We were prepared to be skeptical about this report. That’s why – Dragtimes put a McLaren 765LT on a chassis and wheeled 770 horsepower. Remember, wheel power is less than the crankshaft, this is where car manufacturers get their official rating. In this case, the rating of the 765LT is 755 hp, so McLaren underestimates its engine by more than 100 hp, or there is something stupid with the numbers. More on that in a bit.
We were willing to question everything, from the dyno setup to whether the car was in stock, but that’s why we are not nearly as skeptical as at the beginning of this saga. We came down another 765LT dyno test, which was accidentally published today by Hennessey Performance. And you know what? Their pull was even higher, 780 to the rear wheels to be exact. Yes, 780.
Do not bother to grind the numbers in your head. We have already done math, and depending on the power loss of the propulsion, these statistics suggest that the 765LT’s dual turbocharged 4.0-liter V8 is actually between 885 and 900 hp. It’s not just more than McLaren claims, it’s in a different freaking solar system. So, with two dynos recording very similar power numbers on two separate cars, we are less skeptical. However, before you jump out of our skin about McLaren’s seemingly hilarious hp understatement, there are a few points to consider.
Gears can affect the ability of the horsepower. To accurately measure engine power, it is best to use a gear that is closest to the ratio 1: 1. The Dragtimes team pulled their 770 hp into fifth gear, but also tried a sixth time , which produced 757 hp. The Hennessey attractions were all fifth, so there is at least an apple-to-apple comparison. Could sixth traction be more accurate? This is information we do not have at hand. And of course, the dyno must also be set up correctly.
Calculating parasitic power loss can also be difficult. Old-school automatic transmissions can absorb more than 25 percent of engine power, but modern dual-clutch transmissions are arguably more efficient. The mid-engine design also means that no large drive shaft can rotate, reducing power loss. In this case, 13 percent power loss is a number used by Dragtimes, based on past experience and some dual-clutch gearbox information Ford got on the GT.
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Here is the stupid point we referred to earlier, which definitely makes a difference. Both cars were tested by dynos with race fuel. The Dragtimes team had 100-octane juice in the tank and Hennessey’s crew remained large at 109-octane. We are not experts on how McLaren’s engine management system handles the tuning for rengas, but the fuel absolutely make a difference. In the first place, Hennessey’s first turn on the 765LT yielded 747.6 horsepower on 93-octane pump gas and a hot engine. After allowing the car to cool for an hour – and after pouring 109 octane fuel into the tank – it hit 780 hp.
Here’s the thing. No of these points and exceptions are enough to get us close to McLaren’s official 755 hp rating. And you know what? Seeing the 765LT quarter-mile times run under 10 seconds is a further indication that McLaren, for reasons we do not quite understand, is seriously pulling the chain of everyone when it comes to this bonkers supercar.