Here’s How Cadillac’s Raucous LMDh Hybrid Racecar Starter Works

Cadillac brings bump starting into the 21st century.

byRobert Bacon|
Here’s How Cadillac’s Raucous LMDh Hybrid Racecar Starter Works

If you haven’t heard the eargasm that is Cadilliac’s hybrid V-LMDh firing into life, where have you been? The automaker made three of these cars to race this year, and they made their debut last weekend at the Rolex 24 at Daytona where they placed third, fourth, and fifth. So the V-LMDh is quick, but that’s not its party piece.

Any gearhead who spends time on Instagram, TikTok, or YouTube has probably seen the V-LMDh spinning its rear wheels to the sound of electric motors before its eight cylinders roar to life. It’s a symphony that’ll wake you up faster than your morning coffee, and that’s all thanks to the car's starting mechanism.

But this isn’t your regular hybrid starter igniting the engine when the electric motors run out of puff. It’s a more exciting piece of engineering. Let me explain.

What Is the Cadillac V-LMDh?

Cadillac’s V-LMDh is the third generation of the brand's prototype hybrid race car, and the automaker has made three models in three colors: blue, gold, and red. The gold and red machines will race in the IMSA WeatherTech SportsCar Championship in the U.S. The blue car is destined for FIA World Endurance Championship events, including the 24 hours of Le Mans.

As for its starter, when the vehicle's ICE takes over from the electric motor, the process is unlike anything we know on a road-going vehicle. It sounds like it ate a Toyota Prius and spat it back out in a tenth of a second, and that’s all down to its unique starter system.

Here's How Does Cadillac’s V-LMDh Starter System Work 

Cadillac’s V-LMDh rolls out of pit lanes to the whine of an electric motor, but by the time it’s on the track its naturally-aspirated 5.5-liter V8 is singing. The transition between the electric motor and the internal combustion engine is reminiscent of a bump start, but it's a tad more complex than that.

To start the process, the clutch is opened, which decouples the ICE from the gearbox. Then, the electric motor delivers power directly to the gearbox and accelerates the car to pit lane speed (37 mph). Once the vehicle reaches pit lane speed, the ECU releases the clutch and blends power between the EV and ICE systems, which fires its raspy V8 into life.

Plainly put, the electric motor replaces the starter that’s conventionally used in ICE vehicles.


How Much Power Does the V-LMDh Make?

The GTP/LMDh class, with which the V-LMDh competes, limits all vehicles' internal combustion engines to a 640-horsepower output, but when the hybrid system is engaged, the output limit is upped to 671 horsepower. All of its power runs through a seven-speed sequential gearbox. So, that’s what the V-LMDh makes, but how it makes it is possibly more interesting than any of the other cars in this class. 

The LMC55R engine in the V-LMDh is the only naturally aspirated powertrain in this class. What’s more, it has the second-highest redline at 8,800 RPM. All of the other vehicles it's competing against use a V6 or V8 configuration with twin turbochargers.


One video of this beast firing up isn’t enough, so here’s a compilation.

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