedes -AMG GT4 is Daimlers invitation to join this performance party. Although the Mercedes-AMG GT4 bears a superficial resemblance to its GT3 sibling ( read our 2020 Mercedes-AMG GT3 review here ) , the differences are profound when the two are parked side by side. Every exterior panel on the GT3 except the roof has been tugged and tweaked and transformed in the pursuit of ultimate aerodynamic performance. The massive rear wing looks like it was stolen from a small aircraft. Near the tarmac its all splitters and skirts and venturis. The GT4, by contrast, is like a road-going Mercedes-AMG GT R Pro thats been to boot camp. Theres a bigger rear wing thats thrust higher into the airflow, a more aggressive front splitter, and 18-inch center-lock forged alloy wheels, but otherwise it looks remarkably like the road car. Dont be deceived. Theres a lot of real race car in the Mercedes-AMG GT4, even though it shares its light and extremely rigid aluminum space frame with the GT R Pro and has the same 4.0-liter twin-turbo V-8 under the hood. Racing-specific body parts such as the hood, the front apron, and the front splitter are made of lightweight composites. The massive steel brakes, for example, are the same as those fitted to the GT3, as is, apart from the input shaft, the six-speed sequential shift transmission. The rollcage is different from the GT3s, but the general layout and execution of the cockpit is the same as in the pro-league Mercedes racer, as is the FIA-certified carbon safety seat. One feature offered in the GT4 you cant get in the GT3: an optional full race passenger seat. Thrill ride, anyone? Theres just one seat in the GT4 being fettled by the Mercedes-AMG mechanics in the pit garage at the EuroSpeedway Lausitz this cool Friday morning, however, and its all mine. Mercedes-AMG team and development driver Thomas Jger runs me through the finer points of the car as I adjust the position of the pedals and the steering wheel, and fiddle with the six-point safety harness. Although the twin-turbo V-8 under the hood can develop north of 600 hp in road car trim, the GT4s motorsport-style neural network, which allows finer settings for the ABS, traction control, transmission, and engine mapping, means the engine can be set to pump out anywhere between 400 hp and 510 hp, depending on the balance of performance regulations under which the car is racing. Our car has about 430 hp, which, according toJger, is typical for its current balance of performance rating in the GT4 class. That means the 3,064-pound racer (it weighs 231 pounds more than the GT3) has a slightly worse weight-to-power ratio than the 577-hp, 3,539-pound GT R road car. The plus side is the engine is thus relatively understressed, which is why it can run an impressive 25,000 racing miles before Mercedes-AMG recommends a full rebuild. Jger admits the six-speed sequential-shift transmission was an expensive choice for a GT4 racer, but it works better with the racing electronics, is easier to set up at the track, and is more durable, able to be run for 7,500 miles before a major rebuild is recommended. That the GT4 has less downforce than the GT3 is visually obvious, but theres also less mechanical grip, toothough both cars roll on 18-inch wheels, the GT4 has slightly narrower tires front and rear, and its production-car-based suspension less able to be finely finessed in terms of setup. Lausitzs early-morning curfew lifts, and I roll down pit lane. The tires, fresh out of toasty-hot blankets, are warm, but the track is cold, as I discover when the GT4 suddenly snaps and spins as I accelerate out of the second corner. Embarrassed, I cruise back to the pits so the mechanics can give everything a quick once over. Jger gives a no-big-deal kinda shrug when I start apologizing, and simply suggests I switch the traction control back to its most aggressive setting until everything gets warmed up. The first couple of laps are tentative, but then I start to get into a groove. A lion of an engine in AMGs fastest road cars, the growling twin-turbo V-8 initially feels to be more of a pussycat in the GT4. Its perception rather than reality: With up to 442 lb-ft on tap from about 2,000 rpm, the engines a torque monster that arrives at the rev limit without any apparent effort, making the GT4 seem slower and more relaxed than it really is. And although it might not have the weight-to-power ratio of the GT R Pro road car, the fact the GT4 is carrying about 475 pounds less is patently obvious though corners and under brakes, where it feels much more agile and alert. That said, the GT4 moves around more than the GT3, is busier under brakes, doesnt dive for apexes with the same intensity, and the traction control and ABS interventions are much less subtle. The $220,000 (plus tax) 2020 Mercedes-AMG GT4 is an excellent package for those wanting to make the first step into proper sports car racing. Its not just quick and entertaining. Its a car whose performance can be readily accessed by drivers with a range of abilities, a car that enables them to hone their skills in preparation for the step up to a full-on GT3 racer. Or to simply race for the fun of it, enjoying the challenge of driving a high-performance car faster and farther than would ever be possible on a public road. With the added thrill of wheel-to-wheel action, of course. No factory race car is cheap, but the Mercedes-AMG Motorsport ecosystem makes the GT4 a cost-effective package. During the cars development, prototypes completed more than 37,000 miles of race testing on 10 tracks in Europe and the U.S. and ran a 30-hour endurance test at EuroSpeedway Lausitz, so those 25,000-mile engine and 7,500-mile transmission rebuild intervals should be legit. And the Mercedes-AMG Customer Service Portal ensures plenty of car prep know-how and technical support is available for privateer teams. In addition to the GT4-dedicated European Series Northern Cup and European Series Southern Cup, the Mercedes-AMG GT4 is eligible to compete in the IMSA Continental Tire SportsCar Challenge and the Pirelli World Challenge in the U.S., the Blancpain GT Series Asia, and the Australian GT Trophy in Australia. The car is also eligible for races in the global 24H Endurance Series as well as the nine-race VLN Endurance Series at the Nrburgring Nordschleife in Germany. 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