Two different locations have two dynos that reveal huge numbers. But there’s a catch.
This report was not what we expected. Dragtimes placed a McLaren765LT on an engine dyno, and it produced 770 horsepower at its wheels. Keep in mind that wheel power is lower than crankshaft horsepower, which is how automakers determine their official ratings. The rating for the 765LT engine is 755 horsepower. This means McLaren either underrates the engine by more than 100 hp or has something a little off. We’ll get to that later.
Although we were prepared to ask questions about everything, from the dyno setup and whether the car was in stock, here are some reasons why we don’t feel as skeptical now as we did at the beginning. We found another765LT dyno, which was posted by Hennessey Performance today. You know what? Their pull was even greater, 780 to their rear wheels. Yes, 780.
Do not bother to crunch the numbers in your head. The 765LT’s twin-turbocharged, 4.0-liter V8 produces between 885 to 900 horsepower, depending on how much power is lost from the driveline. This is not just McLaren’s claim, it’s also in a completely different solar system. We are less skeptical that two different dynos have very similar power figures for two cars. There are some things to remember before you get too excited about McLaren’s supposedly hilarious hp understatement.
The gearing can have an impact on wheel-horsepower ratings. A gear that is closest to a 1:1 ratio is the best for measuring engine power. Dragtimes’ 770 horsepower pull was made in fifth gear. However, they also tried sixth, which produced 757 horsepower. Hennessey pulled in fifth gear, so it’s at most an apples-to–apples comparison. Are sixth-gear pulls more accurate? This is information we don’t know. The dyno must be correctly set up.
It can be difficult to calculate parasitic power loss. Modern dual-clutch transmissions, which are more efficient than older automatic transmissions, can absorb up to 25% of an engine’s power. A mid-engine design means that there is no large driveshaft to turn which reduces power loss. Dragtimes uses a 13 percent power loss to calculate this figure based on past experiences and dual-clutch gearbox information gleaned from Ford on GT.
Here’s the funny part we mentioned earlier. It makes a big difference. Both cars were run on race fuel and both cars were dyno-tested. Dragtimes had 100-octane fuel in their tank, while the Hennessey crew lived comfortably on 109. Although we don’t know much about McLaren’s engine management system, the fuel is a significant difference. Hennessey’s first run with the 765LT produced 747.6 horsepower using 93 octane pumps gas and a warm engine. After cooling the car for an hour, and then adding 109 octane racing fuel to the tank, it reached 780 horsepower.
Here’s the deal. None These points and exceptions will get us close to McLaren’s 755 horsepower rating. You know what? The 765LT running sub-10 second quarter-mile times in the 765LT is another indication that McLaren is serious pulling everyone’s leg when it comes to this insane supercar.