We were ready to be skeptical about this report. Here’s why – Dragtimes put a McLaren 765LT in a chassis dynamometer and pulled 770 horsepower on the wheels. Remember that the power of the wheels is less than that of the crankshaft, which is where car manufacturers get their official ratings. In that case, the 765LT’s rating is 755 hp, so either McLaren underestimates its engine by more than 100 hp, or there is something stupid with the numbers. More on that in a moment.
We were ready to question everything from the dynamometer configuration to whether the car was original, but here it is because we are not as skeptical as we were at the beginning of this saga. We found other 765LT dyno test, coincidentally posted today by Hennessey Performance. And you know what? The traction was even greater, 780 on the rear wheels to be exact. Yes, 780.
Don’t worry about analyzing the numbers in your head. We have already done the math, and depending on the power loss of the transmission system, these statistics suggest that the 765LT’s dual-turbocharged 4.0-liter V8 actually has somewhere between 885 and 900 hp. This is not just a little more than what McLaren claims, but in a different solar system. So, yes, with two dynamics recording very similar power values in two separate cars, we are less skeptical. However, before we jump out of our skin because of McLaren’s seemingly hilarious euphemism, there are a few points to consider.
The gear can affect the wheel’s power ratings. To get an accurate measurement of the engine power, it is best to use a gear closer to the 1: 1 ratio. The Dragtimes team made its pull of 770 hp in the fifth gear, but also tried the sixth, which returned 757 hp. Hennessey’s pulls were all in fifth place, so there is at least a comparative comparison. Could the sixth gear pulls be more accurate? This is information that we do not have at hand. And, of course, the dynamometer also needs to be set up correctly.
Calculating the loss of parasitic potency can also be complicated. Old-school automatic transmissions could absorb more than 25 percent of the engine’s power, but modern double-clutch transmissions are considered more efficient. The central engine design also means that there is no large drive shaft to turn, which reduces power loss. In this case, 13 percent power loss is a number used by Dragtimes, based on past experience and some double-clutch gearbox information collected from Ford on the GT.
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Now, here’s the stupid point we mentioned earlier that definitely makes a difference. Both cars were tested on a dynamometer for racing use. The Dragtimes team had 100 octane juice in the tank and the Hennessey crew was living on 109 octane. We are not experts on how McLaren’s engine management system handles the adjustment of racing gas, but the fuel absolutely makes a difference. Case in point, Hennessey’s first 765LT race returned 747.6 horsepower with 93 octane and a hot engine. After letting the car cool for an hour – and after pouring 109 octane into the tank – it reached 780 hp.
Here’s the thing. none these points and exceptions are enough to take us anywhere near the official 755 hp McLaren rating. And you know what? Seeing the 765LT running in quarter mile times under 10 seconds is another indication that, for reasons we don’t fully understand, McLaren is pulling everyone’s chain when it comes to this crazy supercar.